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Cosmetic concerns in posterior fossa skull base surgery
Neurosurg Clin N Am 13 (2002) 475–489
Cosmetic concerns in posterior fossa skull base surgery Gavin Wayne Britz, MDa, Marcelo D. Vilela, MDa, Neal Futran, MDb, Robert Rostomily, MDa,* a
Department of Neurological Surgery, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA b Department of Otolaryngology, Head and Neck Surgery, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
This chapter provides an overview of surgical techniques and principles, that when applied to specific posterior fossa approaches, improve cosmetic outcome. Techniques that employ anatomic planes for exposure also allow the best anatomic integrity at closure, reduce the risks of complications that impact wound healing, and thus produce a good cosmetic outcome. Although cosmetic defects produced by posterior fossa surgery are not as obvious as those resulting from anterior or middle fossa procedures, patients nevertheless inspect their surgical sites after posterior fossa surgery and are acutely aware of the cosmetic result. As in other neurosurgical procedures, a poor cosmetic result can overshadow an otherwise successful operation. This article provides an overview of surgical techniques and principles that improve cosmetic outcome when applied to specific posterior fossa approaches. It is the contention of these authors that all things being equal (relative to surgical access), approaches that use anatomic planes for exposure also allow the best anatomic integrity at closure, reduce the risks of complications that affect wound healing, and thus produce a good cosmetic outcome. This article briefly reviews general surgical principles with implications for cosmesis and examples of these techniques applied
to specific posterior fossa surgical approaches as well as reconstructive procedures.
* Corresponding author. Department of Neurological Surgery, University of Washington, 1959 NE Pacific Street, Room RR-744, Seattle, WA 98195, USA. E-mail address: [email protected] (R. Rostomily).
Cosmetic aspects of surgical exposure and repair
Basic principles of wound healing It is beyond the scope of this article to address the basic biology of wound healing, but it is worth mentioning briefly the variables that affect wound healing and subsequent cosmetic results. Nutritional state, preexisting illnesses like cancer, exposure to radiation therapy, smoking, and metabolic diseases like diabetes can all affect wound healing [1,2]. Correctable systemic factors should be aggressively managed before surgery. Local factors that affect wound healing include oxygen tension, tissue edema, and infection. Low oxygen tension can be prevented by preservation of the local blood supply; thus, knowledge of the vascular anatomy in relation to the skin and soft tissue incisions is vital. The vascular anatomy of the skin and soft tissues of the posterior fossa is illustrated in Fig. 1. Although most standard neurosurgical approaches to the posterior fossa do not critically impair the robust collateral blood supply in this region, it must be considered when performing multiple approaches or in the setting of reoperation after infection as well as in the debilitated or previously irradiated patient.
Posterior fossa surgical approaches require violation and repair of skin, muscle, bone, and dura. The technique used to handle these tissue layers
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Fig. 1. The major arteries from the external carotid artery form collateral connections that provide robust blood supply to the scalp of the posterior fossa.
during each phase of a surgical procedure either directly or indirectly has an impact on the eventual cosmetic result. The general surgical principles with relevance to cosmetic results during exposure and repair of posterior fossa approaches are briefly reviewed here. Scalp, muscle, and soft tissue dissection and repair The cosmetic aspects of the techniques of skin incision (electrocautery versus scalpel) and closure (suture versus staples) are reviewed in more detail elsewhere in this issue. For posterior fossa approaches, incisions that extend into the cervical region should be made in a natural skin crease. For closure, sutures may be preferable to staples when there is concern about cerebrospinal fluid (CSF) leakage. The possible cosmetic differences attributable to the different techniques for skin incision and closure are likely marginal compared with the cosmetic impact of tissue injury that can be produced through poor surgical technique [3,4]. The use of muscle-splitting techniques that respect fascial planes and detach muscles from their anatomic bony attachments rather than muscle transection preserves muscle bulk, facilitates anatomic repair, minimizes swelling and ischemia that can lead to deep infection or seroma formation, and reduces postoperative pain. The utilization of the
fine-tipped electrocautery or Hoan dissector is useful for performing these dissections. Appropriate repair of soft tissue should provide hemostasis without compromise of blood supply, eliminate dead space to prevent fluid accumulations and a potential nidus for infection, and reapproximate muscles into their anatomic position under tension to preserve muscle bulk. Bone removal and repair During posterior fossa surgery, bone removal is accomplished with a craniotomy, craniectomy with cranioplasty repair, or craniectomy alone. Reconstituting the native skull contour with the former two options is preferred for cosmetic purposes, but a craniectomy is indicated for emergency decompressive procedures or in situations where postoperative swelling is a concern. The reconstitution of the bony contour provides additional benefits of acting as a support to help seal dural closures, thus preventing pseudomeningocele formation. Aside from cosmetic issues, the use of craniotomy or cranioplasty versus craniectomy has been advocated in the acoustic neuroma patient undergoing a suboccipital craniotomy (SOC), because it may prevent postoperative headaches [5–8]. The validity of this contention remains controversial. The increasing number of new materials available for cranioplasty has produced a
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myriad of techniques suitable for repair of bony defects. Current choices for repair of bony defects include native split-bone grafts; soft tissue grafts, such as fat, bone extenders, or cements; traditional methylmethacrylate cranioplasty material; bioabsorbable or titanium mesh for structural support; and customized or preformed implants. One must carefully consider the goal of the repair as well as the costs and advantages of each approach or material before proceeding. There is no literature to guide decision making, and each surgeon must use the technique and materials that are believed to be the most cost-effective and appropriate for a particular application. A summary of available
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materials for cranial reconstruction and their potential advantages and disadvantages is provided in Table 1. The specific techniques that we employ for various procedures are outlined here. Dural opening and closure Dural opening and repair can directly affect cosmesis through pseudomeningocele formation or can indirectly affect cosmesis when CSF fistulae promote wound breakdown and infections that require additional wound repair and debridement or bone flap removal. The goal of dural repair is to achieve a watertight closure if possible. The
Table 1 Summary of materials available for cranial reconstruction Materials
Advantages
Disadvantages
Autogenous grafts: craniotomy plate, split-thickness bone graft Tantalum
Inexpensive, less susceptible to infection
Possibility of reabsorption over time, may have limited supply to cover the defect, difficult to conform to the defect Expensive, higher risk of infection, radiopaque with artifacts on both CT and MRI, heavy, has a risk of erosion through the scalp, thermoconductive Higher infection risk, has a risk of erosion through the scalp, minor artifact on CT, susceptible to fracture with trauma
Polymethylmethacrylate
Titanium mesh
Bioabsorbable mesh Custom surgical Implants (eg, Medpor; Porex Surgical, GA) Hydroxyapatite cement
Bone graft extenders, (eg, Novabone; Porex Surgical)
No reabsorption, no limitation of supply, can be molded to conform to the defect, good tensile strength
Relatively inexpensive, no reabsorption, unlimited supply, can mould to conform to the defect, medium strength, inert with minimal tissue reaction, adheres tightly to bone, not thermoconductive, no paramagnetic artifacts on MRI Well tolerated by soft tissues and bone, easily contoured to fit defect
Provides structural support, easily contoured to fit defect Customized to fit defect, open pore structure allows for tissue ingrowth, easily further customized with scissors or scalpel, immediate good structural and cosmetic support Extremely biocompatible with no inflammation or foreign body reaction, osteoconductive and allows for ingrowth of new bone, unlimited supply, may be used to augment autogenous grafts Used to augment autogenous bone grafts with limited supply, easily placed around preferred site
No reabsorption, higher infection risk, often has to be used in conjunction with polymethylmethacrylate to provide adequate strength, artifacts on MRI or CT although minor, expensive Bioabsorbable and therefore limited long-term support, minimal strength Higher risk of infection, expensive, needs to be ordered before surgery
Initial brittleness that limits its use for larger defects, difficult to conform to defect, expensive
Expensive, cannot be used exclusively
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use of a continuous linear dural incision and avoidance of cauterization helps to preserve the native dura for primary watertight closure. If a primary repair is not possible, dural patch grafts with autologous tissue (pericranium, fascia lata, and temporalis fascia), allograft, or artificial dural substitutes can be secured with a running suture and fibrin glue to obtain a watertight closure [9–20]. The use of transient lumbar drainage can further facilitate the sealing of this and other tenuous dural closures. In rare cases, tissue transfer with a pedicled or free flap may be required to prevent CSF leaks (see below). Cosmetic issues in specific posterior fossa approaches Surgical approaches to the posterior fossa The surgical approaches that provide access to the posterior fossa include midline approaches, lateral approaches (paramedian and retrosigmoid), far lateral approaches, and the petrosal or combined presigmoid transtentorial approaches [21]. Needless to say, a variety of lesions can be addressed by these approaches. From a cosmetic perspective, the choice of approach should be matched to the pathologic findings such that adequate exposure and repair are achieved without unnecessary tissue dissection or bony removal. Specific techniques that can be used to improve cosmesis for the retrosigmoid (RSA), far lateral, and petrosal approaches are emphasized. Lastly, the cosmetic issues for more radical reconstructive techniques are reviewed. Midline posterior fossa approaches Cosmetic concerns for the midline approaches are generally restricted to bony removal, muscle repair, and skin incision. The latter two factors have already been reviewed, and adherence to the general principles of tissue and skin edge handling, muscle dissection in the avascular midline, and avoidance of excessive monopolar cautery that can damage muscle tissue should optimize the cosmetic outcome for these factors. The muscles that insert superiorly along the nuchal midline include the trapezius, splenius capitis, and semispinalis capitis. The anatomy of the superficial musculature encountered in the basic posterior fossa approaches is shown in Fig. 2. These above-mentioned muscles are taken down as a unit in a subperiosteal fashion and should be reattached in proximity to the nuchal line with the suture
Fig. 2. Anatomic diagram showing the relation between the muscular layers of the posterior fossa.
anchored to a cuff of tissue or to plates or holes drilled into the bone. We prefer the latter choices because they do not require division of the muscle at its insertion and the anchoring is more secure. Atrophy or retraction of muscle at the nuchal line can produce a noticeable defect, particularly in patients with short hair or in those who have undergone a craniectomy. As mentioned previously, the decision to perform a craniotomy, craniectomy with cranioplasty, or craniectomy alone must be based on the clinical situation, the surgeon’s preference, and the available cranioplasty materials. Any method of bony reconstruction that securely reconstitutes the normal bony and soft tissue contour of the posterior fossa has the same positive cosmetic outcome. Delayed cranioplasty can also be performed, but the cosmetic result can be compromised by any intervening muscular atrophy that must be accounted for when contouring the cranioplasty. In cases of Arnold-Chiari type I malformations, one performs a craniectomy to expand the posterior fossa. Although modest bony removal is essential to treat the underlying pathophysiology, excessive bony removal not only creates a potentially poor cosmetic result but can produce symptoms caused by cerebellar ‘‘sag.’’ Retrosigmoid approach Lesions in the lateral cerebellar hemisphere and or cerebellopontine angle (CPA) generally require
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a lateral approach. Variations of the commonly employed RSA can be modified to address lesions in either location and thus serve to demonstrate surgical techniques and issues that affect cosmetic outcome for treatment of lesions in both locations [22–26]. The type of incision one uses for the RSA can dictate the muscle dissection employed to access the suboccipital bone and, ultimately, the cosmetic outcome from surgery. Three different incisions commonly used for the RSA are shown schematically in Fig. 3. The vertical incision employs a muscle-splitting technique that allows rapid access to the suboccipital bone, but the division of muscles may increase postoperative pain and local inflammation, impair muscle healing, and enhance atrophy. In addition to the potential loss of muscle bulk, this approach is more likely to divide the lesser occipital nerve as it courses between the sternocleidomastoid muscle (SCM) and splenius capitis muscle to produce numbness in the postauricular region or neuroma formation. The absence of a layered wound may increase the CSF leak and subsequent infection risk, which can compromise the cosmetic result.
Fig. 3. Illustration of three common skin incisions applied to the retrosigmoid approach to the posterior fossa: the vertical or straight incision, a retroauricular C-shaped incision, and a U-shaped incision.
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An inverted U-shaped flap involves a midline incision that traverses horizontally above the nuchal line and then inferiorly along the mastoid parallel to the midline incision. The subcutaneous tissues and muscles are elevated as a unit and detached from their anatomic insertions, thus allowing preservation of muscle bulk and the lesser occipital nerve. During closure, the muscles can be anchored under tension at their nuchal insertion using one of the techniques described previously to prevent atrophy. This approach is relatively fast but has the disadvantage of having muscle bulk at the inferior aspect of the wound, which can limit exposure, and a nonlayered closure with the lateral limb of the incision overlying the dural opening, which may be more prone to CSF leak. We prefer the C-shaped retroauricular incision for the RSA (see Fig. 3). The steps in this approach are demonstrated in Fig. 4. Briefly, the apex of the incision approximates the medial border of the SCM to facilitate the elevation of a myocutaneous flap that incorporates the SCM. The medial extent and superior and inferior extension of the incision are modified according to the lesion size and location. For large lesions requiring exposure to the foramen magnum, the incision can be extended below the level of the mastoid tip and hairline in the normal cervical skin creases so as to provide a more cosmetic result. The inferior border of the SCM is elevated if possible, but it can be split along its fibers for smaller exposure. By extending the flap inferiorly, the muscle can generally be elevated forward without division to provide generous access to the suboccipital region. After the elevation of the myocutaneous flap, the splenius capitis and deeper suboccipital muscles are encountered. These can be detached as a unit or dissected sequentially with preservation of the lesser occipital nerve between the SCM and splenius and the occipital artery in its course between the splenius capitis and suboccipital muscles. These muscles are retracted inferomedially to allow generous exposure of the suboccipital region. A craniotomy is fashioned by drilling a narrow trough over the inferior and medial edges of the transverse and sigmoid sinuses, respectively, and completing the bone cut with a craniotome or high-speed drill. This allows elevation of a more generous bone flap that does not require augmentation at closure to cover the defect. The mastoid emissary vein is directly visualized under the flap and can be coagulated and divided to free the flap without producing a tear at its point of entry into the sigmoid sinus. In cases in which there is
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Fig. 4. Intraoperative photographs of a right-sided retroauricular C-shaped incision and muscle-splitting retrosigmoid craniotomy. (A) Skin incision with the course of the transverse and sigmoid sinus and mastoid marked. (B) Myocutaneous scalp flap with the sternocleidomastoid muscle elevated and the splenius capitis muscle exposed. Note the course of the preserved lesser occipital nerve (arrow). (C ) The splenius capitis muscle elevated as a separate layer. (D) The splenius capitis and suboccipital muscles elevated from the nuchal line to provide exposure of the suboccipital bone. (E ) The bone flap created by drilling over the medial edge of the sigmoid sinus and inferior edge of the transverse sinus gives full exposure for a cerebellopontine angle approach and can be replaced to fill the defect without the need for cranioplasty.
concern about dural adhesion, a burr hole can be placed at the asterion and at the inferomedial corner of the planned craniotomy to allow dural stripping and inspection before bone flap elevation. This technique often requires additional drilling of the mastoid bone to provide exposure to the medial edge of the sigmoid sinus, however. The muscle layers are reapproximated in their anatomic positions and anchored to their sites
of insertion to apply tension and preserve muscle bulk. The layered coverage that results from this technique helps to prevent CSF leakage. We have adopted this approach not only because it provides an excellent cosmetic result, but because it has eliminated leakage of spinal fluid through the wound and reduced the incidence of pseudomeningocele formation and postoperative pain.
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Far lateral approaches The cosmetic issues relevant to the far lateral approaches are similar to those encountered in the RSA. Additional muscle dissection and bone removal provide the lateral exposure needed for ventral and ventrolateral exposure of the posterior fossa and craniocervical junction as well as the mid- to lower clivus. The indications for and details of the many variations of far lateral approaches are reviewed in more detail elsewhere [27–33]. The following discussion describes general strategies to minimize cosmetic defects from these approaches. Two approaches commonly used to provide far lateral surgical access employ either a U- or Cshaped incision (Fig. 5). These two approaches differ largely in the techniques used for muscle dissection to access the suboccipital bone, mastoid, and cervical lamina/facets. In both approaches, the extent of dissection and bone removal is dictated by the underlying pathologic findings and the amount of the exposure required to access lesions of the ventral/lateral and inferior posterior fossa as well as the craniocervical junction. The U-shaped incision starts at or below the mastoid tip and extends to the mastoid base, medially along the nuchal line, and then vertically into the midline cervical region as described previously
Fig. 5. Two common skin incisions used for far lateral approaches: the U-shaped incision and the retroauricular C-shaped incision.
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for the midline approach. This incision allows reflection of the skin and muscles back away from the surgical site in one large flap, which avoids muscle transection. As is the case with the Ushaped incision in the RSA, the elevation of muscles en bloc may create enough bulk to obscure lateral exposure. Another consideration with this approach is that the incision or dissection through the skin, soft tissues, and dura lies more directly in line and may thus increase the chances of CSF fistula formation when a watertight dural repair is not achieved. The approach using the C-shaped incision differs from that employing the U-shaped approach largely in the technique used for muscle dissection. Although its potential advantages include reduced muscle bulk, obscuring the exposure, one advantage relevant to cosmetic outcomes includes a reduced risk of CSF leak. By dissecting the muscles in layers and repairing them by anchoring them to their respective sites of attachment, a multilayered closure that resists CSF leaks, preserves muscle bulk, and provides excellent lateral exposure is achieved. As with the RSA, the skin and SCM are reflected as a myocutaneous flap and then the splenius capitis, semispinalis capitis, and rectus capitis muscles are detached off the nuchal line and suboccipital bone and reflected inferomedially. The muscles of the suboccipital triangle are identified before the dissection of the vertebral artery. The basic surgical steps and exposure achieved by this approach are outlined in Fig. 6. As mentioned previously, varying amounts of bone removal involving the suboccipital bone, condyle, and mastoid process are employed in the far lateral approaches. The need for bone repair is dependent on the extent of bone removal. Because of the inward curvature of the suboccipital region, much of the bony removal with this approach is hidden deep under the soft tissues and reduces the cosmetic deformity after smaller exposures. In the more extensive bony removals, particularly those that involve the mastoid area, bony reconstruction may be used. This bony reconstruction can involve the different bone sources as discussed previously. The choices of repair for extensive mastoid removal are discussed below in the section on the petrosal approach. A secondary consideration in cosmesis for the far lateral approach is the significant reduction in mobility at the occipital-cervical joint when fusion is needed after greater than 50% occipital condyle resection. The awkward movement produced by limiting movement (approximately 50% in all
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Fig. 6. Far lateral approach employing a retroauricular C-shaped incision. (A) Skin incision with elevation of the sternocleidomastoid muscle as a myocutaneous flap. (B) The splenius is reflected to expose the longissimus capitis muscle (LC). (C ) The deeper muscles of the suboccipital triangle and the transverse process of C1 (at the tip of the dissector) are exposed after reflection of the longissimus capitis and semispinalis capitis muscles. (D) After a small suboccipital craniotomy, mastoidectomy, C1 hemilaminectomy, and partial condylectomy, the vertebral artery (VA) is mobilized and lateral posterior fossa and upper cervical dura are exposed. (E ) After dural opening, excellent exposure to this lower clival/upper cervical ventral meningioma is demonstrated.
planes) can have the same emotional impact as a severe cosmetic defect. Therefore, one must carefully consider the necessity for condyle resection, particularly because many ventral lesions can be resected with less aggressive approaches [15]. Presigmoid petrosal approach The presigmoid petrosal approach provides access to lesions in the petroclival and tentorial
notch areas; when combined with frontotemporal or pterional and orbitozygomatic approaches, it can be used to access lesions that extend to the cavernous sinus and middle fossa [34–37]. For the standard petrosal approach, a C-shaped retroauricular incision that extends along the superior temporal line and down into the neck in line with the cervical skin folds is employed (Fig. 7A). If a combined approach is required, a modified skin
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Fig. 7. The incisions used for the standard petrosal approach (A) and when used in combination (B) with frontotemporal or pterional craniotomies with or without orbitozygomatic osteotomy.
incision that extends above the temporal line into the frontotemporal region is made. A preauricular incision that joins the postauricular incision provides for the combined approach. Care must be taken to keep the base of the scalp flaps large enough to ensure adequate blood supply (see Fig. 7B). The details and variations of the petrosal approach have been outlined elsewhere, and we focus on the major cosmetic issues related to this approach. Similar to the techniques used in the RSA or far lateral approaches, the scalp is elevated as a myocutaneous flap and the deeper muscles are dissected without transection to maintain bulk and provide good layers for closure. The additional exposure of the squamous temporal bone requires elevation and anterior reflection of the posterior aspect of the temporalis muscle. The mastoidectomy creates a defect over the site of the presigmoid dural incision, which can lead to a significant cosmetic deformity and a propensity for CSF leak if not adequately repaired. There are numerous ways to provide a good dural repair and cosmetic closure. Although the presigmoid dura cannot be primarily repaired in a watertight fashion, it can be reapproximated with several dural sutures that also provide a latticework to support interlocking pieces of autologous fat graft, which effects a ‘‘ball-valve’’ closure. This is augmented with fibrin glue and supported externally
either with a solid graft or with the soft tissue closure and dressings. A lumbar drain is used for several days to allow the repair to seal adequately. Small defects can be packed with fat or other autologous tissue (fascia lata, pericranium) that is anchored into the opening with a lattice of dural suture to effect a ball-valve closure. The bony defect over the sigmoid sinus and mastoid creates the most significant cosmetic defect from this approach. A large number of strategies similar to those used for bony reconstruction of retrosigmoid craniectomies are available for reconstruction of the defect created by the petrosal approach. Among the choices are split-thickness autograft, bioabsorbable or titanium meshes, bone cement, methylmethacrylate, and mastoid prosthetic devices (Fig. 8). We prefer autograft if suitable donor bone is available. An additional benefit from reconstruction is the support it provides for dural repair. Cosmetic aspects of ‘‘reconstructive’’ surgery Reconstruction after posterior fossa surgery may be required for chronically nonhealing wounds or when extensive soft tissue or bony removal is performed during tumor resection (Figs. 9 and 10) [38–42]. The approach to posterior fossa reconstruction and the optimization of cosmetic outcome starts with careful evaluation of the patient and the potential defect. This includes
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Fig. 8. (A) The resulting defect after a petrosal approach is illustrated. (B) The use of a preformed Medpor (Porex Surgical, Fairburn, GA) implant (I) to repair the defect is shown. A variety of other materials and techniques are suitable for this repair, including split-thickness autograft (see text for discussion).
assessment of the location and size of the defect with radiologic evaluation of the depth and bony or dural defects. Previous surgery or radiation or ongoing wound infection affects the viability of the skin around the defect, reducing the available tissue for local flaps. Of course, the pathologic characteristics of the presenting lesion are also important in planning reconstruction. The simplest method of reconstruction should be considered in all cases while ensuring adequate resection of the lesion. In the posterior neck, the abundant collateral soft tissue blood supply allows for wide elevation of these tissues so that many wounds can be closed primarily or with simple
adjacent tissue transfer. When larger defects exist, however, local tissues useful in the anterior cranium, such as pericranial flaps and temporalis flaps, do not exist. Moreover, the thick posterior neck and occipital tissues do not lend themselves to skin graft reconstruction, because this would result in a poor cosmetic and functional result. Excellent cosmesis has been achieved with tissue expansion when hair-bearing skin has been lost, and repeated expansion is possible for large defects. The main advantage is the ability to replace one tissue with the same tissue. This technique requires a separate procedure to place the expanders and time for tissue expansion to occur, however, which
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Fig. 9. Repair of a nonhealing posterior fossa wound with chronic cerebrospinal fluid leakage in a 48-year-old man with multiple resections, radiation therapy, and local chemotherapy for recurrent medulloblastoma. (A) Demonstration of the site of chronic wound breakdown with dural graft exposed. (B) After wound debridement, a larger defect is evident that cannot be primarily repaired. The exposed bovine pericardial dural patch was replaced. (C ) This pedicled lower island trapezius flap based on the transverse cervical and dorsal scapular vessels was used for reconstruction. Note the proximal de-epithelialized portion of skin that must lie in the subcutaneous tunnel. (D) The final reconstruction with the epithelialized skin paddle forming the lower triangular area of the final scalp closure. The patient did well with no further wound complications.
may delay surgery for the primary tumor. Tissue expansion is not generally recommended for infected cases because of the risk of the expander becoming infected and losing the expanded flap or for use in radiated skin because of decreased compliance and a higher rate of skin necrosis. For larger posterior fossa defects, there are several well-vascularized regional flaps from the back that provide good skin color match and appropriate tissue thickness. Because the patient is often placed in the prone or lateral decubitus position for tumor extirpation, the back is the ideal donor site. The trapezius system of flaps offers a superior flap, which is easily elevated and useful for rotational coverage of small neck defects. Its short arc of rotation limits its use in the posterior fossa. More commonly, the lower island trapezius flap based on the transverse cervical and dorsal scapular arteries is used because of its ability to cover most posterior defects with minimal tension on
the wounds. This pedicled flap allows tissue to be transferred for up to 15 cm below the scapular tip and can reach the occiput easily. The skin color and texture provide an excellent match to the posterior scalp. Donor site morbidity is minimal, and the wound is closed primarily. Also on the back, the latissimus dorsi flap based on the thoracodorsal vessels provides abundant muscle and skin to cover any posterior fossa defect. Its arc of rotation at the axilla allows it to reach to the top of the head if necessary. At times, the skin portion may be much thicker than the posterior scalp; the flap can be transferred as muscle only, and a split-thickness skin graft can be applied. When pedicled flaps cannot comfortably reach and cover the defect or the geometry of the flap inset could compromise vascularity, free tissue transfer provides optimal results. Tissue can be placed optimally unencumbered by pedicle length
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Fig. 10. Resection of a recurrent scalp melanoma in a 68-year-old woman with invasion of the occipital bone. (A) Preoperative picture showing an extensive scalp lesion. (B) MRI with gadolinium showing extensive involvement of soft tissue. (C ) Extensive resection of scalp and right suboccipital bone. (D) Dissection of a myocutaneous latissimus free flap that was inserted into the right transverse cervical artery and right internal jugular vein. (E ) Final intraoperative view with latissimus flap at the inferior portion of the reconstruction and meshed split-thickness skin graft above. Note that the cutaneous paddle of the flap resides along the cervical region, where the tissue is normally thicker, and that the skin graft is used to cover the thinner area of the cranial scalp. (F ) Postoperative result after wounds have matured.
or position. Well-vascularized tissue from a variety of donor sites can minimize the risk of CSF leak, cover exposed calvarium, tolerate the burden of radiation and/or a contaminated wound, and provide optimal function and cosmesis. As described previously, the latissimus dorsi myogenous or
myocutaneous flap is easily harvested and has a predictable blood supply with a long vascular pedicle to reach donor vessels, large size, and minimal donor site morbidity. It is the flap of choice to reconstruct large scalp defects on any area of the head.
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dealing with complex and chronic wound-healing problems or extensive soft tissue and bony lesions in the posterior fossa. Summary Although cosmetic defects produced by posterior fossa surgery may not seem obvious, a poor cosmetic result can overshadow an otherwise successful operation. It is important to approach the operation with knowledge that each phase of a surgical procedure either directly or indirectly influences the eventual cosmetic result. The careful use of anatomic dissection and repair and attempts to reconstitute bony defects to their native contour as well as avoidance of complications all contribute to excellent cosmetic outcomes. Acknowledgments The authors thank medical illustrator Raquel Lourenco Abreu for her preparation of all illustrations included in this article and Paul Schwartz and Janet Schukar for invaluable assistance with figure preparation. References
Fig. 10 (continued )
One other excellent free-flap choice is the fasciocutaneous scapula flap based on the subscapular vessels. It has excellent color match to the posterior neck and occipital skin as well as thickness and consistency that match surrounding tissue. The shorter pedicle length when compared with that of the latissimus dorsi flap may sometimes limit its use because of the difficulty in reaching suitable recipient neck vessels. The expertise of a team of surgeons versed in different cosmetic aspects of reconstructive surgery is invaluable to the neurosurgeon when
[1] Phillips SJ. Physiology of wound healing and surgical wound care. ASAIO J 2000;46(Suppl):S2–5. [2] Yamaguchi Y, Yoshikawa K. Cutaneous wound healing: an update. J Dermatol 2001;28:521–34. [3] Chughtai T, Chen LQ, Salasidis G, Nguyen D, Tchervenkov C, Morin JF. Clips versus suture technique: is there a difference? Can J Cardiol 2000;16: 1403–7. [4] Kearns SR, Connolly EM, McNally S, McNamara DA, Deasy J. Randomized clinical trial of diathermy versus scalpel incision in elective midline laparotomy. Br J Surg 2001;88:41–4. [5] Koperer H, Deinsberger W, Jodicke A, Boker DK. Postoperative headache after the lateral suboccipital approach: craniotomy versus craniectomy. Minim Invasive Neurosurg 1999;42:175–8. [6] Levo H, Pyykko I, Blomstedt G. Postoperative headache after surgery for vestibular schwannoma. Ann Otol Rhinol Laryngol 2000;109:853–8. [7] Levo H, Blomstedt G, Hirvonen T, Pyykko I. Causes of persistent postoperative headache after surgery for vestibular schwannoma: Clin Otolaryngol 2001;26:401–6. [8] Santarius T, D’Sousa AR, Zeitoun HM, Cruickshank G, Morgan DW. Audit of headache following resection of acoustic neuroma using three different techniques of suboccipital approach. Rev Laryngol Otol Rhinol (Bord) 2000;121:75–8.
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[9] Anson JA, Marchand EP. Bovine pericardium for dural grafts: clinical results in 35 patients. Neurosurgery 1996;39:764–8. [10] Atiyeh BS, Hamdan AM, Nassar SI, Hanbali FS, Hashim HA. Vascularized fascial patch for repair of suboccipital dural defect. Ann Plast Surg 1996; 37:422–7. [11] Barbolt TA, Odin M, Leger M, Kangas L, Hoiste J, Liu SH. Biocompatibility evaluation of dura mater substitutes in an animal model. Neurol Res 2001; 23:813–20. [12] Fisher WS 3rd, Braun D. Closure of posterior fossa dural defects using a dural substitute: technical note. Neurosurgery 1992;31:155–6. [13] Filippi R, Schwarz M, Voth D, Reisch R, Grunert P, Perneczky A. Bovine pericardium for duraplasty: clinical results in 32 patients. Neurosurg Rev 2001;24:103–7. [14] Nagata K, Kawamoto S, Sashida J, Abe T, Mukasa A, Imaizumi Y. Mesh-and-glue technique to prevent leakage of cerebrospinal fluid after implantation of expanded polytetrafluoroethylene dura substitute—technical note. Neurol Med Chir (Tokyo) 1999;39:316–9. [15] Nanda A, Vincent DA, Vannemreddy PS, Baskaya MK, Chanda A. Far-lateral approach to intradural lesions of the foramen magnum without resection of the occipital condyle. J Neurosurg 2002; 96:302–9. [16] Sekhar LN, Sarma S, Morita A. Dural reconstruction with fascia, titanium mesh, and bone screws: technical note. Neurosurgery 2001;49:749–52. [17] Tachibana E, Saito K, Fukuta K, Yoshida J. Evaluation of the healing process after dural reconstruction achieved using a free fascial graft. J Neurosurg 2002;96:280–6. [18] Verheggen R, Schulte-Baumann WJ, Hahm G, Lang J, Freudenthaler S, Schaake T, et al. A new technique of dural closure—experience with a vicryl mesh. Acta Neurochir (Wien) 1997;139:1074–9. [19] Warren WL, Medary MB, Dureza CD, Bellotte JB, Flannagan PP, Oh MY, et al. Dural repair using acellular human dermis: experience with 200 cases: technique assessment. Neurosurgery 2000;46: 1391–6. [20] Weber PC, Lambert PR, Cunningham CD 3rd, Richardson MS, Genao RB. Use of Alloderm in the neurotologic setting. Am J Otolaryngol 2002;23: 148–52. [21] Cantore G, Ciappetta P, Delfini R. Choice of neurosurgical approach in the treatment of cranial base lesions. Neurosurg Rev 1994;17:109–25. [22] Camins MB, Oppenheim JS. Anatomy and surgical techniques in the suboccipital transmeatal approach to acoustic neuromas. Clin Neurosurg 1992;38: 567–88. [23] Kurpad SN, Cohen AR. Posterior fossa craniotomy: an alternative to craniectomy. Pediatr Neurosurg 1999;31:54–7.
[24] Lang Jr J, Samii A. Retrosigmoidal approach to the posterior cranial fossa. An anatomical study. Acta Neurochir (Wien) 1991;111:147–53. [25] Rhoton Jr AL. The cerebellopontine angle and posterior fossa cranial nerves by the retrosigmoid approach. Neurosurgery 2000;47(Suppl):S93–129. [26] Wazen JJ, Sisti M, Lam SM. Cranioplasty in acoustic neuroma surgery. Laryngoscope 2000;110: 1294–7. [27] Babu RP, Sekhar LN, Wright DC. Extreme lateral transcondylar approach: technical improvements and lessons learned. J Neurosurg 1994;81:49–59. [28] Dowd GC, Zeiller S, Awasthi D. Far lateral transcondylar approach: dimensional anatomy. Neurosurgery 1999;45:95–100. [29] Rhoton Jr AL. The far-lateral approach and its transcondylar, supracondylar, and paracondylar extensions. Neurosurgery 2000;47(Suppl):S195–209. [30] Spallone A, Makhmudov UB, Mukhamedjanov DJ, Tcherekajev VA. Petroclival meningioma. An attempt to define the role of skull base approaches in their surgical management. Surg Neurol 1999;51: 412–20. [31] Spektor S, Anderson GJ, McMenomey SO, Horgan MA, Kellogg JX, Delashaw Jr JB. Quantitative description of the far-lateral transcondylar transtubercular approach to the foramen magnum and clivus. J Neurosurg 2000;92:824–31. [32] Tedeschi H, Rhoton Jr AL. Lateral approaches to the petroclival region. Surg Neurol 1994;41:180–216. [33] Wen HT, Rhoton Jr AL, Katsuta T, de Oliveira E. Microsurgical anatomy of the transcondylar, supracondylar, and paracondylar extensions of the farlateral approach. J Neurosurg 1997;87:555–85. [34] Baldwin HZ, Miller CG, van Loveren HR, Keller JT, Daspit CP, Spetzler RF. The far lateral/combined supra- and infratentorial approach. A human cadaveric prosection model for routes of access to the petroclival region and ventral brain stem. J Neurosurg 1994;81:60–8. [35] Kirazli T, Oner K, Ovul L, Bilgen C, Ogut F. Petrosal presigmoid approach to the petro-clival and anterior cerebellopontine region (extended retrolabyrinthine, transtentorial approach). Rev Laryngol Otol Rhinol (Bord) 2001;122:187–90. [36] Sekhar LN, Schessel DA, Bucur SD, Raso JL, Wright DC. Partial labyrinthectomy petrous apicectomy approach to neoplastic and vascular lesions of the petroclival area. Neurosurgery 1999;44:537–52. [37] Taha JM, Tew Jr JM, van Loveren HR, Keller JT, el-Kalliny M. Comparison of conventional and skull base surgical approaches for the excision of trigeminal neurinomas. J Neurosurg 1995;82: 719–25. [38] Chang DW, Robb GL. Microvascular reconstruction of the skull base. Semin Surg Oncol 2000;19: 211–7. [39] Chang DW, Langstein HN, Gupta A, De Monte F, Do KA, Wang X, et al. Reconstructive
G.W. Britz et al / Neurosurg Clin N Am 13 (2002) 475–489 management of cranial base defects after tumor ablation. Plast Reconstr Surg 2001;107:1346–57. [40] Manstein ME, Manstein CH, Manstein G. Paraspinous muscle flaps. Ann Plast Surg 1998;40:458–62. [41] Okii N, Nishimura S, Kurisu K, Takeshima Y, Uozumi T. In vivo histological changes occurring in
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hydroxyapatite cranial reconstruction—case report. Neurol Med Chir (Tokyo) 2001;41:100–4. [42] Urken ML, Cheney ML, Sullivan MJ, Biller HF. Atlas of regional and free flaps for head and neck reconstruction. New York: Raven Press; 1995. p. 29–48, 237–60.
Cosmetic concerns in posterior fossa skull base surgery Gavin Wayne Britz, MDa, Marcelo D. Vilela, MDa, Neal Futran, MDb, Robert Rostomily, MDa,* a
Department of Neurological Surgery, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA b Department of Otolaryngology, Head and Neck Surgery, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
This chapter provides an overview of surgical techniques and principles, that when applied to specific posterior fossa approaches, improve cosmetic outcome. Techniques that employ anatomic planes for exposure also allow the best anatomic integrity at closure, reduce the risks of complications that impact wound healing, and thus produce a good cosmetic outcome. Although cosmetic defects produced by posterior fossa surgery are not as obvious as those resulting from anterior or middle fossa procedures, patients nevertheless inspect their surgical sites after posterior fossa surgery and are acutely aware of the cosmetic result. As in other neurosurgical procedures, a poor cosmetic result can overshadow an otherwise successful operation. This article provides an overview of surgical techniques and principles that improve cosmetic outcome when applied to specific posterior fossa approaches. It is the contention of these authors that all things being equal (relative to surgical access), approaches that use anatomic planes for exposure also allow the best anatomic integrity at closure, reduce the risks of complications that affect wound healing, and thus produce a good cosmetic outcome. This article briefly reviews general surgical principles with implications for cosmesis and examples of these techniques applied
to specific posterior fossa surgical approaches as well as reconstructive procedures.
* Corresponding author. Department of Neurological Surgery, University of Washington, 1959 NE Pacific Street, Room RR-744, Seattle, WA 98195, USA. E-mail address: [email protected] (R. Rostomily).
Cosmetic aspects of surgical exposure and repair
Basic principles of wound healing It is beyond the scope of this article to address the basic biology of wound healing, but it is worth mentioning briefly the variables that affect wound healing and subsequent cosmetic results. Nutritional state, preexisting illnesses like cancer, exposure to radiation therapy, smoking, and metabolic diseases like diabetes can all affect wound healing [1,2]. Correctable systemic factors should be aggressively managed before surgery. Local factors that affect wound healing include oxygen tension, tissue edema, and infection. Low oxygen tension can be prevented by preservation of the local blood supply; thus, knowledge of the vascular anatomy in relation to the skin and soft tissue incisions is vital. The vascular anatomy of the skin and soft tissues of the posterior fossa is illustrated in Fig. 1. Although most standard neurosurgical approaches to the posterior fossa do not critically impair the robust collateral blood supply in this region, it must be considered when performing multiple approaches or in the setting of reoperation after infection as well as in the debilitated or previously irradiated patient.
Posterior fossa surgical approaches require violation and repair of skin, muscle, bone, and dura. The technique used to handle these tissue layers
1042-3680/02/$ - see front matter Ó 2002, Elsevier Science (USA). All rights reserved. PII: S 1 0 4 2 - 3 6 8 0 ( 0 2 ) 0 0 0 2 8 - 1
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Fig. 1. The major arteries from the external carotid artery form collateral connections that provide robust blood supply to the scalp of the posterior fossa.
during each phase of a surgical procedure either directly or indirectly has an impact on the eventual cosmetic result. The general surgical principles with relevance to cosmetic results during exposure and repair of posterior fossa approaches are briefly reviewed here. Scalp, muscle, and soft tissue dissection and repair The cosmetic aspects of the techniques of skin incision (electrocautery versus scalpel) and closure (suture versus staples) are reviewed in more detail elsewhere in this issue. For posterior fossa approaches, incisions that extend into the cervical region should be made in a natural skin crease. For closure, sutures may be preferable to staples when there is concern about cerebrospinal fluid (CSF) leakage. The possible cosmetic differences attributable to the different techniques for skin incision and closure are likely marginal compared with the cosmetic impact of tissue injury that can be produced through poor surgical technique [3,4]. The use of muscle-splitting techniques that respect fascial planes and detach muscles from their anatomic bony attachments rather than muscle transection preserves muscle bulk, facilitates anatomic repair, minimizes swelling and ischemia that can lead to deep infection or seroma formation, and reduces postoperative pain. The utilization of the
fine-tipped electrocautery or Hoan dissector is useful for performing these dissections. Appropriate repair of soft tissue should provide hemostasis without compromise of blood supply, eliminate dead space to prevent fluid accumulations and a potential nidus for infection, and reapproximate muscles into their anatomic position under tension to preserve muscle bulk. Bone removal and repair During posterior fossa surgery, bone removal is accomplished with a craniotomy, craniectomy with cranioplasty repair, or craniectomy alone. Reconstituting the native skull contour with the former two options is preferred for cosmetic purposes, but a craniectomy is indicated for emergency decompressive procedures or in situations where postoperative swelling is a concern. The reconstitution of the bony contour provides additional benefits of acting as a support to help seal dural closures, thus preventing pseudomeningocele formation. Aside from cosmetic issues, the use of craniotomy or cranioplasty versus craniectomy has been advocated in the acoustic neuroma patient undergoing a suboccipital craniotomy (SOC), because it may prevent postoperative headaches [5–8]. The validity of this contention remains controversial. The increasing number of new materials available for cranioplasty has produced a
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myriad of techniques suitable for repair of bony defects. Current choices for repair of bony defects include native split-bone grafts; soft tissue grafts, such as fat, bone extenders, or cements; traditional methylmethacrylate cranioplasty material; bioabsorbable or titanium mesh for structural support; and customized or preformed implants. One must carefully consider the goal of the repair as well as the costs and advantages of each approach or material before proceeding. There is no literature to guide decision making, and each surgeon must use the technique and materials that are believed to be the most cost-effective and appropriate for a particular application. A summary of available
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materials for cranial reconstruction and their potential advantages and disadvantages is provided in Table 1. The specific techniques that we employ for various procedures are outlined here. Dural opening and closure Dural opening and repair can directly affect cosmesis through pseudomeningocele formation or can indirectly affect cosmesis when CSF fistulae promote wound breakdown and infections that require additional wound repair and debridement or bone flap removal. The goal of dural repair is to achieve a watertight closure if possible. The
Table 1 Summary of materials available for cranial reconstruction Materials
Advantages
Disadvantages
Autogenous grafts: craniotomy plate, split-thickness bone graft Tantalum
Inexpensive, less susceptible to infection
Possibility of reabsorption over time, may have limited supply to cover the defect, difficult to conform to the defect Expensive, higher risk of infection, radiopaque with artifacts on both CT and MRI, heavy, has a risk of erosion through the scalp, thermoconductive Higher infection risk, has a risk of erosion through the scalp, minor artifact on CT, susceptible to fracture with trauma
Polymethylmethacrylate
Titanium mesh
Bioabsorbable mesh Custom surgical Implants (eg, Medpor; Porex Surgical, GA) Hydroxyapatite cement
Bone graft extenders, (eg, Novabone; Porex Surgical)
No reabsorption, no limitation of supply, can be molded to conform to the defect, good tensile strength
Relatively inexpensive, no reabsorption, unlimited supply, can mould to conform to the defect, medium strength, inert with minimal tissue reaction, adheres tightly to bone, not thermoconductive, no paramagnetic artifacts on MRI Well tolerated by soft tissues and bone, easily contoured to fit defect
Provides structural support, easily contoured to fit defect Customized to fit defect, open pore structure allows for tissue ingrowth, easily further customized with scissors or scalpel, immediate good structural and cosmetic support Extremely biocompatible with no inflammation or foreign body reaction, osteoconductive and allows for ingrowth of new bone, unlimited supply, may be used to augment autogenous grafts Used to augment autogenous bone grafts with limited supply, easily placed around preferred site
No reabsorption, higher infection risk, often has to be used in conjunction with polymethylmethacrylate to provide adequate strength, artifacts on MRI or CT although minor, expensive Bioabsorbable and therefore limited long-term support, minimal strength Higher risk of infection, expensive, needs to be ordered before surgery
Initial brittleness that limits its use for larger defects, difficult to conform to defect, expensive
Expensive, cannot be used exclusively
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use of a continuous linear dural incision and avoidance of cauterization helps to preserve the native dura for primary watertight closure. If a primary repair is not possible, dural patch grafts with autologous tissue (pericranium, fascia lata, and temporalis fascia), allograft, or artificial dural substitutes can be secured with a running suture and fibrin glue to obtain a watertight closure [9–20]. The use of transient lumbar drainage can further facilitate the sealing of this and other tenuous dural closures. In rare cases, tissue transfer with a pedicled or free flap may be required to prevent CSF leaks (see below). Cosmetic issues in specific posterior fossa approaches Surgical approaches to the posterior fossa The surgical approaches that provide access to the posterior fossa include midline approaches, lateral approaches (paramedian and retrosigmoid), far lateral approaches, and the petrosal or combined presigmoid transtentorial approaches [21]. Needless to say, a variety of lesions can be addressed by these approaches. From a cosmetic perspective, the choice of approach should be matched to the pathologic findings such that adequate exposure and repair are achieved without unnecessary tissue dissection or bony removal. Specific techniques that can be used to improve cosmesis for the retrosigmoid (RSA), far lateral, and petrosal approaches are emphasized. Lastly, the cosmetic issues for more radical reconstructive techniques are reviewed. Midline posterior fossa approaches Cosmetic concerns for the midline approaches are generally restricted to bony removal, muscle repair, and skin incision. The latter two factors have already been reviewed, and adherence to the general principles of tissue and skin edge handling, muscle dissection in the avascular midline, and avoidance of excessive monopolar cautery that can damage muscle tissue should optimize the cosmetic outcome for these factors. The muscles that insert superiorly along the nuchal midline include the trapezius, splenius capitis, and semispinalis capitis. The anatomy of the superficial musculature encountered in the basic posterior fossa approaches is shown in Fig. 2. These above-mentioned muscles are taken down as a unit in a subperiosteal fashion and should be reattached in proximity to the nuchal line with the suture
Fig. 2. Anatomic diagram showing the relation between the muscular layers of the posterior fossa.
anchored to a cuff of tissue or to plates or holes drilled into the bone. We prefer the latter choices because they do not require division of the muscle at its insertion and the anchoring is more secure. Atrophy or retraction of muscle at the nuchal line can produce a noticeable defect, particularly in patients with short hair or in those who have undergone a craniectomy. As mentioned previously, the decision to perform a craniotomy, craniectomy with cranioplasty, or craniectomy alone must be based on the clinical situation, the surgeon’s preference, and the available cranioplasty materials. Any method of bony reconstruction that securely reconstitutes the normal bony and soft tissue contour of the posterior fossa has the same positive cosmetic outcome. Delayed cranioplasty can also be performed, but the cosmetic result can be compromised by any intervening muscular atrophy that must be accounted for when contouring the cranioplasty. In cases of Arnold-Chiari type I malformations, one performs a craniectomy to expand the posterior fossa. Although modest bony removal is essential to treat the underlying pathophysiology, excessive bony removal not only creates a potentially poor cosmetic result but can produce symptoms caused by cerebellar ‘‘sag.’’ Retrosigmoid approach Lesions in the lateral cerebellar hemisphere and or cerebellopontine angle (CPA) generally require
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a lateral approach. Variations of the commonly employed RSA can be modified to address lesions in either location and thus serve to demonstrate surgical techniques and issues that affect cosmetic outcome for treatment of lesions in both locations [22–26]. The type of incision one uses for the RSA can dictate the muscle dissection employed to access the suboccipital bone and, ultimately, the cosmetic outcome from surgery. Three different incisions commonly used for the RSA are shown schematically in Fig. 3. The vertical incision employs a muscle-splitting technique that allows rapid access to the suboccipital bone, but the division of muscles may increase postoperative pain and local inflammation, impair muscle healing, and enhance atrophy. In addition to the potential loss of muscle bulk, this approach is more likely to divide the lesser occipital nerve as it courses between the sternocleidomastoid muscle (SCM) and splenius capitis muscle to produce numbness in the postauricular region or neuroma formation. The absence of a layered wound may increase the CSF leak and subsequent infection risk, which can compromise the cosmetic result.
Fig. 3. Illustration of three common skin incisions applied to the retrosigmoid approach to the posterior fossa: the vertical or straight incision, a retroauricular C-shaped incision, and a U-shaped incision.
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An inverted U-shaped flap involves a midline incision that traverses horizontally above the nuchal line and then inferiorly along the mastoid parallel to the midline incision. The subcutaneous tissues and muscles are elevated as a unit and detached from their anatomic insertions, thus allowing preservation of muscle bulk and the lesser occipital nerve. During closure, the muscles can be anchored under tension at their nuchal insertion using one of the techniques described previously to prevent atrophy. This approach is relatively fast but has the disadvantage of having muscle bulk at the inferior aspect of the wound, which can limit exposure, and a nonlayered closure with the lateral limb of the incision overlying the dural opening, which may be more prone to CSF leak. We prefer the C-shaped retroauricular incision for the RSA (see Fig. 3). The steps in this approach are demonstrated in Fig. 4. Briefly, the apex of the incision approximates the medial border of the SCM to facilitate the elevation of a myocutaneous flap that incorporates the SCM. The medial extent and superior and inferior extension of the incision are modified according to the lesion size and location. For large lesions requiring exposure to the foramen magnum, the incision can be extended below the level of the mastoid tip and hairline in the normal cervical skin creases so as to provide a more cosmetic result. The inferior border of the SCM is elevated if possible, but it can be split along its fibers for smaller exposure. By extending the flap inferiorly, the muscle can generally be elevated forward without division to provide generous access to the suboccipital region. After the elevation of the myocutaneous flap, the splenius capitis and deeper suboccipital muscles are encountered. These can be detached as a unit or dissected sequentially with preservation of the lesser occipital nerve between the SCM and splenius and the occipital artery in its course between the splenius capitis and suboccipital muscles. These muscles are retracted inferomedially to allow generous exposure of the suboccipital region. A craniotomy is fashioned by drilling a narrow trough over the inferior and medial edges of the transverse and sigmoid sinuses, respectively, and completing the bone cut with a craniotome or high-speed drill. This allows elevation of a more generous bone flap that does not require augmentation at closure to cover the defect. The mastoid emissary vein is directly visualized under the flap and can be coagulated and divided to free the flap without producing a tear at its point of entry into the sigmoid sinus. In cases in which there is
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Fig. 4. Intraoperative photographs of a right-sided retroauricular C-shaped incision and muscle-splitting retrosigmoid craniotomy. (A) Skin incision with the course of the transverse and sigmoid sinus and mastoid marked. (B) Myocutaneous scalp flap with the sternocleidomastoid muscle elevated and the splenius capitis muscle exposed. Note the course of the preserved lesser occipital nerve (arrow). (C ) The splenius capitis muscle elevated as a separate layer. (D) The splenius capitis and suboccipital muscles elevated from the nuchal line to provide exposure of the suboccipital bone. (E ) The bone flap created by drilling over the medial edge of the sigmoid sinus and inferior edge of the transverse sinus gives full exposure for a cerebellopontine angle approach and can be replaced to fill the defect without the need for cranioplasty.
concern about dural adhesion, a burr hole can be placed at the asterion and at the inferomedial corner of the planned craniotomy to allow dural stripping and inspection before bone flap elevation. This technique often requires additional drilling of the mastoid bone to provide exposure to the medial edge of the sigmoid sinus, however. The muscle layers are reapproximated in their anatomic positions and anchored to their sites
of insertion to apply tension and preserve muscle bulk. The layered coverage that results from this technique helps to prevent CSF leakage. We have adopted this approach not only because it provides an excellent cosmetic result, but because it has eliminated leakage of spinal fluid through the wound and reduced the incidence of pseudomeningocele formation and postoperative pain.
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Far lateral approaches The cosmetic issues relevant to the far lateral approaches are similar to those encountered in the RSA. Additional muscle dissection and bone removal provide the lateral exposure needed for ventral and ventrolateral exposure of the posterior fossa and craniocervical junction as well as the mid- to lower clivus. The indications for and details of the many variations of far lateral approaches are reviewed in more detail elsewhere [27–33]. The following discussion describes general strategies to minimize cosmetic defects from these approaches. Two approaches commonly used to provide far lateral surgical access employ either a U- or Cshaped incision (Fig. 5). These two approaches differ largely in the techniques used for muscle dissection to access the suboccipital bone, mastoid, and cervical lamina/facets. In both approaches, the extent of dissection and bone removal is dictated by the underlying pathologic findings and the amount of the exposure required to access lesions of the ventral/lateral and inferior posterior fossa as well as the craniocervical junction. The U-shaped incision starts at or below the mastoid tip and extends to the mastoid base, medially along the nuchal line, and then vertically into the midline cervical region as described previously
Fig. 5. Two common skin incisions used for far lateral approaches: the U-shaped incision and the retroauricular C-shaped incision.
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for the midline approach. This incision allows reflection of the skin and muscles back away from the surgical site in one large flap, which avoids muscle transection. As is the case with the Ushaped incision in the RSA, the elevation of muscles en bloc may create enough bulk to obscure lateral exposure. Another consideration with this approach is that the incision or dissection through the skin, soft tissues, and dura lies more directly in line and may thus increase the chances of CSF fistula formation when a watertight dural repair is not achieved. The approach using the C-shaped incision differs from that employing the U-shaped approach largely in the technique used for muscle dissection. Although its potential advantages include reduced muscle bulk, obscuring the exposure, one advantage relevant to cosmetic outcomes includes a reduced risk of CSF leak. By dissecting the muscles in layers and repairing them by anchoring them to their respective sites of attachment, a multilayered closure that resists CSF leaks, preserves muscle bulk, and provides excellent lateral exposure is achieved. As with the RSA, the skin and SCM are reflected as a myocutaneous flap and then the splenius capitis, semispinalis capitis, and rectus capitis muscles are detached off the nuchal line and suboccipital bone and reflected inferomedially. The muscles of the suboccipital triangle are identified before the dissection of the vertebral artery. The basic surgical steps and exposure achieved by this approach are outlined in Fig. 6. As mentioned previously, varying amounts of bone removal involving the suboccipital bone, condyle, and mastoid process are employed in the far lateral approaches. The need for bone repair is dependent on the extent of bone removal. Because of the inward curvature of the suboccipital region, much of the bony removal with this approach is hidden deep under the soft tissues and reduces the cosmetic deformity after smaller exposures. In the more extensive bony removals, particularly those that involve the mastoid area, bony reconstruction may be used. This bony reconstruction can involve the different bone sources as discussed previously. The choices of repair for extensive mastoid removal are discussed below in the section on the petrosal approach. A secondary consideration in cosmesis for the far lateral approach is the significant reduction in mobility at the occipital-cervical joint when fusion is needed after greater than 50% occipital condyle resection. The awkward movement produced by limiting movement (approximately 50% in all
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Fig. 6. Far lateral approach employing a retroauricular C-shaped incision. (A) Skin incision with elevation of the sternocleidomastoid muscle as a myocutaneous flap. (B) The splenius is reflected to expose the longissimus capitis muscle (LC). (C ) The deeper muscles of the suboccipital triangle and the transverse process of C1 (at the tip of the dissector) are exposed after reflection of the longissimus capitis and semispinalis capitis muscles. (D) After a small suboccipital craniotomy, mastoidectomy, C1 hemilaminectomy, and partial condylectomy, the vertebral artery (VA) is mobilized and lateral posterior fossa and upper cervical dura are exposed. (E ) After dural opening, excellent exposure to this lower clival/upper cervical ventral meningioma is demonstrated.
planes) can have the same emotional impact as a severe cosmetic defect. Therefore, one must carefully consider the necessity for condyle resection, particularly because many ventral lesions can be resected with less aggressive approaches [15]. Presigmoid petrosal approach The presigmoid petrosal approach provides access to lesions in the petroclival and tentorial
notch areas; when combined with frontotemporal or pterional and orbitozygomatic approaches, it can be used to access lesions that extend to the cavernous sinus and middle fossa [34–37]. For the standard petrosal approach, a C-shaped retroauricular incision that extends along the superior temporal line and down into the neck in line with the cervical skin folds is employed (Fig. 7A). If a combined approach is required, a modified skin
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Fig. 7. The incisions used for the standard petrosal approach (A) and when used in combination (B) with frontotemporal or pterional craniotomies with or without orbitozygomatic osteotomy.
incision that extends above the temporal line into the frontotemporal region is made. A preauricular incision that joins the postauricular incision provides for the combined approach. Care must be taken to keep the base of the scalp flaps large enough to ensure adequate blood supply (see Fig. 7B). The details and variations of the petrosal approach have been outlined elsewhere, and we focus on the major cosmetic issues related to this approach. Similar to the techniques used in the RSA or far lateral approaches, the scalp is elevated as a myocutaneous flap and the deeper muscles are dissected without transection to maintain bulk and provide good layers for closure. The additional exposure of the squamous temporal bone requires elevation and anterior reflection of the posterior aspect of the temporalis muscle. The mastoidectomy creates a defect over the site of the presigmoid dural incision, which can lead to a significant cosmetic deformity and a propensity for CSF leak if not adequately repaired. There are numerous ways to provide a good dural repair and cosmetic closure. Although the presigmoid dura cannot be primarily repaired in a watertight fashion, it can be reapproximated with several dural sutures that also provide a latticework to support interlocking pieces of autologous fat graft, which effects a ‘‘ball-valve’’ closure. This is augmented with fibrin glue and supported externally
either with a solid graft or with the soft tissue closure and dressings. A lumbar drain is used for several days to allow the repair to seal adequately. Small defects can be packed with fat or other autologous tissue (fascia lata, pericranium) that is anchored into the opening with a lattice of dural suture to effect a ball-valve closure. The bony defect over the sigmoid sinus and mastoid creates the most significant cosmetic defect from this approach. A large number of strategies similar to those used for bony reconstruction of retrosigmoid craniectomies are available for reconstruction of the defect created by the petrosal approach. Among the choices are split-thickness autograft, bioabsorbable or titanium meshes, bone cement, methylmethacrylate, and mastoid prosthetic devices (Fig. 8). We prefer autograft if suitable donor bone is available. An additional benefit from reconstruction is the support it provides for dural repair. Cosmetic aspects of ‘‘reconstructive’’ surgery Reconstruction after posterior fossa surgery may be required for chronically nonhealing wounds or when extensive soft tissue or bony removal is performed during tumor resection (Figs. 9 and 10) [38–42]. The approach to posterior fossa reconstruction and the optimization of cosmetic outcome starts with careful evaluation of the patient and the potential defect. This includes
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Fig. 8. (A) The resulting defect after a petrosal approach is illustrated. (B) The use of a preformed Medpor (Porex Surgical, Fairburn, GA) implant (I) to repair the defect is shown. A variety of other materials and techniques are suitable for this repair, including split-thickness autograft (see text for discussion).
assessment of the location and size of the defect with radiologic evaluation of the depth and bony or dural defects. Previous surgery or radiation or ongoing wound infection affects the viability of the skin around the defect, reducing the available tissue for local flaps. Of course, the pathologic characteristics of the presenting lesion are also important in planning reconstruction. The simplest method of reconstruction should be considered in all cases while ensuring adequate resection of the lesion. In the posterior neck, the abundant collateral soft tissue blood supply allows for wide elevation of these tissues so that many wounds can be closed primarily or with simple
adjacent tissue transfer. When larger defects exist, however, local tissues useful in the anterior cranium, such as pericranial flaps and temporalis flaps, do not exist. Moreover, the thick posterior neck and occipital tissues do not lend themselves to skin graft reconstruction, because this would result in a poor cosmetic and functional result. Excellent cosmesis has been achieved with tissue expansion when hair-bearing skin has been lost, and repeated expansion is possible for large defects. The main advantage is the ability to replace one tissue with the same tissue. This technique requires a separate procedure to place the expanders and time for tissue expansion to occur, however, which
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Fig. 9. Repair of a nonhealing posterior fossa wound with chronic cerebrospinal fluid leakage in a 48-year-old man with multiple resections, radiation therapy, and local chemotherapy for recurrent medulloblastoma. (A) Demonstration of the site of chronic wound breakdown with dural graft exposed. (B) After wound debridement, a larger defect is evident that cannot be primarily repaired. The exposed bovine pericardial dural patch was replaced. (C ) This pedicled lower island trapezius flap based on the transverse cervical and dorsal scapular vessels was used for reconstruction. Note the proximal de-epithelialized portion of skin that must lie in the subcutaneous tunnel. (D) The final reconstruction with the epithelialized skin paddle forming the lower triangular area of the final scalp closure. The patient did well with no further wound complications.
may delay surgery for the primary tumor. Tissue expansion is not generally recommended for infected cases because of the risk of the expander becoming infected and losing the expanded flap or for use in radiated skin because of decreased compliance and a higher rate of skin necrosis. For larger posterior fossa defects, there are several well-vascularized regional flaps from the back that provide good skin color match and appropriate tissue thickness. Because the patient is often placed in the prone or lateral decubitus position for tumor extirpation, the back is the ideal donor site. The trapezius system of flaps offers a superior flap, which is easily elevated and useful for rotational coverage of small neck defects. Its short arc of rotation limits its use in the posterior fossa. More commonly, the lower island trapezius flap based on the transverse cervical and dorsal scapular arteries is used because of its ability to cover most posterior defects with minimal tension on
the wounds. This pedicled flap allows tissue to be transferred for up to 15 cm below the scapular tip and can reach the occiput easily. The skin color and texture provide an excellent match to the posterior scalp. Donor site morbidity is minimal, and the wound is closed primarily. Also on the back, the latissimus dorsi flap based on the thoracodorsal vessels provides abundant muscle and skin to cover any posterior fossa defect. Its arc of rotation at the axilla allows it to reach to the top of the head if necessary. At times, the skin portion may be much thicker than the posterior scalp; the flap can be transferred as muscle only, and a split-thickness skin graft can be applied. When pedicled flaps cannot comfortably reach and cover the defect or the geometry of the flap inset could compromise vascularity, free tissue transfer provides optimal results. Tissue can be placed optimally unencumbered by pedicle length
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Fig. 10. Resection of a recurrent scalp melanoma in a 68-year-old woman with invasion of the occipital bone. (A) Preoperative picture showing an extensive scalp lesion. (B) MRI with gadolinium showing extensive involvement of soft tissue. (C ) Extensive resection of scalp and right suboccipital bone. (D) Dissection of a myocutaneous latissimus free flap that was inserted into the right transverse cervical artery and right internal jugular vein. (E ) Final intraoperative view with latissimus flap at the inferior portion of the reconstruction and meshed split-thickness skin graft above. Note that the cutaneous paddle of the flap resides along the cervical region, where the tissue is normally thicker, and that the skin graft is used to cover the thinner area of the cranial scalp. (F ) Postoperative result after wounds have matured.
or position. Well-vascularized tissue from a variety of donor sites can minimize the risk of CSF leak, cover exposed calvarium, tolerate the burden of radiation and/or a contaminated wound, and provide optimal function and cosmesis. As described previously, the latissimus dorsi myogenous or
myocutaneous flap is easily harvested and has a predictable blood supply with a long vascular pedicle to reach donor vessels, large size, and minimal donor site morbidity. It is the flap of choice to reconstruct large scalp defects on any area of the head.
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dealing with complex and chronic wound-healing problems or extensive soft tissue and bony lesions in the posterior fossa. Summary Although cosmetic defects produced by posterior fossa surgery may not seem obvious, a poor cosmetic result can overshadow an otherwise successful operation. It is important to approach the operation with knowledge that each phase of a surgical procedure either directly or indirectly influences the eventual cosmetic result. The careful use of anatomic dissection and repair and attempts to reconstitute bony defects to their native contour as well as avoidance of complications all contribute to excellent cosmetic outcomes. Acknowledgments The authors thank medical illustrator Raquel Lourenco Abreu for her preparation of all illustrations included in this article and Paul Schwartz and Janet Schukar for invaluable assistance with figure preparation. References
Fig. 10 (continued )
One other excellent free-flap choice is the fasciocutaneous scapula flap based on the subscapular vessels. It has excellent color match to the posterior neck and occipital skin as well as thickness and consistency that match surrounding tissue. The shorter pedicle length when compared with that of the latissimus dorsi flap may sometimes limit its use because of the difficulty in reaching suitable recipient neck vessels. The expertise of a team of surgeons versed in different cosmetic aspects of reconstructive surgery is invaluable to the neurosurgeon when
[1] Phillips SJ. Physiology of wound healing and surgical wound care. ASAIO J 2000;46(Suppl):S2–5. [2] Yamaguchi Y, Yoshikawa K. Cutaneous wound healing: an update. J Dermatol 2001;28:521–34. [3] Chughtai T, Chen LQ, Salasidis G, Nguyen D, Tchervenkov C, Morin JF. Clips versus suture technique: is there a difference? Can J Cardiol 2000;16: 1403–7. [4] Kearns SR, Connolly EM, McNally S, McNamara DA, Deasy J. Randomized clinical trial of diathermy versus scalpel incision in elective midline laparotomy. Br J Surg 2001;88:41–4. [5] Koperer H, Deinsberger W, Jodicke A, Boker DK. Postoperative headache after the lateral suboccipital approach: craniotomy versus craniectomy. Minim Invasive Neurosurg 1999;42:175–8. [6] Levo H, Pyykko I, Blomstedt G. Postoperative headache after surgery for vestibular schwannoma. Ann Otol Rhinol Laryngol 2000;109:853–8. [7] Levo H, Blomstedt G, Hirvonen T, Pyykko I. Causes of persistent postoperative headache after surgery for vestibular schwannoma: Clin Otolaryngol 2001;26:401–6. [8] Santarius T, D’Sousa AR, Zeitoun HM, Cruickshank G, Morgan DW. Audit of headache following resection of acoustic neuroma using three different techniques of suboccipital approach. Rev Laryngol Otol Rhinol (Bord) 2000;121:75–8.
488
G.W. Britz et al / Neurosurg Clin N Am 13 (2002) 475–489
[9] Anson JA, Marchand EP. Bovine pericardium for dural grafts: clinical results in 35 patients. Neurosurgery 1996;39:764–8. [10] Atiyeh BS, Hamdan AM, Nassar SI, Hanbali FS, Hashim HA. Vascularized fascial patch for repair of suboccipital dural defect. Ann Plast Surg 1996; 37:422–7. [11] Barbolt TA, Odin M, Leger M, Kangas L, Hoiste J, Liu SH. Biocompatibility evaluation of dura mater substitutes in an animal model. Neurol Res 2001; 23:813–20. [12] Fisher WS 3rd, Braun D. Closure of posterior fossa dural defects using a dural substitute: technical note. Neurosurgery 1992;31:155–6. [13] Filippi R, Schwarz M, Voth D, Reisch R, Grunert P, Perneczky A. Bovine pericardium for duraplasty: clinical results in 32 patients. Neurosurg Rev 2001;24:103–7. [14] Nagata K, Kawamoto S, Sashida J, Abe T, Mukasa A, Imaizumi Y. Mesh-and-glue technique to prevent leakage of cerebrospinal fluid after implantation of expanded polytetrafluoroethylene dura substitute—technical note. Neurol Med Chir (Tokyo) 1999;39:316–9. [15] Nanda A, Vincent DA, Vannemreddy PS, Baskaya MK, Chanda A. Far-lateral approach to intradural lesions of the foramen magnum without resection of the occipital condyle. J Neurosurg 2002; 96:302–9. [16] Sekhar LN, Sarma S, Morita A. Dural reconstruction with fascia, titanium mesh, and bone screws: technical note. Neurosurgery 2001;49:749–52. [17] Tachibana E, Saito K, Fukuta K, Yoshida J. Evaluation of the healing process after dural reconstruction achieved using a free fascial graft. J Neurosurg 2002;96:280–6. [18] Verheggen R, Schulte-Baumann WJ, Hahm G, Lang J, Freudenthaler S, Schaake T, et al. A new technique of dural closure—experience with a vicryl mesh. Acta Neurochir (Wien) 1997;139:1074–9. [19] Warren WL, Medary MB, Dureza CD, Bellotte JB, Flannagan PP, Oh MY, et al. Dural repair using acellular human dermis: experience with 200 cases: technique assessment. Neurosurgery 2000;46: 1391–6. [20] Weber PC, Lambert PR, Cunningham CD 3rd, Richardson MS, Genao RB. Use of Alloderm in the neurotologic setting. Am J Otolaryngol 2002;23: 148–52. [21] Cantore G, Ciappetta P, Delfini R. Choice of neurosurgical approach in the treatment of cranial base lesions. Neurosurg Rev 1994;17:109–25. [22] Camins MB, Oppenheim JS. Anatomy and surgical techniques in the suboccipital transmeatal approach to acoustic neuromas. Clin Neurosurg 1992;38: 567–88. [23] Kurpad SN, Cohen AR. Posterior fossa craniotomy: an alternative to craniectomy. Pediatr Neurosurg 1999;31:54–7.
[24] Lang Jr J, Samii A. Retrosigmoidal approach to the posterior cranial fossa. An anatomical study. Acta Neurochir (Wien) 1991;111:147–53. [25] Rhoton Jr AL. The cerebellopontine angle and posterior fossa cranial nerves by the retrosigmoid approach. Neurosurgery 2000;47(Suppl):S93–129. [26] Wazen JJ, Sisti M, Lam SM. Cranioplasty in acoustic neuroma surgery. Laryngoscope 2000;110: 1294–7. [27] Babu RP, Sekhar LN, Wright DC. Extreme lateral transcondylar approach: technical improvements and lessons learned. J Neurosurg 1994;81:49–59. [28] Dowd GC, Zeiller S, Awasthi D. Far lateral transcondylar approach: dimensional anatomy. Neurosurgery 1999;45:95–100. [29] Rhoton Jr AL. The far-lateral approach and its transcondylar, supracondylar, and paracondylar extensions. Neurosurgery 2000;47(Suppl):S195–209. [30] Spallone A, Makhmudov UB, Mukhamedjanov DJ, Tcherekajev VA. Petroclival meningioma. An attempt to define the role of skull base approaches in their surgical management. Surg Neurol 1999;51: 412–20. [31] Spektor S, Anderson GJ, McMenomey SO, Horgan MA, Kellogg JX, Delashaw Jr JB. Quantitative description of the far-lateral transcondylar transtubercular approach to the foramen magnum and clivus. J Neurosurg 2000;92:824–31. [32] Tedeschi H, Rhoton Jr AL. Lateral approaches to the petroclival region. Surg Neurol 1994;41:180–216. [33] Wen HT, Rhoton Jr AL, Katsuta T, de Oliveira E. Microsurgical anatomy of the transcondylar, supracondylar, and paracondylar extensions of the farlateral approach. J Neurosurg 1997;87:555–85. [34] Baldwin HZ, Miller CG, van Loveren HR, Keller JT, Daspit CP, Spetzler RF. The far lateral/combined supra- and infratentorial approach. A human cadaveric prosection model for routes of access to the petroclival region and ventral brain stem. J Neurosurg 1994;81:60–8. [35] Kirazli T, Oner K, Ovul L, Bilgen C, Ogut F. Petrosal presigmoid approach to the petro-clival and anterior cerebellopontine region (extended retrolabyrinthine, transtentorial approach). Rev Laryngol Otol Rhinol (Bord) 2001;122:187–90. [36] Sekhar LN, Schessel DA, Bucur SD, Raso JL, Wright DC. Partial labyrinthectomy petrous apicectomy approach to neoplastic and vascular lesions of the petroclival area. Neurosurgery 1999;44:537–52. [37] Taha JM, Tew Jr JM, van Loveren HR, Keller JT, el-Kalliny M. Comparison of conventional and skull base surgical approaches for the excision of trigeminal neurinomas. J Neurosurg 1995;82: 719–25. [38] Chang DW, Robb GL. Microvascular reconstruction of the skull base. Semin Surg Oncol 2000;19: 211–7. [39] Chang DW, Langstein HN, Gupta A, De Monte F, Do KA, Wang X, et al. Reconstructive
G.W. Britz et al / Neurosurg Clin N Am 13 (2002) 475–489 management of cranial base defects after tumor ablation. Plast Reconstr Surg 2001;107:1346–57. [40] Manstein ME, Manstein CH, Manstein G. Paraspinous muscle flaps. Ann Plast Surg 1998;40:458–62. [41] Okii N, Nishimura S, Kurisu K, Takeshima Y, Uozumi T. In vivo histological changes occurring in
489
hydroxyapatite cranial reconstruction—case report. Neurol Med Chir (Tokyo) 2001;41:100–4. [42] Urken ML, Cheney ML, Sullivan MJ, Biller HF. Atlas of regional and free flaps for head and neck reconstruction. New York: Raven Press; 1995. p. 29–48, 237–60.