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Draf III Extension in the Endoscopic Endonasal Transethmoidal, Transcribriform Approach Through the Back Wall of the Frontal Sinus: A Cadaveric Study
Accepted Manuscript Draf III extension in the endoscopic endonasal transethmoidal, transcribriform approach through the back wall of the frontal sinus: a cadaveric study Osaama H. Khan, MD MSc., Roheen Raithatha, MD, Paolo Castelnuovo, MD, Vijay K. Anand, MD, Theodore H. Schwartz, MD PII:
S1878-8750(15)01067-0
DOI:
10.1016/j.wneu.2015.08.051
Reference:
WNEU 3155
To appear in:
World Neurosurgery
Received Date: 18 March 2015 Revised Date:
14 August 2015
Accepted Date: 18 August 2015
Please cite this article as: Khan OH, Raithatha R, Castelnuovo P, Anand VK, Schwartz TH, Draf III extension in the endoscopic endonasal transethmoidal, transcribriform approach through the back wall of the frontal sinus: a cadaveric study, World Neurosurgery (2015), doi: 10.1016/j.wneu.2015.08.051. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Draf III extension in the endoscopic endonasal transethmoidal, transcribriform approach through the back wall of the frontal sinus: a cadaveric study
Vijay K. Anand, MD4, Theodore H. Schwartz, MD5,6 1
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Osaama H. Khan, MD MSc.1, Roheen Raithatha, MD2, Paolo Castelnuovo MD3,
Division of Neurosurgery, Toronto Western Hospital, University of Toronto,
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Toronto, ON, Canada 2
Assistant Clinical Professor of Otolaryngology, Department of Otolaryngology -
Head and Neck Surgery, Mount Sinai School of Medicine, New York, NY USA
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Division of Otorhinolaryngology, Department of Biotechnology and Life Sciences,
University of Insubria, Varese, Italy 4
Department of Otolaryngology - Head and Neck Surgery, Weill Cornell Medical
College, New York-Presbyterian Hospital, New York, NY, USA 5
Department of Neurological Surgery, Weill Cornell Medical College, New York-
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Presbyterian Hospital, New York, NY, USA
Department of Neurosciences, Brain and Mind Institute, Weill Cornell Medical
College, New York-Presbyterian Hospital, New York, NY, USA
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Corresponding Author
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Theodore H. Schwartz, MD, FACS Department of Neurosurgery Weill Cornell Medical College New York Presbyterian Hospital 525 E. 68th Street New York, NY 10021 Telephone: 212-746-5620 Fax: 212-746-5592 Email: [email protected]
Keywords: frontal sinus, meningioma, minimally invasive surgery, laboratory, transcribriform, transethmoid, frontal sinus drillout, draf 3, modified endoscopic lothrop
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Running Title: endoscopic endonasal Draf III
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Abstract
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Objective: The Draf III (modified endoscopic Lothrop) has been proposed to extend the endonasal transethmoidal, transfovea ethmoidalis and transcribriform approach through the back wall of the frontal sinus. The exposure is time-
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consuming, increases the risk of cerebrospinal fluid (CSF) leak and the
indications for use are not well-described. There is little data quantifying the
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advantage it conveys over the approach without the Draf III.
Methods: An endoscopic, endonasal transfovea, transcribriform approach was performed in 5 fresh, injected cadaver heads. Anatomic boundaries and measurements of the exposure were compared before and after addition of a
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Draf III. Pre- and post- dissection CT scans were obtained and additional radiographic measurements were made to quantify the additional exposure provided by the Draf III. Two clinical cases are presented where a Draf III was
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utilized.
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Results: Radiographic measurements: The mean anterior to posterior boundary from frontal sinus to planum sphenoidale pre-Draf III was 3.0 cm and post-Draf III was 3.8 cm with an average change of 0.8 cm. Cadaveric measurements: Following the Draf III, the mean anterior to posterior boundary from the posterior wall of frontal sinus to the planum sphenoidale increased from 3.0 cm to 4.3 cm. Average increase of 1.3 cm with an average increased area of view of 1.79 cm2.
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Conclusions: This study quantifies the increase field of view provided by the Draf III during anterior skull base dissection. Recommendations for pre-operative
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individuals would benefit from the additional exposure.
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examination of radiographic evidence are provided to help identify which
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Introduction The limits of endoscopic endonasal surgery continue to expand as anatomical studies offer new perspectives for the skull base surgeon.
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We have previously described the endoscopic endonasal corridors to the skull base which include the transnasal, transsphenoidal, transethmoidal and
transmaxillary to reach a variety of locations in the anterior, posterior midline and
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parasagittal skull base (Schwartz, Fraser et al. 2008).
The transfovea ethmoidalis, transcribriform approach can be further
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expanded with the additional use of a Draf III (modified endoscopic Lothrop) using the frontal sinus as a corridor into the anterior fossa (Dubin and Kuhn 2005, Greenfield, Anand et al. 2010) (Draf 1991, Gross, Gross et al. 1995, May 1996, Kassam, Snyderman et al. 2005, Draf 2006, de Notaris, Esposito et al. 2008).
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However, extending this approach with a Draf III is time-consuming and significantly increases the risk of CSF leak since the defect created may extend forward beyond the limits of a nasoseptal flap. Therefore, one must justify this
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additional risk by understanding when the Draf III is necessary and when it can be avoided by quantifying and characterizing the additional exposure provided.
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The aim of this study was to use both radiographic measurements and cadaver dissection to describe the additional exposure provided by the Draf III to help surgeons decide when to select this additional maneuver to expose additional components of the anterior skull base. Two clinical cases where the Draf III was utilized are included.
Methods:
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Five formalin-fixed and preserved adult cadaveric heads injected with colored latex (red for arteries, blue for veins) were obtained for dissection.
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Institutional Review Board approval at Weill Cornell Medical College was obtained for this study.
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Radiographical Measurements
Pre-dissection CT sinus scans were obtained using a fine-cut BrainLab
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(Westchester, IL) protocol with 1.25 mm thickness cuts. Pre-dissection measurements were made of the anterior cranial fossa floor from anterior limit of the planum sphenoidale to the posterior wall of frontal sinus (rostral-caudal) and the coronal measurement of the cribriform plate and fovea ethmoidalis at the
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level of posterior frontal sinus floor between the lamina papyracea (Fig. 1 A,B). Post-dissection CT scans were then similarly obtained for the two scenarios, first without and then with the addition of the Draf III. Measurements were then made
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from the anterior limit of the planum sphenoidale to the superior point of defect of the posterior wall of the frontal sinus and again of coronal measurements as
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described above (Figure 1 C,D).
Cadaver Dissection
All dissections were performed at the Surgical Innovations Laboratory for Skull Base Microsurgery at the Weill Cornell Brain and Spine Center with the
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supervision of the senior authors (VA and TS). After the cadaveric head was placed in a Mayfield head holder (Integra, Plainsboro, NJ, USA) with 3-pin fixation, the head was slightly extended to enhance the trajectory to the anterior
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skull base. Endoscopes with 0°, 30° and 45° (4mm; Karl Storz, Tuttlingen, Germany) were used for visualization. Endoscopic images as well as
documentation of the transcranial exposure were recorded and stored by the Karl
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Storz AIDA™ system. Endoscopic sinus and skull base surgical instruments
(Storz) and high-speed cutting burrs (Anspach, Palm Beach Gardens, Florida,
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USA) were used for dissection. Using a binasal approach and under endoscopic guidance, bilateral uncinectomy and maxillary sinusotomy were performed. A total ethmoidectomy was performed ensuring that all ethmoid air cells were removed to the level of the lamina papyracea. The lamina papyracea,
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representing the medial wall of the orbit and the lateral wall of the ethmoid sinuses, was exposed but never violated. The frontal sinus was then visualized using angled endoscopes (30˚ and 45˚). The nasofrontal beak was subsequently
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thinned down using large cutting burs once the posterior wall of the common frontal sinus cavity was visualized (Figure 2a). Measurements were then
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obtained by placing a ruler into the field (Figure 2b). The Draf III was then completed, as previously described (Farhat and Kountakis 2004). In brief, bilateral removal of the frontal sinus floor and the superior nasal septum bilaterally was performed. Further measurements of the anterior skull base were then obtained.
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Results Technical observations Dissection of cadaver heads revealed subjectively superior views obtained with
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the 30° endoscope for anterior skull base dissectio n and the 45° endoscope for
completion of the Draf III. Despite satisfactory drilling of the nasofrontal beak, its projection posteriorly into the field contributed in limiting of frontal sinus bony
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Anatomical measurements
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drilling by obstruction of visualization of dissection instruments.
The mean anterior to posterior boundary from posterior wall of frontal sinus to the anterior limit of the planum sphenoidale was 3.0 cm (SD= 0.69, range 2.1 – 4.0). Following Draf III dissection, the mean anterior to posterior boundary from
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posterior wall of frontal sinus to the planum sphenoidale was 4.3 cm (SD 0.73, range 3.6 – 5.5 cm) with an average change from pre-dissection of 1.3 cm (SD 0.32, range 0.9 – 1.6 cm) (p<0.001). The width of the floor of exposure was a
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mean of 1.9 cm (SD 0.39, range 1.6 – 2.5).
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Radiographic measurements
Pre-dissection
The mean anterior to posterior boundary from the back wall of the frontal sinus to anterior limit of the planum sphenoidale was 3.0 cm (SD = 0.5, range 2.3 – 3.5). Measurements from the back wall of frontal sinus to where the Draf III would
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potentially expose (Figure 1, panel B, measurement *) had a mean of 1.1 cm (SD = 0.23, range 0.95 – 1.3). The mean coronal distance between orbital walls was
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2.2 cm (SD = 0.1, range 2.1 – 2.3).
Post-dissection
Following Draf III dissection, the mean anterior to posterior boundary from
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posterior wall of frontal sinus to anterior planum sphenoidale was 3.8 cm (SD 0.4, range 3.1 – 4.2), with an average change from pre-dissection of 0.8 cm (SD 0.4,
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range 0.4 – 15 cm) (p<0.001). The mean coronal distance between orbital walls was 2.2 cm (SD 0.1, range 1.9 – 2.3) with an average change from pre-
Case 1
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dissection of 0.1 cm.
51 year-old female referred from endocrinology for workup of ACTH-secreting
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tumour with MRI imaging showing a sinonasal mass extending intracranially (Figure 3 A,B,C) with no involvement of the sella or pituitary gland. An
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endoscopic endonasal DRAF III approach (as described above) was used to achieve a gross-total resection. A nasoseptal flap was used as previously described (AlQahtani, Bignami et al. 2014). No post-operative CSF leak was observed. Pathology revealed an esthesioneuroblastoma (Kadish C). Follow-up at 16 months (Figure 3 D,E,F) showed no local recurrence of tumor, however, at
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24 months body CT imaging showed bony metastasis and the patient died at 26 months post surgery.
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Case 2.
53 year-old male wood worker with intestinal type sinonasal adenocarcinoma
presented with imaging shown in Figure 4 (A,B,C) . An endoscopic endonasal
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DRAF III approach (as described above) was used to achieve a gross-total
resection. A nasoseptal flap was used as previously described (AlQahtani,
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Bignami et al. 2014). No postoperative CSF leak was observed. At one year
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follow-up (Figure 4 D,E,F) no recurrence was evident on imaging.
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Discussion The endoscopic endonasal transcribriform, transfoveal ethmoidalis approach offers a direct midline trajectory for removal of anterior skull base
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lesions which lie between the orbits. The approach has been described in
cadaver dissection and in small case series for removal of olfactory groove
meningiomas, esthesioneuroblastomas, meningoceles as well as a variety of
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other more rare pathologies (Greenfield, Anand et al. 2010) (Draf 1991, Gross, Gross et al. 1995, May 1996, Kassam, Snyderman et al. 2005, Draf 2006, de
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Notaris, Esposito et al. 2008). In order to extend the approach more anteriorly, additional removal of the back wall of the frontal sinus can be performed, the socalled “Draf III procedure”, which also acts as a shelf for tucking graft material during skull base reconstruction (Scott, Wormald et al. 2003, Batra, Kanowitz et
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al. 2010).
The Draf III is an endoscopic modification off a more traditional approach called a Lothrop, first reported in 1914 as a combined external and transnasal
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approach to the frontal sinus (Lothrop 1914). In 1991 Draf introduced several
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endoscopic approaches to the frontal sinus (Draf 1991) and has since performed modifications (Draf 2006, Dubin 2005). The modified endoscopic Lothrop procedure, described by May and Gross (May 1996) rejuvenated the approach with the advent of endoscopic technology and techniques. This is now considered synonymous to a Draf III and also known as a “frontal sinus drillout.” Its primary use is in the treatment of advanced frontal sinusitis and involves removal of the frontal sinus floor bilaterally, with inter-frontal sinus septectomy
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and resection of the superior nasal septum to create a wide medial frontal sinus drainage pathway (May 1996, Gross, Zachmann et al. 1997). Wide opening of the frontal sinuses promotes drainage and minimizes the risk of postoperative
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frontal sinus stenosis and iatrogenic mucocele formation (Batra, Kanowitz et al. 2010). The use of this procedure in the field of endoscopic skull base surgery has broadened to expand the exposure for of the endonasal removal of
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meningoencephaloceles, esthesioneuroblastomas, olfactory groove
meningiomas (Liu 2011) and post-traumatic CSF leaks (Sieskiewicz, 2011). The
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Draf I comprises an ethmoidectomy including the cell septa in the region of the frontal recess whereby the inferior part of Killian’s infundibulum and its mucosa are not violated. Draf IIa involves extended drainage by resecting the floor of the frontal sinus between the lamina papyracea and the middle turbinate and Draf IIb
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extends further anterior to the ventral margin of the olfactory fossa (Draf 2005). However, the Draf III is time-consuming and increases the risk of CSF leak substantially. For example, leak rates for olfactory groove meningiomas
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have been reported on average at 31.6% compared with 21.3% for tuberculum
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sella meningiomas (Komotar, Starke et al. 2013). For this reason, some groups have described the use of a pericranial flap that can be harvested above the cranium and pulled downwards into the nasal cavity to assist with watertight closure (Moshaver, Harris et al. 2006). However, large series of this technically demanding closure are not available and its utility unclear. The purpose of this study was to determine the specific advantages afforded by the Draf III to determine how to employ it selectively, when needed during the transethmoidal,
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transcribriform approach (Farhat 2004, Draf 2006), our findings can be separated into three areas: i) radiographic ii) visualization iii) dissection. The purpose of this study was not focused on reconstruction techniques and repair of CSF leaks.
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A cadaveric study investigating septal flap coverage has been previously
published by Castelnuovo and colleagues (AlQahtani, Bignami et al. 2014). In
brief, bilateral nasoseptal flaps are harvested, with one superiorly based septal
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flap, anterior to olfactory cleft, is vascularized through septal branches of anterior ethmoidal artery and covers the posterior frontal sinus wall and the contralateral
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flap harvested similarly but maintaining the pedicle anterior to the axilla of the middle turbinate laterally and covers the anterior sinus wall. This flap coverage allows for average size of 2 x 3 cm.
Rhinologists have appreciated for years that the most challenging areas to
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access in the frontal sinus are located most superiorly and medially, which often remain out of sight due to the convex shape of the posterior table. However, when dealing with intracranial skull base lesions, the superior area has not been
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essential since an open cranial approach would be favored to reach intracranial locations. Indeed, the supraorbital eyebrow approach is another minimally
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invasive approach that provides exposure to the anterior skull base without the risk of CSF leak or lateral limitations of the lamina papyracea (Fatemi, Dusick et al. 2009). However, views into the depths of the cribriform plate or posterior wall of the frontal sinus can be challenging without endoscope assistance. Nevertheless, tumor that extend to the superior aspect of the posterior wall of the frontal sinus generally elevate the brain and can be approached from above
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without any brain retraction. For visualization while the 0° degree scope provide s excellent view of the
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planum sphenoidale and the 30° provides excellent v iew of the anterior skull base, the 45° scope allows the most optimal view of the through the frontal sinus corridor provided by the Draf III (Batra 2010).
The 70° can be used to further
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expand the field of view but can be very difficult to use for guiding surgical
instruments resulting in the greatest distortion of the two-dimensional view. For
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this reason, it was not used in this study. The acute angle between the anterior portion of the nostrils and the frontal sinus also represents an anatomic limitation to surgical manipulation inside the frontal sinus cavity under direct visual control.
Our cadaveric results are similar to previous reported measurements of
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33.7 mm (range 29–40 mm) in the anteroposterior direction (posterior wall of frontal sinus to planum sphenoidale), and 23.5 mm (range 20–27 mm) and 19.1 mm (range 17–22 mm) in the transverse direction (orbit to orbit) at the level of
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the anterior ethmoidal artery and posterior ethmoidal artery, respectively (Batra,
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Kanowitz et al. 2010). The differences that we have reported in the radiographic and cadaveric measurements are likely due to the slight subjectivity in which slice on the CT is used for the measurement; however, our measurements did fit within the standard error. Previous cadaver studies of the Draf III have shown that the limits of instrumentation in the lateral and anterior frontal sinus are dependent on the degree of frontal sinus opening (Becker, Bomeli et al. 2006). Thus, the larger the
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opening, the more degrees of freedom but the more difficult the closure. Clearly, just being able to see a region does not mean that bimanual surgery is feasible in
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that region. Care must also be taken to identify the anterior and posterior ethmoidal arteries early, prior to dissection of the anterior skull base. Depending on the intracranial
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pathology that is being approached, these vessels might require ligation such as in olfactory groove meningiomas. A thorough knowledge of the anatomy as it
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appears through the endoscope is also important because other structures, such as the cap of the agger nasi cells or a supraorbital ethmoid air cell, can easily be mistaken for the frontal sinus ostium (Sillers, Kuhn et al. 1995). With the routine use of neuronavigation for endoscopic procedures, this pitfall can be avoided and
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the safety of the approach maximized.
Case selection for use of the Draf III depends on the i) size and location of pathology and ii) nasal/frontal sinus anatomy. If the lesion size extends
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superiorly intracranially, beyond the distance where instruments can reach, a craniotomy would be a better approach. More aggressive pathologies (such as
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carcinomas that require negative margins) would be less amenable to this approach. It is important to have a discussion with experienced ENT colleagues and their experience in this approach. As reported previously (AlQahtani, Bignami et al. 2014), a vascularized flap does allow for coverage for reconstruction and redue CSF leak; however, there is a paucity of cases in the literature to adequately comment on success of preventing CSF leak. Nonetheless, we recommend that a multi-layered reconstruction via a “gasket-
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seal” closure coupled with naso-septal flap and tissue sealant followed by lumbar drain for 24 hours - just as we do in closure of olfactory groove and tuberculum
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sellae meningioms (Khan, Anand et al. 2014, Ottenhausen, Banu et al. 2014). We found two instruments, not commonly used by neurosurgeons, to help limit unwanted dissection of adjacent tissues, i) Microdebrider (Medtronic,
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Minneapolis, MN) ii) 70-degree drill sheaths. The former is useful for removal of ethmoid air cells and the latter for drilling the anterior and posterior walls of the
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frontal sinus. This further emphasizes the importance of working with experienced sinonasal otolaryngologists for these approaches.
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Conclusion
While the Draf III clearly increases the field of view and area of exposure of the transethmoidal and transcribriform approaches, the increased exposure
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comes at a cost. We recommend a thorough understanding anatomically, and radiographically of precisely the area of increased exposure provided by the Draf
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III and its use only selectively. Many lesions that require the Draf III may be best approached from above, either through a standard bicoronal approach or a supraorbital eyebrow minicraniotomy which may be the shortest distance to the tumor, particularly tumors that abut the posterior wall of the frontal sinus and elevate the brain thus obviating the need for brain retraction. Disclosures
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The authors have no financial disclosures.
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Figure 1
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Figure 1. Coronal and sagittal CT images (bone windows) of a cadaver head,
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illustrating pre-dissection (A,B) and post-dissection (C,D) measurements. Measurement of distance (mm) between the lamina papyracea (w,y), and distance from anterior planum to posterior floor/wall of frontal sinus (x) and from anterior planum to posterior wall of frontal sinus defect (z) were performed on all five cadaver heads. Another measurement, located under the * illustrated on panel B, is a solid line measuring from the back wall of frontal sinus to where the
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Draf III would potentially expose. Panel D illustrates that how the nasofrontal
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beak limits further removal of posterior wall of frontal sinus.
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Figure 2
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Figure 2. Endoscopic view of the anterior skull base with a 45° endoscope. Frontal sinus (FS), orbit (O), olfactory cleft (OC), planum sphenoidale (PS, black bar), posterior wall of frontal sinus (w).
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Figure 3
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Case 1: Preoperative (A,B,C) coronal and sagittal MR images with contrast showing enhancing lesion in the nasal cavity extending into the cribiform, ethmoid and anterior cranial fossa. Postoperative (D,E,F) images shows a gross total resection via a DRAF III approach with reconstruction of the floor with a multilayered closure and vascularized nasoseptal flap.
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Figure 4.
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Figure 4.
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Case 2: Preoperative coronal and sagittal (A,C) MR images and sagittal CT (B) demonstrating enhancing lesion in the nasal cavity extending into the cribiform plate, ethmoid cells and anterior cranial fossa directly behind the frontal sinus. Postoperative (D,E,F) axial, coronal and sagittal MR images shows a gross total resection via a DRAF III approach with reconstruction of the floor with a multilayered closure and vascularized nasoseptal flap.
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Highlights:
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1. The paper details experiments on cadaveric dissections coupled with radiographic assessments that serve to understand the advantages for endonasal neurosurgeons that endoscopic trans-frontal sinus provides in anterior skull base pathologies. 2. Study quantifies the field of view the Draf III provides 3. The individual variabilties in skull base anatomy plays a role in the different advantages this approach provides 4. Guidelines for pre-operative examination of radiographic evidence are provided to help identify which individuals would benefit from the additional exposure
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Abbreviations
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Cm - centimeter CSF – cerebrospinal fluid CT – commuted tomography Fig – figure mm - millimeter SD – standard deviation
S1878-8750(15)01067-0
DOI:
10.1016/j.wneu.2015.08.051
Reference:
WNEU 3155
To appear in:
World Neurosurgery
Received Date: 18 March 2015 Revised Date:
14 August 2015
Accepted Date: 18 August 2015
Please cite this article as: Khan OH, Raithatha R, Castelnuovo P, Anand VK, Schwartz TH, Draf III extension in the endoscopic endonasal transethmoidal, transcribriform approach through the back wall of the frontal sinus: a cadaveric study, World Neurosurgery (2015), doi: 10.1016/j.wneu.2015.08.051. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Draf III extension in the endoscopic endonasal transethmoidal, transcribriform approach through the back wall of the frontal sinus: a cadaveric study
Vijay K. Anand, MD4, Theodore H. Schwartz, MD5,6 1
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Osaama H. Khan, MD MSc.1, Roheen Raithatha, MD2, Paolo Castelnuovo MD3,
Division of Neurosurgery, Toronto Western Hospital, University of Toronto,
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Toronto, ON, Canada 2
Assistant Clinical Professor of Otolaryngology, Department of Otolaryngology -
Head and Neck Surgery, Mount Sinai School of Medicine, New York, NY USA
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3
Division of Otorhinolaryngology, Department of Biotechnology and Life Sciences,
University of Insubria, Varese, Italy 4
Department of Otolaryngology - Head and Neck Surgery, Weill Cornell Medical
College, New York-Presbyterian Hospital, New York, NY, USA 5
Department of Neurological Surgery, Weill Cornell Medical College, New York-
6
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Presbyterian Hospital, New York, NY, USA
Department of Neurosciences, Brain and Mind Institute, Weill Cornell Medical
College, New York-Presbyterian Hospital, New York, NY, USA
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Corresponding Author
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Theodore H. Schwartz, MD, FACS Department of Neurosurgery Weill Cornell Medical College New York Presbyterian Hospital 525 E. 68th Street New York, NY 10021 Telephone: 212-746-5620 Fax: 212-746-5592 Email: [email protected]
Keywords: frontal sinus, meningioma, minimally invasive surgery, laboratory, transcribriform, transethmoid, frontal sinus drillout, draf 3, modified endoscopic lothrop
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Running Title: endoscopic endonasal Draf III
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Abstract
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Objective: The Draf III (modified endoscopic Lothrop) has been proposed to extend the endonasal transethmoidal, transfovea ethmoidalis and transcribriform approach through the back wall of the frontal sinus. The exposure is time-
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consuming, increases the risk of cerebrospinal fluid (CSF) leak and the
indications for use are not well-described. There is little data quantifying the
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advantage it conveys over the approach without the Draf III.
Methods: An endoscopic, endonasal transfovea, transcribriform approach was performed in 5 fresh, injected cadaver heads. Anatomic boundaries and measurements of the exposure were compared before and after addition of a
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Draf III. Pre- and post- dissection CT scans were obtained and additional radiographic measurements were made to quantify the additional exposure provided by the Draf III. Two clinical cases are presented where a Draf III was
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utilized.
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Results: Radiographic measurements: The mean anterior to posterior boundary from frontal sinus to planum sphenoidale pre-Draf III was 3.0 cm and post-Draf III was 3.8 cm with an average change of 0.8 cm. Cadaveric measurements: Following the Draf III, the mean anterior to posterior boundary from the posterior wall of frontal sinus to the planum sphenoidale increased from 3.0 cm to 4.3 cm. Average increase of 1.3 cm with an average increased area of view of 1.79 cm2.
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Conclusions: This study quantifies the increase field of view provided by the Draf III during anterior skull base dissection. Recommendations for pre-operative
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individuals would benefit from the additional exposure.
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examination of radiographic evidence are provided to help identify which
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Introduction The limits of endoscopic endonasal surgery continue to expand as anatomical studies offer new perspectives for the skull base surgeon.
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We have previously described the endoscopic endonasal corridors to the skull base which include the transnasal, transsphenoidal, transethmoidal and
transmaxillary to reach a variety of locations in the anterior, posterior midline and
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parasagittal skull base (Schwartz, Fraser et al. 2008).
The transfovea ethmoidalis, transcribriform approach can be further
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expanded with the additional use of a Draf III (modified endoscopic Lothrop) using the frontal sinus as a corridor into the anterior fossa (Dubin and Kuhn 2005, Greenfield, Anand et al. 2010) (Draf 1991, Gross, Gross et al. 1995, May 1996, Kassam, Snyderman et al. 2005, Draf 2006, de Notaris, Esposito et al. 2008).
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However, extending this approach with a Draf III is time-consuming and significantly increases the risk of CSF leak since the defect created may extend forward beyond the limits of a nasoseptal flap. Therefore, one must justify this
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additional risk by understanding when the Draf III is necessary and when it can be avoided by quantifying and characterizing the additional exposure provided.
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The aim of this study was to use both radiographic measurements and cadaver dissection to describe the additional exposure provided by the Draf III to help surgeons decide when to select this additional maneuver to expose additional components of the anterior skull base. Two clinical cases where the Draf III was utilized are included.
Methods:
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Five formalin-fixed and preserved adult cadaveric heads injected with colored latex (red for arteries, blue for veins) were obtained for dissection.
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Institutional Review Board approval at Weill Cornell Medical College was obtained for this study.
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Radiographical Measurements
Pre-dissection CT sinus scans were obtained using a fine-cut BrainLab
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(Westchester, IL) protocol with 1.25 mm thickness cuts. Pre-dissection measurements were made of the anterior cranial fossa floor from anterior limit of the planum sphenoidale to the posterior wall of frontal sinus (rostral-caudal) and the coronal measurement of the cribriform plate and fovea ethmoidalis at the
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level of posterior frontal sinus floor between the lamina papyracea (Fig. 1 A,B). Post-dissection CT scans were then similarly obtained for the two scenarios, first without and then with the addition of the Draf III. Measurements were then made
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from the anterior limit of the planum sphenoidale to the superior point of defect of the posterior wall of the frontal sinus and again of coronal measurements as
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described above (Figure 1 C,D).
Cadaver Dissection
All dissections were performed at the Surgical Innovations Laboratory for Skull Base Microsurgery at the Weill Cornell Brain and Spine Center with the
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supervision of the senior authors (VA and TS). After the cadaveric head was placed in a Mayfield head holder (Integra, Plainsboro, NJ, USA) with 3-pin fixation, the head was slightly extended to enhance the trajectory to the anterior
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skull base. Endoscopes with 0°, 30° and 45° (4mm; Karl Storz, Tuttlingen, Germany) were used for visualization. Endoscopic images as well as
documentation of the transcranial exposure were recorded and stored by the Karl
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Storz AIDA™ system. Endoscopic sinus and skull base surgical instruments
(Storz) and high-speed cutting burrs (Anspach, Palm Beach Gardens, Florida,
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USA) were used for dissection. Using a binasal approach and under endoscopic guidance, bilateral uncinectomy and maxillary sinusotomy were performed. A total ethmoidectomy was performed ensuring that all ethmoid air cells were removed to the level of the lamina papyracea. The lamina papyracea,
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representing the medial wall of the orbit and the lateral wall of the ethmoid sinuses, was exposed but never violated. The frontal sinus was then visualized using angled endoscopes (30˚ and 45˚). The nasofrontal beak was subsequently
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thinned down using large cutting burs once the posterior wall of the common frontal sinus cavity was visualized (Figure 2a). Measurements were then
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obtained by placing a ruler into the field (Figure 2b). The Draf III was then completed, as previously described (Farhat and Kountakis 2004). In brief, bilateral removal of the frontal sinus floor and the superior nasal septum bilaterally was performed. Further measurements of the anterior skull base were then obtained.
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Results Technical observations Dissection of cadaver heads revealed subjectively superior views obtained with
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the 30° endoscope for anterior skull base dissectio n and the 45° endoscope for
completion of the Draf III. Despite satisfactory drilling of the nasofrontal beak, its projection posteriorly into the field contributed in limiting of frontal sinus bony
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Anatomical measurements
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drilling by obstruction of visualization of dissection instruments.
The mean anterior to posterior boundary from posterior wall of frontal sinus to the anterior limit of the planum sphenoidale was 3.0 cm (SD= 0.69, range 2.1 – 4.0). Following Draf III dissection, the mean anterior to posterior boundary from
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posterior wall of frontal sinus to the planum sphenoidale was 4.3 cm (SD 0.73, range 3.6 – 5.5 cm) with an average change from pre-dissection of 1.3 cm (SD 0.32, range 0.9 – 1.6 cm) (p<0.001). The width of the floor of exposure was a
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mean of 1.9 cm (SD 0.39, range 1.6 – 2.5).
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Radiographic measurements
Pre-dissection
The mean anterior to posterior boundary from the back wall of the frontal sinus to anterior limit of the planum sphenoidale was 3.0 cm (SD = 0.5, range 2.3 – 3.5). Measurements from the back wall of frontal sinus to where the Draf III would
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potentially expose (Figure 1, panel B, measurement *) had a mean of 1.1 cm (SD = 0.23, range 0.95 – 1.3). The mean coronal distance between orbital walls was
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2.2 cm (SD = 0.1, range 2.1 – 2.3).
Post-dissection
Following Draf III dissection, the mean anterior to posterior boundary from
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posterior wall of frontal sinus to anterior planum sphenoidale was 3.8 cm (SD 0.4, range 3.1 – 4.2), with an average change from pre-dissection of 0.8 cm (SD 0.4,
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range 0.4 – 15 cm) (p<0.001). The mean coronal distance between orbital walls was 2.2 cm (SD 0.1, range 1.9 – 2.3) with an average change from pre-
Case 1
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dissection of 0.1 cm.
51 year-old female referred from endocrinology for workup of ACTH-secreting
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tumour with MRI imaging showing a sinonasal mass extending intracranially (Figure 3 A,B,C) with no involvement of the sella or pituitary gland. An
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endoscopic endonasal DRAF III approach (as described above) was used to achieve a gross-total resection. A nasoseptal flap was used as previously described (AlQahtani, Bignami et al. 2014). No post-operative CSF leak was observed. Pathology revealed an esthesioneuroblastoma (Kadish C). Follow-up at 16 months (Figure 3 D,E,F) showed no local recurrence of tumor, however, at
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24 months body CT imaging showed bony metastasis and the patient died at 26 months post surgery.
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Case 2.
53 year-old male wood worker with intestinal type sinonasal adenocarcinoma
presented with imaging shown in Figure 4 (A,B,C) . An endoscopic endonasal
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DRAF III approach (as described above) was used to achieve a gross-total
resection. A nasoseptal flap was used as previously described (AlQahtani,
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Bignami et al. 2014). No postoperative CSF leak was observed. At one year
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follow-up (Figure 4 D,E,F) no recurrence was evident on imaging.
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Discussion The endoscopic endonasal transcribriform, transfoveal ethmoidalis approach offers a direct midline trajectory for removal of anterior skull base
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lesions which lie between the orbits. The approach has been described in
cadaver dissection and in small case series for removal of olfactory groove
meningiomas, esthesioneuroblastomas, meningoceles as well as a variety of
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other more rare pathologies (Greenfield, Anand et al. 2010) (Draf 1991, Gross, Gross et al. 1995, May 1996, Kassam, Snyderman et al. 2005, Draf 2006, de
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Notaris, Esposito et al. 2008). In order to extend the approach more anteriorly, additional removal of the back wall of the frontal sinus can be performed, the socalled “Draf III procedure”, which also acts as a shelf for tucking graft material during skull base reconstruction (Scott, Wormald et al. 2003, Batra, Kanowitz et
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al. 2010).
The Draf III is an endoscopic modification off a more traditional approach called a Lothrop, first reported in 1914 as a combined external and transnasal
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approach to the frontal sinus (Lothrop 1914). In 1991 Draf introduced several
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endoscopic approaches to the frontal sinus (Draf 1991) and has since performed modifications (Draf 2006, Dubin 2005). The modified endoscopic Lothrop procedure, described by May and Gross (May 1996) rejuvenated the approach with the advent of endoscopic technology and techniques. This is now considered synonymous to a Draf III and also known as a “frontal sinus drillout.” Its primary use is in the treatment of advanced frontal sinusitis and involves removal of the frontal sinus floor bilaterally, with inter-frontal sinus septectomy
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and resection of the superior nasal septum to create a wide medial frontal sinus drainage pathway (May 1996, Gross, Zachmann et al. 1997). Wide opening of the frontal sinuses promotes drainage and minimizes the risk of postoperative
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frontal sinus stenosis and iatrogenic mucocele formation (Batra, Kanowitz et al. 2010). The use of this procedure in the field of endoscopic skull base surgery has broadened to expand the exposure for of the endonasal removal of
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meningoencephaloceles, esthesioneuroblastomas, olfactory groove
meningiomas (Liu 2011) and post-traumatic CSF leaks (Sieskiewicz, 2011). The
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Draf I comprises an ethmoidectomy including the cell septa in the region of the frontal recess whereby the inferior part of Killian’s infundibulum and its mucosa are not violated. Draf IIa involves extended drainage by resecting the floor of the frontal sinus between the lamina papyracea and the middle turbinate and Draf IIb
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extends further anterior to the ventral margin of the olfactory fossa (Draf 2005). However, the Draf III is time-consuming and increases the risk of CSF leak substantially. For example, leak rates for olfactory groove meningiomas
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have been reported on average at 31.6% compared with 21.3% for tuberculum
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sella meningiomas (Komotar, Starke et al. 2013). For this reason, some groups have described the use of a pericranial flap that can be harvested above the cranium and pulled downwards into the nasal cavity to assist with watertight closure (Moshaver, Harris et al. 2006). However, large series of this technically demanding closure are not available and its utility unclear. The purpose of this study was to determine the specific advantages afforded by the Draf III to determine how to employ it selectively, when needed during the transethmoidal,
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transcribriform approach (Farhat 2004, Draf 2006), our findings can be separated into three areas: i) radiographic ii) visualization iii) dissection. The purpose of this study was not focused on reconstruction techniques and repair of CSF leaks.
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A cadaveric study investigating septal flap coverage has been previously
published by Castelnuovo and colleagues (AlQahtani, Bignami et al. 2014). In
brief, bilateral nasoseptal flaps are harvested, with one superiorly based septal
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flap, anterior to olfactory cleft, is vascularized through septal branches of anterior ethmoidal artery and covers the posterior frontal sinus wall and the contralateral
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flap harvested similarly but maintaining the pedicle anterior to the axilla of the middle turbinate laterally and covers the anterior sinus wall. This flap coverage allows for average size of 2 x 3 cm.
Rhinologists have appreciated for years that the most challenging areas to
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access in the frontal sinus are located most superiorly and medially, which often remain out of sight due to the convex shape of the posterior table. However, when dealing with intracranial skull base lesions, the superior area has not been
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essential since an open cranial approach would be favored to reach intracranial locations. Indeed, the supraorbital eyebrow approach is another minimally
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invasive approach that provides exposure to the anterior skull base without the risk of CSF leak or lateral limitations of the lamina papyracea (Fatemi, Dusick et al. 2009). However, views into the depths of the cribriform plate or posterior wall of the frontal sinus can be challenging without endoscope assistance. Nevertheless, tumor that extend to the superior aspect of the posterior wall of the frontal sinus generally elevate the brain and can be approached from above
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without any brain retraction. For visualization while the 0° degree scope provide s excellent view of the
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planum sphenoidale and the 30° provides excellent v iew of the anterior skull base, the 45° scope allows the most optimal view of the through the frontal sinus corridor provided by the Draf III (Batra 2010).
The 70° can be used to further
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expand the field of view but can be very difficult to use for guiding surgical
instruments resulting in the greatest distortion of the two-dimensional view. For
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this reason, it was not used in this study. The acute angle between the anterior portion of the nostrils and the frontal sinus also represents an anatomic limitation to surgical manipulation inside the frontal sinus cavity under direct visual control.
Our cadaveric results are similar to previous reported measurements of
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33.7 mm (range 29–40 mm) in the anteroposterior direction (posterior wall of frontal sinus to planum sphenoidale), and 23.5 mm (range 20–27 mm) and 19.1 mm (range 17–22 mm) in the transverse direction (orbit to orbit) at the level of
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the anterior ethmoidal artery and posterior ethmoidal artery, respectively (Batra,
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Kanowitz et al. 2010). The differences that we have reported in the radiographic and cadaveric measurements are likely due to the slight subjectivity in which slice on the CT is used for the measurement; however, our measurements did fit within the standard error. Previous cadaver studies of the Draf III have shown that the limits of instrumentation in the lateral and anterior frontal sinus are dependent on the degree of frontal sinus opening (Becker, Bomeli et al. 2006). Thus, the larger the
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opening, the more degrees of freedom but the more difficult the closure. Clearly, just being able to see a region does not mean that bimanual surgery is feasible in
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that region. Care must also be taken to identify the anterior and posterior ethmoidal arteries early, prior to dissection of the anterior skull base. Depending on the intracranial
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pathology that is being approached, these vessels might require ligation such as in olfactory groove meningiomas. A thorough knowledge of the anatomy as it
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appears through the endoscope is also important because other structures, such as the cap of the agger nasi cells or a supraorbital ethmoid air cell, can easily be mistaken for the frontal sinus ostium (Sillers, Kuhn et al. 1995). With the routine use of neuronavigation for endoscopic procedures, this pitfall can be avoided and
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the safety of the approach maximized.
Case selection for use of the Draf III depends on the i) size and location of pathology and ii) nasal/frontal sinus anatomy. If the lesion size extends
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superiorly intracranially, beyond the distance where instruments can reach, a craniotomy would be a better approach. More aggressive pathologies (such as
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carcinomas that require negative margins) would be less amenable to this approach. It is important to have a discussion with experienced ENT colleagues and their experience in this approach. As reported previously (AlQahtani, Bignami et al. 2014), a vascularized flap does allow for coverage for reconstruction and redue CSF leak; however, there is a paucity of cases in the literature to adequately comment on success of preventing CSF leak. Nonetheless, we recommend that a multi-layered reconstruction via a “gasket-
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seal” closure coupled with naso-septal flap and tissue sealant followed by lumbar drain for 24 hours - just as we do in closure of olfactory groove and tuberculum
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sellae meningioms (Khan, Anand et al. 2014, Ottenhausen, Banu et al. 2014). We found two instruments, not commonly used by neurosurgeons, to help limit unwanted dissection of adjacent tissues, i) Microdebrider (Medtronic,
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Minneapolis, MN) ii) 70-degree drill sheaths. The former is useful for removal of ethmoid air cells and the latter for drilling the anterior and posterior walls of the
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frontal sinus. This further emphasizes the importance of working with experienced sinonasal otolaryngologists for these approaches.
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Conclusion
While the Draf III clearly increases the field of view and area of exposure of the transethmoidal and transcribriform approaches, the increased exposure
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comes at a cost. We recommend a thorough understanding anatomically, and radiographically of precisely the area of increased exposure provided by the Draf
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III and its use only selectively. Many lesions that require the Draf III may be best approached from above, either through a standard bicoronal approach or a supraorbital eyebrow minicraniotomy which may be the shortest distance to the tumor, particularly tumors that abut the posterior wall of the frontal sinus and elevate the brain thus obviating the need for brain retraction. Disclosures
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The authors have no financial disclosures.
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AlQahtani, A., M. Bignami, P. Terranova, E. Digilio, F. Basilico, S. Abdulrahman and P. Castelnuovo (2014). "Newly designed double-vascularized nasoseptal flap to prevent restenosis after endoscopic modified Lothrop procedure (Draf III): laboratory investigation." Eur Arch Otorhinolaryngol 271(11): 2951-2955. Batra, P. S., S. J. Kanowitz and A. Luong (2010). "Anatomical and technical correlates in endoscopic anterior skull base surgery: a cadaveric analysis." Otolaryngology-head and neck surgery : official journal of American Academy of OtolaryngologyHead and Neck Surgery 142(6): 827-831. Becker, S. S., S. R. Bomeli and C. W. Gross (2006). "Limits of endoscopic visualization and instrumentation in the frontal sinus." Otolayngology - Head and Neck Surgery 135: 917 - 921. de Notaris, M., I. Esposito, L. M. Cavallo, A. C. Burgaya, A. P. Galino, F. Esposito, J. M. Poblete, E. Ferrer and P. Cappabianca (2008). "Endoscopic endonasal approach to the ethmoidal planum: anatomic study." Neurosurgical review 31(3): 309-317. Draf, W. (1991). "Endonasal micro-endoscopic frontal sinus surgery. The Fulda concept. ." Operative Techniques in Otolaryngology Head Neck Surgery 2: 234-240. Draf, W. (2005). Endonasal Frontal Sinus Drainage Type I-III According to Draf. The Fontal Sinus. S. E. Kountakis, B. Senior and W. Draf. Berlin, Springer Berlin Heidelberg: 219-232. Draf, W. (2006). "The frontal T in the refinement of endonasal frontal sinus type III drainage." Operative Techniques in Otolaryngology 17: 121-125. Dubin, M. G. and F. A. Kuhn (2005). "Endoscopic modified Lothrop (Draf III) with frontal sinus punches." The Laryngoscope 115(9): 1702-1703. Farhat, F. T. and S. E. Kountakis (2004). "Endoscopic modified Lothrop procedure." Operative Techniques in Otolaryngology - Head and Neck Surgery 15: 4-7. Fatemi, N., J. R. Dusick, M. A. de Paiva Neto, D. Malkasian and D. F. Kelly (2009). "Endonasal versus supraorbital keyhole removal of craniopharyngiomas and tuberculum sellae meningiomas." Neurosurgery 64(5 Suppl 2): 269-284; discussion 284-266. Greenfield, J. P., V. K. Anand, A. Kacker, M. J. Seibert, A. Singh, S. M. Brown and T. H. Schwartz (2010). "Endoscopic endonasal transethmoidal transcribriform transfovea ethmoidalis approach to the anterior cranial fossa and skull base." Neurosurgery 66(5): 883-892; discussion 892. Gross, C. W., G. C. Zachmann, D. G. Becker, C. L. Vickery, D. F. Moore, Jr., W. H. Lindsey and W. E. Gross (1997). "Follow-up of University of Virginia experience with the modified Lothrop procedure." American journal of rhinology 11(1): 49-54. Gross, W. E., C. W. Gross, D. Becker, D. Moore and D. Phillips (1995). "Modified transnasal endoscopic Lothrop procedure as an alternative to frontal sinus obliteration." Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery 113(4): 427-434.
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Kassam, A., C. H. Snyderman, A. Mintz, P. Gardner and R. L. Carrau (2005). "Expanded endonasal approach: the rostrocaudal axis. Part I. Crista galli to the sella turcica." Neurosurgical focus 19(1): E3. Khan, O. H., V. K. Anand and T. H. Schwartz (2014). "Endoscopic endonasal resection of skull base meningiomas: the significance of a "cortical cuff" and brain edema compared with careful case selection and surgical experience in predicting morbidity and extent of resection." Neurosurg Focus 37(4): E7. Komotar, R. J., R. M. Starke, D. M. Raper, V. K. Anand and T. H. Schwartz (2013). "Endoscopic endonasal versus open repair of anterior skull base CSF leak, meningocele, and encephalocele: a systematic review of outcomes." Journal of neurological surgery. Part A, Central European neurosurgery 74(4): 239-250. Lothrop, H. A. (1914). "XIV. Frontal Sinus Suppuration: The Establishment of Permanent Nasal Drainage; the Closure of External Fistulae; Epidermization of Sinus." Annals of surgery 59(6): 937-957. May, M. (1996). "Frontal sinus surgery: endonasal, endoscopic, osteoplasty rather then external osteoplasty." Operative Techniques in Otolaryngology Head Neck Surgery 2: 226-231. Moshaver, A., J. R. Harris and H. Seikaly (2006). "Use of anteriorly based pericranial flap in frontal sinus obliteration." Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery 135(3): 413-416. Ottenhausen, M., M. A. Banu, D. G. Placantonakis, A. J. Tsiouris, O. H. Khan, V. K. Anand and T. H. Schwartz (2014). "Endoscopic endonasal resection of suprasellar meningiomas: the importance of case selection and experience in determining extent of resection, visual improvement, and complications." World Neurosurg 82(3-4): 442-449. Schwartz, T. H., J. F. Fraser, S. Brown, A. Tabaee, A. Kacker and V. K. Anand (2008). "Endoscopic cranial base surgery: classification of operative approaches." Neurosurgery 62(5): 991-1002; discussion 1002-1005. Scott, N. A., P. Wormald, D. Close, R. Gallagher, A. Anthony and G. J. Maddern (2003). "Endoscopic modified Lothrop procedure for the treatment of chronic frontal sinusitis: a systematic review." Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery 129(4): 427-438. Sillers, M. J., F. A. Kuhn and A. Wood (1995). "Endoscopic surgery of the frontal recess." Current Opinion Otolaryngology Head Neck Surgery 3: 36-40.
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Figure 1
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Figure 1. Coronal and sagittal CT images (bone windows) of a cadaver head,
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illustrating pre-dissection (A,B) and post-dissection (C,D) measurements. Measurement of distance (mm) between the lamina papyracea (w,y), and distance from anterior planum to posterior floor/wall of frontal sinus (x) and from anterior planum to posterior wall of frontal sinus defect (z) were performed on all five cadaver heads. Another measurement, located under the * illustrated on panel B, is a solid line measuring from the back wall of frontal sinus to where the
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Draf III would potentially expose. Panel D illustrates that how the nasofrontal
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beak limits further removal of posterior wall of frontal sinus.
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Figure 2
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Figure 2. Endoscopic view of the anterior skull base with a 45° endoscope. Frontal sinus (FS), orbit (O), olfactory cleft (OC), planum sphenoidale (PS, black bar), posterior wall of frontal sinus (w).
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Figure 3
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Case 1: Preoperative (A,B,C) coronal and sagittal MR images with contrast showing enhancing lesion in the nasal cavity extending into the cribiform, ethmoid and anterior cranial fossa. Postoperative (D,E,F) images shows a gross total resection via a DRAF III approach with reconstruction of the floor with a multilayered closure and vascularized nasoseptal flap.
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Figure 4.
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Figure 4.
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Case 2: Preoperative coronal and sagittal (A,C) MR images and sagittal CT (B) demonstrating enhancing lesion in the nasal cavity extending into the cribiform plate, ethmoid cells and anterior cranial fossa directly behind the frontal sinus. Postoperative (D,E,F) axial, coronal and sagittal MR images shows a gross total resection via a DRAF III approach with reconstruction of the floor with a multilayered closure and vascularized nasoseptal flap.
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Highlights:
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1. The paper details experiments on cadaveric dissections coupled with radiographic assessments that serve to understand the advantages for endonasal neurosurgeons that endoscopic trans-frontal sinus provides in anterior skull base pathologies. 2. Study quantifies the field of view the Draf III provides 3. The individual variabilties in skull base anatomy plays a role in the different advantages this approach provides 4. Guidelines for pre-operative examination of radiographic evidence are provided to help identify which individuals would benefit from the additional exposure
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Abbreviations
AC C
EP
TE D
M AN U
SC
RI PT
Cm - centimeter CSF – cerebrospinal fluid CT – commuted tomography Fig – figure mm - millimeter SD – standard deviation