- Email: [email protected]
Skullbase surgery
Theme Symposium
SKULLBASE SURGERY C. Rayappa Consultant ENT– Head and Neck and Skullbase Surgeon, Apollo Speciality Hospital, Chennai, India. Correspondence to: Dr. C. Rayappa, AA-2, 3rd Main Road, Anna Nagar, Chennai-600 040, India. E-mail: [email protected] Key words: Skullbase Surgery Techniques.
THE greatest single advance during the last two decades in the field of oncologic surgery of the head and neck has been the development of skull base surgery. A variety of neoplastic and non-neoplastic lesions affect the base of the skull, and in the past these were considered beyond the scope of surgical management. Because of their inaccessible location, the complex regional anatomy, the difficulty of accurately defining the extent of the lesion radiologically, and the fear of causing life-threatening complications, these tumours were considered unresectable and the skull base was considered a “no man’s land”. In the past, the skull-base was the borderline, which separated the areas of work of the neurosurgeons and ENTHead and Neck surgeons. Today, the collaborative work of ENT surgeons, neurosurgeons and plastic surgeons have given rise to many innovative approaches to the skull-base for resecting these tumours as well as reconstruction of the complex defects created at the skullbase. A team consisting experts from various disciplines make these extensive surgeries possible and safe (Table 1).
Tumours of the cranial base arise from or are in the vicinity of bony structures at the base of the brain (Table 2). Despite their varied histology (Table 3) and biologic behavior, all these tumours have a common feature - they are difficult to reach and are close to critical structures. The base of the skull represents a transition area through which important blood vessels, like the internal carotid and vertebral arteries enter and cranial nerves exit. In addition, large venous sinuses draining blood from the brain confluence at the skull base as they exit the cranial vault. They are difficult to reach because they are located ventral to the brain and posterior to the facial skeletons and aerodigestive system. ANATOMY The cranial base is divided into 3 portions - anterior, middle and posterior - that correspond to the respective cranial fossae.
Advances in diagnostic imaging and microsurgery have contributed significantly toward the successful management of these difficult clinical problems.
Anterior cranial base is made up of frontal, ethmoid and sphenoid bones. Extracranially, it is related to the orbit, ethmoid sinus and nasal cavity. Intracranially it is related to the olfactory bulbs and frontal lobes.
Table 1: Skull base team.
Table 2: Site of origin of skull base tumours. Extracranial tissues Paranasal sinuses Pharynx Connective tissues Skull base bone and cartilage Chordoma Osteosarcoma Chondrosarcoma Intracranial tissues Meninges Blood vessels Cranial nerves Pituitary gland
ENT - Head & Neck Surgeon Neurosurgeon Microvascular Reconstructive Surgeon Neuroanaesthetist Neuroradiologist Intensivist Pathologist Radiation oncologist Prosthodontist Psychiatrist Nursing team Occupational therapist Physiotherapist
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(DSA), will give important information about tumour vascularity, feeder vessels and the state of the carotid arteries. Vascular tumour can be embolized before surgery to reduce blood loss.
Table 3: Skull base tumours. Histology and biological behaviour Anterior skull base tumours Angiofibroma Meningioma Olfactory Neuroblastoma Paranasal sinus malignancy Middle skull base tumours Meningioma Schwannoma (origin in V nerve) Clivus chordoma Angiofibroma Nasopharyngeal Ca (RT failure) Posterior skull base tumours Glomus jugulare Schwannoma of lower cranial nerves Meningioma
If the ICA is encased by tumour, abrupt internal carotid occlusion during surgery results in a stroke rate of 26% and a mortality rate of 12% [1]. Therefore, a balloon occlusion test is performed to assess the cross circulation through circle of Willis. If there is good cross circulation, permanent balloon occlusion is performed and the artery can be sacrificed. If there is no cross circulation, the patient will require bypass surgery. The fundamental problem in tumours involving the skull base is that access to these tumours is difficult. The principles that must be adhere to in embarking upon skull base surgery are: 1.
Middle cranial base is composed of the body and greater wings of the sphenoid and part of the temporal bones. Intracranially, it is related to pituitary gland, cavernous sinus and temporal lobes. The petrous temporal bone houses the middle and inner ear structures and the petrous segment of ICA. Extracranially, it is related to infratemporal fossae, which contain the masticatory and pharyngeal muscles, cranial nerves, internal carotid artery, external carotid artery, eustachian tube and a venous plexus that communicates with the cavernous sinus. Posterior cranial base is formed by the clivus in the middle and the posterior surface of the temporal bones on either side. Intracranially it is related to the brain stem and cerebellum. The facial and vestibulocochlear nerves enter the IAC. The jugular foramen is situated just caudal and lateral to the IAC and contains the jugular bulb and the glossopharyngeal, vagus and accessory nerves. The hypoglossal canal is immediately medial and rostral to the occipital condyles. Ventrally, the posterior cranial base is situated over the nasopharynx separated only by the mucosa and the constrictor muscles. IMAGING Modern imaging techniques have made it easier to diagnose and ‘visualize’ the site of a skullbase tumour and to plan management. CT scan remains the best tool, particularly in its ability to delineate bone destructions. MRI is considered superior for the evaluation of the soft tissue extent of the disease and for brain invasion. It gives a better image of the surrounding blood vessels and perineural spread of tumour. Formal angiography or digital subtraction angiography Apollo Medicine, Vol.1, December 2004
2.
One must obtain adequate exposure of the area of surgical resection. There should be minimal or no brain retraction.
The operative approaches for skull base surgery depend on the anatomic location and extent of invasion of disease process. The surgical approaches are therefore different for the anterior cranial fossa, middle cranial fossa and posterior cranial fossa and clivus regions. ANTERIOR CRANIAL FOSSA A variety of suggested techniques are available for craniofacial resections for tumours involving the anterior skull base. The individual technique employed varies with each surgeon and his personal preference. However, the standard surgical technique for resection of the anterior central skull base for malignant tumours of the ethmoid is described. The neurosurgeon makes a bicoronal incision, elevates a vascularised pericranial flap, bifrontal craniotomy and then elevates the dura off the skull base. The ENT surgeon makes a lateral rhinotomy incision and does en-bloc resection of the ethmoid, medial wall of maxilla, septum and the cranial base. The defect is covered with a pericranial flap (Figs. 1a-f) [2]. The extent of extracranial resection (e.g., maxilla, eye, etc.) depends on the extent of the tumour. MIDDLE CRANIAL FOSSA The extra cranial areas related to this are the nasopharynx, infratemporal fossa and pterygomaxillary fissure. Maxillary tumours extending posteriorly and invading the pterygoid muscles were considered inoperable in the past. These tumours are removed now-a-days
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Fig. 1d. After en-bloc removal of the tumour containing skin, orbit, contents of temporal and ITF, subtotal petrosectomy, anterior and middle skullbase and dura. Fig 1a. 45-year-old patient with recurrent Ca following maxillectomy, radiotherapy and palliative chemotherapy.
Fig. 1e. 3-D reconstruction of postoperative CT scan shows the extent of bone removal. Fig. 1b. MRI shows the tumour infiltrating the orbit and dura (yellow arrow).
Fig. 1c. Coronal section MRI shows the tumour infiltrating the muscles of temporal and infratemporal fossa (yellow arrow).
Fig. 1f. Two years post surgery clinical photograph showing acceptable cosmesis. Resected area was reconstructed using anterolateral thigh microvascular flap.
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Theme Symposium
Key Messages •
Team approach.
•
Cerebral blood flow determination using temporary balloon occlusion test increases the safety of carotid resection or replacement in selected cases. Embolization of highly vascular tumours to reduce bleeding during surgery.
•
Tumours infiltrating the pterygoid muscles and ICA and recurrent nasopharyngeal carcinoma (which were considered inoperable in the past) can be resected safely using skull base surgical techniques.
•
Wide access can be gained to the middle region of the skull base through the facial translocation procedure, while still preserving the appearance and function of the face.
•
The primary short-term complications of the cranial base surgery are CSF leak, meningitis and cortical oedema.
•
The primary and most debilitating long-term complications of cranial base surgery are due to cranial nerve dysfunction, especially lower cranial nerve palsies (swallowing and vocal cord function)
•
Cranial base surgery offers the greatest benefit when performed as a primary therapeutic modality. Early diagnosis is essential.
using an extended transfacial subcranial approach (Figs. 2a-f) [3]. Tumours of the nasopharynx (e.g., nasopharyngeal carcinoma) and infratemporal fossa lie behind the maxilla and medial to the ramus of the mandible and facial nerve, preventing direct access for three-dimensional clearance. Craniofacial disassembly technique (facial translocation approach) (Figs. 3a-c) [4-6] is a systematic, stepwise dissection of facial soft tissues based on the knowledge of regional vascular territories and functional anatomy, followed by osteotomies and dismantling of the craniofacial skeleton. The maxilla is mobilized, like opening a book, and this can be done unilaterally or bilaterally. This exposes the nasopharynx, clivus and infratemporal fossa widely. Temporal craniotomy/craniectomy exposes the intracranial portions of the tumour. This reduces the need for brain retraction and therefore helps to minimize postoperative neurological dysfunction. This allows the surgeon greater oncological precision during the extirpative phase, with preservation of the functional and aesthetic units of the face for reconstruction.
Infratemporal approaches Infratemporal approaches [ITA] of Fisch [10] encompass three distinct variations for use in specific clinical situations. Type A approach provides exposure of jugular foramen and petrous internal carotid artery. This approach is used mainly for glomus jugulare tumours. Type B approach gives additional anterior exposure to reach lesions of the clivus such as chordomas, glomus tumour and meningiomas. Type C approach expands this access to include the parasellar region, cavernous sinus, and foramen rotundum and foramen lacerum. Removal of the pterygoid plates in this approach facilitates access to the nasopharynx. This Type C approach (Figs. 5a-d) is used in the resections of small nasopharyngeal carcinomas, adenoid cystic carcinomas and angiofibromas. All these variations involve mastoidectomy, facial nerve dissection and/or transposition and obliteration of middle ear cleft.
The lateral compartment of the middle cranial base and posterior cranial base are accessed via transtemporal or infratemporal routes.
The cranial base surgeon must be familiar with the advantages and limitations of each of these routes. For extensive lesions, it often becomes necessary to combine approaches.
Transtemporal approaches
RECONSTRUCTION
These include the trans-cochlear [7], translabyrinthine [8] and combined techniques. These are lateral, primarily extradural techniques that traverse the mastoid and petrous portions of the temporal bone to provide exposure of lesions at the petrous apex, clivus and cerebello-pontine angle (for lesions such as acoustic neuroma, petroclival meningioma and aggressive cholesteatoma). For malignant tumours involving the ear varying degree of Petrosectomy (resection of temporal bone) is carried out [9] (Figs. 4a-d).
After resecting the tumour, reconstruction of the cranial base defect, separating the brain from the microbes of the upper aerodigestive tract, is an important step to avoid the dreaded complication of CSF leak and meningitis. The first step is watertight closure of the dura either primarily or using a fascia lata graft. In smaller resections, reconstruction is accomplished by bringing the pericranial flap or temporalis muscle under the cranial defect. Closure of extensive resections usually necessitates the use of vascularised tissue like a microvascular flap. The most
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Fig. 2a. Post radiotherapy MRI of a 65 years old patient shows Ca of right maxillary sinus infiltrating the pterygoid muscles (yellow circle). Tumour was infiltrating the orbit as well.
Fig. 2c. After en-bloc removal of tumour using transfacial subcranial approach
Fig. 2b. After raising the upper and lower cheek flaps, mandible is divided at the angle.
Fig. 2d . Specimen containing ramus of mandible, maxilla, eye and the contents of infratemporal fossa [ITF] removed in toto.
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Fig. 3a. Sagittal section of MRI shows a tumour (Giant cell tumour), which has destroyed the clivus and filling the nasal cavity and reaching anterior, middle and posterior skullbase. Fig. 2e. Four years postop CT scan showing no recurrence. Yellow arrows showing the area of midface and ITF reconstructed using rectus abdominis microvascular flap.
Fig. 3b.Skin incision is strategically placed along the side of the nose and inferior fornix of conjunctiva. Osteotomies are made at specific sites in the maxilla to release it from the skull. Both maxillae are rotated like 'opening a book', maintaining the soft tissue attachment to preserve the vascularity. This 'Midfacial split' approach exposes central skullbase and both ITF widely.
Fig. 2f . Clinical photograph taken 5 years post surgery shows acceptable cosmesis. Apollo Medicine, Vol.1, December 2004
Fig. 3c. Postoperative photograph showing good cosmesis. No alteration in nasal breathing, mouth opening, chewing and occlusion.
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Fig 4a. Lines showing different levels of Petrosectomy lateral, subtotal and total Petrosectomy.
Fig 4d. Two years post surgery CT scan shows the extent of temporal bone resection (yellow arrow).
commonly used free flaps by our team are the rectus abdominis flap and anterolateral thigh flap. COMPLICATIONS Postoperative problems are usually related to fluid and electrolyte balance, brain swelling, delayed vascular occlusion, CSF leaks and most frequently difficulties arising as a consequence of cranial nerve palsies. CONCLUSION
Fig 4b. Post radiotherapy CT scan shows destroyed bony external auditory canal and mastoid air cells (yellow arrow).
Skull base surgery is a challenging and exciting new frontier in oncological surgery for patients who were previously considered inoperable and incurable. The prognosis is variable, with tumour-free survival rates ranging from 30% to 60%, depending on the tumour type, the degree of tumour extension and the approach used. Today, for most patients with skull base tumours, a return to normal or near-normal quality of life can be anticipated. REFERENCES 1. Linskey ME, Jungreis CA, Yonas H, et al. Stroke risk after abrupt internal carotid artery sacrifice: accuracy of preoperative assessment with balloon test occlusion and stable Xenon-enhanced CT. AJNR Am J Neuroradiol 1994; 15: 829-843. 2. Ketcham AS, Wilkins RH, Van Buren JM, Smith RR. A combined intracranial facial approach to the paranasal sinuses. Am J Surg 1963; 106: 698-703. 3. Donald PJ. Extended transfacial subcranial approach. In: Donald PJ, ed. Surgery of the Skull Base. Philadelphia: Lippincott-Raven Publishers 1998: 287-308. 4. Janecka IP. Facial translocation approach. In: Janecka IP, Tiedemann K, eds. Skullbase Surgery: Anatomy, Biology and Technology. Philadelphia: Lippincott-Raven Publishers 1997; 183-220.
Fig 4c. Intraoperative picture shows ICA, Jugular bulb and sigmoid sinus after subtotal Petrosectomy. 129
5. Catalano PJ, Biller HF. Extended osteoplastic Maxillotomy. Arch Otolaryngol Head Neck Surg. 1993; 119: 394-400. Apollo Medicine, Vol.1, December 2004
Theme Symposium
Fig 5a. 36 years old male had chemo-radiation fot nasopharyngeal carcinoma and it recurred. Coronal CT scan shows tumour (red arrows) in the nasopharynx and ITF reaching the skullbase. The tumour surrounds the internal carotid artery.
Fig 5c. Two years postoperative CT scan shows the resected area reconstructed with rectus abdominis microvascular flap (yellow arrows). No local recurrence.
Fig 5b. After subtotal Petrosectomy en-bloc resection of roof of nasopharynx, lateral wall of nasopharynx & Oropharynx, ICA, contents of ITF were done using Modified ITF type-C approach. Yellow arrowPosterior end of nasal septum; White arrow-Opposite side Eustachian tube orifice; Black arrow-ligated distal end of the ICA. 6. Wei WI, Lam KH, Sham JS. New approach to the nasopharynx: the maxillary swing approach. Head Neck. 1991; 13: 200-207. 7. House WF, Hitselberger WE. The Transcochlear approach to the skull base. Arch Otolaryngol Head Neck Surg 1976; 102: 334-342. 8. House WF. Translabyrinthine approach. In: House WF, Luetje CM, eds. Acoustic Tumours. Baltimore, University Park Press, 1979. 9. Curran AJ, Gullane PJ, Bance ML, Donald PJ. Temporal bone resection. In: Donald PJ, ed. Surgery of the Skull Base. Philadelphia, Lippincott-Raven Publishers 1998: 377-408. 10. Fisch U. Infratemporal fossa approach to tumours of the temporal bone and base of skull. J Laryngol Otol 1978; 92: 949-967. Apollo Medicine, Vol.1, December 2004
Fig 5d. Two years postoperative clinical photograph shows good cosmesis.
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SKULLBASE SURGERY C. Rayappa Consultant ENT– Head and Neck and Skullbase Surgeon, Apollo Speciality Hospital, Chennai, India. Correspondence to: Dr. C. Rayappa, AA-2, 3rd Main Road, Anna Nagar, Chennai-600 040, India. E-mail: [email protected] Key words: Skullbase Surgery Techniques.
THE greatest single advance during the last two decades in the field of oncologic surgery of the head and neck has been the development of skull base surgery. A variety of neoplastic and non-neoplastic lesions affect the base of the skull, and in the past these were considered beyond the scope of surgical management. Because of their inaccessible location, the complex regional anatomy, the difficulty of accurately defining the extent of the lesion radiologically, and the fear of causing life-threatening complications, these tumours were considered unresectable and the skull base was considered a “no man’s land”. In the past, the skull-base was the borderline, which separated the areas of work of the neurosurgeons and ENTHead and Neck surgeons. Today, the collaborative work of ENT surgeons, neurosurgeons and plastic surgeons have given rise to many innovative approaches to the skull-base for resecting these tumours as well as reconstruction of the complex defects created at the skullbase. A team consisting experts from various disciplines make these extensive surgeries possible and safe (Table 1).
Tumours of the cranial base arise from or are in the vicinity of bony structures at the base of the brain (Table 2). Despite their varied histology (Table 3) and biologic behavior, all these tumours have a common feature - they are difficult to reach and are close to critical structures. The base of the skull represents a transition area through which important blood vessels, like the internal carotid and vertebral arteries enter and cranial nerves exit. In addition, large venous sinuses draining blood from the brain confluence at the skull base as they exit the cranial vault. They are difficult to reach because they are located ventral to the brain and posterior to the facial skeletons and aerodigestive system. ANATOMY The cranial base is divided into 3 portions - anterior, middle and posterior - that correspond to the respective cranial fossae.
Advances in diagnostic imaging and microsurgery have contributed significantly toward the successful management of these difficult clinical problems.
Anterior cranial base is made up of frontal, ethmoid and sphenoid bones. Extracranially, it is related to the orbit, ethmoid sinus and nasal cavity. Intracranially it is related to the olfactory bulbs and frontal lobes.
Table 1: Skull base team.
Table 2: Site of origin of skull base tumours. Extracranial tissues Paranasal sinuses Pharynx Connective tissues Skull base bone and cartilage Chordoma Osteosarcoma Chondrosarcoma Intracranial tissues Meninges Blood vessels Cranial nerves Pituitary gland
ENT - Head & Neck Surgeon Neurosurgeon Microvascular Reconstructive Surgeon Neuroanaesthetist Neuroradiologist Intensivist Pathologist Radiation oncologist Prosthodontist Psychiatrist Nursing team Occupational therapist Physiotherapist
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(DSA), will give important information about tumour vascularity, feeder vessels and the state of the carotid arteries. Vascular tumour can be embolized before surgery to reduce blood loss.
Table 3: Skull base tumours. Histology and biological behaviour Anterior skull base tumours Angiofibroma Meningioma Olfactory Neuroblastoma Paranasal sinus malignancy Middle skull base tumours Meningioma Schwannoma (origin in V nerve) Clivus chordoma Angiofibroma Nasopharyngeal Ca (RT failure) Posterior skull base tumours Glomus jugulare Schwannoma of lower cranial nerves Meningioma
If the ICA is encased by tumour, abrupt internal carotid occlusion during surgery results in a stroke rate of 26% and a mortality rate of 12% [1]. Therefore, a balloon occlusion test is performed to assess the cross circulation through circle of Willis. If there is good cross circulation, permanent balloon occlusion is performed and the artery can be sacrificed. If there is no cross circulation, the patient will require bypass surgery. The fundamental problem in tumours involving the skull base is that access to these tumours is difficult. The principles that must be adhere to in embarking upon skull base surgery are: 1.
Middle cranial base is composed of the body and greater wings of the sphenoid and part of the temporal bones. Intracranially, it is related to pituitary gland, cavernous sinus and temporal lobes. The petrous temporal bone houses the middle and inner ear structures and the petrous segment of ICA. Extracranially, it is related to infratemporal fossae, which contain the masticatory and pharyngeal muscles, cranial nerves, internal carotid artery, external carotid artery, eustachian tube and a venous plexus that communicates with the cavernous sinus. Posterior cranial base is formed by the clivus in the middle and the posterior surface of the temporal bones on either side. Intracranially it is related to the brain stem and cerebellum. The facial and vestibulocochlear nerves enter the IAC. The jugular foramen is situated just caudal and lateral to the IAC and contains the jugular bulb and the glossopharyngeal, vagus and accessory nerves. The hypoglossal canal is immediately medial and rostral to the occipital condyles. Ventrally, the posterior cranial base is situated over the nasopharynx separated only by the mucosa and the constrictor muscles. IMAGING Modern imaging techniques have made it easier to diagnose and ‘visualize’ the site of a skullbase tumour and to plan management. CT scan remains the best tool, particularly in its ability to delineate bone destructions. MRI is considered superior for the evaluation of the soft tissue extent of the disease and for brain invasion. It gives a better image of the surrounding blood vessels and perineural spread of tumour. Formal angiography or digital subtraction angiography Apollo Medicine, Vol.1, December 2004
2.
One must obtain adequate exposure of the area of surgical resection. There should be minimal or no brain retraction.
The operative approaches for skull base surgery depend on the anatomic location and extent of invasion of disease process. The surgical approaches are therefore different for the anterior cranial fossa, middle cranial fossa and posterior cranial fossa and clivus regions. ANTERIOR CRANIAL FOSSA A variety of suggested techniques are available for craniofacial resections for tumours involving the anterior skull base. The individual technique employed varies with each surgeon and his personal preference. However, the standard surgical technique for resection of the anterior central skull base for malignant tumours of the ethmoid is described. The neurosurgeon makes a bicoronal incision, elevates a vascularised pericranial flap, bifrontal craniotomy and then elevates the dura off the skull base. The ENT surgeon makes a lateral rhinotomy incision and does en-bloc resection of the ethmoid, medial wall of maxilla, septum and the cranial base. The defect is covered with a pericranial flap (Figs. 1a-f) [2]. The extent of extracranial resection (e.g., maxilla, eye, etc.) depends on the extent of the tumour. MIDDLE CRANIAL FOSSA The extra cranial areas related to this are the nasopharynx, infratemporal fossa and pterygomaxillary fissure. Maxillary tumours extending posteriorly and invading the pterygoid muscles were considered inoperable in the past. These tumours are removed now-a-days
124
Theme Symposium
Fig. 1d. After en-bloc removal of the tumour containing skin, orbit, contents of temporal and ITF, subtotal petrosectomy, anterior and middle skullbase and dura. Fig 1a. 45-year-old patient with recurrent Ca following maxillectomy, radiotherapy and palliative chemotherapy.
Fig. 1e. 3-D reconstruction of postoperative CT scan shows the extent of bone removal. Fig. 1b. MRI shows the tumour infiltrating the orbit and dura (yellow arrow).
Fig. 1c. Coronal section MRI shows the tumour infiltrating the muscles of temporal and infratemporal fossa (yellow arrow).
Fig. 1f. Two years post surgery clinical photograph showing acceptable cosmesis. Resected area was reconstructed using anterolateral thigh microvascular flap.
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Apollo Medicine, Vol.1, December 2004
Theme Symposium
Key Messages •
Team approach.
•
Cerebral blood flow determination using temporary balloon occlusion test increases the safety of carotid resection or replacement in selected cases. Embolization of highly vascular tumours to reduce bleeding during surgery.
•
Tumours infiltrating the pterygoid muscles and ICA and recurrent nasopharyngeal carcinoma (which were considered inoperable in the past) can be resected safely using skull base surgical techniques.
•
Wide access can be gained to the middle region of the skull base through the facial translocation procedure, while still preserving the appearance and function of the face.
•
The primary short-term complications of the cranial base surgery are CSF leak, meningitis and cortical oedema.
•
The primary and most debilitating long-term complications of cranial base surgery are due to cranial nerve dysfunction, especially lower cranial nerve palsies (swallowing and vocal cord function)
•
Cranial base surgery offers the greatest benefit when performed as a primary therapeutic modality. Early diagnosis is essential.
using an extended transfacial subcranial approach (Figs. 2a-f) [3]. Tumours of the nasopharynx (e.g., nasopharyngeal carcinoma) and infratemporal fossa lie behind the maxilla and medial to the ramus of the mandible and facial nerve, preventing direct access for three-dimensional clearance. Craniofacial disassembly technique (facial translocation approach) (Figs. 3a-c) [4-6] is a systematic, stepwise dissection of facial soft tissues based on the knowledge of regional vascular territories and functional anatomy, followed by osteotomies and dismantling of the craniofacial skeleton. The maxilla is mobilized, like opening a book, and this can be done unilaterally or bilaterally. This exposes the nasopharynx, clivus and infratemporal fossa widely. Temporal craniotomy/craniectomy exposes the intracranial portions of the tumour. This reduces the need for brain retraction and therefore helps to minimize postoperative neurological dysfunction. This allows the surgeon greater oncological precision during the extirpative phase, with preservation of the functional and aesthetic units of the face for reconstruction.
Infratemporal approaches Infratemporal approaches [ITA] of Fisch [10] encompass three distinct variations for use in specific clinical situations. Type A approach provides exposure of jugular foramen and petrous internal carotid artery. This approach is used mainly for glomus jugulare tumours. Type B approach gives additional anterior exposure to reach lesions of the clivus such as chordomas, glomus tumour and meningiomas. Type C approach expands this access to include the parasellar region, cavernous sinus, and foramen rotundum and foramen lacerum. Removal of the pterygoid plates in this approach facilitates access to the nasopharynx. This Type C approach (Figs. 5a-d) is used in the resections of small nasopharyngeal carcinomas, adenoid cystic carcinomas and angiofibromas. All these variations involve mastoidectomy, facial nerve dissection and/or transposition and obliteration of middle ear cleft.
The lateral compartment of the middle cranial base and posterior cranial base are accessed via transtemporal or infratemporal routes.
The cranial base surgeon must be familiar with the advantages and limitations of each of these routes. For extensive lesions, it often becomes necessary to combine approaches.
Transtemporal approaches
RECONSTRUCTION
These include the trans-cochlear [7], translabyrinthine [8] and combined techniques. These are lateral, primarily extradural techniques that traverse the mastoid and petrous portions of the temporal bone to provide exposure of lesions at the petrous apex, clivus and cerebello-pontine angle (for lesions such as acoustic neuroma, petroclival meningioma and aggressive cholesteatoma). For malignant tumours involving the ear varying degree of Petrosectomy (resection of temporal bone) is carried out [9] (Figs. 4a-d).
After resecting the tumour, reconstruction of the cranial base defect, separating the brain from the microbes of the upper aerodigestive tract, is an important step to avoid the dreaded complication of CSF leak and meningitis. The first step is watertight closure of the dura either primarily or using a fascia lata graft. In smaller resections, reconstruction is accomplished by bringing the pericranial flap or temporalis muscle under the cranial defect. Closure of extensive resections usually necessitates the use of vascularised tissue like a microvascular flap. The most
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Fig. 2a. Post radiotherapy MRI of a 65 years old patient shows Ca of right maxillary sinus infiltrating the pterygoid muscles (yellow circle). Tumour was infiltrating the orbit as well.
Fig. 2c. After en-bloc removal of tumour using transfacial subcranial approach
Fig. 2b. After raising the upper and lower cheek flaps, mandible is divided at the angle.
Fig. 2d . Specimen containing ramus of mandible, maxilla, eye and the contents of infratemporal fossa [ITF] removed in toto.
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Theme Symposium
Fig. 3a. Sagittal section of MRI shows a tumour (Giant cell tumour), which has destroyed the clivus and filling the nasal cavity and reaching anterior, middle and posterior skullbase. Fig. 2e. Four years postop CT scan showing no recurrence. Yellow arrows showing the area of midface and ITF reconstructed using rectus abdominis microvascular flap.
Fig. 3b.Skin incision is strategically placed along the side of the nose and inferior fornix of conjunctiva. Osteotomies are made at specific sites in the maxilla to release it from the skull. Both maxillae are rotated like 'opening a book', maintaining the soft tissue attachment to preserve the vascularity. This 'Midfacial split' approach exposes central skullbase and both ITF widely.
Fig. 2f . Clinical photograph taken 5 years post surgery shows acceptable cosmesis. Apollo Medicine, Vol.1, December 2004
Fig. 3c. Postoperative photograph showing good cosmesis. No alteration in nasal breathing, mouth opening, chewing and occlusion.
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Fig 4a. Lines showing different levels of Petrosectomy lateral, subtotal and total Petrosectomy.
Fig 4d. Two years post surgery CT scan shows the extent of temporal bone resection (yellow arrow).
commonly used free flaps by our team are the rectus abdominis flap and anterolateral thigh flap. COMPLICATIONS Postoperative problems are usually related to fluid and electrolyte balance, brain swelling, delayed vascular occlusion, CSF leaks and most frequently difficulties arising as a consequence of cranial nerve palsies. CONCLUSION
Fig 4b. Post radiotherapy CT scan shows destroyed bony external auditory canal and mastoid air cells (yellow arrow).
Skull base surgery is a challenging and exciting new frontier in oncological surgery for patients who were previously considered inoperable and incurable. The prognosis is variable, with tumour-free survival rates ranging from 30% to 60%, depending on the tumour type, the degree of tumour extension and the approach used. Today, for most patients with skull base tumours, a return to normal or near-normal quality of life can be anticipated. REFERENCES 1. Linskey ME, Jungreis CA, Yonas H, et al. Stroke risk after abrupt internal carotid artery sacrifice: accuracy of preoperative assessment with balloon test occlusion and stable Xenon-enhanced CT. AJNR Am J Neuroradiol 1994; 15: 829-843. 2. Ketcham AS, Wilkins RH, Van Buren JM, Smith RR. A combined intracranial facial approach to the paranasal sinuses. Am J Surg 1963; 106: 698-703. 3. Donald PJ. Extended transfacial subcranial approach. In: Donald PJ, ed. Surgery of the Skull Base. Philadelphia: Lippincott-Raven Publishers 1998: 287-308. 4. Janecka IP. Facial translocation approach. In: Janecka IP, Tiedemann K, eds. Skullbase Surgery: Anatomy, Biology and Technology. Philadelphia: Lippincott-Raven Publishers 1997; 183-220.
Fig 4c. Intraoperative picture shows ICA, Jugular bulb and sigmoid sinus after subtotal Petrosectomy. 129
5. Catalano PJ, Biller HF. Extended osteoplastic Maxillotomy. Arch Otolaryngol Head Neck Surg. 1993; 119: 394-400. Apollo Medicine, Vol.1, December 2004
Theme Symposium
Fig 5a. 36 years old male had chemo-radiation fot nasopharyngeal carcinoma and it recurred. Coronal CT scan shows tumour (red arrows) in the nasopharynx and ITF reaching the skullbase. The tumour surrounds the internal carotid artery.
Fig 5c. Two years postoperative CT scan shows the resected area reconstructed with rectus abdominis microvascular flap (yellow arrows). No local recurrence.
Fig 5b. After subtotal Petrosectomy en-bloc resection of roof of nasopharynx, lateral wall of nasopharynx & Oropharynx, ICA, contents of ITF were done using Modified ITF type-C approach. Yellow arrowPosterior end of nasal septum; White arrow-Opposite side Eustachian tube orifice; Black arrow-ligated distal end of the ICA. 6. Wei WI, Lam KH, Sham JS. New approach to the nasopharynx: the maxillary swing approach. Head Neck. 1991; 13: 200-207. 7. House WF, Hitselberger WE. The Transcochlear approach to the skull base. Arch Otolaryngol Head Neck Surg 1976; 102: 334-342. 8. House WF. Translabyrinthine approach. In: House WF, Luetje CM, eds. Acoustic Tumours. Baltimore, University Park Press, 1979. 9. Curran AJ, Gullane PJ, Bance ML, Donald PJ. Temporal bone resection. In: Donald PJ, ed. Surgery of the Skull Base. Philadelphia, Lippincott-Raven Publishers 1998: 377-408. 10. Fisch U. Infratemporal fossa approach to tumours of the temporal bone and base of skull. J Laryngol Otol 1978; 92: 949-967. Apollo Medicine, Vol.1, December 2004
Fig 5d. Two years postoperative clinical photograph shows good cosmesis.
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