Acta Neurochirurgica, Supp\. 53, 166-170 (1991) © by Springer-Verlag 1991
The Petrosal Approach: Indications, Technique, and Results O. AI-Meftyl, S. Ayoubi2, and R. R. Smith 3 1 Division of Neurological Surgery, Loyola University Medical Center, Chicago, Illinois, U.s.A., 2 Hurstwood Park Neurological Center, Haywards Heath, U.K., 3Department of Neurosurgery, University of Mississippi Medical Center, Jackson, Mississippi, U.S.A.,
Summary
Operative Technique
Surgical access to the clivus and petrous apex remains a formidable challenge. Intradural tumours at the clivus and petroclival area are superbly exposed via the petrosal approach described here. To date, we have operated on 33 patients having benign tumours using this approach. Total removal was achieved in all patients except 3 with meningiomas. There was no mortality, morbidity included 1 patient with hemiparesis and several with cranial nerve deficits.
Positioning and Monitoring
Keywords: Petrosal approach; clivus; brain tumour; meningioma.
Introduction The petrosal approach is used for intradural tumours located in the clival and petroclival areas. It allows access to tumours extending from the suprasellar area and the cavernous sinus to as caudal as the foramen magnum. This approach is centered on the petrous ridge, analogous to the pterional approach, which is centered on the sphenoid ridge. This approach has evolved over the years. As early as 1904, Fraenkel and HuntS described a suboccipital-translabyrinthine approach to a cerebellopontine angle (CPA) tumour. Bailey 4 used a combined supratentorial-infra tentorial approach through a single bone flap with sectioning of the sigmoid sinus, which was reunited at the time of closure. Morrison and King 9 used a subtemporal and translabyrinthine approach, preserving the sigmoid sinus. Hakuba and his colleagues 6 preserved the labyrinth and used this approach for removing a clival meningioma. Our early experience using this approach for clival meningiomas 2 was very encouraging, inducing us to use it for a variety of intradural lesions at the clival and petroclival areas. Those cases are reported here.
The patient is placed supine on the operating table. The ipsilateral shoulder is elevated by placing a folded towel underneath it. The head and trunk are elevated 20 to 30°; the head is turned and tilted to the opposite side, inclined toward the floor, and fixed in a Mayfield headrest (Fig. 1). Brain stem auditory evoked potentials and median nerve somatosensory evoked potentials are recorded bilaterally. An electromyogram (EMG) is recorded from several facial muscle groups to locate the facial nerve and monitor its function on the operative side. Other cranial nerves are monitored as required. 0
Bone Removal
A reverse question mark incision is made, extending from the zygoma, circling above the ear, and descending 1 cm behind the mastoid process. The skin flap is raised to the level of the external auditory meatus. A large triangular pericranial flap is elevated, with its base at the base of the skin flap. This will be used at the time of closure to cover the drilled temporal bone. The temporal muscle is retracted anteriorly. The insertion of the sternomastoid muscle is detached from the mastoid bone and the muscle is retracted posteroinferiorly. At this stage, the mastoid and the temporal squama and the occipital bones are exposed. Located at the junction of the lambdoidal, occipital mastoid, and parietal mastoid sutures, the asterion is the key landmark in this area. Four burr holes are drilled. The first one is made just medial and inferior to the asterion; this opens into
The Petrosal Approach: Indications, Technique, and Results
Fig. 1. Artist's illustration of patient's position and the skin incision for a right-sided petrosal approach. EMG needle electrodes (arrows) are inserted in muscle group innervated by the facial nerve. Inset: Skull model depicting position of the burr holes and outlining the bone flap. (Reproduced with permission from AI-Mefty 0, Schenk MP, Smith RR (in press) Petroclival meningiomas. In: Wilkins RH, Rengachary SS (eds) Neurosurgical operative atlas. Williams & Wilkins, Baltimore)
the posterior fossa below the transverse sigmoid sinus junction. The second hole is made at the squamal and mastoid junctions of the temporal bone, along the projection of the superior temporal line. This opens into the supratentorial compartment. These two holes flank the sigmoid sinus. The third and fourth holes are made medial to the latter two holes on each side of the transverse sinus. With the foot attachment of a craniotome, the temporal bone and a portion of the occipital bone above the tentorium are incised between the supratentorial burr hole. The occipital bone below the tentorium is incised between the infratemporal burr holes. The foot attachment of the craniotome is not used to cross the sinus. The bone over the sinus is carefully drilled until the sinus is exposed between each of the burr holes flanking the sinus (Fig. 2). The single bone flap is then elevated and carefully separated from the sinus and the dura. The bone severely adheres to the sinus at the transverse sigmoid junction. A complete mastoidectomy is performed, using a diamond drill when working near vital structures. The sigmoid sinus is skeletonized down to the jugular bulb, exposing the dura on both sides of the sinus. The dura
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Fig. 2. Artist's illustration (right side): Surgeon's view: the temporal (TM) and sternomastoid muscles (SM) are elevated and retracted. A pericranial triangular flap (F) is elevated and saved for later covering of the drilled surface of the temporal bone. The position of the burr holes flanking the transverse sigmoid sinus is outlined. A craniotome with foot attachment (1) is used to make the bony cut in the temporal and posterior fossae, while a drill (2) is used to cross over the sinus. Inset: The bone flap has been removed, the dura of the temporal and posterior fossa are exposed, the right sigmoid sinus (SS) is skeletonized, and the petro us bone has been extensively drilled. The anatomical landmarks in the temporal bone (the facial canal and the semicircular canals) are demonstrated. (Reproduced with permission from AI-Mefty 0, Schenk MP, Smith RR (in press) Petroclival meningiomas. In: Wilkins RH, Rengachary SS (eds) Neurosurgical operative atlas. Williams & Wilkins, Baltimore)
anterior to the sigmoid sinus is exposed only enough to open and close the dura. The sinodural angle of Citelli, which identifies the position of the superior petrosal sinus, is exposed. The superficial mastoid cells behind the posterior wall of the external ear canal, as well as the deep retrofacial air cells, are resected to identify but not open the facial canal and the lateral and posterior semicircular canals. Drilling is continued along the pyramid to thin the petrous bone towards its apex. Open air cells are obliterated with bone wax. Opening the Dura and Incising the Tentorium
The supratentorial dura is opened on the floor of the temporal fossa. The posterior fossa dura anterior to the sigmoid sinus is opened along the anterior margin of the sinus, and the incision is extended toward the supratentorial incision. The superior
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Tumour Resection
Fig. 3. Artist's illustration (right side): Surgeon's view demonstrating exposure of the tumour via a pre-sigmoid sinus avenue. The sigmoid sinus (SS) and cerebellum (e) are retracted medially while the temporal lobe (T L) is retracted superiorly. The tentorium (T) is incised along the pyramid through the incisura. The brain stem, cranial nerves (III-XI), and tumour (Tu) are visualized. Inset: Demonstration of tentorial sectioning along the pyramid toward the incisura. (Reproduced with permission from AI-Mefty 0, Schenk MP, Smith RR (in press) Petroclival meningiomas. In: Wilkins RH, Rengachary SS (eds) Neurosurgical operative atlas. Williams & Wilkins, Baltimore)
petrosal sinus is clipped or coagulated and divided. The vein of Labbe is dissected off the cortical surface and preserved. The temporal lobe is gently retracted so that no tension will be placed on the dissected vein. The trochlear nerve is identified as the tentorium is incised parallel to the pyramid (Fig. 3 Inset). This incision is extended through the incisura, incising the tentorial notch at a point behind the area where the fourth nerve pierces the notch. When the tentorium is incised, the operative field opens to allow wide exposure of the upper pole of the tumour and the anterior and lateral aspects of the brain stem (Fig. 3). The trigeminal nerve rootlets, which are frequently stretched by the tumour, are identified under the tentorium. A retractor is placed anteriorly, retracting medially the sigmoid sinus, the cerebellum, and the cut edge of the tentorium. The arachnoid and cerebellomedullary cisterns are then opened, and cerebrospinal fluid (CSF) is drained to obtain further relaxation.
The tumour's insertion on the pyramid is coagulated, and the meningeal feeders over the tentorium are divided, reducing the blood supply to the tumour. In some cases, the petrous tip (anterior to the internal auditory meatus and medial to the carotid canal) is drilled away, facilitating tumour removal, particularly of the attachment of a meningioma. The seventh and eighth cranial nerves are usually posterior to a small tumour but may be engulfed by larger tumours. A suitable area on the surface of the tumour is coagulated and the arachnoid over the tumour is opened. The tumour is then debulked using suction, bipolar coagulation and microscissors, a laser or a Cavitron Ultrasonic Surgical Aspirator (CUSA, Cooper Medical Devices, Mountain View, California). This should be done carefully because the anterior (AICA) and posterior inferior (PICA) cerebellar arteries or the cranial nerves may be embedded in the tumour. Dissection must be maintained within the arachnoid plane to preserve vital neurovascular structures. The tumour capsule is dissected from surrounding structures within this plane. Cranial nerves and the basilar artery and its branches may be encased in the tumour, demanding meticulous dissection. Alternating the visual field between the supra- and infratentorial routes allows careful dissection of all cranial nerves and the brain stem. The abducens nerve is dissected from the tumour and is followed distally. With the assistance of stimulation and EMG recording to locate the facial nerve, the seventh and eighth nerves are dissected free. The lower cranial nerves are gently dissected from the inferior pole of the tumour to avoid hypotension and bradycardia from vagal stimulation. The basilar artery is usually displaced to the opposite side. The artery and its branches are carefully dissected from the tumour. Once the tumour is removed, its site of insertion is extensively vaporized with the laser. Extensions of the tumour into the internal auditory meatus or the jugular foramen are handled by drilling the bone to fully expose and remove the tumour. Closure
The temporal and presigmoid dura is closed watertight. The triangular pericranial flap raised at the start of surgery is turned over the drilled surface of the petro us bone to avoid CSF leakage, and secured with fibrin glue. The temporal muscle is rotated over the defect and sutured to the sternomastoid muscle and the soft tissues and skin are closed in layers.
The Petrosal Approach: Indications, Technique, and Results
169
(b) (a)
Fig. 4. MR images of a large epidermoid tumour with extensive supra- and infratentorial extensions, optimally managed through the petrosal approach. a) Preoperative axial view, b) postoperative axial view, c) preoperative sagittal view, d) postoperative sagittal view
Case Material
Discussion
Our series consists of 33 patients: 21 with meningiomas, 7 with schwan nom as, and 5 with epidermoid tumours. These were operated on during the years 1983 through 1989. There was no mortality. Total removal was achieved for all but 3 patients with meningiomas (Fig. 4). To date, there has been no recurrence in those having total removal. Because all the tumours in this series were slow-growing, the follow-up period is short. A longer follow-up is needed. Complications included hemiparesis and dysphasia from venous infarction of the temporal lobe in one patient, permanent facial nerve palsy in 2 patients, temporary facial nerve palsy in 3 patients, temporary lower cranial nerve palsy in 3 patients, loss of hearing in one patient, and decreased hearing in another. Hearing improved in one patient. Pulmonary embolism occurred in 5 patients, CSF leak in two, one of whom needed surgical repair, and a pseudo-meningocele, which subsided after spinal drainage, occurred in one.
Approaches to the posterior cranial base fall into 3 main categories l . Intradural approaches include the suboccipital, subtemporal, frontotemporal, and combined suboccipital and temporal approaches. Anterior extradural approaches include the transoral, transcervical, transsphenoidal, transethmoidal, transmaxillotomy, and trans basal approaches. Lateral approaches include the infratemporal, transcochlear, petrosal, and transtemporal. We found the petrosal approach as presented above to be superior for intradural tumours located in the c1ival and petroclival areas 3 . This approach has several
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advantages: the cerebellum and temporal lobes are minimally retracted, the operative distance to the clivus is shortened by 3 cm, the surgeon has a direct line of sight to the lesion and the anterior and lateral aspects of the brain stem, the neural and otological structures including the cochlea, the labyrinth and the facial nerves are preserved, the transverse and sigmoid sinuses as well as the vein of Labbe and the basal occipital veins are preserved, the tumour's blood supply is intercepted early in the procedure, multiple axes for dissection are provided, and dissection is performed along a longitudinal axis, alleviating the need for temporal lobe retraction. Coagulation of the vein of Labbe or the basilar occipital vein leads to temporal lobe venous infarction with potentially devastating neurological deficits. Malis 8 has emphasized ligation of the sigmoid sinus lateral to the entrance of the vein of Labbe to preserve venous flow through the other side. Our technique, however, preserves the sinus and avoids injury to the vein. To date, we have not found it necessary to ligate and section the sinus. In fact, we believe sigmoid sinus ligation should be avoided. A fatal outcome has been reported subsequent to sigmoid sinus ligation. 7 ,lo Furthermore, not infrequently, the dominant draining vein of the temporal lobe enters the sinus further laterally than its usual anatomic location, If a tear occurs in the sinus wall, it is repaired with sutures or a patch graft. In our series, reconstruction of the sinus with venous graft was carried out in one case in which the sinus was injured beyond repair. Because of the potential risk to the sinus, the venous anatomy should be delineated preoperatively with digital angiography,
confirming not only the patency of the opposite side, but the connection between the two sides at the torcula heropili. Acknowledgement The authors are grateful to Julie Hipp for her editorial assistance.
References 1. AI-Mefty 0 (1989) Surgery of the cranial base. Kluwer, Boston, pp 239-258 2. AI-Mefty 0, Fox JL, Smith RR (1988) Petrosal approach for petroclival meningiomas. Neurosurgery 22: 510-517 3. AI-Mefty 0, Schenk MP, Smith RR (1991) Petroclival meningiomas. In: Wilkins RH, Rengachary SS (eds) Neurosurgical operative atlas. Williams & Wilkins, Baltimore 4. Bailey P (1939) Concerning the technique of operation for acoustic neurinoma. Zentralbl Neurochir 4: 1-5 5. Fraenkel J, Hunt JR (1904) Contribution to the surgery of neurofibroma of the acoustic nerve. Ann Surg 40: 293-319 6. Hakuba A, Nishimura S, Tanaka K, Kishi H, Nakamura T (1977) Clivus meningioma: Six cases of total removal. Neurol Med Chir (Tokyo) 17: 63-77 7. Hitselberger WE, House WF (1966) A combined approach to the cerebellopontine angle. Arch Otolaryngol 84: 267-285 8. Malis LI (1985) Surgical resection of tumours of the skull base. In: Wilkins RH, Rengachary SS (eds) Neurosurgery, Vol 1. McGraw-Hili, New York, pp 1011-1021 9. Morrison AW, King TT (1973) Experiences with a translabyrinthine-transtentorial approach to the cerebellopontine angle: Technical note. J Neurosurg 38: 382-390 10. Symon L (1982) Surgical approaches to the tentorial hiatus. In: Krayenbiihl H et al (eds) Advances and technical standards in neurosurgery, Vol 9. Springer, Wien New York, pp 69-112 Correspondence: Prof. O. AI-Mefty, M.D., Division of Neurological Surgery, Loyola University Medical Center, 2160 S. First avenue, Maywood, Illinois 60153, U.S.A.
The Petrosal Approach: Indications, Technique, and Results O. AI-Meftyl, S. Ayoubi2, and R. R. Smith 3 1 Division of Neurological Surgery, Loyola University Medical Center, Chicago, Illinois, U.s.A., 2 Hurstwood Park Neurological Center, Haywards Heath, U.K., 3Department of Neurosurgery, University of Mississippi Medical Center, Jackson, Mississippi, U.S.A.,
Summary
Operative Technique
Surgical access to the clivus and petrous apex remains a formidable challenge. Intradural tumours at the clivus and petroclival area are superbly exposed via the petrosal approach described here. To date, we have operated on 33 patients having benign tumours using this approach. Total removal was achieved in all patients except 3 with meningiomas. There was no mortality, morbidity included 1 patient with hemiparesis and several with cranial nerve deficits.
Positioning and Monitoring
Keywords: Petrosal approach; clivus; brain tumour; meningioma.
Introduction The petrosal approach is used for intradural tumours located in the clival and petroclival areas. It allows access to tumours extending from the suprasellar area and the cavernous sinus to as caudal as the foramen magnum. This approach is centered on the petrous ridge, analogous to the pterional approach, which is centered on the sphenoid ridge. This approach has evolved over the years. As early as 1904, Fraenkel and HuntS described a suboccipital-translabyrinthine approach to a cerebellopontine angle (CPA) tumour. Bailey 4 used a combined supratentorial-infra tentorial approach through a single bone flap with sectioning of the sigmoid sinus, which was reunited at the time of closure. Morrison and King 9 used a subtemporal and translabyrinthine approach, preserving the sigmoid sinus. Hakuba and his colleagues 6 preserved the labyrinth and used this approach for removing a clival meningioma. Our early experience using this approach for clival meningiomas 2 was very encouraging, inducing us to use it for a variety of intradural lesions at the clival and petroclival areas. Those cases are reported here.
The patient is placed supine on the operating table. The ipsilateral shoulder is elevated by placing a folded towel underneath it. The head and trunk are elevated 20 to 30°; the head is turned and tilted to the opposite side, inclined toward the floor, and fixed in a Mayfield headrest (Fig. 1). Brain stem auditory evoked potentials and median nerve somatosensory evoked potentials are recorded bilaterally. An electromyogram (EMG) is recorded from several facial muscle groups to locate the facial nerve and monitor its function on the operative side. Other cranial nerves are monitored as required. 0
Bone Removal
A reverse question mark incision is made, extending from the zygoma, circling above the ear, and descending 1 cm behind the mastoid process. The skin flap is raised to the level of the external auditory meatus. A large triangular pericranial flap is elevated, with its base at the base of the skin flap. This will be used at the time of closure to cover the drilled temporal bone. The temporal muscle is retracted anteriorly. The insertion of the sternomastoid muscle is detached from the mastoid bone and the muscle is retracted posteroinferiorly. At this stage, the mastoid and the temporal squama and the occipital bones are exposed. Located at the junction of the lambdoidal, occipital mastoid, and parietal mastoid sutures, the asterion is the key landmark in this area. Four burr holes are drilled. The first one is made just medial and inferior to the asterion; this opens into
The Petrosal Approach: Indications, Technique, and Results
Fig. 1. Artist's illustration of patient's position and the skin incision for a right-sided petrosal approach. EMG needle electrodes (arrows) are inserted in muscle group innervated by the facial nerve. Inset: Skull model depicting position of the burr holes and outlining the bone flap. (Reproduced with permission from AI-Mefty 0, Schenk MP, Smith RR (in press) Petroclival meningiomas. In: Wilkins RH, Rengachary SS (eds) Neurosurgical operative atlas. Williams & Wilkins, Baltimore)
the posterior fossa below the transverse sigmoid sinus junction. The second hole is made at the squamal and mastoid junctions of the temporal bone, along the projection of the superior temporal line. This opens into the supratentorial compartment. These two holes flank the sigmoid sinus. The third and fourth holes are made medial to the latter two holes on each side of the transverse sinus. With the foot attachment of a craniotome, the temporal bone and a portion of the occipital bone above the tentorium are incised between the supratentorial burr hole. The occipital bone below the tentorium is incised between the infratemporal burr holes. The foot attachment of the craniotome is not used to cross the sinus. The bone over the sinus is carefully drilled until the sinus is exposed between each of the burr holes flanking the sinus (Fig. 2). The single bone flap is then elevated and carefully separated from the sinus and the dura. The bone severely adheres to the sinus at the transverse sigmoid junction. A complete mastoidectomy is performed, using a diamond drill when working near vital structures. The sigmoid sinus is skeletonized down to the jugular bulb, exposing the dura on both sides of the sinus. The dura
167
Fig. 2. Artist's illustration (right side): Surgeon's view: the temporal (TM) and sternomastoid muscles (SM) are elevated and retracted. A pericranial triangular flap (F) is elevated and saved for later covering of the drilled surface of the temporal bone. The position of the burr holes flanking the transverse sigmoid sinus is outlined. A craniotome with foot attachment (1) is used to make the bony cut in the temporal and posterior fossae, while a drill (2) is used to cross over the sinus. Inset: The bone flap has been removed, the dura of the temporal and posterior fossa are exposed, the right sigmoid sinus (SS) is skeletonized, and the petro us bone has been extensively drilled. The anatomical landmarks in the temporal bone (the facial canal and the semicircular canals) are demonstrated. (Reproduced with permission from AI-Mefty 0, Schenk MP, Smith RR (in press) Petroclival meningiomas. In: Wilkins RH, Rengachary SS (eds) Neurosurgical operative atlas. Williams & Wilkins, Baltimore)
anterior to the sigmoid sinus is exposed only enough to open and close the dura. The sinodural angle of Citelli, which identifies the position of the superior petrosal sinus, is exposed. The superficial mastoid cells behind the posterior wall of the external ear canal, as well as the deep retrofacial air cells, are resected to identify but not open the facial canal and the lateral and posterior semicircular canals. Drilling is continued along the pyramid to thin the petrous bone towards its apex. Open air cells are obliterated with bone wax. Opening the Dura and Incising the Tentorium
The supratentorial dura is opened on the floor of the temporal fossa. The posterior fossa dura anterior to the sigmoid sinus is opened along the anterior margin of the sinus, and the incision is extended toward the supratentorial incision. The superior
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Tumour Resection
Fig. 3. Artist's illustration (right side): Surgeon's view demonstrating exposure of the tumour via a pre-sigmoid sinus avenue. The sigmoid sinus (SS) and cerebellum (e) are retracted medially while the temporal lobe (T L) is retracted superiorly. The tentorium (T) is incised along the pyramid through the incisura. The brain stem, cranial nerves (III-XI), and tumour (Tu) are visualized. Inset: Demonstration of tentorial sectioning along the pyramid toward the incisura. (Reproduced with permission from AI-Mefty 0, Schenk MP, Smith RR (in press) Petroclival meningiomas. In: Wilkins RH, Rengachary SS (eds) Neurosurgical operative atlas. Williams & Wilkins, Baltimore)
petrosal sinus is clipped or coagulated and divided. The vein of Labbe is dissected off the cortical surface and preserved. The temporal lobe is gently retracted so that no tension will be placed on the dissected vein. The trochlear nerve is identified as the tentorium is incised parallel to the pyramid (Fig. 3 Inset). This incision is extended through the incisura, incising the tentorial notch at a point behind the area where the fourth nerve pierces the notch. When the tentorium is incised, the operative field opens to allow wide exposure of the upper pole of the tumour and the anterior and lateral aspects of the brain stem (Fig. 3). The trigeminal nerve rootlets, which are frequently stretched by the tumour, are identified under the tentorium. A retractor is placed anteriorly, retracting medially the sigmoid sinus, the cerebellum, and the cut edge of the tentorium. The arachnoid and cerebellomedullary cisterns are then opened, and cerebrospinal fluid (CSF) is drained to obtain further relaxation.
The tumour's insertion on the pyramid is coagulated, and the meningeal feeders over the tentorium are divided, reducing the blood supply to the tumour. In some cases, the petrous tip (anterior to the internal auditory meatus and medial to the carotid canal) is drilled away, facilitating tumour removal, particularly of the attachment of a meningioma. The seventh and eighth cranial nerves are usually posterior to a small tumour but may be engulfed by larger tumours. A suitable area on the surface of the tumour is coagulated and the arachnoid over the tumour is opened. The tumour is then debulked using suction, bipolar coagulation and microscissors, a laser or a Cavitron Ultrasonic Surgical Aspirator (CUSA, Cooper Medical Devices, Mountain View, California). This should be done carefully because the anterior (AICA) and posterior inferior (PICA) cerebellar arteries or the cranial nerves may be embedded in the tumour. Dissection must be maintained within the arachnoid plane to preserve vital neurovascular structures. The tumour capsule is dissected from surrounding structures within this plane. Cranial nerves and the basilar artery and its branches may be encased in the tumour, demanding meticulous dissection. Alternating the visual field between the supra- and infratentorial routes allows careful dissection of all cranial nerves and the brain stem. The abducens nerve is dissected from the tumour and is followed distally. With the assistance of stimulation and EMG recording to locate the facial nerve, the seventh and eighth nerves are dissected free. The lower cranial nerves are gently dissected from the inferior pole of the tumour to avoid hypotension and bradycardia from vagal stimulation. The basilar artery is usually displaced to the opposite side. The artery and its branches are carefully dissected from the tumour. Once the tumour is removed, its site of insertion is extensively vaporized with the laser. Extensions of the tumour into the internal auditory meatus or the jugular foramen are handled by drilling the bone to fully expose and remove the tumour. Closure
The temporal and presigmoid dura is closed watertight. The triangular pericranial flap raised at the start of surgery is turned over the drilled surface of the petro us bone to avoid CSF leakage, and secured with fibrin glue. The temporal muscle is rotated over the defect and sutured to the sternomastoid muscle and the soft tissues and skin are closed in layers.
The Petrosal Approach: Indications, Technique, and Results
169
(b) (a)
Fig. 4. MR images of a large epidermoid tumour with extensive supra- and infratentorial extensions, optimally managed through the petrosal approach. a) Preoperative axial view, b) postoperative axial view, c) preoperative sagittal view, d) postoperative sagittal view
Case Material
Discussion
Our series consists of 33 patients: 21 with meningiomas, 7 with schwan nom as, and 5 with epidermoid tumours. These were operated on during the years 1983 through 1989. There was no mortality. Total removal was achieved for all but 3 patients with meningiomas (Fig. 4). To date, there has been no recurrence in those having total removal. Because all the tumours in this series were slow-growing, the follow-up period is short. A longer follow-up is needed. Complications included hemiparesis and dysphasia from venous infarction of the temporal lobe in one patient, permanent facial nerve palsy in 2 patients, temporary facial nerve palsy in 3 patients, temporary lower cranial nerve palsy in 3 patients, loss of hearing in one patient, and decreased hearing in another. Hearing improved in one patient. Pulmonary embolism occurred in 5 patients, CSF leak in two, one of whom needed surgical repair, and a pseudo-meningocele, which subsided after spinal drainage, occurred in one.
Approaches to the posterior cranial base fall into 3 main categories l . Intradural approaches include the suboccipital, subtemporal, frontotemporal, and combined suboccipital and temporal approaches. Anterior extradural approaches include the transoral, transcervical, transsphenoidal, transethmoidal, transmaxillotomy, and trans basal approaches. Lateral approaches include the infratemporal, transcochlear, petrosal, and transtemporal. We found the petrosal approach as presented above to be superior for intradural tumours located in the c1ival and petroclival areas 3 . This approach has several
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O. AI-Mefty et at.: The Petrosal Approach: Indications, Technique, and Results
advantages: the cerebellum and temporal lobes are minimally retracted, the operative distance to the clivus is shortened by 3 cm, the surgeon has a direct line of sight to the lesion and the anterior and lateral aspects of the brain stem, the neural and otological structures including the cochlea, the labyrinth and the facial nerves are preserved, the transverse and sigmoid sinuses as well as the vein of Labbe and the basal occipital veins are preserved, the tumour's blood supply is intercepted early in the procedure, multiple axes for dissection are provided, and dissection is performed along a longitudinal axis, alleviating the need for temporal lobe retraction. Coagulation of the vein of Labbe or the basilar occipital vein leads to temporal lobe venous infarction with potentially devastating neurological deficits. Malis 8 has emphasized ligation of the sigmoid sinus lateral to the entrance of the vein of Labbe to preserve venous flow through the other side. Our technique, however, preserves the sinus and avoids injury to the vein. To date, we have not found it necessary to ligate and section the sinus. In fact, we believe sigmoid sinus ligation should be avoided. A fatal outcome has been reported subsequent to sigmoid sinus ligation. 7 ,lo Furthermore, not infrequently, the dominant draining vein of the temporal lobe enters the sinus further laterally than its usual anatomic location, If a tear occurs in the sinus wall, it is repaired with sutures or a patch graft. In our series, reconstruction of the sinus with venous graft was carried out in one case in which the sinus was injured beyond repair. Because of the potential risk to the sinus, the venous anatomy should be delineated preoperatively with digital angiography,
confirming not only the patency of the opposite side, but the connection between the two sides at the torcula heropili. Acknowledgement The authors are grateful to Julie Hipp for her editorial assistance.
References 1. AI-Mefty 0 (1989) Surgery of the cranial base. Kluwer, Boston, pp 239-258 2. AI-Mefty 0, Fox JL, Smith RR (1988) Petrosal approach for petroclival meningiomas. Neurosurgery 22: 510-517 3. AI-Mefty 0, Schenk MP, Smith RR (1991) Petroclival meningiomas. In: Wilkins RH, Rengachary SS (eds) Neurosurgical operative atlas. Williams & Wilkins, Baltimore 4. Bailey P (1939) Concerning the technique of operation for acoustic neurinoma. Zentralbl Neurochir 4: 1-5 5. Fraenkel J, Hunt JR (1904) Contribution to the surgery of neurofibroma of the acoustic nerve. Ann Surg 40: 293-319 6. Hakuba A, Nishimura S, Tanaka K, Kishi H, Nakamura T (1977) Clivus meningioma: Six cases of total removal. Neurol Med Chir (Tokyo) 17: 63-77 7. Hitselberger WE, House WF (1966) A combined approach to the cerebellopontine angle. Arch Otolaryngol 84: 267-285 8. Malis LI (1985) Surgical resection of tumours of the skull base. In: Wilkins RH, Rengachary SS (eds) Neurosurgery, Vol 1. McGraw-Hili, New York, pp 1011-1021 9. Morrison AW, King TT (1973) Experiences with a translabyrinthine-transtentorial approach to the cerebellopontine angle: Technical note. J Neurosurg 38: 382-390 10. Symon L (1982) Surgical approaches to the tentorial hiatus. In: Krayenbiihl H et al (eds) Advances and technical standards in neurosurgery, Vol 9. Springer, Wien New York, pp 69-112 Correspondence: Prof. O. AI-Mefty, M.D., Division of Neurological Surgery, Loyola University Medical Center, 2160 S. First avenue, Maywood, Illinois 60153, U.S.A.
