Transotic Approach

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Chapter 51 Transotic Approach

Ugo Fisch, Joseph M. Chen

The transotic approach to the cerebellopontine angle (CPA) was first introduced in 1979 by one of us (U.F.) in response to the limitations of the translabyrinthine technique. The objective of this approach is to obtain a direct lateral exposure and the widest possible access to the CPA through the medial wall of the temporal bone, from the superior petrosal sinus to the jugular bulb, and from the internal carotid artery to the sigmoid sinus. The tympanic and mastoid portions of the fallopian canal are left in situ. This transtemporal access is achieved at the expense of bony exenteration, rather than cerebellar retraction.

Despite well-documented technical details,1 there is a general misconception equating the transotic approach with the transcochlear approach of House and Hitselberger.2 Significant differences exist between the two approaches in the extent of exposure, the management of the facial nerve, and the obliteration of the surgical cavity. As a natural extension of subtotal petrosectomy, which forms the basis of lateral and posterior skull base surgery at the University of Zurich,1 the transotic approach was initially designed for acoustic neuromas and has since expanded to include other pathology. Several modifications were also made over the years to optimize its use.3–5

INDICATIONS

Acoustic Neuroma

Although the transotic approach, similar to the translabyrinthine approach, can be used for tumors of all sizes, it is ideal for tumors 2.5 cm or less in their mediolateral extent, in patients with no serviceable hearing. In this clinical setting, the transotic approach offers the best possible exposure for tumor extirpation and preservation of facial nerve with minimal morbidity.

At the University of Zurich, tumors larger than 2.5 cm that cause significant brainstem compression are managed by the neurosurgery department as a matter of departmental policy. Small intracanalicular tumors in patients with good hearing (using the 50/50 rule of at least 50 dB hearing loss and 50% discrimination score) are managed through a middle cranial fossa (transtemporal-supralabyrinthine) approach (see Chapter 35).

Other Lesions

Other lesions involving the CPA or the temporal bone with invasion of the internal auditory canal (IAC) or the otic capsule could also be approached via the transotic technique. These lesions include the following:

• Epithelial cysts (congenital cholesteatoma)
• Arachnoid cysts
• Hemangiomas
• Giant cholesterol and mucosal cysts
• Jugular foramen schwannomas
• Temporal paragangliomas (glomus tumors)

These lesions can be quite extensive and may require a combined infratemporal fossa type A or B approach for added exposure.

PREOPERATIVE EVALUATION

The evaluation for retrocochlear lesions, such as acoustic neuromas, is standard at the University of Zurich and includes routine audiometry, auditory brainstem response, electronystagmography, and magnetic resonance imaging (MRI) with gadolinium enhancement. High-resolution computed tomography (CT) is still performed for bony assessment of lesions within or invading the temporal bone. Facial nerve status is recorded clinically using the Fisch grading system6 and quantified by electroneuronography before surgery.

In addition to a candid discussion of surgical and postoperative complications, patients are informed of the advantages of the transotic approach specifically with regard to the preservation of the facial nerve and the complete obliteration of the surgical cavity, with blind sac closure of the external auditory canal to minimize cerebrospinal fluid (CSF) leak. The option of conservative management by close monitoring with serial MRI to follow tumor growth is presented to all patients and is recommended for patients with nonprogressive long-standing symptoms (especially elderly patients), patients with small tumors and normal hearing, patients with significant medical illnesses, or patients who refuse to undergo surgery. These patients are told that rapid tumor growth ultimately requires surgical attention, and that facial nerve function and hearing preservation may be compromised as a result of the delay in surgery.

SURGICAL TECHNIQUE

Preoperative Preparation

The patient is premedicated with clonidine, metoclopramide, and midazolam before surgery. A perioperative antibiotic, ceftriaxone (Rocephin), 2 g intravenously for 24 hours, is given at the time of surgery until the removal of intravenous infusion, usually by the 3rd day after surgery.

Surgical Site Preparation, Positioning, and Draping

The surgical site is prepared in the operating room after induction of anesthesia. Hair over the temporal area is shaved 9 cm above and 5 cm behind the pinna. The skin is washed with povidone-iodine. The abdomen and the contralateral leg are also shaved and prepared for fat harvesting and the possible need of a sural nerve graft.

The positioning and draping for this procedure are similar to positioning and draping described in Chapter 1, with some minor differences. The patient is secured in supine position on the Fisch operating table (see Chapter 35), with the head turned away from the surgeon. A large plastic bag is incorporated into the draping to catch excess irrigation and blood.

Intraoperative Monitoring and Concerns

Intraoperative facial nerve monitoring using the Xomed nerve integrity monitor (NIM-II) and percutaneous electromyography needles is standard with this approach. Intracranial pressure is controlled by deep anesthesia induced intravenously before introduction of inhalational anesthetics. Partial pressure of carbon dioxide is maintained at 30 to 40 mm Hg. Pharmacologic manipulation with dexamethasone (Decadron), 4 mg every 8 hours perioperatively and 4 days postoperatively, and mannitol, 0.5 mg/kg intravenously intraoperatively, is also standard. Furosemide is added when necessary. Lumbar CSF drainage is not routinely performed. Hypotensive anesthesia with nitroglycerin or clonidine (Catapres), or both, is used in most cases to maintain a systolic blood pressure of 80 to 100 mm Hg.

Skin Incision

A postauricular incision is placed along the hairline to keep it behind the operative cavity (Fig. 51-1). The incision is made from the mastoid tip to the temporal region for the surgical approach; its superior extension is made at the time of wound closure for the exposure of the temporalis muscle flap.

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FIGURE 51-1 Skin incision.

FIGURE 51-2. A and B, Blind sac closure of external auditory canal.

FIGURE 51-3. Subtotal petrosectomy. EAC, external auditory canal.

FIGURE 51-4. Position of internal auditory canal in relation to anterior and posterior compartments of operative cavity.

Blind Sac Closure of External Auditory Canal

A mastoid periosteal flap is developed while the postauricular skin flap is elevated. The external auditory canal is transected, and its skin is elevated, everted externally, and closed as a blind sac. A second layer of closure using the mastoid periosteal flap ensures a complete seal (Fig. 51-2).

Subtotal Petrosectomy: Exposure of Jugular Bulb and Petrous Carotid

A complete mastoidectomy is performed, and the remaining external auditory canal skin, tympanic membrane, and ossicles are removed in a stepwise fashion. The tympanic bone is progressively thinned out, and a complete exenteration of the pneumatic spaces (retrofacial, retrolabyrinthine, supralabyrinthine, hypotympanic, infralabyrinthine, and pericarotid) is carried out. Figure 51-3 shows the surgical cavity at the completion of this step. The middle fossa dura, sigmoid sinus, and jugular bulb are blue-lined; the fallopian canal and the vertical portion of the petrous carotid artery are skeletonized. The mastoid tip is removed to reduce the depth of the surgical cavity.

Obliteration of Eustachian Tube

The mucosa of the membranous eustachian tube orifice is coagulated, and the bony canal is obliterated with bone wax at the isthmus. An additional muscle plug is used before closure.

Exenteration of Otic Capsule

With the completion of subtotal petrosectomy, the surgical cavity is divided into two compartments by the fallopian canal (Fig. 51-4). Because the enlarged IAC lies mostly deep within the anterior compartment, the advantage of the transotic approach to access this region fully is clear.

To begin this step, the semicircular canals are removed, and the vestibule is opened as in the translabyrinthine approach. The posterior aspect of the IAC is exposed from the fundus to the porus, leaving a thin layer of bone over the meatal dura. The posterior fossa dura of the posterior compartment is exposed caudal to the superior petrosal sinus and anterior to the sigmoid sinus. Retrofacial cells are subsequently removed to gain access over the inferior aspect of the IAC.

Attention is now focused on the anterior compartment. The cochlea is drilled away to expose the enlarged IAC, which lies predominantly within this compartment, and as the dissection is carried forward, the dura anterior to the porus is also exposed to the level of the vertical segment of the ICA. Bony reduction between the jugular bulb and the inferior aspect of the IAC requires working beneath and over the fallopian canal, which is left in its anatomic position across the surgical field. Sufficient bone is left surrounding the canal to prevent accidental fracture. The cochlear aqueduct is identified between the jugular bulb and the IAC. The arachnoid of the aqueduct is opened to allow the outflow of CSF, decompressing the lateral cistern before the posterior fossa dura is opened. The tensor tympani muscle and bone medial to it are removed to gain more anterior access; likewise, bone medial to the vertical carotid artery is removed as much as possible.

Unroofing of Labyrinthine Portion of Facial Nerve

Since 1988, the unroofing of the labyrinthine segment of the facial nerve from the meatal foramen to the geniculate ganglion has been incorporated as a standard step in the transotic approach. The meatal foramen can be found approximately 2 mm anterior and superior to the meatal fundus. This exposure provides additional room for the portion of the facial nerve most likely to sustain traction injury and edema subsequent to tumor manipulation. Also, the labyrinthine portion of the facial nerve serves as an important landmark while further access over the porus is gained along the superior petrosal sinus.

The completed exposure is shown in Figure 51-5. The posterior fossa dura surrounding the porus is circumferentially exposed from the carotid artery to the sigmoid sinus, and from the jugular bulb to the level of the superior petrosal sinus.

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FIGURE 51-5 A and B, Exposure of internal auditory canal and posterior fossa dura.

FIGURE 51-6. Intrameatal tumor dissection.

Tumor Removal

A few instruments are required for tumor removal. Bayonet and angled bipolar forceps, cup forceps, microraspatories, and a long suction with finger control are the most essential instruments. The intrameatal portion of the tumor is approached first and is separated from the facial nerve until the level of the porus. Figure 51-6 illustrates the advantage of the additional space obtained with the transotic exenteration, whereby the intrameatal portion of the tumor can be easily displaced and mobilized during its removal.

The posterior fossa dura is incised between the sinodural angle and the posterior edge of the porus. The incision is extended superiorly and inferiorly along the porus (Fig. 51-7). It is important to elevate the dura with a hook before making an incision to prevent the inadvertent injury of vessels over the cerebellum. The dural edges must be cauterized before extending the incision to facilitate hemostasis. One must also be acutely aware of the variations of the course of the anterior inferior cerebellar artery (AICA) and its branches.

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FIGURE 51-7 Dural incisions. CSF, cerebrospinal fluid; PFD, posterior fossa dura.

FIGURE 51-8. Initial cerebellopontine angle (CPA) exposure. AICA, anterior inferior cerebellar artery.

FIGURE 51-9. Intracapsular tumor reduction.

FIGURE 51-10. Intracranial facial nerve dissection. AICA, anterior inferior cerebellar artery.

FIGURE 51-11. View of cerebellopontine angle after tumor removal. AICA, anterior inferior cerebellar artery.

The superior and inferior dural flaps are retracted with 4-0 polyglactin 910 (Vicryl) sutures, which are clipped to the wound edges (Fig. 51-8). The full extent of the tumor usually can be shown. The posterior pole of the tumor abuts against the cerebellum and the petrosal vein, and the AICA courses anteroinferior to the tumor.

Intracapsular reduction of the tumor can now begin and is continued until tumor margins can be seen without tension being placed on the facial nerve. During this step, the meatal dura at the superior pole of the porus is not detached to render some stability to the tumor. It is crucial to handle the tumor meticulously; manipulations should be carried out with suction over a Cottonoid, and the displaced facial nerve should always be in view to avoid undue traction (Fig. 51-9).

Bleeding is diminished by coagulation of all visible vessels over the tumor capsule. The main blood supply to the tumor generally runs along CN VIII, and some may come from branches of the AICA. These vessels should be coagulated, cut on the tumor, and gently pulled away.

With sufficient reduction, separation of the facial nerve can now be attempted. The advantage of the transotic approach is now easily appreciated because the displaced facial nerve can be followed in its entirety. The dural attachments of the tumor at the porus are cut, and the nerve can be gently grasped with bipolar forceps and teased away from the tumor (Fig. 51-10). Likewise, the AICA can be separated from the nerve by using the tips of the forceps or by pulling on the coagulated branches.

At the inferior pole of the tumor, the origin of CN VIII and the course of the AICA looping around it are identified. In many instances, the root exit zone of the facial nerve, always anterior to CN VIII, is identified only after CN VIII is cut. The anterior access of the transotic approach offers an unparalleled view to an area that is usually partially hidden from the surgeon during suboccipital or translabyrinthine surgery.7,8 In this exact region, the facial nerve is most tenuous and frequently appears as a thin, transparent band. Any manipulation not under direct vision can easily rupture the nerve. When it is completely detached from all vital structures, the tumor can now be removed. The CPA and all its structures are exposed in Figure 51-11.

The facial nerve is stimulated electrically to obtain a threshold response. Despite a normal response intraoperatively, the patient may still show an immediate or delayed facial paralysis because of impaired vascular supply and the inevitable trauma to the nerve during dissection. If stimulation fails to produce a response or facial contraction, and if the anatomic integrity of the nerve is precarious, it is best to proceed with nerve grafting immediately. Failure to do so while waiting for the improbable return of facial function may delay reinnervation for 2 years. The details of intracranial/intratemporal and hypoglossal/facial crossover grafting techniques are beyond the scope of this chapter and are discussed elsewhere.1,9

Wound Closure

A musculofascial graft that is slightly larger than the dural defect is taken from the temporalis muscle. It is placed under the dura and fixed in place with the two 4-0 Vicryl sutures used previously as stay sutures (Fig. 51-12). These sutures are passed through the edges of the graft and secured to the dura. A second temporalis fascial graft is used to cover the opened IAC. A small muscle graft is also used as a plug to supplement the prior wax obliteration of the eustachian tube. Both grafts are stabilized with fibrin glue.

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FIGURE 51-12 Dural closure. IAM, internal auditory meatus.

FIGURE 51-13. Fat obliteration of surgical cavity.

FIGURE 51-14. Temporalis muscle flap. SCM, Sternocleidomastoid.

FIGURE 51-15. Cross-sectional views of transotic approach versus translabyrinthine approach. AN, acoustic neuroma; C, carotid; CER, cerebellum; CVN, cochleovestibular nerve; EAM, external auditory meatus; FN, facial nerve; ME, middle ear; SS, sigmoid sinus.

A second layer of closure with abdominal fat grafts is to follow. A large piece of fat is first passed under the fallopian canal and firmly anchored (Fig. 51-13). Several small pieces of fat are used to fill out the surgical cavity and are stabilized with fibrin glue.

The posterior half of the temporalis muscle is now transposed and sutured in place with 2-0 Vicryl sutures. Additional fat is placed under the muscle flap to create a slight compressive tension (Fig. 51-14). This type of closure has consistently minimized the incidence of postoperative CSF leaks, which is another advantage of the transotic approach. A small plastic suction drain is inserted over the muscle flap while the skin incision is closed in two layers with 2-0 polyglycolic acid (Dexon) and 3-0 nylon sutures.

DRESSING AND POSTOPERATIVE CARE

The suction drain is removed as soon as a compression dressing is applied. The dressing is left in place for 5 days, and if there is any evidence of CSF leak or subcutaneous CSF accumulation, the compression dressing is reapplied.

The patient is transferred to the postanesthesia care unit extubated and fully awake. Routine and neurologic vital signs are closely monitored every 30 to 60 minutes. Adequate analgesics and antiemetics are ordered to keep the patient comfortably at bed rest, usually for 72 hours after surgery. Ambulation and oral intake are started slowly thereafter. Subcutaneous heparin is often given during the early convalescent period. An oral antibiotic, trimethoprim and sulfamethoxazole (Bactrim Forte) or ciprofloxacin (Ciproxin), is prescribed for at least 5 days after intravenous fluid and ceftriaxone therapy are discontinued. Head and abdominal wound sutures are removed on day 12, and leg sutures are removed after 2 weeks. The patient is discharged from the hospital at this time, barring any complication.

TIPS AND PITFALLS

The transotic approach is more than a combination of the translabyrinthine and transcochlear approaches. It uses the complete infralabyrinthine compartment of the temporal bone, from the carotid artery to the sigmoid sinus, and from the jugular bulb to the superior petrosal sinus. It provides the largest possible transtemporal access to the CPA, which can be best appreciated by comparing the cross-sectional surgical exposure of the transotic approach with the translabyrinthine approach shown in Figure 51-15.

The preservation of the facial nerve in its anatomic position within the fallopian canal does not limit the visibility or illumination. Enough bone must be kept surrounding the canal initially during subtotal petrosectomy and subsequently while the otic capsule is exenterated. Skeletonization of the fallopian canal must be done progressively as the surgical cavity enlarges, and with only diamond burrs. Bone surrounding the proximal tympanic segment of the facial nerve and the superior aspect of the IAC should be left intact to support the facial nerve.

If the fallopian canal is inadvertently fractured during dissection, it is likely to remain undisplaced and not to impede surgery. If no significant torsion or traction has occurred, no major adverse effects should result, provided that no further manipulation occurs. The fractured edges can be supported with fibrin glue, and at the time of closure, abdominal fat adequately renders support from beneath. If the fracture is displaced and unstable, a small, malleable aluminum strip can be used as a retractor and can maintain the fallopian canal in position. If this is impossible, the nerve may have to be fully unroofed and transposed anteriorly as in the infratemporal fossa type A approach. This situation has not occurred in our hands, however. The three fundamental principles for the removal of acoustic neuromas are as follows:

1. Perform intracapsular reduction of the tumor to gain better visibility progressively around the circumference of the tumor
2. Expose tumor from lateral to medial, coagulate all visible vessels over the tumor capsule, and remove the devascularized portion in a piecemeal fashion
3. Separate the facial nerve from the tumor and not vice versa

CSF outflow after the opening of the cochlear aqueduct decompresses the lateral cistern before the dural incision is made. It also indicates that the pars nervosa of the jugular foramen and the lower cranial nerves have not yet been reached by the tumor.

Even in the presence of a high jugular bulb, a few millimeters of exposure can be obtained between it and the IAC to allow adequate access to the inferior pole of the tumor. Unroofing and compressing the jugular bulb to gain more exposure are unnecessary and dangerous. If access to the CPA is severely limited by the jugular bulb, the facial nerve can be unroofed and transposed anteriorly, as in the infratemporal fossa type A approach.

Bony exenteration to expose the posterior fossa dura should be done in a stepwise manner, gaining as much exposure of the posterior fossa dura around the porus as possible. The time spent in the initial bony exenteration may be tedious at first, but it is well rewarded by much expanded access and improved illumination, which facilitate tumor removal dramatically.

The dura should not be opened until all bony work has been completed, and hemostasis has been perfectly controlled. While incising the dura, the surgeons should beware of the AICA, which may loop underneath, and make the initial cut in the center of the exposure to avoid this artery, which usually lies in the inferior half of the CPA. Intracapsular reduction of the tumor is performed while it is still attached to the meatal dura at the superior pole of the porus to prevent excessive traction on the facial nerve. It also stabilizes the tumor during reduction. The major blood supply of acoustic tumors runs along CN VIII; one should always check for vessels on the undersurface of the tumor before removal. The most delicate portion of the facial nerve is just proximal to the acoustic porus, where the nerve can be flattened to a thin transparent band. It is most frequently pushed anteriorly and superiorly. The surgeon must keep an eye on this area while working deeper in the CPA.

If the facial nerve appears to be significantly traumatized and cannot be stimulated at the end of surgery, one must proceed directly to an intracranial-intratemporal grafting or CN XII-VII cross-innervation procedure, depending on the clinical setting. Spontaneous return of function with conservative treatment is not likely to occur. Posterior fossa dura should not be resected to gain exposure; the dural edges are retracted with stay sutures. One should not forget to obliterate the eustachian tube with bone wax and a muscle plug to prevent CSF rhinorrhea. Fat graft anchored under the fallopian canal supports the musculofascial repair and prevents lateralization of these autogenous tissues.

RESULTS

Between 1979 and 1990, 147 consecutive transotic approaches were performed for the removal of unilateral acoustic neuromas by the senior author (U.F.). Tumors in this series were limited in size from 1 to 2.5 cm in mediolateral extension. Tumors may fill the lateral cistern, abutting but without significantly compressing the brainstem.

Complete tumor removal was achieved in all cases. Optimal visualization of the facial nerve was obtained, and the anatomic preservation of the nerve was possible in 139 cases (94.6%). In eight cases in which facial nerve integrity could not be preserved, intracranial-intratemporal nerve grafting resulted in an average of 66% return of facial function by the Fisch facial nerve grading system (or House-Brackmann grade III or better), during a mean follow-up of 4 years.

In this series, 66 patients were available for follow-up of at least 2 years. Tumors 1 to 1.4 cm were removed with no incidence of permanent facial injury, and 80% of patients with tumors 1.5 to 2.5 cm had normal or near-normal facial function (Table 51-1). Since 1988, the unroofing of the labyrinthine portion of the facial nerve has been a standard step in the transotic approach, which is believed to be a major contributing factor in the diminished incidence of delayed facial palsy in acoustic neuroma surgery.

TABLE 51-1 Facial Function Two Years Postoperatively

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COMPLICATIONS AND MANAGEMENT

The obliteration of the surgical cavity and eustachian tube, along with the blind sac closure of the external auditory canal, has significantly reduced the incidence of CSF leak. In the series mentioned earlier, 4% of patients developed a subcutaneous CSF collection without leakage, and the collections usually resolved within 3 to 4 weeks with conservative management, including bed rest and prolonged compressive dressing over the surgical site.

Three patients (4%) developed either immediate or delayed CSF leaks and were treated with lumbar drainage and bed rest; only one required surgical revision. One patient had meningitis and responded to antibiotic treatment without sequelae. Most notably is the lack of any other central nervous system complication in this series. One death occurred as a result of postoperative pulmonary embolism and cardiorespiratory failure. Wound infection with necrosis of the abdominal fat graft or temporalis muscle flap was a rare complication and was thought to be the inciting cause in the case of meningitis.

ALTERNATIVE TECHNIQUES

When and how acoustic neuromas should be operated on are issues of ongoing and often emotional debates. If surgery is contemplated, the aim is to try to obtain the safest and best possible exposure that would allow complete tumor extirpation and the preservation of facial nerve. Hearing preservation is of secondary concern if the opposite ear is functional.

Translabyrinthine and suboccipital approaches are perhaps the most established and popular techniques, whereas the middle fossa approach has traditionally been reserved for small tumors in patients with serviceable hearing; an extended version of the middle fossa approach has gained popularity in some centers to remove tumors measuring 4.5 cm10,11 despite a seemingly high morbidity.12 The relative efficacy of each of these approaches is difficult to quantify without a randomized multi-institutional study.

Our own experience with the translabyrinthine removal of acoustic neuromas before 1979 was unsatisfactory in many respects, and the problems were subsequently rectified with the transotic approach.1 There are three advantages of the transotic approach over the translabyrinthine approach, as follows:

1. A wider surgical access with a near-circumferential exposure of the IAC and the porus acusticus; this added exposure is particularly important in the presence of a high-riding jugular bulb and an anteriorly positioned sigmoid sinus
2. The direct visualization and access to the anterior CPA where the facial nerve is most tenuous and vulnerable
3. A much reduced rate of CSF leakage as a result of permanent closure of the ear canal and eustachian tube and complete obliteration of the surgical cavity

REFERENCES

1. Fisch U., Mattox D. Microsurgery of the Skull Base. New York: Thieme Publishers; 1988.

2. House W.F., Hitselberger W.E. The transcochlear approach to the skull base. Arch Otolaryngol Head Neck Surg. 1976;102:334-342.

3. Jenkins H.A., Fisch U. The transotic approach to resection of difficult acoustic tumors of the cerebellopontine angle. Am J Otol. 1980;2:70-76.

4. Gantz B.J., Fisch U. Modified transotic approach to the cerebellopontine angle. Arch Otolaryngol Head Neck Surg. 1983;109:252-256.

5. Chen J.M., Fisch U. The transotic approach in acoustic neuroma surgery. J Otolaryngol. 1993;22:331-336.

6. Burres S., Fisch U. The comparison of facial grading systems. Arch Otolaryngol Head Neck Surg. 1986;112:755-758.

7. Whittaker C.K., Leutje C.M. Translabyrinthine removal of large acoustic neuromas. Am J Otol. 1985;7(Suppl):155-160.

8. Gardner G., Robertson J.H. Transtemporal approaches to the cranial cavity. Am J Otol. 1985;7(Suppl):114-120.

9. Fisch U., Lanser M.J. Facial nerve grafting. Otolaryngol Clin North Am. 1991;24:691-708.

10. Wigand M.E., Haid T. Extended middle cranial fossa approach for acoustic neuroma surgery. Skull Base Surg. 1991;1:183-187.

11. Kanzaki J., Ogawa K., Yamamoto M., et al. Results of acoustic neuroma surgery by the extended middle cranial fossa approach. Acta Otolaryngol Suppl (Stockh). 1991;487:17-21.

12. Kanzaki J., Ogawa K., Tsuchihashi N., et al. Postoperative complications in acoustic neuroma surgery by the extended middle cranial fossa approach. Acta Otolaryngol Suppl (Stockh). 1991;487:75-79.

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