Middle Cranial Fossa-Vestibular Neurectomy

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Chapter 35 Middle Cranial Fossa—Vestibular Neurectomy

The treatment of Meniere’s disease continues to evoke controversy, as evidenced by a multitude of treatment modalities and their claims of efficacy. Medical management in an attempt to alter or stall the course of this condition has proved ineffective, with the exception of symptomatic relief of vertiginous attacks with the use of pharmacologic agents. In recent years, in light of the questionable efficacy of endolymphatic sac operation and the undesirable sequelae of myriad ablative procedures, vestibular neurectomy has been accepted as the most effective means to manage recalcitrant and disabling Meniere’s disease.

With either the middle fossa or the posterior fossa approach, ablation of vestibular functions and vertigo is reported to be 85% to 99%,¹^–⁴ greatly exceeding the results of other treatment protocols. Technical difficulties have been cited by many authors as the major reason for abandoning the middle cranial fossa approach in favor of a predominantly neurosurgical approach from the posterior, especially as collaborative efforts between otoneurology and neurosurgery increase. Many centers in Europe and South America continue to use the middle fossa approach, however, with great success.³^–⁶

The middle cranial fossa vestibular neurectomy performed at the University of Zurich is also known as the transtemporal-supralabyrinthine approach. In contrast to the middle fossa approach of House,⁷ which involves significant elevation of the middle fossa dura and retraction of the temporal lobe, the transtemporal-supralabyrinthine access to the internal auditory canal (IAC) is gained through bony reduction, with only minimal retraction of the dura.

PATIENT SELECTION

Patients with unilateral Meniere’s disease who have incapacitating attacks of vertigo of at least 6 months’ duration despite maximal medical therapy are candidates for vestibular neurectomy. These patients usually have residual and fluctuant hearing. Patients with severe to profound hearing loss and extremely poor speech discrimination are better managed by translabyrinthine cochleovestibular neurectomy. The severity of the vertiginous attacks indicative of surgical management is subjective, and depends more on the patient’s functional capacity than on the frequency of attacks.

In bilateral Meniere’s disease, surgery could still be contemplated if a dominant side can be identified. Four patients at the University of Zurich underwent bilateral vestibular neurectomies in stages (separated by at least 1 year after good vestibular compensation); postoperative vestibular compensation was shorter and easier after the second operation. These patients have remained symptom-free for 16 to 20 years since surgery. Patients with Meniere’s disease suitable for a vestibular neurectomy account for approximately 10% of the whole group.

Unilateral peripheral vertigo without the full spectrum of Meniere’s disease may also benefit from vestibular neurectomy.⁸ In these patients, it is important to confirm the side of pathology with vestibular function tests if there is no hearing loss to provide a lateralizing sign. Other indications for vestibular neurectomy are rare. Labyrinthine trauma with residual hearing and disabling vertigo after successful stapedectomy with good hearing could be considered. Contraindications of surgery include an only hearing ear, signs of central vestibular dysfunction, and poor medical condition. Age older than 70 years is a relative contraindication subject to individual assessment.

PREOPERATIVE EVALUATION AND COUNSELING

Before surgery, the patient generally undergoes a full auditory-vestibular evaluation that includes full audiometry, electronystagmography, and auditory brainstem response. Electrocochleography and dehydration tests are not part of the test battery performed at the University of Zurich. A high-resolution computed tomography (CT) scan and magnetic resonance imaging (MRI) are obtained to rule out a cerebellopontine angle lesion, and to determine perilabyrinthine pneumatization. A Stenvers view is routinely obtained to show the contours of the floor of the middle cranial fossa and the relationship of the meatal plane and superior semicircular canal (SCC) with respect to the arcuate eminence. Immunologic evaluation is obtained if autoimmune disorders or significant allergies are suspected. Immunologic evaluation is not a standard part of the test battery.

Patients are usually referred from other otologists and have been managed conservatively for a prolonged period without relief. They are made aware of the efficacy of vestibular neurectomy and its related complications, particularly complications pertaining to hearing and facial nerve.

PREOPERATIVE MEDICATION

The patient is premedicated with clonidine, metoclopramide, and midazolam before surgery. A perioperative antibiotic, ceftriaxone (Rocephin), 2 g intravenously for 24 hours, is started at the time of surgery and continued for the duration of the intravenous infusion, usually for 5 days.

SURGICAL SITE PREPARATION, POSITIONING, AND DRAPING

The surgical site is prepared in the operating room after the induction of anesthesia. Hair over the temporal region is shaved 9 cm above and 5 cm behind the pinna. The skin is washed with povidone-iodine (Betadine). The patient is secured on the Fisch operating table (Fig. 35-1) in supine position with the head turned to the side. Draping is standard except for a large-reservoir plastic bag, which is at the head of the table to catch excess irrigation fluid and blood.

FIGURE 35-1 Fisch table.

(From Fisch U, Mattox DE: Microsurgery of the Skull Base. New York, Thieme, 1988, p 17.)

INTRAOPERATIVE MONITORING AND ANESTHETIC CONCERNS

Intraoperative facial nerve monitoring using the Xomed nerve integrity monitor with percutaneous electromyography needles is standard. Unipolar and bipolar stimulating forceps are available. Intracranial pressure is controlled by deep anesthesia induced intravenously before introducing inhalation anesthetic. The partial pressure of carbon dioxide is maintained between 30 mm Hg and 40 mm Hg. Pharmacologic manipulation with dexamethasone (Decadron), 4 mg every 8 hours perioperatively for 4 days, and mannitol, 0.5 mg/kg intravenously intraoperatively, are also standard. Furosemide is added when necessary. Lumbar cerebrospinal fluid 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 between 80 mm Hg and 90 mm Hg.

SPECIAL INSTRUMENTS

1. Fisch operating table (Contraves/Zeiss): Motorized table with the center of rotation at the temporal bone, allowing easy remote control for optimal positional changes that can be operated by the scrub nurse or the anesthesiologist (see Fig. 35-1)

2. Articulated middle fossa retractor (Fischer-13-18-200): Self-retaining retractor that allows adjustments in the angle of retraction, tilting, and sideways shifting of the retractor blade (Fig. 35-2)

3. Temporalis muscle retractor (Fischer-13-18-200): Strong, self-retaining retractor with a wide opening span, essential for the exposure of the zygomatic root (Fig. 35-3)

4. Angled microraspatory (Fischer-13-18-308 [left], 13-18-306 [right]): Specially designed to facilitate dural elevation; its shoulder retracts the dura away, and the tip is used to separate dural attachments to bone (Fig. 35-4)

FIGURE 35-2 Middle fossa retractor. (From Fisch U, Mattox DE: Microsurgery of the Skull Base. New York, Thieme, 1988, p 426.)

FIGURE 35-3. Temporal muscle retractor. (From Fisch U, Mattox DE: Microsurgery of the Skull Base. New York, Thieme, 1988, p 426.)

FIGURE 35-4. Angled raspatory. (From Fisch U, Mattox DE: Microsurgery of the Skull Base. New York, Thieme, 1988, p 427.)

FIGURE 35-5. A, Middle cranial fossa (MCF) topography. B and C, Correct (B) and incorrect (C) approaches.

(Redrawn from Fisch U, Mattox DE: Microsurgery of the Skull Base. New York, Thieme, 1988, p 430.)

SURGICAL TECHNIQUE

The objective of the transtemporal-supralabyrinthine approach for vestibular neurectomy is to gain access to the IAC through the exenteration of the supralabyrinthine bone, while dural elevation and retraction are limited to no more than 1.5 cm (Fig. 35-5).

Skin Incision

A preauricular incision is made from approximately the lower edge of the zygomatic root and extended to the temporal area at an angle for about 7 cm (Fig. 35-6). The depth of the incision is made to the temporalis fascia, and branches of the superficial temporal artery are divided and clamped. Retraction of the skin edges is provided by securing arterial clamps to the drapes.

FIGURE 35-6 Skin incision.

FIGURE 35-7. A and B, Muscle flaps.

FIGURE 35-8. Craniotomy.

Temporal Muscle Flap

After some undermining, the temporalis muscle is well exposed with a self-retaining retractor. Five muscle flaps (Fig. 35-7) are developed, elevated from the temporal squama, and retracted away with stay sutures. The temporal squama should be exposed from the root of the zygoma to the parietosquamous suture line. A temporalis muscle retractor should be used for the inferior exposure, where the identification of the zygomatic root is essential in the accurate positioning of the craniotomy.

Craniotomy

A 2 × 3 cm craniotomy (Fig. 35-8) is made perpendicular to, and at least 1 cm above, the temporal line, centered over the zygomatic root. This craniotomy is performed with a 5 mm cutting burr on a straight handpiece, and when dura is blue-lined, a 4 mm diamond burr is used. Care is taken to avoid injuring the dura and branches of the middle meningeal artery, which usually cross the undersurface of the bone flap in its midportion, but could be variable.

The bone flap is elevated from the dura with a dura raspatory and is kept in Ringer’s solution for later use. The dura is elevated from the edges of the craniotomy to facilitate the placement of the middle fossa retractor. In the region of the middle meningeal arterial branches, this step must be done with care. Sharp edges are removed with a small rongeur to prevent dural laceration. The craniotomy is extended inferiorly toward the zygomatic arch to the floor of the middle cranial fossa. Lateral extensions of 1 cm on each side provide better visibility for the next step (Fig. 35-9).

FIGURE 35-9 A and B, Craniotomy extension.

FIGURE 35-10. Cerebrospinal fluid decompression.

FIGURE 35-11. A and B, Dural elevation.

Dural Elevation

Dural elevation is performed with the microscope. It is perhaps the most delicate part of the operation; if it is not done properly, troublesome hemorrhage can occur. It is important to keep the dural elevation to a minimum and to avoid the region of the middle meningeal artery anteriorly, where significant vascular channels between dura and cranium can be found around the foramen spinosum.

In addition to pharmacologic reduction of the intracranial pressure with mannitol and dexamethasone, cerebrospinal fluid decompression through a small dural incision facilitates dural elevation further; this should be done by first coagulating a small central portion of the dura and then elevating this area with a hook before making an incision (Fig. 35-10). With the use of a curved suction and angled microraspatory, dural elevation is performed from posteriorly forward. Vascular channels are coagulated and cut close to bone. Persistent bleeding from bone can be controlled by drilling over it with a diamond burr. Oozing from dural vessels at the corners can be controlled with oxidized cellulose (Oxycel) packed beneath a Cottonoid. The dural attachment to the petrosquamous suture is also coagulated and cut.

Exposure of the Meatal Plane and Arcuate Eminence

Dural elevation is extended to the superior petrosal sulcus and over the arcuate eminence. Moving anteriorly, the meatal plane is reached; this is an area bound by the arcuate eminence, superior petrosal sulcus, and facial hiatus (Fig. 35-11). When the meatal plane is not well defined because of a flat arcuate eminence, it can be identified after blue-lining the superior SCC. If the attachment of the greater superficial petrosal nerve limits the exposure of the meatal plane, it can be separated from dura gently to avoid traction injury of the facial nerve. Meticulous hemostasis in this region is important, and direct coagulation is avoided because of the proximity of the facial nerve.

Introduction of the Middle Cranial Fossa Retractor

The middle cranial fossa retractor can be introduced at this point without the use of a microscope. The self-retaining jaws are firmly attached to the edges of the craniotomy first; the multidirectional stage is slid over the self-retaining portion and loosely placed. The dura is retracted with a suction to reveal the meatal plane to allow the accurate placement of the retractor blade, which is positioned parallel to the superior petrosal sulcus, its tip just beyond the arcuate eminence (Fig. 35-12). When the desired position is attained, screws on the multidirectional stage are tightened. Fine adjustments subsequently are done under the microscope.

FIGURE 35-12 Retractor in position.

FIGURE 35-13. Blue-lining superior semicircular canal (SCC).

FIGURE 35-14. A and B, Medial internal auditory canal (IAC) exposure.

FIGURE 35-15. Lateral internal auditory canal exposure.

Bony Exenteration and Blue Lining of the Superior Semicircular Canal

The operating table is now placed in Trendelenburg position to visualize better the area over the retractor blade. Bone posterior and lateral to the arcuate eminence is removed with a cutting burr (5 mm), enabling wider access for the final exposure and the progressive identification of the superior SCC. Because of the variable relationship of the superior SCC to the arcuate eminence, its identification is best accomplished from a posterolateral approach through the pneumatic cells; the yellow compact bone of the SCC can be readily exposed. To blue-line the SCC, removal of bone should be done with small diamond burrs (2.3 mm, 3.1 mm, 4.0 mm) in a wide rotatory fashion (Fig. 35-13).

Exposure of the Internal Auditory Canal

When the blue-line of the superior SCC is identified, using a 60-degree angle centered over the superior canal ampulla, the area of the meatal plane overlying the IAC can be defined. If the surgeon stays within this angle, there is no danger of damaging the facial nerve or the basal turn of the cochlea. The initial drilling is focused over the meatal plane, staying as close as possible to the blue-lined SCC. The axis of the drill is directed medioinferiorly, toward the superior lip of the porus and the medial roof of the IAC. These areas are progressively thinned out, until they are blue-lined (Fig. 35-14). The lateral exposure of the IAC involves the removal of bone over the meatal fundus and tegmen tympani (Fig. 35-15). This small triangular area is bordered by the ampulla of the superior SCC, and the facial nerve in its labyrinthine and tympanic portions; only 3 mm separates the superior ampulla from the genu of the facial nerve. The tegmen is opened if necessary to expose the malleus head and incus for better orientation. Bone over the meatal foramen and the distal superior vestibular nerve (SVN) is removed to identify the vertical crest (Bill’s bar), which gives the fundus its inverted-W shape. If this is not well defined, the SVN proximal to the ampulla should be exposed. The meatal foramen of the facial nerve should not be unroofed to avoid facial nerve injury.

At least one third of the upper circumference of the IAC must be exposed to perform a vestibular neurectomy properly. In particular, the posterior edge of the meatal roof deep in front of the superior SCC must be removed to expose the SVN adequately.

Vestibular Neurectomy

When the IAC is unroofed from the fundus to the porus, dura over the SVN is opened with a 1 mm hook. The nerve is identified and cut sharply with a neurectomy knife distal to the vestibular crest (Fig. 35-16). Avulsion of the SVN with a hook is discouraged because of the high incidence of deafness associated with this maneuver as a result of either traction or vascular injury to the cochlear nerve.

FIGURE 35-16 A-D, Superior vestibular nerve (SVN) section. IVN, inferior vestibular nerve.

The meatal dura is incised along the posterior edge toward the porus. The cut end of the SVN is retracted with a microsuction to expose the saccular and singular branches of the inferior vestibular nerve, which are sectioned with a neurectomy knife. The entire vestibular nerve is stabilized with the suction while the vestibulofacial anastomoses are cut sharply with a neurectomy scissor. The vestibular nerve is now everted with Scarpa’s ganglion in full view, which is slightly darker and has a pronounced vascular pattern over it. The vessels are coagulated, and the nerve is resected proximal to the ganglion with neurectomy scissors (Fig. 35-17). The facial nerve should be exposed only partially, retaining most of its dural cover for protection. The cochlear nerve is hidden beneath the facial nerve and need not be exposed.

FIGURE 35-17 A and B, Vestibular neurectomy.

FIGURE 35-18. Bone flap reconstruction.

FIGURE 35-19. Dural suspension.

FIGURE 35-20. Muscle closure.

Repair of the Floor of the Middle Cranial Fossa

The IAC is covered with a free muscle plug and stabilized with fibrin glue. The tegmen defect is reconstructed with the thinner half of the craniotomy bone flap (wrapped in a gauze and fractured with a rongeur). This bony fragment usually straddles the tegmen defect perfectly, and is fixed in position with fibrin glue (Fig. 35-18). The middle fossa retractor is now removed.

Wound Closure

The dura is elevated with a dural hook and suspended to the adjacent temporalis muscle with 4-0 polyglactin 910 (Vicryl) sutures (Fig. 35-19). This action obliterates the dead space between dura and bone, and prevents the formation of an epidural hematoma. The supralabyrinthine cavity is obliterated with the long, anteriorly based muscle flap (No. 1), which is sutured to its opposing flap (No. 5). The craniotomy bone flap is placed over the upper bony defect, and the remaining muscle flaps are sutured over it (Fig. 35-20). A single 3 mm suction drain is placed over the temporalis muscle and brought out through a separate stab incision posteriorly. The skin is closed in two layers with 2-0 catgut and 3-0 nylon sutures.

DRESSING AND POSTOPERATIVE CARE

A compression dressing based over the surgical site is applied after skin closure and is left for 5 days. The patient is kept in the postanesthesia care unit for at least 24 hours after surgery, with close monitoring of routine and neurologic vital signs every 30 to 60 minutes. Adequate analgesics and antiemetics are ordered to keep the patient comfortably at bed rest. Ambulation and oral intake are started slowly in 2 or 3 days. Subcutaneous heparin is often given in the early convalescent period.

Intravenous antibiotic (ceftriaxone) is discontinued when the patient no longer requires intravenous infusion. Oral sulfamethoxazole and trimethoprim (Bactrim Forte) or ciprofloxacin (Ciproxin) is prescribed for at least 5 days. The drain is removed when the daily drainage is less than 10 mL, and scalp sutures are removed after 10 days.

TIPS AND PITFALLS

• The root of the zygoma must be well identified to guide the placement of the craniotomy accurately. The craniotomy should be perpendicular to the temporal line, its width not exceeding 2 cm, because of the limited opening span of the middle fossa retractor.

• The floor of the middle fossa is usually at the level of the temporal line.

• The elevation of the dura should not exceed 1 cm. The necessary access is gained by removing bone at the floor of the middle fossa.

• If the arcuate eminence is not prominent (flattened middle fossa), the dura should be elevated in the area where it is anticipated, that is, in line with the external auditory canal. The pneumatic cells are removed posterior to this region to identify the superior SCC.

• The meatal plane should be identified before the retractor is placed. It is often more medial than expected, and may be hidden by a shelf of bone.

• The blue-lined superior SCC is the only essential landmark for the identification of the IAC, but the surgeon should not hesitate to open the tegmen tympani to identify the malleus and incus or the tympanic portion of the facial nerve if more landmarks are needed.

• Adequate exposure of the IAC requires lowering of bone between the superior ampulla and the geniculum of the facial nerve (genicular crest). This procedure must be performed with the utmost care.

• When attempting to identify the blue-line of the IAC, the surgeon must work medially toward the porus, rather than laterally to avoid injuring the labyrinthine segment.

• The vertical crest (Bill’s bar) should be clearly identified by thinning the bone over the meatal foramen. The meatal dura should not be opened before the completion of bone removal because the pressure of the cerebrospinal fluid suspends the facial and vestibular nerves against the dura and facilitates identification.

• The intrameatal facial nerve often appears to impinge on and partially cover the SVN. The posterior roof of the IAC close to the superior SCC must be removed to expose adequately and identify the cleavage plane between the nerves for the subsequent neurectomy.

• The surgeon should always cut the vestibular nerve with a neurectomy knife, rather than avulse the nerves with a hook. This prevents inadvertent traction on the cochlear nerve and its vascular supply, resulting in deafness.

• One should look for a loop of the anterior inferior cerebellar artery before cutting the nerve close to the porus.

• Lateral suspension of the dura decreases the dead space and prevents epidural hematoma formation.

• To avoid perforation, overzealous blue-lining of the superior SCC and its ampulla is discouraged. If perforation does occur, the area of opening should be immediately covered with a piece of fascia, with bone dust pâté or wax applied over it, and stabilized with fibrin glue.

• The basal turn of the cochlea should not be encountered if the “60 rule” (see Fig. 35-14) is followed. One must be cautious, however, when a change of color is observed in the bone while working anteriorly within the 60 degree angle. Working deep in the bone without an adequate view around the tip of the burr can be avoided by removing the lateral bone overhang between the superior ampulla, labyrinthine, and tympanic segments of the facial nerve.

RESULTS

Follow-up of 3 to 15 years was available in 281 vestibular neurectomy patients operated on at the University of Zurich from 1967 to 1988.⁸ Of these, 218 of the operations were for Meniere’s disease, including four patients who underwent staged operations for bilateral disease, and 63 operations were for other forms of peripheral vestibular disorder. The success rate of transtemporal vestibular neurectomy to alleviate intractable vertigo was 98.2% for patients with Meniere’s disease, and 96.8% for patients with peripheral vestibular disorder.

In 61% of the patients with Meniere’s disease, evidence suggests a stabilizing effect of the surgery on residual hearing. An initial hearing improvement of more than 15 dB was seen in 12% of patients, with some improvement lasting 7 years, but invariably hearing deterioration ensued. Although difficult to explain, this hearing improvement could be due to (1) the division of cochlear efferents traveling with the vestibular nerve, (2) the reduction in the rate of endolymph production resulting from the devascularization and destruction of the dark cell areas, or (3) a change in the parasympathetic innervation of the inner ear subsequent to the sectioning of the olivocochlear bundle in the vestibulofacial anastomosis.⁹

COMPLICATIONS

Vestibular compensation usually takes a few weeks, and most patients return to work in a few months. Twenty percent of patients complain of a mild, transient dizziness after rapid head movements in the first postoperative year. Two percent experience incomplete vestibular compensation and continue to experience disabling vertigo.

Complications specifically associated with this approach include a sensorineural hearing loss in 2%. This complication is most likely a result of traction injury of the cochlear nerve and unrecognized perforation of the SCC. Transient facial paresis is seen in 3.2% of cases and occurs 5 to 7 days after surgery. Recovery is expected within 1 to 3 months. Transient cerebrospinal fluid rhinorrhea during the first 5 to 7 days occurs in 6% of patients, all successfully treated with conservative measures. One case of epidural hematoma was noted and required evacuation with no sequela. No meningitis, temporal lobe epilepsy, or atrophy was associated with this technique.

ALTERNATIVE TECHNIQUES

The indication for endolymphatic sac surgery seems to be hearing preservation only in patients with early-stage disease. The long-term results at the University of Zurich have been as disappointing as the results reported by others.¹⁰^–¹² Endolymph-perilymph shunting procedures and peripheral labyrinthine ablation by either medical or surgical means continue to find support in many centers.¹³^–¹⁷ Many procedures are of historical interest only, whereas others, such as intratympanic injection of vestibulotoxic medications, show some promise; however, the results in the control of vertigo and in prevention of hearing loss make them undesirable alternatives. Vestibular neurectomy and neurotomy (nerve section) seem to offer the best control of intractable vertigo refractory to medical therapy.

Retrolabyrinthine and retrosigmoid vestibular nerve sections ^1,^2,¹¹ have been proposed more recently as alternatives to the middle fossa (transtemporal-supralabyrinthine) vestibular neurectomy. It is, however, more logical to divide the vestibular nerve fibers in the distal IAC where fibers are distinct to achieve a complete section, while preserving the cochlear nerve. Also, the resection of the vestibular nerve, including Scarpa’s ganglion, ensures that regeneration does not occur. One is less likely to encounter large vessels in the distal portion of the IAC. These three important anatomic considerations are inadequately addressed with the posterior fossa approaches and must be kept in mind when comparing long-term results of the various surgical options.

Although the surgical access to the IAC in the transtemporal-supralabyrinthine approach is narrower compared with the access of the standard middle fossa approach, the dangers associated with temporal lobe retraction are practically eliminated. The posterior fossa approach entails more risks of severe cerebrospinal fluid leaks, meningitis, deafness, permanent facial paralysis, and intracranial hemorrhage, not to mention the common sequela of permanent headache ² that is often not emphasized. We concur that the transtemporal-supralabyrinthine approach is challenging and demands a thorough knowledge of the temporal bone; however, these challenges are similar to those of other neurotologic procedures.

REFERENCES

1. House J.W., Hitselberger W.E., Mc Elveen J., et al. Retrolabyrinthine section of the vestibular nerve. Otolaryngol Head Neck Surg. 1984;92:212-215.

2. Silverstein H., Norrell H. Microsurgical posterior fossa vestibular neurectomy: An evolution in technique. Skull Base Surg. 1991;1:16-25.

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

4. Garcia-Ibanez E., Garcia-Ibanez J.L. Middle fossa vestibular neurectomy: A report of 373 cases. Otolaryngol Head Neck Surg. 1980;88:486-490.

5. Castro D. Transtemporal-supralabyrinthine vestibular neurectomy for Ménière’s disease. In: Fisch U., Yasargil M.G., editors. Neurological Surgery of the Ear and Skull Base. Berkeley: Kugler & Ghedini Publications, 1989.

6. Portmann M., Sterkers J.M., Charachon R., Chouard C.H. Le Conduit Auditif Interne-Anatomie, Pathologie, Chirurgie. Paris: Librairie Arnette; 1973. 102-117

7. House W.F. Surgical exposure of the internal auditory canal and its contents through the middle cranial fossa. Laryngoscope. 1961;71:1363-1365.

8. Kronenberg J., Fisch U., Dillier N. Long-term evaluation of hearing after transtemporal supralabyrinthine vestibular neurectomy. In: Nadol J.B., editor. The Second International Symposium on Ménière’s Disease. Amsterdam: Kugler & Ghedini Publications; 1989:481-488.

9. Chouard C.H. Acousticofacial anastomosis in Ménière’s disorder. Arch Otolaryngol Head Neck Surg. 1975;101:296-300.

10. Bretlau P., Thomsen J., Tos M., Johnsen N.J. Placebo effect in surgery for Ménière’s disease: Nine-year follow-up. Am J Otol. 1989;10:259-261.