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Vestibular nerve section via retrolabyrinthine craniotomy
Abstract
Meniere's disease can cause debilitating dizziness and vertigo despite maximal medical management. In select patients, treatment with vestibular nerve section provides optimal outcomes for symptom control and hearing preservation. Vestibular nerve section is also indicated in other vestibular disorders, including refractory uncompensated vestibular neuritis. Surgical approaches for vestibular nerve section include the retrolabyrinthine, retrosigmoid, middle fossa, and translabyrinthine craniotomies. The advantages of the retrolabyrinthine approach include rapid access, excellent visualization of the facial and cochlear nerves, and the possibility of hearing preservation in conjunction with consistent outcomes for vestibular symptoms. In this chapter, we discuss the retrolabyrinthine approach for vestibular nerve section, providing the reader with an overview of when, why, and how to employ the technique.
... Vestibular nerve sectioning was first described in the early 1900s using a suboccipital approach [67]. Since that time, additional approaches to VNS have been described, including retrolabyrinthine, middle fossa, and combined retrolabyrinthine/retrosigmoid approaches. ...
... Brackmann and Hitselberger and is the preferred approach at the House Clinic today. Benefits of the retrolabyrinthine approach include hearing preservation, reduced cerebellar retraction, direct view of the vestibulocochlear and facial nerves, and consistent outcomes for symptom relief [67]. One indication for proceeding directly to VNS rather than medical management or ELS surgery is drop attacks. ...
Meniere's disease is a peripheral audiovestibular disorder characterized by vertigo, hearing loss, tinnitus, and aural fullness. Management of these symptoms includes medical and surgical treatment. Many patients with Meniere's disease can be managed using nonablative therapy, such as intratympanic steroids and endolymphatic shunt surgery, prior to ablative techniques such as intratympanic gentamicin. Recognition of concurrent migraine symptoms may aid in medical therapy and also underscore the importance of preserving vestibular function where possible. The goal of this review is to explain the importance of nonablative therapy options and discuss treatment protocols after medical failure.
BACKGROUND AND OBJECTIVES
Exposure of the root entry zone (REZ) of the trigeminal nerve (TN) for microvascular decompression is commonly obtained with a retrosigmoid approach, with or without endoscopic assistance. We hypothesized that adequate exposure of the TN REZ could be obtained through an endoscopic retrolabyrinthine (RL) approach. We aim to quantify exposure of the REZ of the TN using endoscopic RL approach, with and without drilling of the suprameatal tubercle of the internal auditory canal.
METHODS
Surgical dissection was performed bilaterally on 3 embalmed cadaveric human heads at the anatomy laboratory of the House Institute. Heads were scanned for volumetric analysis using 3D Slicer software both before and after dissection. Extent of exposure was quantified in 2 ways: first, by assessment of the surgeon's ability to visualize 16 predetermined anatomic landmarks with the endoscope and second, we estimated the “working” area by placing fiducials under the fully endoscopic view and calculating the resultant 3D volume.
RESULTS
Using the standard endoscopic RL approach, an average of 13.8 landmarks (range 12-16) was visualized. The estimated working volume exposed by the RL on each side of each head varied from 189.28 to 527.85 mm ³ . Drilling of the suprameatal tubercle provided both increases in landmark visualization and, on average, an additional 55 mm ³ of working volume.
CONCLUSION
The endoscopic RL approach is a viable alternative to the standard retrosigmoid approach. Potential advantages of the RL include a more lateral trajectory that minimizes the need for cerebellar retraction and a shorter working distance and shallower angle to the cerebellopontine angle. Potential disadvantages include longer surgery time, increased technical difficulty of exposure, and potential for cerebrospinal fluid leak and or hearing loss.
Objective This study evaluates the utility of endoscopy for retrolabyrinthine vestibular nerve section (RLVNS).
Design/Setting This is a retrospective review for RLVNSs by the senior author. The endoscope's utility was assessed and assigned a grade based on operative findings.
Participants/Main Outcome Measures Fifteen patients (eight males and seven females; 53 and 47%, respectively) were identified with mean age 56.7 years. Indications included Ménière's disease (MD) in 12 of 15 patients (80%), uncompensated vestibular neuritis in 2 patients (13%), and other vestibular neuropathy in 1 patient (7%). Vertigo resolved in 14 of 15 patients (93%). Complications included decreased hearing in two patients (13%) and deep venous thrombosis in one patient (7%). There were no facial nerve complications or mortalities.
Results Sectioning vestibular division of the vestibular–cochlear nerve was achieved without perceived benefit of endoscopy in the 80% of cases (grade 0, n = 12). Endoscopy was helpful in patients with a small mastoid (grade 1, n = 2, 13.3%), and deemed necessary where the flocculus of the cerebellum was adherent to the eighth nerve arachnoid at the porus acusticus (grade 2, n = 1, 6.7%).
Conclusion RLVNS is a safe and efficacious procedure for the treatment of vertigo; the surgical endoscope may be a useful adjunct in selected cases. Patients with MD may expect the greatest benefit from surgery.
Vestibular neurectomy is considered the reference treatment of incapacitating vertigo accompanying Meniere disease, with an efficiency rate of 85-95% in most literature reports. The aim of this study is to evaluate if vestibular neurectomy can provide a complete vestibular deafferentation by investigating complete vestibular function after surgery.
Prospective study. Twenty-four patients suffering from incapacitated Meniere vertigo crisis beneficiated from a vestibular neurectomy by retrosigmoid approach. The average time between surgery and vestibular evaluation was 1 year. We performed (i) kinetic test, (ii) caloric test and (iii) vibration-induced nystagmus (VIN) at 30, 60 and 100Hz under videonystagmography recording, (iv) vestibular evoked myogenic potentials (VEMP), (v) video head impulsed test (VHIT) for each semicircular canals and (vi) an evaluation of visual vertical and horizontal subjective (VVS and HVS).
On clinical evaluation, all the patients except one had never experienced any recurrence of vertigo crisis after surgery. The 24 patients would definitely undergo the surgery again. On vestibular evaluation, on the operated side, all patients showed a total areflexia at caloric test; 23 patients had no VEMP response; 23 patients had abolished canals response to VHIT. All the patients had VVS and HVS deviated towards the operated side; 23 patients had a high velocity VIN from 30 to 60Hz.
This study proves that vestibular neurectomy can provide a complete vestibular deafferentation. We discuss this vestibular evaluation protocol and the main difficulties encounter during surgery, which could lead to partial nerve section and partial relief, and explain residual vestibular function after vestibular neurectomy.
Excellent exposure of the cerebellopontine angle is obtained by an approach through the mastoid posterior to the labyrinth. Since the major portion of the dissection is extradural, this approach is associated with a very low morbidity.
The retrolabyrinthine approach has been used for several years for selective partial section of the posterior root of the trigeminal nerve in cases of trigeminal neuralgia. Complete relief of pain has been accomplished in 25 of 28 cases, and the other 3 patients had partial relief of pain.
The only complications in these patients were partial hearing impairment in 2, and 1 partial abducens nerve paralysis which subsequently recovered completely. Two patients required secondary closure of cerebrospinal fluid leaks.
This approach has also been used for exploration and biopsy of cerebellopontine angle tumors and for treatment of other cranial nerve problems. We conclude that the retrolabyrinthine approach is the preferred route to the cerebellopontine angle in a variety of clinical conditions.
The cochlear and vestibular nerves rotate 90 degrees from the inner ear to the brain stem. Most of the rotation occurs within the internal auditory canal (IAC); only minimal rotation occurs in the cerebellopontine (CP) angle. At the labyrinthine end of the IAC, the cochlear nerve--which at first lies anterior to the inferior vestibular nerve (saccular nerve)--rapidly fuses with the inferior vestibular nerve. It then rotates to become inferior as the nerves leave the porus acousticus. The cochleovestibular (C-V) cleavage plane lies in a superior-inferior direction in the lateral IAC and rotates to become anterior-posterior in the CP angle. In 25% of patients in whom no C-V cleavage plane can be seen, it is not possible to completely transect all vestibular fibers. The surgical implications are that the most complete vestibular neurectomy can be done only in the lateral IAC, the cochlear and inferior vestibular nerves, because of their intimate association, should not be separated in the mid-IAC, in order to prevent damage to the cochlear nerve, and to create a complete denervation of the vestibular labyrinth, only the posterior ampullary nerve along with the superior vestibular nerve should be transected.
When symptoms of dizziness and episodic vertigo cannot be controlled through medical management or drainage procedures such as endolymphatic subarachnoid shunt operations, selective vestibular nerve section may be necessary. In the 1920s eighth cranial nerve sections were performed by neurosurgeons through the suboccipital approach but were frequently associated with hearing loss and facial paralysis. The middle fossa approach has been popularized by Dr. William House and others as a method of selectively sectioning the vestibular nerve and preserving facial and cochlear function. More recently the suboccipital retrolabyrinthine approach has been described as a method of selectively sectioning the vestibular nerve. We have reviewed 42 cases of suboccipital retrolabyrinthine selective section of the vestibular nerve performed at the Otologic Medical Group over the past 2 years. The shortest follow-up on these patients has been 6 months. Thirty-two patients had preoperative diagnosis of Meniere's disease, and of these patients 25 had had previous endolymphatic subarachnoid shunt surgery. Eighty-five percent (27 patients) experienced complete relief of vertigo following surgery, while 6% (two patients) stated they were improved. Three patients reported no relief. There were 10 patients with dizziness who had a diagnosis other than Meniere's disease. In this diverse group three experienced complete relief of vertigo, five were improved, and two reported no improvement of vertigo following surgery. None of the patients lost his hearing as a result of the surgery and there was no facial weakness. One patient had postoperative CSF rhinorrhea and another had meningitis.
The unrecognized rotation of the vestibular and cochlear nerves from the labyrinth to the brain stem : Its implications to surgery of the eighth cranial nerve.
- Silverstein H.
- Norell H.
- Haberkamp T.