Current Results of the Surgical Management of Acoustic Neuroma

SURGERY

Cliff A. Megerian, John S. Hanekamp, Matthew J. Cosenza, N. Scott Litofsky. Selective retrosigmoid vestibular neuroectomy without internal auditory canal drill-out: An anatomic study. Otol Neurotol 2002;23:218-228

Objective: It is well established that selective vestibular nerve section by means of the retrosigmoid or posterior fossa approach can be accomplished with or without drill-out of the internal auditory canal (IAC) by virtue of the presence or absence of a surgically accessible cleavage plane between the vestibular and cochlear nerves. Some reports have indicated that a majority of patients would be amenable to successful separation of the vestibular nerve from the cochlear nerve medial to the IAC, thus obviating the need for IAC drill-out and associated complications. However, other reports have indicated routine difficulty in finding a satisfactory vestibulocochlear cleavage plane within the cerebellopontine angle. This in situ cadaver study was undertaken to determine whether normal anatomic relationships support the hypothesis that selective vestibular nerve section can be accomplished by means of the posterior fossa approach without the need for concomitant IAC drill-out in a majority of circumstances.

Methods: A retrosigmoid approach to the posterior fossa was performed bilaterally on 36 intact human cadavers. After displacement of the cerebellum, an operating surgical microscope was used to visualize the cerebellopontine angle in the surgical position. The ability to develop a satisfactory cleavage plane between the vestibular and cochlear nerves without the need for drill-out of the IAC was established in each case.

Results: Seventy-two vestibulocochlear nerve bundles in 36 intact human cadavers were analyzed. A vestibulocochlear nerve cleavage plane within the cerebellopontine angle amenable to neurectomy medial to the porus of the IAC was observed in 81% left and 69% right vestibulocochlear nerve bundles (average, 75%). The facial nerve was found deep or anterior to the vestibulocochlear nerve bilaterally in all cases examined. The anterior inferior cerebellar artery, or a branch of the artery, was found to cross the plane between the facial and vestibulocochlear nerve bundles within the lateral cerebellopontine angle in 47% of the cases on the left and in 50% of cases on the right.

Conclusions: A vestibulocochlear nerve cleavage plane amenable for selective vestibular nerve transection without drilling the IAC was found in 75% of the 72 cerebellopontine angles studied. The facial nerve consistently lies deep or anterior to the vestibulocochlear nerve within the cerebellopontine angle with the retrosigmoid approach. These findings support the rational and feasibility of avoiding drill-out of the IAC in the majority of circumstances when performing selective vestibular neurectomy by means of the posterior fossa approach for Ménière's syndrome and other vestibular disorders.

Jacques Magnan, Marco Barbieri, Renato Mora, Sreerama Murphy, Renaud Meller, Michel Bruzzo, André Chays. Retrosigmoid approach for small and medium-sized acoustic neuromas. Otol Neurotol 2002;23:141-145

Objective: Clinical study of the keyhole acoustic neuroma retrosigmoid approach for facial nerve and hearing preservation.

Study Design: This was a prospective case review from October 1993 to December 1998 in a referral hospital care unit.

Patients: A total of 119 consecutive patients with a tumor size of <25 mm in the cerebellopontine angle corrected by a retrosigmoid approach were included in the study.

Interventions: Standard audiometric and imaging assessments, complete tumor removal by using endoscopy-assisted control, and nerve monitoring.

Main Outcome Measures: House-Brackmann facial nerve grade and hearing level by the American Academy of Otolarnygology-Head and Neck Surgery classification.

Results: Grades I and II facial nerve function was obtained in 96% of cases, measurable hearing was preserved in 49% of cases, and 30% of cases achieved serviceable hearing.

Conclusion: The retrosigmoid approach is a safe and reliable approach in random patients with small and medium-sized acoustic neuromas.

H. F. El-Garem, M. Badr-El-Dine, A. M. Talaat, J. Magnan. Endoscopy as a tool in minimally invasive trigeminal neuralgia surgery. Otol Neurotol 2002;23:132-135

Objective: The aim of this study was assessment of the use of endoscopy in minimally invasive surgery of the cerebellopontine angle in cases of trigeminal neuralgia..

Methods: This study comprises 42 cases of trigeminal neuralgia that underwent operation with endoscopic-assisted microvascular decompression between October 1992 and October 1998. This study was performed in the Ear, Nose, and Throat Department, Nord Hospital, in Marseille, France. The decompression was performed by means of a minimally invasive retrosigmoid approach without a cerebellar retractor. The cerebellopontine angle was then explored by a 30-degree endoscope that gives a panoramic view of this space, with clear visualization of the trigeminal nerve from the pons to Meckel's cave, allowing for the identification of the precise location of the site of the conflict. Microvascular decompression was performed under the microscope by separating the offending vessel from the trigeminal nerve; separation was maintained by the insertion of a piece of Teflon.

Results: The site of conflict was detected at the root entry zone of the nerve in 35 patients (83.3%) and at Meckel's cave in 7 patients (16.7%). In 32 cases (76.2%), the type of contact between the vessel and the nerve was of the simple type (1 vessel coming in contact with the nerve in a single point); in 6 cases (14.3%), it was a multiple type (2 vessels touching the nerve in the same point); and in 4 cases (9.5%), it was a nutcracker type (2 vessels compressing the nerve between them). After at least 1-year follow-up and a single operation (cases that required a second operation for revision were considered failures), a successful result was obtained in 31 cases (73.8%), and an improvement was obtained in 4 cases (9.5%). The operation was a failure or early recurrence occurred in 7 cases (16.7%). Postoperative complications were rare. A cerebrospinal fluid leak occurred in only 1 case (2.4%) and was subsequently treated with lumbar puncture and a compressive bandage.

Conclusion: The minimally invasive retrosigmoid endoscopic-assisted microvascular decompression is an acceptable treatment of primary trigeminal neuralgia. Endoscopy provides a unique way to explore the cerebellopontine angle and to identify the exact location of the neurovascular conflict.