Timothy C. Hain,
Last edited: 8/01. Please read our disclaimer.
Defined Complications Education Index
A vestibular nerve section describes the process of cutting the vestibular part of the cochleovestibular cranial nerve. This is generally done in an attempt to eliminate recurrent attacks of vertigo. The first was performed by Frazier in 1904, in an attempt to control symptoms of Meniere's disease.
As an overview, these procedures are rapidly falling from favor, because a newer procedure -- transtympanic gentamicin, is replacing them in most centers.
The usual reason for a vestibular nerve section is control of unilateral Meniere's disease, where there is some hearing (better than 80 DB PTA). On extremely rare occasions it is performed for other reasons such as recurrent vestibular neuritis. Relative contraindications are bilateral vestibular disease, old age, poor medical condition, or CNS involvement. Where there is hearing to preserve, the main surgical alternative to vestibular nerve section is transtympanic gentamicin (TTG) treatment. If hearing is not an issue then a labyrinthectomy can be done. Results of labyrinthectomy are very similar to vestibular nerve section (Eisenman et al, 2001). At this writing, to this author, TTG treatment seems more reasonable than vestibular nerve section or labyrinthectomy in most cases because of the lack of major complications and also because of the lack of a need for general anesthesia. There are only rare exceptions to this general rule.
The vestibular nerve may be sectioned (cut or severed) via the middle fossa, retrolabyrinthine and retrosigmoid approaches, with similar efficacy. Surgical treatment is traditionally felt to be indicated when the patient is incapacitated with unilateral Meniere's disease and quality of life is affected. Historically 20% of patients eventually have had surgery done (Silverstein and Rosenberg, 1992), but with the advent of transtympanic gentamicin treatment, operative treatments are being replaced by outpatient procedures.
On the diagram below, one can visualize the retrolabyrinthine approach, which entails an attempt to cut the nerve from on the right side of this diagram, going through the mastoid sinus and into the cranial cavity to get access. The picture on the right was taken by Dr. Alan Micco, and shows the actual appearance of the surgery.
The middle fossa approach is similar, but access to the cranial cavity is obtained with the assistence of a neurosurgeon, from a slightly higher location. In the retrosigmoid approach, access to the nerve is obtained by going through the posterior (back of head) part of the skull.
Although 95 percent of patients are satisfied with the procedure immediately after their surgery, there are substantial risk of a serious complication in all of the described surgical procedures. All available procedures -- retrolabyrinthine, retrosigmoid, and middle-fossa have significant risks. For this reason, transtympanic gentamicin treatment is gradually replacing all of these operations.
Failure of procedure: Although from the name of the procedure one would expect that the entire vestibular nerve would be cut, in reality this is not always possible. According to Eisenmen (2001) there is evidence for retained vestibular function in about half of patients following nerve section or labyrinthectomy. Some of the fibers of the vestibular nerve run very close to the cochlear (hearing nerve), and because of this they may be spared. Saccule derived nerve fibers may be purposefully spared because they tend to run close to the cochlear nerve (Silverstein et al, 1994). Sometimes there is an attempt to cut these fibers at another site with a singular neurectomy. Singular neurectomies, however, are somewhat difficult and unreliable even in very experienced hands.
Neuromas may form from the cut stub of the nerve, and nerve may regrow in a few individuals (Pulek and Patterson, 1997).
CSF leak. About 10% of cases with retrolabyrinthine nerve sections develop a cerebrospinal fluid (CSF) leak, which is treated with continuous lumbar drainage for several days.
Facial weakness. The facial nerve runs adjacent to the vestibular nerve, and it can be damaged by procedures that intend to damage the vestibular nerve. This complication is rare in recent times due to better surgical technique and the availability of facial nerve monitors.
Headache. Postoperative headaches are common in the retrosigmoid approach, and about 25% of patients undergoing this procedure there are severe headaches requiring medication 2 years later.
Other: The middle-fossa approach is essentially a neurosurgical approach. The skull must be opened and the brain retracted. Neurosurgical procedures intrinsicially have considerably more risk than those where the brain is not exposed. Our view is that middle fossa nerve sections are rarely indicated, as transtympanic gentamicin treatment has similar effectiveness with much less risk.
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Acknowledgments: The cutaway figure of the ear above is courtesy of Northwestern University.