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In a study published in 2003 by researchers from the Department of Otolaryngology at the University of California, investigators analyzed the success rate of hearing preservation following excision of large acoustic neuromas partially situated in the cerebellopontine angle. The surgical approach studied was the suboccipital or retrosigmoid approach. Overall, only 6% of the patients retained good hearing postoperatively. Thus, patients who wish to attempt hearing conservation in the presence of a large tumor, it is important to choose carefully between the translabyrinthine approach, which has a lower rate of complications but where there's no chance of hearing preservation, and the retrosigmoid approach where there is an increased risk of persistent headaches, increased incidence of postoperative vestibular dysfunction and a slightly increased risk of tumor recurrence but still presents a chance for hearing conservation. To read more about this study, please click on this link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&listuids=12806299&queryhl=4&itool=pubmed_docsum

The rates of preservation of facial nerve function continue to improve with more effective intraoperative monitoring. The degree of function of the facial nerve is evaluated by the House-Brackmann scale, a widely used facial nerve grading system that rates facial function on a scale from Level I (normal) to Level VI (no movement and complete loss of muscle tone). It is commonly employed to assess facial nerve function following surgery for acoustic neuroma. To learn more about the House-Brackmann Facial Nerve Grading System, please follow this link: http://www.entusa.com/bells_palsy.htm

It is estimated by some researchers that 5-10% of patients may experience facial paralysis or paresis following excision of small tumors. Some studies indicate that up to 60% of patients experience some residual facial weakness following excision for large tumors. Other studies estimate facial nerve functioning at approximately 80% following microsurgical excision of the tumor. Up to 25% of patients with poor facial nerve function at the time of discharge will eventually achieve normal function. The prognosis of patients with low facial nerve function at 6 weeks postoperatively (level III or higher) is poor. Facial palsy is reported to occur in 10-30% of patients, the majority of who make a full recovery.

Regarding the rates of the preservation of hearing and facial nerve function, the following results have been noted in the medical literature:

• Middle Fossa Approach - For the middle fossa approach, hearing preservation is considered successful (within 15 dB of preoperative hearing level) in up to 50% of patients undergoing this procedure. Up to 68% of patients retain functional hearing (less than the 15 dB designation of success). Facial nerve function is retained in up to 95% of patients.

A study published in 2003 evaluating the effect of age on the outcome of middle fossa surgery for acoustic neuromas noted that for older patients there is a lower chance for preserving hearing than for younger patients. However, older age does not affect the outcome of surgery regarding facial function. There was also a higher rate of cerebrospinal fluid leakage in older patients.