Surgical Therapy for Acoustic Neuroma
Surgery for acoustic neuromas has been performed since the early 1900's. The initial successes were few and far between by the early pioneering neurosurgeons who treated this problem. The past twenty years have witnessed an astounding improvement in our abilities to successfully deal with these tumors while preserving the neurological function of the patient.
Since the early 1960's, surgeons at the House Clinic have been at the forefront of innovations in the surgical treatment of acoustic neuromas. Many of the most significant advances in surgical approaches to the skull base have originated from House Clinic surgeons. The treatment of acoustic neuromas and other brain tumors is constantly undergoing refinement and evaluation at the House Clinic. Because of this commitment to "cutting edge" and quality patient care, the House Clinic has become the largest referral center for acoustic neuromas world wide. Each year, more than 200 patients with acoustic neuromas are treated by members of the House Clinic team; more than at any other center in the world.
In contemporary surgical treatment of these tumors, the vast majority of patients lead a normal life following their surgery. The two main concerns that patients typically have is preservation of facial nerve function and of hearing. The facial nerve exits the brain stem and is anatomically in a position adjacent to the vestibulocochlear nerve. The anatomical relationships of the nerves to the structures of the inner ear and the brain stem can be seen in the section on anatomy. Preservation of facial nerve function is extremely important because of its cosmetic implications. Normal movement of the face on each side is controlled by the facial nerve. Any disruption leads to a loss of normal muscular tone and movement in that side of the face. Our results at the House Clinic with facial nerve preservation are greater than ninety-eight percent (98%) in terms of preserving the anatomical continuity of the nerve.
Preserving anatomical continuity of the nerve means that the nerve is intact and was not disrupted by the surgical procedure. Even with an intact nerve, the functional abilities of the nerve may not be complete. However, results from our series over the years have shown excellent results in terms of functional outcome of the facial nerve. In a recently reviewed series of over three hundred and eighty (380) patients who underwent a middle fossa-type approach at the House Clinic, ninety-five percent (95%) of these patients maintained excellent facial nerve function after surgery. Only five percent (5%) suffered minor weakness of the facial nerve function. Preservation of facial nerve function is dependent to some degree on the size of the tumor that is removed. The influence of tumor size on facial nerve functional outcomes is illustrated by another recent study from our group observing a recently treated group of over one hundred and ninety (190) patients via a translabyrinthine approach with tumors measuring greater than 3cm in size. In this group of patients, eighty percent (80%) had an acceptable functional outcome. (House-Brackmann grades 1-3)However, only fifty-five percent (55%) of patients had an excellent outcome (House-Brackmann grades 1-2). The aforementioned series of over 380 patients all had tumors smaller than 2cm in diameter. This comparison is a good illustration of the influence of tumor size on outcome.
One of the major recent focuses of acoustic neuroma surgery is the preservation of hearing. Major strides have been made in recent years in terms of improving the results of hearing preservation with surgery. Much like facial nerve results, the size of tumor is an influential factor. Also important is how well the patient hears prior to surgery. Hearing is determined by a test called an audiogram. This is performed by an audiologist. If the results of the audiogram indicate that the hearing level is sufficient to indicate a reasonable chance of success with saving the hearing during surgery, then a surgical approach is selected that is designed to save hearing. Otherwise, it may be advisable to choose a treatment approach that sacrifices hearing in order to obtain a total resection of the tumor.
Most patients with adequate pre-operative hearing levels have small tumors which are mostly confined to the internal auditory canal. In these cases, at the House Clinic we routinely recommend and perform a middle fossa approach. Continued refinements in this approach have led to superior hearing preservation results. Some patients also are candidates for a retrosigmoid approach. These are patients whom have small tumors that have only a small portion of the tumor located within the internal auditory canal. However, this is a minority of patients with acoustic neuromas who have only a small component in the internal auditory canal. In patients with small tumors who have been operated by the middle fossa approach at the House Clinic since 1992, good hearing has been preserved in roughly two thirds of those patients. Any measurable level of hearing was preserved in eighty percent (80%) of those patients.