An acoustic neuroma is a slow growing benign non-cancerous fibrous tissue growth located at the base of the skull. It most often occurs on the eight cranial, or balance nerve that leads from the brainstem to the nerve ear. Acoustic neuromas are non-malignant meaning that they do not spread to other parts of the body. There is no knowing cause and affect approximately 1 in 100,000 people.
Although most acoustic neuromas are found in females between the ages of 30 to 60, there is no known cause of the condition, and it is not genetic.
The first symptoms of an acoustic neuroma include:
gradual hearing loss in one ear
decrease in the ability to recognize the differences between sounds
ringing in the ears, call tinnitus
As the neuroma gradually enlarges, symptoms may include:
balance problem
facial numbness and/or tingling
weakness of the facial muscles
Treatment Options
Treatment for an acoustic neuroma depends on a patient’s age, general health, the size and location of the tumor, and its rate of growth. Treatment may include observation if the tumor is very small or surgical removal of the tumor.
Surgical Therapy
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 affiliated with the House Ear & Neurosurgey Center at St. Vincent Medical Center 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 our surgeons. The treatment of acoustic neuromas and other brain tumors is constantly undergoing refinement and evaluation at the Clinic. Because of this commitment to “cutting edge” and quality patient care, the House Ear & Neurosurgery Center 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 our surgical 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. 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 with facial nerve preservation are greater than ninety-eight percent (98%).
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 completely remove the tumor.
SURGICAL APPROACHES
The choice of surgical approach depends upon the size of the tumor and the level of hearing detected on the audiogram. Again, the larger the tumor the lower the chances of saving hearing. The three most common surgical approaches for acoustic neuromas are the translabyrinthine, middle fossa and retrosigmoid approach. All of these procedures are performed under general anesthesia. Patients in general spend 5 days in the hospital, including the day of surgery.
Translabyrinthine Approach
Our affiliated physicians have the largest experience in the world with this surgical approach for acoustic neuromas and other skull base tumors. The translabyrinthine approach involves an incision that is made behind the ear. The mastoid bone and the balance canal structures of the inner ear are removed in order to expose the tumor. This approach results in complete tumor removal in nearly every case. One of the main advantages of this approach is that there is little or no movement of the brain required to provide excellent exposure of the tumor. Another advantage is early and direct localization of the facial nerve which allows separation of the nerve from the tumor, optimizing facial nerve outcome. After completion of tumor removal, the opening in the mastoid bone is closed with a fat graft which is taken from the abdomen.
This approach sacrifices the hearing and balance mechanism of the inner ear. As a consequence, the ear is made permanently deaf. Although the balance mechanism is removed on the operated ear, the balance mechanism in the opposite ear provides stabilization for the patient. Patients may experience vertigo immediately after surgery; however, this generally improves within the first five days following surgery and the patient has no further problems. In cases of larger tumors, patients rarely experience any vertigo after surgery.
Middle Fossa Approach
The middle fossa approach is another treatment that House Ear & Neurosurgery Center surgeons developed and currently utilize more than any other center in the world. This approach is used for small tumors and in cases when hearing can be saved. An incision is made beginning just in front of the ear and extends upward in a curved fashion. A small opening in the bone is made above the ear, and the membrane that covers the brain is elevated away from the bone and gently held away from the skull. Bone is then removed over the top of the internal auditory canal to expose the tumor. Tumor removal is complete in the vast majority of cases. Every effort is made to preserve hearing and still completely remove the tumor. In the cases of small tumors, hearing is preserved in the majority of cases.
Retrosigmoid Approach
With this approach, an incision is made behind the ear and an opening in the skull is made behind the mastoid bone. The portion of the brain called the cerebellum is held away in order to expose the tumor. In most cases the tumor can be completely removed. Every effort is made in this approach to preserve hearing and still completely remove the acoustic neuroma. In some cases, because of invasion of the auditory nerve by the tumor, it is necessary to sacrifice hearing in order to completely remove the tumor. The success of hearing preservation in these cases is largely dependent upon the size of the tumor and the condition of the auditory nerve in relation to the tumor.