What is an Acoustic Neuroma?
An acoustic neuroma, also referred to as a vestibular schwannoma, is a benign tumor of the eighth cranial (or acoustic) nerve. Located in the base of the skull near the brainstem, the acoustic nerve is involved with the sense of hearing and with control and balance. About 2,500 new cases of acoustic neuromas are diagnosed each year.
What are the Symptoms of an Acoustic Neuroma?
The most frequent and earliest symptom of an acoustic neuroma is hearing loss, though headaches are also common. Hearing loss is caused by the pressure the lesion exerts on the acoustic nerve.
The hearing loss is on the side of the head where the tumor is present, while the other side is unaffected. The hearing loss often progresses slowly at first; however, in some cases it can be quite rapid. Other symptoms can include tinnitus or ringing in the ear, dizziness, and balance difficulty. If the tumor is large it may also cause facial numbness or weakness, and on rare occasions patients complain of headaches.
The neurosurgeon may suspect a patient has an acoustic neuroma in cases of hearing loss in one ear. To confirm a diagnosis, a neurosurgeon will request an MRI (magnetic resonance imaging). This imaging technique accurately identifies the location and size of the tumor, which is important in determining appropriate treatment.
What are the Treatment Options?
Treatment options for acoustic neuromas include observation, surgery or radiation. The physician will go over all possible treatment options with the patient and recommend which is most appropriate.
Observation may be appropriate when the tumor is small, noted incidentally, or if the patient is medically too unstable due to other factors to undergo intervention. Observation will usually involve serial MRI examinations at scheduled points in the future.
In some cases in which the patient has usable hearing in the affected ear, observation is appropriate to extend the ability to hear from that affected ear.
Surgical intervention is recommended for total removal of the lesion. This involves a craniotomy where a portion of the skull is removed to allow access to the brain and is then returned to position afterwards. This is also the only approach where the tissue can be examined and a definitive determination made as to its tissue type.
The surgery is performed with the operating microscope, which aids in identification of surrounding structures. In some cases hearing may be preserved; in many patients, hearing loss is so severe before surgery that it cannot be preserved.
The postoperative course involves 24 to 36 hours in the intensive care unit and about five days of recovery in the hospital.
For small tumors stereotactic radiosurgery is an option.