Acoustic Neuroma



Overview

Vestibular schwannomas are non-cancerous, benign tumors found at the skull base that arise from the nerve of hearing and balance.  Vestibular schwannomas are found in about 1 in every 100,000 people in the United States each year.  Also known as “acoustic neuromas,” these tumors are usually diagnosed in adults in one ear and are not hereditary.  Less commonly, vestibular schwannomas can affect both ears, or be associated with other benign growths in connection with a genetic disease called neurofibromatosis-2.

Symptoms

The following are the most common symptoms of a vestibular schwannoma; however, each individual may experience symptoms differently.  Because vestibular schwannomas are typically slow growing, it is possible that these symptoms develop gradually or go unnoticed for years.  On the other hand, a large tumor may cause any or all of these symptoms.

The most common symptoms are:

  • Asymmetric hearing loss and tinnitus.
     

Other symptoms may include:

  • Dizziness/imbalance
  • Facial numbness, weakness, or twitch
  • Brainstem compression or hydrocephalus

Diagnosis

A patient’s history, physical examination, hearing test, and imaging studies are used in the diagnosis of vestibular schwannoma.  Most commonly, an MRI of the skull base best demonstrates the tumor.  If an MRI cannot be performed, a CT scan might be used.  Formal hearing tests (audiograms) often demonstrate not only a decrease in the ability to hear softer tones, but also a decrease in word clarity or speech discrimination. At times, balance tests or a specialized hearing test using electrodes (auditory brainstem response test) may be helpful.

Treatment

Treatment for vestibular schwannoma varies depending on a tumor’s size and growth over time, the patient’s hearing and balance, as well as the patient’s age and general medical condition.  The patient and physician team collaborate together to determine the best path to optimize quality-of-life and tumor control.

Options include:

  • Monitoring – Some patients are monitored with repeated MRIs and hearing tests.  Some schwannomas have already stopped growing by the time they are discovered and do not require procedural intervention.
  • Surgery – Surgery is often performed jointly with an otologist/neurotologist (ENT surgeon specializing in the ear and lateral skull base) and a neurosurgeon.  Surgery involves the use of a high-powered microscope to enable the surgeon to dissect the tumor off of delicate structures such as the facial nerve.  Multiple surgical approaches can be used to reach the tumor.  The best approach depends on the size and location of the tumor, as well as the patient’s level of hearing.
  • Stereotactic Radiation – A computer-guided delivery system is used to deliver highly focused beams of x-ray radiation to the tumor, while minimizing effects to the surrounding tissue.  While radiation does not remove the tumor, it can be effective in stopping the growth of a tumor.
  • Combination of the above – In some cases, tumors that grow after radiation may later require surgery.  In other cases, tumor remnants after surgery can grow and be treated with radiation.
  • In addition to addressing the tumor itself, treatment of vestibular schwannoma also involves managing the symptoms associated with the tumor and any effects of surgery or radiation.  This may include rehabilitation of any hearing loss and vestibular or balance therapy.

Cross section of the skull base showing a small vestibular schwannoma on the patient’s right side.  The tumor arises from the hearing and balance nerve.  It fills the inner bony ear canal, called the internal auditory canal, where the nerve providing motion to the face also resides.

Cross section of the skull base showing a large vestibular schwannoma on the patient’s right side.  The tumor has grown into the cerbellopontine angle, the space between the inner ear canal and the brainstem. The tumor has grown large enough to push on the sensation nerve of the face (trigeminal nerve). It has also grown large enough to push on the brainstem and the cerebellum portion of the brain.