Acoustic Neuroma / Lateral Skull Base Tumors
An acoustic neuroma is a benign tumor found on the vestibularcochlear nerve, the nerve that connects the ear to the brain. This nerve is behind the ear, right under the brain.
A type of auditory tumor, an acoustic neuroma is also known as a vestibular schwannoma. This type of tumor is typically slow- growing, and it may press against the nerves controlling hearing and balance as it grows. An acoustic neuroma is an uncommon cause of hearing loss. If the tumor remains small, many patients will remain asymptomatic. However, if it enlarges enough to exert serious pressure on the brain, it may become life-threatening.
Causes of an Acoustic Neuroma
Most of the time, the cause of an acoustic neuroma is unknown. If acoustic neuromas develop in both auditory nerves, the underlying cause may be a heredity disorder known as neurofibromatosis type 2, but this genetic defect accounts for only a very small percentage of cases. The vast majority of acoustic neuromas are sporadic (non-inherited).
Symptoms of an Acoustic Neuroma
Many patients with small acoustic neuromas will not be symptomatic. As it grows, it presses against the hearing and balance nerves, and large tumors may press against the brain and brainstem. Pressures on these structures generates symptoms. These symptoms may include:
- Loss of hearing in one ear
- Balance problems
- Ringing in the ears, also known as tinnitus
- Difficulty swallowing and hoarseness
- Clumsiness or unsteadiness
- Facial paralysis
Diagnosis of an Acoustic Neuroma
There are several ways a physician may diagnose an acoustic neuroma. The physician may evaluate the ears, balance system, and mobility of the face. It is possible, however, that there will be no physical evidence of the tumor. The following diagnostic tests may be administered to detect the presence of an acoustic neuroma:
- Hearing test
- Auditory brain stem response, or ABR
- Electronystagmography, or ENG
- MRI scan of the brain
Treatment of an Acoustic Neuroma
When an acoustic neuroma remains small, the patient may only need regular checkups and surveillance for growth. Tumors that demonstrate active growth may require treatment with radiation or surgical removal. Radiation is designed to halt tumor growth while surgery facilitates tumor removal. The decision of which treatment to pursue is dependent on many factors, which will be discussed in depth between the patient and the physician.
Risks of Treatment for an Acoustic Neuroma
There are risks associated with both radiation and surgery for treatment of an acoustic tumor. With radiosurgery, risks may include partial or total hearing loss in the affected ear, dizziness, facial weakness, or brain swelling.
If typical surgery is required for the treatment of an acoustic neuroma, risks may include:
- Leakage of cerebrospinal fluid
- Facial nerve paralysis
- Hearing loss
- Brain complications