An acoustic neuroma (more correctly known as a vestibular schwannoma) is a noncancerous (benign) tumor that originates in the cells that wrap around the vestibular nerve (Schwann cells).
These tumors arise from the vestibular (balance) nerve, which is one branch of the vestibulocochlear nerve (8th cranial nerve). The other branch, the cochlear (auditory) nerve, carries sound signals to the brain. Early symptoms as the tumor grows and presses on the auditory nerve include slowly progressing hearing loss in one ear (hence the historical name acoustic neuroma).
(See also Overview of the Inner Ear.)
Early symptoms of acoustic neuroma include
- Slowly progressing hearing loss in one ear
- Noise or ringing in the ear (tinnitus)
- Feeling of pressure or fullness in the ear
- Ear pain
- Imbalance or unsteadiness when the person turns quickly
If the tumor grows larger and compresses other parts of the brain, such as the facial nerve (7th cranial nerve) or the trigeminal nerve (5th cranial nerve), weakness (facial droop) or pain and numbness of the face may result.
How Ear Disorders Affect the Facial Nerve
Because the facial nerve (the 7th cranial nerve) winds through the ear, disorders of the middle and inner ear can affect it. For example, an acoustic neuroma growing on the auditory nerve (the 8th cranial nerve) can push on the facial nerve. The facial nerve then swells and presses against the opening in the skull that it passes through. The pressure on this nerve can cause temporary or permanent facial paralysis (inability to move muscles) on the affected side, inability to fully close the eye, and drooping of the face. Treatment depends on the disorder causing the problem.
- Hearing tests
- Magnetic resonance imaging (MRI)
Early diagnosis of acoustic neuroma is based on a magnetic resonance imaging (MRI) scan and hearing tests. An audiogram (hearing test) is done first. People who have hearing loss in only one ear should then have imaging tests, such as an MRI.
Other hearing tests that may be done include tympanometry (tests how well sound can pass through the eardrum and middle ear) and auditory brain stem response testing (measures nerve impulses in the brain stem resulting from sound signals in the ears).
- Sometimes surgery or radiation therapy
Tumors that are small and not growing or causing symptoms do not require treatment. Tumors that begin growing or cause symptoms are removed with surgery or controlled using radiation therapy. Surgery may be done using a microscope (microsurgery) to avoid damaging the facial nerve, and hearing can sometimes be saved. Radiation therapy may be done using a very precise technique (called stereotactic radiation therapy) so that only the tumor is affected. Whether surgery or stereotactic radiation therapy is done depends on a number of factors including the person's age, health, amount of hearing loss, and size of the tumor.
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