Acoustic neuroma is a noncancerous, slow-growing tumor that occurs in the brain. The most common form of brain tumor, many acoustic neuromas are so small they do not become symptomatic, according to the Mayo Clinic. However, it is possible that the tumor will grow large enough to cause complications, which can range from hearing loss to difficulty maintaining balance.
What It Affects
An acoustic neuroma sits on the eighth cranial nerve in the brain. This cranial nerve has three branches: the cochlear branch, which carries sound, the superior vestibular and inferior vestibular branch, which affects balance. According to the Mayo Clinic, most neuromas grow on the vestibular branch.
Hearing Loss
When tumors grow large enough to be symptomatic, the tumor can press on the brain stem and affects fluid flow between the brain and spinal cord. This fluid buildup can increase pressure in the skull. The result is a sudden loss in hearing, which can also occur in only one ear, which is known as asymmetrical hearing loss.
Ringing in the Ear
Also known as tinnitus, ringing in the ear is most often confined to one ear. If a patient is experiencing hearing loss in only one ear, this is typically the ear that has tinnitus symptoms. A physician may prescribe medications to relieve tinnitus symptoms, but if this condition becomes unbearable or does not respond to treatment, surgery to remove the tumor may become necessary.
Dizziness and Balance Loss
If the neuroma rests on the superior or inferior vestibular branch, this can cause difficulty in how well a person can maintain balance. An acoustic neuroma on this area may first present with symptoms mistaken for clumsiness, then the dizziness may progress.
Facial Numbness or Weakness
If a tumor grows larger, it may press on the trigeminal nerve, which is responsible for facial sensation. If the neuroma presses on the facial nerve, this can cause weakness or paralysis, particularly on the side affected by the tumor. Because this is a sign that the tumor is becoming too large and could potentially rest on the brain stem, surgical removal is most often necessary for these symptoms.
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