Acoustic Neuroma – Vestibular Schwannoma
What are Acoustic Neuromas?
An acoustic neuroma is a benign, or non-cancerous, tumor that grows on the vestibular cochlear nerve. This nerve is located behind the ear and under the brain, and it connects the ear and the brain. The vestibular cochlear nerve is responsible for balance and hearing. Acoustic neuromas are also known as vestibular schwannomas.
Acoustic neuromas do not spread to other parts of the body. Usually, these tumors grow incredibly slow. Although they do not invade the brain, they can put pressure on it when their size increases. This tumor can also harm other nerves when it grows in size.
Causes of Acoustic Neuromas
The causes of acoustic neuromas are not yet fully known. Some genetic defects are suspected of causing this type of tumor. Consistent exposure to loud noise is suggested to be a possible cause. Prior exposure of the head and neck to radiation may also be a contributing factor.
A tumor is an abnormal growth caused by abnormal cell multiplication that does not serve any physiological function. Cell division is regulated by the tumor suppressor genes. These genes also help to repair any damage caused to the DNA. Tumor suppressor genes are constantly at war against the cancer-causing genes called oncogenes. When tumor suppressor genes fail to function properly due to mutations that affect protein encoding, unregulated cell division and growth can occur and cause the development of a tumor.
The body’s natural defense system should optimally detect the abnormal cells and kill them. But tumors may produce substances that obstruct the immune system from recognizing the abnormality of tumor cells and eventually the tumor cells may overpower all internal and external checks to their growth.
Symptoms of Acoustic Neuromas
Since an acoustic neuroma is a very slow growing tumor, the symptoms are often not noticeable in the beginning. As they grow in size, common symptoms may include hearing loss, abnormal sensation of movement, and tinnitus, or ringing in the ear. Other symptoms may include headaches, facial numbness, loss of coordination and balance, drowsiness, ear pain, and cognitive difficulties.
Diagnosis of Acoustic Neuromas
Diagnosis begins with an audiogram. The hearing ability of each ear is evaluated. The evaluation may indicate loss of hearing and speech discrimination.
Imaging techniques such as magnetic resonance imaging, or MRI, and computed tomography, or CT, scan can highlight acoustic tumors. MRI is preferred because it can clearly define acoustic neuromas, even if they are small.
An auditory brainstem response, or ABR, test may also be performed. An abnormal result of the ABR test can imply possible diagnosis of acoustic neuroma. However, an abnormal result of this test should be confirmed by a subsequent MRI.
Treatment Options for Acoustic Neuromas
The choice of treatment will depend on the size and location of the tumor. Radiation therapy may be beneficial, but surgical treatment may be necessary to completely remove the tumor