Acoustic neuromas
| Vestibular schwannoma | |
|---|---|
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| Bilateral schwannomas in a patient with neurofibromatosis 2 | |
| Classification and external resources | |
| Specialty | oncology |
| ICD-10 | D33.3 |
| ICD-9-CM | 225.1 |
| ICD-O | M9560/0 |
| DiseasesDB | 100 |
| MedlinePlus | 000778 |
| eMedicine | ent/239 |
| MeSH | D009464 |
A vestibular schwannoma is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve (8th cranial nerve). A type of schwannoma, this tumor arises from the Schwann cells responsible for the myelin sheath that helps keep peripheral nerves insulated. Although it is commonly called an acoustic neuroma, this a misnomer for two reasons. First, the tumor usually arises from the vestibular division of the vestibulocochlear nerve, rather than the cochlear division. Second, it is derived from the schwann cells of the associated nerve, rather than the actual neurons (neuromas).
Approximately 2,000 to 3,000 cases are diagnosed each year in the United States (6 to 9 per million persons). Most recent publications suggest that the incidence of acoustic neuromas is rising because of advances in MRI scanning. Studies in Denmark published in 2004 showed an annual incidence of 11.5 per million over 25 years, with reported incidence increasing dramatically in each successive period studied. Most cases are diagnosed in people between the ages of 30 and 60, and men and women appear to be affected equally.
Most acoustic neuromas occur spontaneously in those without a family history. One confirmed risk factor is a rare genetic mutation called NF2.
The primary symptoms of vestibular schwannoma are unexplained unilateral hearing loss and tinnitus, and vestibular (disequilibrium) symptoms. Treatment of the condition is by surgery or radiation, and often results in substantial or complete hearing loss in the affected ear. Observation (non-treatment) over time also usually results in hearing loss in the affected ear.
Early symptoms are easily overlooked, sometimes mistaken for the normal changes of aging or attributed to noise exposure earlier in life, often delaying diagnosis.
The first symptom in 90% of those with an acoustic neuroma is unexplained unilateral sensorineural hearing loss, meaning there is damage to the inner ear (cochlea) or nerve pathways from the inner ear to the brain. It involves a reduction in sound level, speech understanding and hearing clarity. In about 70 percent of cases there is a high frequency pattern of loss. The loss of hearing is usually subtle and worsens slowly, although occasionally a sudden loss of hearing can occur. Hearing loss can vary from mild hearing loss to complete deafness.
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