An acoustic neuroma starts out as a small growth that arises from the cochleovestibular nerve within the temporal bone. In its earliest stage, an acoustic neuroma may be contained completely within the internal auditory canal, causing some loss of hearing in the affected ear along with tinnitus and dizziness (see Symptoms of an Acoustic Neuroma).
Acoustic neuromas typically grow very slowly, but as they expand they extend out of the internal auditory canal and begin to compress the cranial nerves that regulate facial movement, facial sensation, hearing, balance, and speech and swallowing. Patients often report having headaches in addition to the symptoms of the earlier stage acoustic neuroma.
As the acoustic neuroma grows, it can compress the cerebellum and even the brainstem itself. Although an acoustic neuroma is benign and not cancerous, it is not harmless. The pressure of the neuroma against healthy brain tissue of the cerebellum and brainstem may affect coordination and motion and lead to a worsening of headaches. It can also lead to numbness in the face on the affected side, as the nerves controlling facial movement are compressed.
Left untreated, an acoustic neuroma can block the flow of cerebrospinal fluid and cause hydrocephalus, which can in turn lead to severe vision problems and difficulty breathing and swallowing. Fortunately, most patients seek treatment long before an acoustic neuroma reaches this stage. As long as that treatment is delivered by a sophisticated, multidisciplinary team at a major medical center, an acoustic neuroma rarely progress to the point of hydrocephalus.
Many patients, however, suffer from hearing problems and dizziness for several years before getting a correct diagnosis. The earlier the diagnosis the smaller the tumor, which makes it easier to treat (see Surgery for Acoustic Neuromas). Advanced treatment options now make it possible to treat small acoustic neuromas while preserving hearing.
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Reviewed by Rupa Gopalan Juthani, M.D.
Last reviewed/last updated: September 2020
