Acoustic neuroma - also known as a 'vestibular schwannoma' or a 'neurinoma' – is a growth (tumour) that develops on the vestibulocochlear nerve (also known as 'auditory' nerve or the '8th cranial nerve'). This nerve connects the inner ear to the brain and transmits information about balance (via the vestibular nerve) and hearing (via the cochlear nerve). An acoustic neuroma is generally a benign (non-cancerous) growth and tends to develop slowly over a period of time, often over many years. Over three hundred people in Australia are diagnosed with acoustic neuroma every year.
The causes of acoustic neuroma are not fully understood. There is a link to people who suffer from a rare inherited condition known as Neurofibramatosis Type 2 (NF-2) where benign tumours, including acoustic neuromas (sometimes on both sides of the head), form in the central nervous system. NF-2 is due to the absence of a tumour suppressant protein, related to a gene malfunction on chromosome.
Symptoms are caused by the gradual impact of the growth of the tumour on the auditory nerve and surrounding tissue. These generally include…
- Problems affecting the relevant ear, including hearing loss / impairment, tinnitus (a buzzing or ringing in the ear) and / or a 'blocked' feeling in that ear.
- Balance issues e.g. dizziness, loss of balance.
- Numb feeling in the face
- Facial pain, twitching.
- Visual problems e.g. double vision.
- Swallowing problems.
- Speech problems.
Initial tests are normally with an ENT (Ear, Nose and Throat) specialist and involve tests of hearing and balance (Auditory and Vestibular tests). Presence of an acoustic neuroma is generally confirmed by either an MRI or CT scan of the Brain.
Most acoustic neuromas are benign, but nonetheless, as the tumour continues to grow, it can exert pressure on the surrounding brain and nerve structures, including the brain stem, cranial nerves and cerebellum. When the tumour is large enough, it can cause blockage of cerebrospinal fluid, and lead to a condition called Hydrocephalus, which if untreated, can result in loss of consciousness, coma and loss of vital body functions such as heart rate, breathing and blood pressure. For this reason, an acoustic neuroma can be fatal. Treatment options include…
- Monitoring the growth of the neuroma. As most acoustic neuromas are slow growing, regular monitoring with MRI scans may be the recommended option if they are small.
- Surgery to remove the growth. This can be performed with hearing preservation microsurgery (Retrosigmoid approach) or hearing sacrifice surgery (Translabyrinthine approach). Surgery is performed in combination with an ENT surgeon. Complications of surgery can include damage to facial nerves, leading to facial weakness, or permanent hearing loss. The most appropriate surgical approach will be determined on many factors, and is done in consultation with the patient and surgical team.
- Radiation therapy to control the growth. This is a procedure known as a 'stereotactic procedure', where radiation beams are delivered to the tumour as the target in a focused manner. Radiation delivery methods include LINAC or 'Gamma knife'. Although the term ‘Radiosurgery’ is used, it does not involve any incisions or actual surgery and involves a one-time high radiation dose. Therefore, this is usually performed as a Day-only procedure.