Acoustic Neuroma

An acoustic neuroma is a benign tumour arising from the Schwann cells or covering of the nerve to hearing and balance and represent about 6-10% of all brain tumours. The tumours are not malignant and do not spread to other parts of the body.

The acoustic neuroma arises from the balance portion of the 8th cranial nerve which is located deep inside the skull. The nerves exit from the brain into a small canal (internal auditory canal) joined to the organ of hearing and balance, as can be seen in the figure below.

An acoustic neuroma in the auditory canal, pressing against the brain

The first symptoms of acoustic neuroma are a nerve hearing loss associated with tinnitus (head noises). The hearing loss is usually progressive but in approximately 1% of cases may be sudden and dramatic. The hearing symptoms are usually associated with imbalance manifested mainly be a tendency to veer or stagger. Episodes of vertigo or spinning attacks are much less common.

As the tumours enlarge, they cause compression of a vital area of the brain, the brainstem. Compression of these vital structures of the brain stem is lethal if not relieved by removing the tumour.

Diagnosis

An acoustic neuroma is best diagnosed with the use of Magnetic Resonance Imaging (MRI). Some tumours are diagnosed with a CT scan. The presence of a one-sided nerve hearing loss detected at a routine hearing test usually leads to the suspicion of acoustic neuroma, though most one-sided hearing losses are not due to acoustic neuroma.

Treatment

The treatment of acoustic neuroma requires careful consideration by experts in the management of these types of tumours. Factors that influence the treatment including tumour size, growth rate (sometimes estimated from serial MRI scans), the patient's age and the hearing levels in the affected and unaffected ear. Surgery is recommended for patients when the tumour is growing or compressing the brain stem. In smaller tumours, with useful hearing, hearing preservation surgery may be recommended. Small tumours in older patients may be observed and growth carefully monitored by serial MRI scans.

The aims of surgery for acoustic neuroma are to remove the tumour with preservation of all neurological or brain function. Acoustic neuromas are in close proximity to vital brain and nerve structures and are a complicated problem.

At Ear Science Institute Australia, the surgeons work in a team comprising Ear and Skull Base Surgeons (Neuro-otologists), Neurosurgeons, Audiologists, Anaesthetists, Specialised Nurses and Balance Physiotherapists. The use of modern surgical, anaesthesia and intensive care techniques including special monitoring of surrounding nerves, especially the facial nerve, minimises damage to the vital structures. In nearly all cases, this team achieves total tumour resection with facial nerve preservation.

Surgery

A specialised acoustic neuroma surgery unit requires the skills to use three major surgical approaches to these tumours. The most commonly used is the translabyrinthine approach which is most suitable for medium or large size tumours and those patients without useful hearing. An attempt to preserve residual hearing in patients with small tumours can be made with alternative approaches through the middle fossa or posterior fossa. Hearing may be preserved in up to 60% of patients but the level of hearing may not always be valuable to the patient.

The Specialised Acoustic Neuroma Unit involving Ear Science Institute Australia surgeons has an international reputation attracting patients from South East Asia, South Africa and throughout Australia. Surgeons visit around the world to adopt new acoustic neuroma surgery techniques.

Surgery - the patient perspective

Surgery should be discussed carefully and clearly with the patient and their family. Before surgery, blood tests, x-rays, hearing tests and other special investigations may be undertaken. The patients are reviewed by the co-surgeon and surgery again discussed.