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| EAR DISORDERS & TREATMENTS > Acoustic Neuroma |
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Introduction
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.
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An acoustic neuroma in the auditory canal,
pressing against the brain
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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 Lions Ear and
Hearing Institute 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.
For more information see:
 Subramaniam K, Eikelboom RH, Eager KM, Atlas MD (2005) Unilateral profound hearing loss and the effect on quality of life after cerebellopointine angle surgery. Otolaryngology - Head and Neck Surgery, 133:339-346.
Subramaniam K, Eager KM, Ivey GE, Eikelboom RH, Atlas MD. (2005) Bone Anchored Hearing Aids - Improving Quality of Life for acoustic neuroma patients with unilateral hearing loss, ANZ Journal of. Surgery. 75:A138.
O'Sullivan PG, Atlas MD (2003). Tumours of the temporal bone, in Scott Brown Textbook of Otolaryngology, 7th edition (ed. M Gleeson), Butterworths, London.
Srinivasan V, Atlas MD, Lowinger D (2002) A new Technique For Hypoglossal-Facial Nerve Repair. Abstract, Proceedings at 9th International Facial Nerve Symposium Otology & Neurotology 23(3): 87.
Briggs RJS, Fagan P, Atlas MD, Kay, Shcchx J, Hollow R, Shaw S, Clark G (2001) Multichannel Auditory brainstem implantation: the Australian experience. Journal of Laryngology and Otology 114, Sup 27, 46-49.
Atlas MD, Becvarovski Z (2001) Reanimation of the lower lid in facial paralysis. Australian Journal of Otolaryngology 4(2): 111-114.
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