Acoustic Neuromas
Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management
Definition
Acoustic neuromas (vestibular schwannomas) are benign, slow growing tumours of the Schwann cells affecting the vestibulocochlear nerve (cranial nerve VIII), leading to hearing loss, tinnitus, and balance disturbances.
Aetiology
- Sporadic cases (most common): associated with somatic mutations.
- Neurofibromatosis type 2 (NF2): bilateral acoustic neuromas due to NF2 gene mutation.
- Radiation exposure: previous cranial irradiation increases risk.
Pathophysiology
- Schwann cell proliferation results in slow-growing tumours affecting the vestibular portion of cranial nerve VIII.
- Progressive compression of the cochlear nerve leads to sensorineural hearing loss and tinnitus.
- Large tumours can exert pressure on the brainstem, cerebellum, or cranial nerves (facial nerve involvement).
Risk Factors
- Family history of neurofibromatosis type 2.
- Previous cranial radiation therapy.
- Genetic mutations affecting tumour suppressor genes.
Signs and Symptoms
- Unilateral sensorineural hearing loss: progressive and asymmetric.
- Tinnitus: persistent ringing or buzzing in the affected ear.
- Vertigo and balance disturbance: due to vestibular nerve involvement.
- Facial numbness or weakness: compression of the trigeminal or facial nerve in large tumours.
- Headache and ataxia: in cases of brainstem or cerebellar compression.
Investigations
- Audiometry: unilateral high frequency sensorineural hearing loss.
- MRI brain: gold standard for detecting acoustic neuromas.
Management
1. Observation:
- For small, asymptomatic tumours, regular MRI monitoring.
2. Surgical Treatment:
- Microsurgical resection: preferred for large or symptomatic tumours.
- Preservation of facial nerve function: critical consideration in surgery.
3. Stereotactic Radiotherapy:
- Used for small to medium-sized tumours to halt progression.
- Gamma Knife or CyberKnife therapy minimises nerve damage.
4. Symptom Management:
- Hearing aids or cochlear implants for hearing loss.
- Vestibular rehabilitation for balance disturbances.
5. Referral:
- ENT specialist: for initial assessment and hearing evaluation.
- Neurosurgery: for surgical intervention in large or symptomatic tumours.
- Oncology: if radiotherapy is being considered.
- Genetics: for patients with suspected neurofibromatosis type 2.