Acoustic Neuroma

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

An acoustic neuroma, also known as vestibular schwannoma, is a benign, slow-growing tumour that develops from the Schwann cells covering the vestibulocochlear nerve (cranial nerve VIII), which connects the inner ear to the brain.

Aetiology

The exact cause of acoustic neuromas is unknown. However, they are associated with genetic mutations, particularly in individuals with neurofibromatosis type II (NF2), a rare genetic disorder.

Pathophysiology

Acoustic neuromas arise from Schwann cells, which produce the myelin sheath surrounding the vestibulocochlear nerve. The tumour typically originates in the internal auditory canal and can extend into the cerebellopontine angle, potentially compressing adjacent cranial nerves, brainstem, and cerebellum as it grows.

Risk Factors

• Family history of neurofibromatosis type II (NF2)
• Exposure to high doses of radiation, especially to the head and neck area
• Possible links to prolonged exposure to loud noise (under investigation)

Signs and Symptoms

Common signs and symptoms of acoustic neuroma include:

• Unilateral hearing loss, often gradual
• Tinnitus (ringing in the affected ear)
• Balance problems or unsteadiness
• Facial numbness or weakness if the tumour compresses the facial nerve
• Headaches and/or dizziness

Investigations

• Clinical history and physical examination
• Audiometry: Hearing tests to assess the degree of hearing loss
• Magnetic Resonance Imaging (MRI) with gadolinium contrast: Gold standard for diagnosis and assessment of tumour size and location
• Computed Tomography (CT) scan if MRI is contraindicated
• Brainstem auditory evoked potentials (BAEPs) to assess auditory nerve function

Management

Primary Care Management

• Initial referral to an ENT specialist or neurologist for further evaluation
• Monitoring and managing associated symptoms such as hearing loss and balance issues
• Regular follow-up and monitoring of hearing function

Specialist Management

• Observation: Regular MRI scans to monitor tumour growth, especially for small, asymptomatic tumours
• Microsurgical removal: Surgical resection of the tumour, which can be performed via several approaches (translabyrinthine, retrosigmoid, or middle fossa) depending on tumour size and location
• Radiotherapy: Stereotactic radiosurgery (e.g., Gamma Knife) to control tumour growth, often used for small to medium-sized tumours or in patients who are not surgical candidates
• Rehabilitation: Vestibular rehabilitation therapy for balance issues and physiotherapy if facial nerve function is affected
• Multidisciplinary approach: Involving ENT specialists, neurosurgeons, audiologists, and radiologists

References

1. NICE. (2024). Acoustic Neuroma: Diagnosis and Management. Retrieved from NICE
2. NHS. (2023). Acoustic Neuroma. Retrieved from NHS
3. British Medical Journal (BMJ). (2022). Acoustic Neuroma: Diagnosis and Management. Retrieved from BMJ
4. American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS). (2021). Clinical Practice Guideline: Acoustic Neuroma. Retrieved from AAO-HNS

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