Makindo Medical Notes

🧠 Acoustic neuroma (vestibular schwannoma) is a benign tumour of Schwann cells affecting cranial nerve VIII. 📈 Accounts for ~8% of primary intracranial tumours and is the most common mass in the cerebellopontine angle. 💡 Always suspect in patients with unilateral sensorineural hearing loss (USNHL) until proven otherwise.

📖 About

• Benign schwannoma of the vestibulocochlear nerve (CN VIII).
• ~8% of intracranial tumours; ~80% of CPA lesions.
• Associated with NF2 → bilateral tumours (merlin gene mutation).
• Slow-growing but cause morbidity through local compression.

🧬 Aetiology

• Schwann cell proliferation (myelinating cells of peripheral nerves).
• Sporadic (majority) or inherited (NF2, autosomal dominant).
• Rare link with prior childhood cranial irradiation.

⚠️ Risk Factors

• Age 40–60 years.
• NF2 or strong family history.
• High-dose cranial irradiation in childhood.

📉 Effects of Tumour Expansion

• CN VIII → unilateral SNHL, tinnitus, imbalance 🎧.
• CN V → facial numbness, loss of corneal reflex.
• CN VII → LMN facial palsy, taste disturbance.
• Cerebellum → ipsilateral ataxia, unsteady gait 🚶.
• Brainstem → compression, hydrocephalus, raised ICP.
• Raised ICP → headache, nausea, papilloedema.

🩺 Clinical Features

• Unilateral SNHL (~95%).
• Tinnitus (buzzing/ringing).
• Vertigo, imbalance, disequilibrium.
• Facial numbness, paraesthesia.
• Facial weakness (late feature).
• Headache, vomiting (raised ICP).
• Ataxia, poor coordination.
• Think NF2 if bilateral lesions.

💡 Exam Pearl: Any patient with USNHL ± unilateral tinnitus → arrange MRI internal auditory meatus (IAM) to exclude vestibular schwannoma.

🔎 Investigations

• Pure tone audiometry → confirms SNHL.
• MRI IAM with gadolinium (gold standard) → “ice-cream cone” lesion 🍦.
• CT if MRI contraindicated → bone erosion, large lesions.
• BAEP (brainstem auditory evoked potentials) → pathway integrity.
• CSF protein ↑ (nonspecific).
• Genetic testing if NF2 suspected.

🧾 Differential Diagnosis

• Cerebellopontine angle meningioma.
• Epidermoid cyst.
• Other schwannomas (rare).
• Metastases.
• Multiple sclerosis (SNHL mimic).

🛠️ Management

• 👀 Observation: small, incidental lesions; elderly/frail patients → serial MRI.
• 🔪 Microsurgery: translabyrinthine, retrosigmoid, or middle fossa approach depending on tumour size/location.
• 🎯 Stereotactic radiosurgery (Gamma Knife / CyberKnife): for small-medium tumours or poor surgical candidates.
• 📡 Fractionated radiotherapy: selected cases.
• 🎧 Rehabilitation: hearing aids, vestibular rehab, facial nerve physiotherapy.
• MDT: neurosurgery, ENT, audiology, neuroradiology, genetics (NF2).

📊 Prognosis

• Good outcome if detected early.
• Hearing preservation depends on tumour size and surgical approach.
• Recurrence risk ~5% → long-term follow-up essential.
• Untreated → progressive compression, hydrocephalus, death.

🔒 Prevention & Screening

• No prevention for sporadic cases.
• NF2 → genetic counselling, baseline + interval MRI scans.

📚 References

• NHS: Acoustic Neuroma
• Radiopaedia: Vestibular Schwannoma
• Vestibular Schwannoma: An Overview (PMC)