Acoustic Neuroma - Hearing Loss and Surgical Approaches

Acoustic neuroma (vestibular schwannoma) is a benign tumour originating from the vestibular branch of the eighth cranial nerve (vestibulocochlear nerve). It is the most common tumour of the cerebellopontine angle (the corner between the pons and the cerebellum) region.

Symptoms

The earliest and most common symptom is unilateral hearing loss; it usually starts at high frequencies and progresses slowly. Tinnitus (ringing in the ears) accompanies it in most patients. Balance disorders, dizziness, and facial numbness (trigeminal nerve compression) may occur as the tumour grows. In large tumours, facial paralysis (facial nerve compression), difficulty swallowing, and even hydrocephalus may develop.

Diagnosis

Thin-slice contrast-enhanced brain MRI (especially the internal acoustic canal protocol) is the gold standard in diagnosis.^1,2 Audiometry (hearing test) and brainstem auditory evoked potentials (BAEP) provide an objective evaluation of hearing function.

Microsurgery: Surgical resection is preferred in large tumours (over 2.5-3 cm) or in cases with brainstem compression.^3,4

Treatment Options

The treatment decision is individualised according to the size of the tumour, hearing status, and the patient's age and preference.

Watch and wait: In small (under 1-1.5 cm), asymptomatic, or minimally symptomatic tumours, especially in elderly patients, follow-up with serial MRI is an appropriate strategy.^5,6 Some of these tumours remain stable for years without growing.

Microsurgery: Surgical resection is preferred in large tumours (over 2.5-3 cm) or in cases with brainstem compression. Retrosigmoid, translabyrinthine, and middle fossa approaches are the most commonly used surgical techniques. The choice of approach depends on the tumour size, hearing status, and the surgeon's experience. Intraoperative facial nerve monitoring is a standard practice during surgery.^7,8

Gamma Knife radiosurgery: It is an effective alternative for small-to-medium-sized (under 3 cm) tumours. Tumour control is at a rate of 90-95 percent.^9,10 The hearing preservation rates of radiosurgery and microsurgery are similar in the medium term, but hearing loss may develop in the long term after radiosurgery.^9,11

Hearing Preservation

One of the most important goals in the treatment of acoustic neuroma is the preservation of hearing. In small tumours, if hearing is preserved, hearing preservation surgery can be attempted with a retrosigmoid or middle fossa approach.^12,13

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