For a Koos Grade 2 vestibular schwannoma in a 68-year-old with comorbidities unfit for surgery, stereotactic radiosurgery is planned. Which statement about modern Gamma Knife treatment is correct?

• A Radiosurgery is contraindicated once the tumour contacts the brainstem
• B Marginal dose of 30 Gy is required because schwannomas are radioresistant
• C Radiosurgery provides better hearing preservation than observation alone
• D Marginal dose of approximately 12 to 13 Gy achieves long-term tumour control in more than 90 percent of cases ✓

Explanation

Modern Gamma Knife radiosurgery uses a marginal dose of about 12 to 13 Gy for vestibular schwannomas up to roughly 2.5 to 3 cm, achieving tumour control exceeding 90 percent with low cranial neuropathy rates. Schwannomas are relatively radiosensitive, so 30 Gy is far too high and increases complications. Radiosurgery carries a risk of hearing deterioration comparable to or worse than observation in some series, and brainstem contact is not a contraindication, only significant mass effect favouring microsurgery.

Reference: Cummings Otolaryngology: Head and Neck Surgery, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.