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Trigeminal nerve integrated dose and pain outcome after gamma knife radiosurgery for trigeminal neuralgia
Hussein Alahmadi, Gelareh Zadeh, Norman Laperriere, Shobhan Vachhrajani, Nura Mazloom, Fred Gentili, and Mojgan Hodaie

Background: Gamma knife radiosurgery (GKRS) is an established treatment for trigeminal neuralgia. Identifying factors that influence outcome will help improve patients’ results.

Methods: We conducted a retrospective review of all patients treated with GKRS for trigeminal neuralgia at our institution from 2005 to 2010. Patients’ clinical features and treatment details were reviewed. Analysis was performed to identify predictors of response and recurrence.

Results: A hundred and forty five patients were treated. Mean follow up period was 24 months. At last follow up, 48 patients (33%) were pain free with no medications, and 48 patients (33%) were pain free maintained on medications. Twenty-eight patients (19%) had pain after the treatment but had significant reduction in their pain severity. Twenty-one patients (15%) did not have any significant pain reduction. Forty-four patients (30%) developed facial numbness. Recurrence occurred in 51 patients (35%). Post-treatment numbness was a predictor of good treatment response (OR 2.720, CI 1.193-6.200, p 0.0173). Higher integrated dose was a predictor of poor pain response to radiosurgery (OR 0.729, CI 0.566-0.940, p 0.0146). At an integrated dose value of 5.3 mJ or less, there was more than 50% chance of pain free outcome. Longer pain duration prior to treatment was the only independent predictor of increased recurrence risk (HR 1.038, 95%CI 1.001- 1.075; p=0.0412).

Conclusion: Radiosurgery is an effective treatment modality for trigeminal neuralgia. Post treatment numbness is associated with good treatment response and higher integrated dose predicts poor outcome after radiosurgery for trigeminal neuralgia.

Keywords: Gamma knife, trigeminal neuralgia, radiosurgery, integrated dose

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