Radiosurgical Corpus Callosotomy: A Review of Literature

Abstract

Background: Microsurgical callosotomy is a procedure still under debate and to best a palliative treatment for drug-resistant epilepsy. Unlike microsurgery, radiosurgical callosotomy is an underpracticed treatment option, with no definite account of its safety and outcome profile.

Objective: To evaluate the safety, efficacy, and complication profile of radiosurgical callosotomy in the literature.

Methods: PubMed, SCOPUS, Web of Science, and ResearchGate were reviewed for radiosurgery and callosotomy in the English language following PRISMA guidelines. The patient profile, radiosurgical parameters (dose and isodose), target volume, extent of radiosurgery (anterior third, half, or posterior third callosotomy), and seizure outcome were evaluated. We evaluated the role of radiosurgery as a primary or secondary treatment modality after microsurgery. A literature review was performed to identify the evidence of radiosurgery.

Results: We identified 7 studies detailing 12 patients of mean age 22.8 years (range, 4-58 years) and a mean of 18.9 years of illness (range, 5-37 years). Five series performed Gamma Knife radiosurgery and 2 performed LINAC radiosurgery. The spectrum of seizures ranged from atonic seizures/drop attack (83%), generalized tonic-clonic seizures (75%), complex partial seizures (67%), absence seizures (50%), myoclonic seizures (33%), to focal seizures (16%). Four patients suffered from Lennox-Gastaut syndrome. The average seizure frequency in 11 patients was 297/month (range, 20/day to 15/month). Three patients became free of drop attacks and 2 free of generalized tonic-clonic seizures, and 1 became completely seizure free. The remaining patients continued to have seizures, albeit at a lower frequency. Complex partial seizures and myoclonic seizures were the least responsive seizure types to radiosurgical corpus callosotomy. All patients tolerated the procedure well. After radiosurgery, 3 patients developed symptomatic edema. The symptoms (headache, nausea, hemiparesis, and transient neurologic deficits) were controlled with a short course of steroids. Two patients needed redo radiosurgery (at the same target in 1 patient and complementary middle third callosotomy to previous anterior third callosotomy in another patient). There were no long-term complications.

Conclusions: Radiosurgery is a viable alternative to microsurgical callosotomy both as a primary and as a secondary treatment modality. It has a specific advantage of better neuropsychological outcomes with comparable seizure control. The neurosurgical community should adopt a more liberal approach with this indication.

Keywords: Disconnection; Drop attacks; Drug-resistant epilepsy; Epilepsy surgery; Gamma Knife.