Abstracts

Rationale: Epilepsy surgery is an effective treatment for medically-resistant temporal lobe epilepsy (TLE). To minimize complications rate and potentially improve neuropsychology outcome stereotactic radiosurgery (SRS) have been explore as an alternative. Two pilot trials have demonstrated the effectiveness of SRS for the treatment of medically-resistant TLE with seizure-free outcome of approximately 65% at last follow-up. Despite encouraging results, no conclusive long-term outcome is available for SRS. This article discusses a single patient that presented with recurrent seizures, worsening headaches and persistent abnormal MRI findings seven years and eight months after SRS.Methods: Case Report She had a history of medically refractory complex partial seizures since childhood. She had failed medical management. Work-up was compatible with left mesial temporal lobe onset with a MRI suggestive of mesial temporal sclerosis. In 2003, at age 23, she underwent gamma knife (GK) (Elekta AB, Stockholm, Sweden) radiosurgery targeting the left temporal mesial area with a dose of 24 Gy at the 50% marginal isodose line. After GK radiosurgery, the patient s seizures decreased in frequency over several months, but auras were persistent. Nine months after treatment, she developed worsening headaches. A follow-up MRI demonstrated a thick, irregular enhancing lesion in the medial part of the temporal lobe. She was placed on corticosteroids with resolution of her headaches. Her seizures and headaches recurred March/2010. MRI showed a 2.2 cm ill-defined enhancing cystic lesion in the mesial temporal lobe with T2 and FLAIR sequence abnormality compatible with vasogenic edema. Patient opted for left temporal lobe resection to control her seizures. Results: Histopathology Histologic examination showed no features compatible with a high-grade glioma. At the level of the hippocampus there was evidence of moderately severe, remote-longstanding hippocampal sclerosis. The vascular lesion was most consistent with radiation induced capillary hemangioma. The entorhinal region was most severely damaged with hemorrhage, necrosis, neuronal loss, astrogliosis, and hemosiderin deposition. There was evidence of radiation vasculopathy. Conclusions: Radiation-induced lesions for SRS in the treatment of mesial TLE are not well documented. GK radiosurgery is a promising technique for the treatment of medically-resistant TLE. However, the ideal candidate is not yet well-defined. The selection of the appropriate technical parameters to obtain a desirable functional effect with minimal or no histological damage remains a challenge. This case illustrates the need for long-term follow-up when radiosurgery is used for epilepsy.