Abstracts

Rationale: Medically intractable non-lesional supplementary sensorimotor area (SSMA) epilepsy remains a challenge of treatment. Its mesial location and proximity to eloquent areas make the complete resection of the epileptogenic zone difficult. We have recently published the results of epilepsy surgery in patients investigated with subdural electrodes, and found that seizures of SSMA origin were a predictor of good outcome, however, this sample included all cases of medically-intractable SSMA epilepsy, including cases with lesions on MRI. This current study examines our surgical experience with non-lesional SSMA epilepsy. Methods: We retrospectively reviewed all consecutive patients admitted to the epilepsy unit with the diagnosis of non-lesional medically intractable SSMA epilepsy between February 1989 and March 2005. Inclusion criteria included an epileptogenic area exclusively over the SSMA confirmed with intracranial electrode recording and a normal MRI. We excluded all patients with an abnormal MRI. We also describe our surgical technique for mapping and resection of the nonlesional SSMA. Demographics as well as clinical data are presented. Results: Ten patients (2 females) were included. The mean age at surgery was 24.2 (range: 3 - 41). Mean age of epilepsy onset was 8.1 years of age (range: 1-14). Classic fencing posture was seen in only 2 patients. All patients underwent placement of subdural electrodes prior to surgery. An average of 11 strips (range: 8-13) were placed in each case. Length of hospital stay was 14 days on average (range: 4-26 days). Following the intracranial recordings, all patients underwent awake craniotomy with mapping of the superior and mesial rolandic region and resection of the SSMA. Mean follow up was 23.4 months (SD /- 15.1). 9 patients had weakness of the contralateral leg and/or hand immediately after surgery and complete resolution was observed in 7. Two patients did not recover completely. In one patient a very mild hand weakness remained present at follow-up without an explanation on MRI and another patient had an intra-operative infarct as a result of injury to the collosomarginal artery leading to a permanent contralateral foot and shoulder weakness. Transient speech difficulties were seen in only 3 patients following surgery. In the 8 patients in whom follow-up was available, and Engel I classification was obtained in 4 patients (50%), III in 2 patients and IV in 2 patients. Conclusions: Good surgical results (50% seizure free and 75% improved) were obtained in this small subset of patients with non-lesional SSMA epilepsy. While significant contralateral weakness was almost universal following surgery, nearly all patients recovered completely.