Abstracts

Rationale: Negative motor seizures (NMS) are characterized by transient inability of conducting voluntary movements in a preserved consciousness. And their localizing value has not been fully elucidated. We investigated the localization and prognosis of patients with NMS. Methods: NMS was defined as inability to move the extremities with variably subsequent evolution to positive motor seizures. A total of 31 subjects with NMS was retrospectively identified from Yonsei Epilepsy Registry. The age of onset, location of lesions on magnetic resonance image (MRI), and outcome of medical or surgical treatment were investigated. Three patients had undergone surgery and two had subdural grid implantation with intracranial EEG monitoring. Two patients had scalp EEG monitoring. Voxel based symptom mapping (VLSM) was used to identify mostly frequently overlapping lesions in cases with structural abnormality in the cortex. Results: Age of seizure onset was 26.0 ± 13.4 and eighteen (60%) was male. Nineteen subjects had focal lesion on MRI, among which 7 were located in the perirolandic cortex, and 6 were in the premotor frontal cortex. VLSM analysis revealed that the lesions were most frequently located in the prefrontal area (n = 5).Outcome of medical treatment (follow-up period of more than 2 years) was available in 23 patients, in which 15 (65%) were free of seizures at their last follow-up with adequate antiepileptic drug treatment.In each 3 patients who had undergone surgical treatment, pathologic diagnosis was as follows: no pathologic diagnosis in resected medial frontal lobe in two, and oligodendroglioma in the left temporal lobe. They were all free of seizures after surgery.In two patients, cortical stimulation at supplementary sensorimotor area elicited symptoms identical to NMS.Another patient showed scalp EEG (Cz electrode) spikes just before the symptom, suggesting the symptomatogenic focus in the midline central area. Conclusions: Our data shows that patients with NMS frequently have possible epileptogenic structural lesions in the prefrontal cortex. Seizure freedom (65%) after medical treatment was favorable. Negative motor area, especially in the medial frontal lobe seems to be responsible for NMS as indicated in the surgical cases.   Funding: none