Abstracts

Epilepsy surgery is a treatment option for patients with medically intractable epilepsy associated with malformations of cortical development (MCD). Electroencephalography (EEG) and magnetic resonance imaging (MRI) allow accurate localization of the epileptogenic zone (EZ) in most patients. However, the topography of MCD lesion and the EZ may not always overlap. Subtraction of interictal from peri-ictal SPECT coregistered to MRI (SISCOM) can detect activated brain regions during epileptic seizures. We evaluated the functional status of the PMG cortex during and between seizures, and the contribution of SISCOM in the presurgical investigation of 12 patients with polymicrogyria. Six patients underwent epilepsy surgery, three patients evolved favorably, and three remained unchanged. Our SISCOM results showed intense peri-ictal hyperperfusion on the polymicrogyric lesion in all patients, and mild to moderate hyperperfusion during the interictal state in eight patients. Contribution rates for EZ detection were SISCOM (92%), peri-ictal SPECT (83%), ictal EEG (75%), interictal EEG (67%), ictal semiology (25%) and interictal SPECT (25%). There was significant correlation between the intensity of perfusion on the site of the polymicrogyric cortex and the spike-rate on interictal EEG (p=0.041). We conclude that PMG lesions may be involved in seizure generation and may have a slight interictal functional activation probably related to the high cortical excitability. Finally, SISCOM technique provided useful information about the localization of the EZ in patients with polymicrogyria.