Abstracts

Rationale: In patients with intractable epilepsy associated with polymicrogyria in the rolandic regions, the presurgical evaluation is a challenge because of unpredictable localizations of primary somatosensory and motor functions. In this study we used Magnetic Resonance Spectroscopy (MRS) and functional MRI (fMRI) to evaluate if there is reorganization of the vital cortex and to evaluate metabolic profile of these malformations in this particular set of patients with epilepsy.Methods: Four patients with polymicrogyria and intractable epilepsy localized to the rolandic areas were studied. The identification of these patients was made by MRI identification and anatomic localization of polymicrogyria. In every patient, we used short echo-time and 4-Tesla proton single voxel MRS (TE/TR= 40/3200 ms) and fMRI (motor and sensory paradigms. The spectroscopic results for creatine and choline were compared as ratios to N-acetylaspartate with data from control tissue regions. For somatosensory mapping, repetitive (block design) tactile stimulation was applied to each hand. For motor mapping, patients performed self-paced motor tasks of both hands by opposing the thumb to each finger. The position of “local maxima” of activity was determined for all paradigms. A localization of either sensory or motor cortical function that was more than 2 standard deviations from the expected anatomic localization (obtained from controls) was considered aberrant or representative of reorganized function.Results: Two patients had unilateral polymicrogyria with schizencephaly, and two had bilateral perisylvian polymicrogyria. The polymicrogyric tissues had a comparable metabolic profile with homogeneous healthy cortical areas, and the pattern of localization in fMRI was as expected despite the extensive malformations, when compared with controls.Conclusions: These preliminary MRSI- and fMRI-based findings indicate that polymicrogyric tissue behaves as healthy cortical tissue. The results need to be expanded, as we collect information on other types of malformations. This study was supported by a grant from the Physicians Services Incorporated Foundation, Toronto, Ontario, Canada.