Abstracts

Rationale: Surgical treatment of intractable epilepsy in patients with malformations of cortical development (MCDs) requires localization of both epileptogenic and eloquent cortices. Current standard of care involves direct cortical stimulation requiring an invasive craniotomy. The present study characterizes the effectiveness of functional MRI (fMRI) as a tool for assessing cortical reorganization in patients with MCDs. The purpose of this study is to determine whether primary functional reorganization occurs in patients with MCDs.Methods: Functional MRI data were obtained for seven controls and nine patients with MCD (cortical dysplasia, polymicrogyria, and heterotopia). Data were acquired on a 3.0T Siemens Magnetom Tim Trio MRI, using a 12 channel head RF coil. fMRI data were acquired with a multi-slice EPI pulse sequence (64x64 acquisition matrix, 5 mm isotropic resolution, repetition time (TR)/Echo time (TE) = 3200/25 ms). A total of 132 image sets were collected, divided into 7 task-rest cycles with 12 sets in each state. The fMRI task comprised of left and right finger tapping. During fMRI acquisition, patients performed self-paced motor tasks of dominant hand (DH) and non-dominant hand (NDH) by opposing the thumb to each finger starting at the index and ending on the fifth digit. The analysis of the fMRI time series data was completed using SPM2. Results: Figure 1 shows fMRI results for 4 right handed controls and 4 MCD patients. In total, reorganization was observed in 8 out of 9 patients compared to controls. Patients with lesions in the primary motor cortex exhibited the smallest activation in the lesion volume and appeared to have greater reorganization. Non dominant hand trials also showed a tendency for reduced activation in the cerebellum. Notable observations include mirrored activation (DH P2) and total reorganization (NDH P3, activation in the anterior brain not seen in this image). No consistent reorganization was observed across patients. More data will be needed to compare the specific types of MCD, although decreases in activation and reorganization were found in each MCD type (polymicrogyria, cortical dysplasia and heterotopia). Conclusions: This preliminary study demonstrated cortical activation differences between patients with MCDs and control subjects. Positively localizing cortical function or identifying reorganization using fMRI technology would serve as a foundation for the development of non-invasive pre-surgical techniques to aid in the surgical treatment of epilepsy.