Chandrasekharan Kesavadas MD, Presenter: Nothing to Disclose

Bejoy Thomas, Abstract Co-Author: Nothing to Disclose

Sreedharan Sujesh, Abstract Co-Author: Nothing to Disclose

Arun Kumar Gupta, Abstract Co-Author: Nothing to Disclose

Presurgical evaluation of seizure patients with FCD in or near the eloquent cortex requires the performance of fMRI to understand whether the sensori- motor, visual or language functions have been reorganized by the malformation. Our study aims at localization of these cerebral functions in patients with focal epilepsy and malformation of cortical development.

Sixteen patients with age range of 5-28 years in the epilepsy programme of our institute, being considered for surgery, had FCD in or near the eloquent cortex. The inclusion of patients in this study was based on the following criteria: MR evidence of FCD, consideration for surgical treatment and need for defining eloquent brain areas. After explaining the procedure, the patient was positioned in a 1.5T MR machine. Anatomic landmark images of the entire head were obtained with 3D FLASH/ 3D FLAIR sequence. fMRI sequence based on blood oxygen level dependent contrast (BOLD) was applied after gradient field mapping. Simple sensorimotor, visual or language paradigms of block design type were used. Other than Inline BOLD (Real time fMRI), the data were also analyzed with statistical parametric mapping (SPM). Reorganization was considered when localization contrasted with that expected upon general anatomic rules.

In 10 patients where the cortical dysplacia was lying in or close to the primary motor/primary sensory cortex or the supplementary motor cortex the BOLD activation was seen within the lesion or in the expected location suggesting absent reorganization. However out of the four patients where language paradigms were performed in two patients there was shift of the language to the uninvolved hemisphere and in 2 there was no language shift. Visual paradigms testing also revealed no reorganization of the visual functions. In all patients the real time fMRI showed similar results to that of SPM processing.

In patients with FCD, the dysplastic cortex shows fMRI activation for sensorimotor and visual functions suggesting lack of reorganization .Shift in language function can however occur to the normal hemisphere.

Brain plasticity in FCD is unpredictable and hence surgery should be cautiously performed.

Kesavadas, C, Thomas, B, Sujesh, S, Gupta, A, Functional MRI (fMRI) Study of Cortical Reorganization in Focal Cortical Dysplasia (FCD).  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5005263.html