WIDESPREAD CEREBRAL STRUCTURAL-CHANGES IN PATIENTS WITH CORTICAL DYSGENESIS AND EPILEPSY

Cerebral cortical dysgenesis (CD), as revealed by MRI, is the second c ommonest cause of medically refractory chronic partial epilepsy. Surgi cal treatment is often disappointing in these cases. This has been att ributed to the probable diffuse nature of the condition but proof of t his in the human brain is lacking. We have quantitatively analysed MRI scans of 30 neurologically normal control subjects and 18 patients wi th CD, examining the regional distribution of grey and subcortical mat ter volumes. In 15 out of the 18 patients, we have demonstrated abnorm alities of this distribution beyond the margins of the visualized lesi on. Nine out of 10 patients with dysgenetic lesions visualized only in one hemisphere had volumetric abnormality in the apparently normal co ntralateral hemisphere. These abnormalities were not visible on reinsp ection of the MRI scans. Such abnormalities were not found in 10 patie nts with isolated hippocampal sclerosis (HS) although the history of g eneralized seizure activity and duration of epilepsy did not differ be tween the two groups of patients. Thus there is evidence for the exist ence of extensive structural disorganization outside visually identifi ed focal lesions in the brains of patients with CD and chronic partial epilepsy. This disruption is nor due to the effects of the epilepsy a nd must instead be associated with its cause. Possible mechanisms prod ucing the abnormalities are discussed. The methodology described may b e applied to other cortical diseases.