Nondominant hemisphere lesions and conversion nonepileptic seizures.

To explore the hypothesis that lateralized hemispheric dysfunction may contribute to the development of conversion symptoms, the authors studied frequency of unilateral cerebral physiological or structural abnormalities in 79 consecutive patients with conversion nonepileptic seizures (C-NES), who were also compared with two groups of epilepsy patients without C-NES. Sixty (76%) of the C-NES patients had unilateral cerebral abnormalities on neuroimaging, of which 85% were structural. Ictal or interictal epileptiform abnormalities on EEG were found in 78% of C-NES patients and focal slowing in another 10%. Fifty (63%) of the C-NES patients had both structural and epileptiform abnormalities. Among the 60 with unilateral abnormalities, 43 (71%) had right hemisphere structural lesions or physiologic dysfunctions (C-NES>non-C-NES, P<0.02). This study supports prior studies and clinical observations that cerebral dysfunction can contribute to the pathogenesis of conversion disorder, and that nondominant hemisphere dysfunction may play a greater role.