Epilepsy accompanied by intracranial arachnoid cysts: studies on volume and regional cerebral blood perfusion using MRI and SPECT

Abstract

To evaluate whether arachnoid cysts (ACs) can directly cause epilepsy by cortical compression, we studied the relationships among seizures, the volume of ACs, and regional cerebral blood perfusion around ACs. Subjects were 11 patients (10.5 ± 7.2 years) with primary intracranial ACs. The AC volume was calculated from axial T 1-weighted magnetic resonance imaging (MRI). N-isopropyl p-iodoamphetamine ( 123I-IMP) single photon emission computed tomography (SPECT) was used to evaluate cerebral blood perfusion. The lesional side to normal side ratio (L/N ratio) was calculated from rectangular and irregular region of interests (ROIs) in frontal and temporal area around the ACs. The volume of ACs in nonepileptic patients was significantly larger than in epileptic patients. In nonepileptic patients, SPECT demonstrated hyperperfusion around ACs, whereas in epileptic patients it showed hypoperfusion. The L/N ratio of rectangular ROIs in the posterior temporal area and irregular ROIs in the temporal area were significantly lower in epileptic patients than in nonepileptic ones. Our results suggest that epilepsy with ACs is related to the cerebral blood perfusion in the surrounding brain structures rather than to the volume of the ACs. Not only compression but also complicated brain parenchymal lesions may participate in the development of epilepsy.