Mechanism of tonic spasms in West syndrome viewed from ictal SPECT findings

To clarify the pathophysiology of tonic spasms, 21 patients with West syndr ome were analyzed using ictal and interictal single photon emission compute d tomography (SPECT). We focused on whether ictal perfusion changes were ob served in the focal cortical region. Eight of the patients studied showed d efinite focal cortical ictal hyperperfusion, indicating that there is a uni que subset of West syndrome that can be classified as infantile localizatio n-related epilepsy. Of those eight patients, only two showed asymmetric spa sms, suggesting that seizure symptomatology in infants gives only limited i nformation on the localization-related nature of epilepsy. Furthermore, the activation of subcortical structures by focal cortical regions might be at tributable to the symmetric seizure phenomena. Thirteen patients showed a d iffuse pattern in their ictal SPECTs; this probably included patients with diffuse hyperperfusion and those with no changes. The following have yet to be determined: (1) whether West syndrome is divided into subgroups based o n the origin of spasm,, in that some patients have the origin in the cortic al hemisphere and some have the origin in structures other than the cortica l hemisphere, such as the brain stern; (2) whether differences in ictal SPE CT patterns reflect a unique nature of tonic spasms in West syndrome, where tonic spasms appear in clusters and the interval of each spasm is differen t among each patient. (C) 2001 Elsevier Science B.V. All rights reserved.