Ictal single photon emission computed tomography (SPECT) and EEG were used to determine the mechanism of clustered spasms in 3 patients with symptomatic West syndrome (WS), in a study at Tokushima University, Japan. Regional cerebral blood flow increased during ictus and decreased during the interictal period in the area coinciding with the CT/MRI delineated focal cerebral lesion. Ictal hyperperfusion of bilateral basal ganglia was detected in 2 of 3 patients. Ictal EEG showed a diffuse slow wave complex corresponding to a clinical spasm. Sharp waves that preceded the delta activity and spasm were located in the same area in which cerebral blood flow increased during ictus. No patient showed a partial seizure. Focal cortical discharge and secondary generalization generate cluster spasms and trigger the brain stem and basal ganglia to produce spasms. Administration of clonazepam or resection of the focal cortical lesion resulted in complete cessation of spasms and disappearance of hypsarrythmia. 
COMMENT. A previous SPECT study from Tokushima University (Ped Neur Briefs Dec 1994)  showed localized cerebral hypoperfusion in the temporal lobes in 7 of 10 patients with infantile spasms, EEG showed corresponding focal abnormalities in 5, and the MRI confirmed localized lesions in only 3. PET studies have shown hypermetabolism of the lenticular nuclei in 32 of 44 infants with both cryptogenic and symptomatic infantile spasms Ped Neur Briefs March 1992) . Every infant with a focal lesion on CT/MRI had a focal abnormality on PET in the same location, but 17 of 28 infants with focal abnormalities on PET had no detectable focal abnormalities on CT/MRI. Chugani HT et al also reported bitemporal hypometabolism on PET in 18 infants with spasms and severe developmental delay.