Ictal 99mTc-HMPAO SPECT in alternating hemiplegia

99mTc-hexamethylpropylenamine oxime (99mTc-HMPAO) single-photon emission computed tomography (SPECT) was performed in a patient with alternating hemiplegia during 2 episodes of the disease. The regional cerebral blood flow patterns correlated with the clinical manifestations during both episodes. Hyperperfusion of the contralateral hemisphere was suggested by asymmetric 99mTc-HMPAO uptake, whereas symmetric 123I-N-isopropyl-p-iodoamphetamine uptake was detected during the interictal period. The results suggested that alternating hemiplegia in infants represents an atypical manifestation of epilepsy, despite the lack of paroxysmal electroencephalographic abnormalities during the episodes. 99mTc-HMPAO SPECT appears to be a useful method for detecting transient regional cerebral blood flow alterations during paroxysmal events because the tracer is rapidly available for emergencies and retains a fixed distribution for 5-8 hours, sufficient time to allow for SPECT acquisition.