ICTAL POSTICTAL AND INTERICTAL SINGLE-PHOTON EMISSION TOMOGRAPHY IN THE LATERALIZATION OF TEMPORAL-LOBE EPILEPSY

Single-photon emission tomography (SPET) using radioligands that are f ixed on first pass through the cerebral circulation shows distinctive and rapidly changing blood flow patterns accompanying temporal lobe se izures. We sought to determine the optimal time to perform SPET studie s for clinical seizure lateralization in temporal lobe epilepsy. Inter ictal, ictal and postictal SPET scans of 73 consecutively studied pati ents with unilateral temporal lobe epilepsy were read by three blinded observers to assess the accuracy of lateralization in each condition. The blinded observers correctly identified the side of focus in 97% o f ictal studies, 72% of postictal studies and 50% of interictal studie s. No incorrect scores were made in the ictal studies, whilst 5% of po stictal and 12% of interictal studies were lateralized to the wrong si de. Inter-observer agreement was best with the ictal studies. The dram atic perfusion changes of ictal SPET provide consistent, reliable and easily interpretable information that is superior to that provided by interictal and postictal studies. Injection of ligand during seizures is therefore the method of choice for SPET to aid the non-invasive lat eralization of temporal seizure foci.