The role of quantitative ictal SPECT analysis in the evaluation of nonepileptic seizures

Nonepileptic seizures may represent difficult diagnostic problems. Identify ing their presence and frequency is critical for determining appropriate tr eatment. The authors investigated the Value of quantitative perfusion chang es as measured by ictal single-photon emission tomography (SPECT) differenc e images in differentiating nonepileptic from epileptic seizures. Eleven pa tients with a clinical suspicion of nonepileptic events had ictal and inter ictal technetium-99m hexamethylpropylene amine SPECT scans during continuou s audiovisual surface electroencephalogram (EEG) monitoring. The authors an alyzed perfusion difference images based on registration, normalization, an d subtraction of ictal and interictal SPECT images. The difference images w ere registered to each patient's magnetic resonance imaging scan to anatomi cally localize ictal perfusion changes. Three of 11 patients also carried t he diagnosis of epilepsy and were taking antiepileptic medication. Five pat ients were taking antiepileptic drugs, but the diagnosis of epilepsy was no t con; firmed. In all patients, continuous video EEG monitoring revealed no ictal EEG findings. In nine Df these patients, visual interpretation of ic tal SPECT was suggestive of localized increased (n = 6) or decreased perfus ion (n = 3). In all patients, however, no bloodflow changes were noted on q uantitative SPECT analysis with injections performed during the seizure lik e event, suggesting the diagnosis of pseudoseizures. The authors' results s uggest that quantitative ictal SPECT analysis is a useful tool in the diagn osis of nonepileptic seizures.