COMPARATIVE-STUDY OF INTERICTAL PET AND ICTAL SPECT IN COMPLEX PARTIAL SEIZURES

Objective - To compare the sensitivity of ictal Tc-99m-HMPAO single ph oton emission computed tomography (SPECT) with interictal F-18-fluorod eoxyglucose positron emission tomography (PET) in localization of the epileptogenic focus in patients with medically intractable complex par tial seizures (MI-CPS). Material and methods - Retrospective analysis was performed on patients with MI-CPS who underwent anterior temporal lobectomy from January 1993 onwards when PET became available to us fo r clinical studies at the Indiana University Medical Center. There wer e 38 female and 29 male patients (total=67) with MI-CPS, 10 to 55.5 ye ars of age (mean 31) and duration of their epilepsy from 1-46 years (m ean 21). Interictal PET was evaluated for evidence of focal hypometabo lism and ictal SPECT for focal perfusion abnormality (hyperperfusion o r hypoperfusion) by visual analysis. Results - Both ictal SPECT and in terictal FDG-PET studies were obtained in 36 patients with MI-CPS. PET showed definite hypometabolism in 30 and questionable hypometabolism in an additional two patients. Ictal SPECT correctly localized the sei zure focus in 27 patients by demonstrating ictal hyperperfusion wherea s in one the hyperperfusion was falsely localized. In an additional se ven patients the ictal SPECT provided probable localization by demonst rating ictal hypoperfusion in the appropriate temporal lobe. The sensi tivity of ictal SPECT and interictal PET was 34/36 and 32/36, respecti vely, the difference was not statistically significant (chi(y)(2)=0.18 , DF=1, P=0.67). In six of the 36 patients the two tests were compleme ntary to each other in providing localizing information. Conclusion - Ictal SPECT and interictal PET are equally sensitive and reliable tech niques in localizing the epileptogenic focus in patients with MI-CPS. They play a critical role in providing localization in MRI negative pa tients allowing surgical resection to be undertaken in many without ad ditional invasive electrographic monitoring.