PERFUSION PATTERNS IN POSTICTAL TC-99M-HMPAO SPECT AFTER COREGISTRATION WITH MRI IN PATIENTS WITH MESIAL TEMPORAL-LOBE EPILEPSY

Objectives-To assess patterns of postictal cerebral blood flow in the mesial temporal lobe by coregistration of postictal Tc-99m-HMPAO SPECT with MRI in patients with confirmed mesial temporal lobe epilepsy. Me thods-Ten postictal and interictal Tc-99m-HMPAO SPECT scans were coreg istered with MRI in 10 patients with confirmed mesial temporal lobe ep ilepsy. Volumetric tracings of the hippocampus and amygdala from the M RI were superimposed on the postictal and interictal SPECT. Asymmetrie s in hippocampal and amygdala SPECT signal were then calculated using the equation: % Asymmetry = 100 x (right - left)/(right + left)/2. Res ults-In the postictal studies, quantitative measurements of amygdala S PECT intensities were greatest on the side of seizure onset in all cas es, with an average % asymmetry of 11.1, range 5.2-21.9. Hippocampal i ntensities were greatest on the side of seizure onset in six studies, with an average % asymmetry of 9.6, range 4.7-12.0. In four scans the hippocampal intensities were less on the side of seizure onset, with a n average % asymmetry of 10.2, range 5.7-15.5. There was no localising quantitative pattern in interictal studies. Conclusions-Postictal SPE CT shows distinctive perfusion patterns when coregistered with MRI, wh ich assist in lateralisation of temporal lobe seizures. Hyperperfusion in the region of the amygdala is more consistently lateralising than hyperperfusion in the region of the hippocampus in postictal studies.