Perfusion patterns in postictal 99mTc-HMPAO SPECTafter coregistration with MRI in patients with mesial temporal lobeepilepsy

OBJECTIVES—To assess patterns of postictalcerebral blood flow in the mesial temporal lobe by coregistration ofpostictal ^99mTc-HMPAO SPECT with MRI in patients withconfirmed mesial temporal lobe epilepsy.
METHODS—Ten postictal and interictal^99mTc-HMPAO SPECT scans were coregistered with MRI in 10 patients with confirmed mesial temporal lobe epilepsy. Volumetrictracings of the hippocampus and amygdala from the MRI were superimposedon the postictal and interictal SPECT. Asymmetries in hippocampal andamygdala SPECT signal were then calculated using the equation:
% Asymmetry =100 × (right − left) / (right + left)/2.
RESULTS—In the postictal studies, quantitativemeasurements of amygdala SPECT intensities were greatest on the side ofseizure onset in all cases, with an average % asymmetry of 11.1, range5.2-21.9.Hippocampal intensities were greatest on the side of seizureonset in six studies, with an average % asymmetry of 9.6, range4.7-12.0.In four scans the hippocampal intensities were less on theside of seizure onset, with an average % asymmetry of 10.2, range5.7-15.5.There was no localising quantitative pattern in interictal studies.
CONCLUSIONS—Postictal SPECT shows distinctiveperfusion patterns when coregistered with MRI, which assist inlateralisation of temporal lobe seizures. Hyperperfusion in the regionof the amygdala is more consistently lateralising than hyperperfusionin the region of the hippocampus in postictal studies.