Optimised interictal HMPAO-SPECT in the evaluation of partial epilepsies

Interictal blood flow single photon emission computed tomography (SPECT) has been considered to be of limited value in the investigation of patients with partial epilepsies. Newer SPECT technologies using brain dedicated multiple detector systems have not been fully evaluated. To study the usefulness of an optimized SPECT technique, we scanned 40 epilepsy patients and ten normal subjects. Interictal [99mTc]hexamethylpropylene amine oxime (HMPAO) SPECT scans were acquired using the GE/CGR Neurocam triple-headed brain-dedicated system. The results of a qualitative analysis of the scans were compared to EEG and optimised MRI findings. Eight of the normal subjects and one of 40 patients had normal SPECT scans. There was a comparable concordance of lateralization between SPECT, MRI and EEG. The majority of our patients had mesial temporal pathology on MRI. Perfusion abnormalities extending beyond the mesial temporal area were common and did not simply relate to structural abnormalities. Quantification of blood flow in multiple brain regions revealed that hypoperfusion did not occur at random. Perfusion in the mesial temporal lobe was related to perfusion in anatomically and functionally related ipsilateral and contralateral brain regions. These hypoperfused areas probably reflect dysfunctioning areas which are related to the epileptogenic process.