Evaluation of focal epilepsy: a SPECT scanning comparison of 123-I-iomazenil versus HM-PAO.

PURPOSE To establish whether regional disturbances of the benzodiazepine receptor distribution in focal epilepsies can be detected by SPECT using 123-I-Iomazenil. PATIENTS AND METHODS Benzodiazepine receptor imaging was carried out in 10 patients interictally. To be eligible for this study the patients had to have a history of focal seizures and no evidence of routine imaging abnormalities as in CT or MR. The patients were selected on the basis of a regional decreased blood flow in HMPAO SPECT that correlated with the site of a stable unifocal EEG abnormality. Benzodiazepine receptor imaging was performed after intravenous administration of approximately 110 MBq 123-I-Iomazenil using SPECT. RESULTS A regional reduced activity was found on sequential SPECT series after 30 and 90 min post injection in the receptor study. The brain region with a reduced receptor density was concordant to the pathologic finding in HMPAO SPECT in all patients. CONCLUSION For the evaluation of patients with focal epilepsies lomazenil SPECT offers several advantages over HMPAO SPECT. Iomazenil binds specifically to the benzodiazepine receptor complex whereas the exact binding sites of HMPAO are still unknown. In contrast to HMPAO, lomazenil can be used for sequential SPECT examinations that may detect dynamic changes of the receptor complex. For the purpose of benzodiazepine receptor imaging, lomazenil is a suitable ligand in patients with focal epilepsies.