Study of cerebral perfusion in focal epilepsy using SPECT with 99Tcm

Locating the epileptogenic focus in patients with drug resistant temporal lobe epilepsy is essential for pre-surgical evaluation of such cases. This is not always possible with a surface electroencephalogram (EEG) and, for that reason, various diagnostic methods have been used employing morphological and functional images. Of these, the ones which can be best related to the EEG images are interictal positron emission tomography (PET) and ictal single photon emission computed tomography (SPECT). Various studies performed with 99Tcm-HMPAO (hexamethypropylene amine oxime) show that the sensitivity of the technique for the location of epileptogenic foci varies between 50 and 70% in the interictal period, but rises to 65-97% if the study is ictal. Recently, the use of 99Tcm-ECD (ethyl cysteinate dimer) in such patients has been described and a high level of agreement was found with both clinical and EEG results. The aim was to evaluate the interictal use of 99Tcm-ECD in ten patients with partial complex epilepsy where there was no evidence of a structural lesion and compare it with extended computerized video EEG in eight of these patients and with standard EEG in two. In one patient, the SPECT was normal, whereas there was a temporal focus in the EEG. In the nine remaining patients, all the epileptogenic foci showed up as hyporperfused zones in the SPECT. The latter also revealed two zones of hypoperfusion which were not apparent in the EEG. Ictal and interictal SPECT were performed on two patients. Here the epileptogenic foci showed up as hyperfused areas in the ictal SPECT and areas with diminished or normal perfusion in the interictal SPECT. It is concluded that SPECT with 99Tcm-ECD is useful for the pre-surgical evaluation of patients with temporal lobe epilepsy. (author). 17 refs, 2 tabs