[Interictal basal brain SPECT versus interictal activated brain SPECT in temporal cryptogenic epilepsy]

Interictal epileptiform activity (IEA) is a common finding in temporal epileptic patients. The nature of the IEA is not entirely understood; it may be microseizures or just a negative phenomenon expressing brain inhibition mechanisms. In order to understand how brain metabolism is during interictal activity we studied a group of patients with SPECT HMPAO during basal condition no ictal activity - and when the same patients were having interictal activity. Temporal, thalamic and cerebellar perfusion were quantified by a digital method.

Two studies were performed in 24 epileptic patients: (9/15:M/F, 36,5 14,6 years). The MRI was normal or had minimal changes. Previous EEG had showed frontotemporal foci. The patients were studied by SPECT HMPAO performed with a STARCAM 3.200 equipment, the images being obtained by high resolution collimator with circular orbit 64 images, 30 s per image. The first study was performed when there was no anomaly in the EEG (basal study). In the second study (activated study) the radioligand was injected when the EEG showed at least 10 graphoelements (spike, polispikes, or sharp waves per EEG page).

Thalamic, temporal and cerebellar perfusion decreased significantly in the activated state compared to the basal one (p < 0.001). The statistical relationship between these three locations was studied. There was a significant relationship (p < 0.001) between thalamic, temporal, and cerebellar perfusion, both in basal state and in the activated one. The correlation index was R2 > 0.9.

For the cases studied, temporal epilepsy is associated to a significant decrease in thalamic, temporal and cerebellar perfusion in the basal state compared to the activated one. This finding may indicate that IEA expresses a post-ictal state.