PREICTAL SPECT IN TEMPORAL-LOBE EPILEPSY - REGIONAL CEREBRAL BLOOD-FLOW IS INCREASED PRIOR TO ELECTROENCEPHALOGRAPHY-SEIZURE ONSET

Peri-ictal SPECT provides unique information on the dynamic changes in regional cerebral blood flow (rCBF) that occur during seizure evoluti on and, thus, could be useful in clarifying the poorly understood inte rplay of the interictal and ictal states in human focal epilepsy. The regional hyperperfusion observed on ictal SPECT is generally believed to be a consequence of electrical seizure activity. However, recent st udies using invasive long-term cortical CBF monitoring have demonstrat ed that rCBF changes occur up to 20 min prior to ictal electroencephal ography (EEG) onset. Because of apparent technical difficulties, no pr eictal SPECT studies have been reported so far. Therefore, we present our results on two patients with temporal lobe epilepsy in whom preict al SPECT scans were performed fortuitously under continuous video-BEG monitoring control. Methods: Technetium-99m-hexamethyl propyleneamine oxime was injected 11 min (Patient 1) and 12 min (Patient 2) before cl inical and EEG seizure onset, as documented from simultaneous video-EE G monitoring in two patients with temporal lobe epilepsy. We obtained accurate anatomical reference of CBF changes visible on SPECT by a spe cial coregistration technique of MRI and SPECT. Results: Whereas inter ictal SPECT showed a hypoperfusion of the temporal lobe ipsilateral to the seizure focus, on preictal SPECT, a significant increase in rCBF in the epileptic temporal lobe could be observed. These rCBF changes w ere not accompanied by any significant changes of the ongoing EEG. Con clusion: Our study provides evidence that rCBF is increased in the epi leptic temporal lobe several minutes before EEG seizure onset. Thus, r CBF changes observed on peri-ictal SPECT scan cannot be considered a m ere consequence of EEG seizure activity but may rather reflect a chang e in neuronal activity precipitating the transition from the intericta l to the ictal state.