Preictal SPECT in temporal lobe epilepsy: regional cerebral blood flow is increased prior to electroencephalography-seizure onset.

UNLABELLED Peri-ictal SPECT provides unique information on the dynamic changes in regional cerebral blood flow (rCBF) that occur during seizure evolution and, thus, could be useful in clarifying the poorly understood interplay 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 studies using invasive long-term cortical CBF monitoring have demonstrated that rCBF changes occur up to 20 min prior to ictal electroencephalography (EEG) onset. Because of apparent technical difficulties, no preictal SPECT studies have been reported so far. Therefore, we present our results on two patients with temporal lobe epilepsy in whom preictal SPECT scans were performed fortuitously under continuous video-EEG monitoring control. METHODS Technetium-99m-hexamethyl propyleneamine oxime was injected 11 min (Patient 1) and 12 min (Patient 2) before clinical and EEG seizure onset, as documented from simultaneous video-EEG monitoring in two patients with temporal lobe epilepsy. We obtained accurate anatomical reference of CBF changes visible on SPECT by a special coregistration technique of MRI and SPECT. RESULTS Whereas interictal 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 were not accompanied by any significant changes of the ongoing EEG. CONCLUSION Our study provides evidence that rCBF is increased in the epileptic temporal lobe several minutes before EEG seizure onset. Thus, rCBF changes observed on peri-ictal SPECT scan cannot be considered a mere consequence of EEG seizure activity but may rather reflect a change in neuronal activity precipitating the transition from the interictal to the ictal state.

[1]  K J Oommen,et al.  Long-term surface cortical cerebral blood flow monitoring in temporal lobe epilepsy. , 1994, Neurosurgery.

[2]  U. Pietrzyk,et al.  Epileptic negative myoclonus , 1996, Neurology.

[3]  U Pietrzyk,et al.  An interactive technique for three-dimensional image registration: validation for PET, SPECT, MRI and CT brain studies. , 1994, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[4]  M. Dichter,et al.  Cellular mechanisms of epilepsy: a status report. , 1987, Science.

[5]  F Plum,et al.  Cerebral metabolic and circulatory responses to induced convulsions in animals. , 1968, Archives of neurology.

[6]  Wilder Penfield,et al.  CEREBRAL BLOOD FLOW DURING INDUCED EPILEPTIFORM SEIZURES IN ANIMALS AND MAN , 1939 .

[7]  C. Elger,et al.  Spatio-temporal dynamics of the primary epileptogenic area in temporal lobe epilepsy characterized by neuronal complexity loss. , 1995, Electroencephalography and clinical neurophysiology.

[8]  C. Rowe,et al.  Patterns of postictal cerebral blood flow in temporal lobe epilepsy , 1991, Neurology.

[9]  R Duncan,et al.  Ictal/postictal SPECT in the pre-surgical localisation of complex partial seizures. , 1993, Journal of neurology, neurosurgery, and psychiatry.

[10]  C. Rowe,et al.  Postictal switch in blood flow distribution and temporal lobe seizures. , 1992, Journal of neurology, neurosurgery, and psychiatry.

[11]  W J McKay,et al.  Temporal Lobe Epilepsy Subtypes: Differential Patterns of Cerebral Perfusion on Ictal SPECT , 1996, Epilepsia.