Xenon/CT cerebral blood flow studies during continuous depth electrode monitoring in epilepsy patients

To observe and describe cerebral blood flow (CBF) alterations immediately following depth electrode stimulation of the temporal lobe in patients with medically intractable epilepsy.

Five patients with partial epilepsy undergoing presurgical evaluation were chosen for xenon/CT cerebral blood flow (Xe/CT CBF) measurement immediately following electrically stimulated seizures via stereotactically placed temporal lobe depth electrodes. Each patient had a baseline Xe/CT CBF study. Four of the five patients had a total of seven temporal lobe stimulations each followed by a Xe/CT CBF study. The other patient had right temporal lobe electrical status epilepticus and was scanned without stimulation or electroencephalogram monitoring.

Of the four baseline or interictal scans, no areas of abnormally low flow were detected, but one baseline scan had elevated flows of 115 mL.100 g-1.min-1 in the left temporal lobe. One stimulation elicited 8 seconds of afterdischarge potentials, but no alteration of CBF was detected. One stimulation elicited an aura but no electrographic seizure was detected. This resulted, however, in bitemporal lobe elevation of CBF. The other five temporal lobe stimulations resulted in 17-63 seconds of afterdischarge potentials and all resulted in elevation of CBF to 69-118 mL.100 g-1.min-1. One of these five stimulations resulted in seizure and localized elevation of CBF. Following seizure activity, elevated CBF began to return to baseline levels by 20 minutes.

This study reveals a direct spatial and temporal relationship of elevated CBF with seizures. This study provides the most direct data to date in human subjects that focal seizure activity elevates CBF. Since seizures are known to increase metabolic activity in the activated tissue, this data also supports the assumption of coupling between CBF and metabolism during the pathologic process of a seizure.