Regional cerebral blood flow of patients with focal epilepsy studied using xenon enhanced CT brain scanning.

Abstract

SUMMARY Stable xenon-enhanced X-ray computed tomography (XeCT) was used to measure the regional cerebral blood flow (rCBF) of 12 patients with drug resistant partial epilepsy and a marked unilateral focus on electroencephalography (EEG). Interictal mean rCBF of fixed regions of interest (ROIs) was reduced by 25% in the cortex of the epileptogenic cerebral lobe compared with the same regions on the contralateral side (p < 0 02). Six control scans showed a mean side to side cortical difference in rCBF of 14%, whereas the epileptogenic focus was associated with a reduction in the cortical rCBF of greater than 30% in six out of the 12 patients. In an additional patient with partial epilepsy XeCT demonstrated significant focal hypoperfusion when interictal EEGs and conventional CT scans showed no abnormalities.Stable xenon-enhanced X-ray computed tomography (XeCT) has previously been used to measure regional cerebral blood flow (rCBF) in normal subjects,' and patients with cerebrovascular disease.2 3 In a group of 19 resting normal subjects no significant differences between the rCBF of left and right cerebral structures were found.' To date there have been no reported measurements using XeCT of rCBF in patients with focal epilepsy.Regions of hypometabolism have been demonstrated interictally in approximately 50-70% of patients with focal epilepsy studied with positron emission tomography (PET).46 Such regions correspond most frequently to foci of mesial temporal sclerosis, although the areas of hypometabolism are generally found to be more extensive than the histological lesions. This is likely to be caused by the inactivation of associated structures.7The presence of mesial temporal sclerosis is of clinical significance because these epileptic patients have a much better prognosis following surgery than patients without histological abnormalities.8 Consequently the detection of focal hypometabolism in patients with partial epilepsy may be of prognostic value. Metabolic studies using PET have demon-

Bilateral decrease in interictal hippocampal blood flow in unilateral mesiotemporal epilepsy

“…Strict comparison of rCBF absolute values obtained by 15 18 Other studies also provide evidence for bilateral abnormalities in unilateral TLE. A decrease in the Nacetylaspartate (NAA) signal on proton MR spectroscopy was observed on both the ipsi-and contralateral sides in 45% of patients with TLE.…”