[en] The ECAT Positron Tomograph was used to scan normal control subjects, stroke patients at various times during recovery, and patients with partial epilepsy during EEG monitoring. ¹⁸F-fluorodeoxyglucose (¹⁸FDG) and ¹³N-Ammonia (¹³NH₃) were used as indicators of abnormalities in local cerebral glucose utilization (LCMR/sub glc/) and relative perfusion, respectively. Hypometabolism, due to deactivation or minimal damage, was demonstrated with the ¹⁸FDG scan in deep structures and broad zones of cerebral cortex which appeared normal on x-ray CT (XCT) and /sup 99m/Tc pertechnetate scans. In patients with partial epilepsy, who had unilateral or focal electrical abnormalities, interictal ¹⁸FDG scan patterns clearly showed localized regions of decreased (20 to 50%) LCMR/sub glc/, which correlated anatomically with the eventual EEG localization

[en] Seventeen patients with partial epilepsy had EEG monitoring concurrent with cerebral emission computed tomography (ECT) after ¹⁸F-fluorodeoxyglucose (¹⁸FDG) and ¹³N-ammonia were given intravenously as indicators of local cerebral glucose utilization (LCMR/sub glc/) and relative perfusion, respectively. In 12 of 15 patients who had unilateral or focal electrical abnormalities, interictal ¹⁸FDG scan patterns clearly showed localized regions of decreased (20% to 50%) LCMR/sub glc/, which correlated anatomically with the eventual EEG localization. These hypometabolic zones appeared normal on x-ray computed tomography in all but three patients and were unchanged on scans repeated on different days. In 5 of 6 patients who underwent temporal lobectomy, the interictal ¹⁸FDG scan correctly detected the pathologically confirmed lesion as a hypometabolic zone, and removal of the lesion site resulted in marked clinical improvement. In contrast, the ictal ¹⁸FDG scan patterns clearly showed foci of increased (82% to 130%) LCMR/sub glc/, which correlated temporally and anatomically with ictal EEG spike foci and were within the zones of interictal hypometabolism (3 studies in 2 patients). ¹³NH₃ distributions paralleled ¹⁸FDG increases and decreases in abnormal zones, but ¹³NH₃ differences were of lesser magnitude. When the relationship of ¹³NH₃ uptake to local blood flow found in dog brain was applied as a correction to the patients' ¹³NH₃ scan data, local alterations in perfusion and glucose utilization were usually matched, both in the interictal and ictal states

[en] Neurophysiologically confirmed long-duration recurrent inhibition of hippocampal pyramidal unit firing was induced by low frequency (2 to 4 Hz) stimulation of the fornix for 60 min following intravenous infusion of [¹⁴C]-2-DG. The resulting autoradiograms showed that long-duration suppression of pyramidal cell firing was accompanied by distinctly increased hippocampal 2-DG uptake, particularly in the stratum pyramidale, which contains a dense plexus of inhibitory interneuronal terminals upon pyramidal cells. Both the pyramidal inhibition and the increased 2-DG uptake were confined to the ipsilateral hippocampus in animals with previously severed fornices and hippocampal commissures. In a second series of rats, the excitatory entorhinohippocampal ''perforant path'' (PP) was stimulated at low frequency (2 to 9 Hz) following 2-DG administration. At 2 to 4 Hz, each PP stimulation resulted in a brief burst of pyramidal unit firing followed by short-duration firing suppression; this result was associated with paradoxically decreased 2-DG uptake in the ipsilateral stratum molecular. By contrast, 7 to 9 Hz entorhinal stimulation induced PP-mediated excitation immediately followed by powerful intrinsic hippocampal inhibition, evidenced by prolonged pyramidal unit suppression after each stimulation. This suppression was accompanied by increased 2-DG uptake in the dentate stratum molecular and hippocampal stratum pyramidale. Thus it appeared that even with entorhinal stimulation, hippocampal 2-DG uptake was more closely associated with long-duration recurrent inhibition than with transient pyramidal excitation. Therefore, although it still remains possible that regions of hypometabolism observed in some previous 2-DG studies may actually reflect mild inhibition, other mechanisms such as disfacilitation are more likely mechanisms for this metabolic pattern

[en] Emission computed tomography (ECT) has been applied using ¹⁸F-fluorodeoxyglucose (¹⁸FDG) and ¹³N-ammonia (¹³NH₃) as indicators of abnormalities in local cerebral glucose utilization (LMCRsub(glc)) and relative perfusion, respectively. The ECAT positron tomograph was used to scan normal control subjects, stroke patients at various times during recovery, and patients with partial epilepsy, both in the interictal and ictal states. (Auth.)

[en] One hundred fifty-three patients with medically refractory partial epilepsy underwent chronic stereotactic depth-electrode EEG (SEEG) evaluations after being studied by positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) and scalp-sphenoidal EEG telemetry. We carried out retrospective standardized reviews of local cerebral metabolism and scalp-sphenoidal ictal onsets to determine when SEEG recordings revealed additional useful information. FDG-PET localization was misleading in only 3 patients with temporal lobe SEEG ictal onsets for whom extratemporal or contralateral hypometabolism could be attributed to obvious nonepileptic structural defects. Two patients with predominantly temporal hypometabolism may have had frontal epileptogenic regions, but ultimate localization remains uncertain. Scalp-sphenoidal ictal onsets were misleading in 5 patients. For 37 patients with congruent focal scalp-sphenoidal ictal onsets and temporal hypometabolic zones, SEEG recordings never demonstrated extratemporal or contralateral epileptogenic regions; however, 3 of these patients had nondiagnostic SEEG evaluations. The results of subsequent subdural grid recordings indicated that at least 1 of these patients may have been denied beneficial surgery as a result of an equivocal SEEG evaluation. Weighing risks and benefits, it is concluded that anterior temporal lobectomy is justified without chronic intracranial recording when specific criteria for focal scalp-sphenoidal ictal EEG onsets are met, localized hypometabolism predominantly involves the same temporal lobe, and no other conflicting information has been obtained from additional tests of focal functional deficit, structural imaging, or seizure semiology

[en] Ictal patterns of local cerebral metabolic rate have been studied in epileptic patients by positron computed tomography with ₁₈F-labeled 2-fluoro-2-deoxy-D-glucose. Partial seizures were associated with activation of anatomic structures unique to each patient studied. Ictal increases and decreases in local cerebral metabolism were observed. Scans performed during generalized convulsions induced by electroshock demonstrated a diffuse ictal increase and postictal decrease in cerebral metabolism. Petit mal absences were associated with a diffuse increase in cerebral metabolic rate. The ictal fluorodeoxyglucose patterns obtained from patients do not resemble autoradiographic patterns obtained from common experimental animal models of epilepsy

[en] Interictal and ictal fluorodeoxyglucose scans were obtained with positron CT from four patients with spontaneous recurrent partial seizures, one with epilepsia partialis continua, and one with a single partial seizure induced by electrical stimulation of the hippocampus. Ictal metabolic patterns were different for each patient studied. Focal and generalized increased and decreased metabolism were observed. Ictal hypermetabolism may exceed six times the interictal rate and could represent activation of excitatory or inhibitory synapses in the epileptogenic region and its projection fields. Hypometabolism seen on ictal scans most likely reflects postictal depression and may indicate projection fields of inhibited neurons. No quantitative relationship between alterations in metabolism and EEG or behavioral measurements of ictal events could be demonstrated

[en] The majority of patients with complex partial seizures of unilateral temporal lobe origin have interictal temporal hypometabolism on [18F]fluorodeoxyglucose positron emission tomography (FDG PET) studies. Often, this hypometabolism extends to ipsilateral extratemporal sites. The use of accurately quantified metabolic data has been limited by the absence of an equally reliable method of anatomical analysis of PET images. We developed a standardized method for visual placement of anatomically configured regions of interest on FDG PET studies, which is particularly adapted to the widespread, asymmetric, and often severe interictal metabolic alterations of temporal lobe epilepsy. This method was applied by a single investigator, who was blind to the identity of subjects, to 10 normal control and 25 interictal temporal lobe epilepsy studies. All subjects had normal brain anatomical volumes on structural neuroimaging studies. The results demonstrate ipsilateral thalamic and temporal lobe involvement in the interictal hypometabolism of unilateral temporal lobe epilepsy. Ipsilateral frontal, parietal, and basal ganglial metabolism is also reduced, although not as markedly as is temporal and thalamic metabolism

[en] The ECAT Positron Tomograph was used to scan normal control subjects, stroke patients at various times during recovery and patients with partial epilepsy during EEG monitoring. Fluorine-18-fluorodeoxyglucose (¹⁸FDG) and ¹³N-ammonia (¹³NH₃) were used as indicators of abnormalities in local cerebral glucose utilization (LCMRsub(glc)) and relative perfusion respectively. In patients with stroke, mean LCMRsub(glc) in the contralateral hemisphere was moderately depressed during the first week, profoundly depressed in irreversible coma, and normal after clinical recovery. Local distributions of ¹⁸FDG and ¹³Nh₃ trapping reflected qualitatively the increases and decreases, as well as coupling and uncoupling, expected in stroke for local alterations in glucose utilization and perfusion. Hypometabolism, due to deactivation or minimal damage, was demonstrated with the ¹⁸FDG scan in deep structures and broad zones of cerebral cortex which appeared normal on X-ray CT (XCT) and ⁹⁹Tcsup(m)-pertechnetate scans. In patients with partial epilepsy, who had unilateral or focal electrical abnormalities, interictal ¹⁸FDG scan patterns clearly showed localized regions of decreased (20-50%) LCMRsub(glc), which correlated anatomically with the eventual EEG localization. In most instances, these hypometabolic zones appeared normal on XCT and were unchanged on scans repeated on different days. In five of six patients who underwent anterior temporal lobectomy, the interictal ¹⁸FDG scan correctly detected the pathologically confirmed lesion as a hypometabolic zone, and removal of the lesion site resulted in marked clinical improvement. In contrast, the ictal ¹⁸FDG scan patterns clearly showed foci of increased (82-130%) LCMRsub(glc) which correlated temporally and anatomically with ictal EEG spike foci, and were within the zones of interictal hypometabolism. (author)