Among patients with prior positive exercise stress tests, mental stress-induced ischemia, defined by new wall motion abnormalities, predicts daily ischemia independent of exercise-induced ischemia. Exaggerated hemodynamic responses during mental stress testing also identify individuals who are more likely to exhibit myocardial ischemia during daily life and mental stress.

Noninvasive quantification of MBF and CFR from dynamic 13N-labeled ammonia positron emission tomography is most reproducible with technique 1 or 3. The ability to account for differences in myocardial partial volume gives preference to technique 3. However, substantial interstudy variability in regional MBF remains, suggesting the importance of procedural factors or real temporal fluctuations in MBF.

To investigate the relationship of temporal lobe hypometabolism demonstrated on PET to surgical outcome and underlying pathology, we reviewed 30 consecutive epilepsy patients who underwent interictal PET studies with 18F fluorodeoxyglucose before temporal lobectomy. Two interpreters blindly reviewed the PET studies and graded them for degree, extent, and location of temporal lobe hypometabolism. Pathologic analysis of en bloc resected tissue showed mesial temporal sclerosis (n = 22), astrocytoma (n = 2), and no pathologic diagnosis (n = 6). Outcome (24 to 40 months' follow-up) was rated as seizure-free (21 patients), significantly improved (five patients), and not significantly improved (four patients). Both the degree and extent of the temporal lobe hypometabolism demonstrated on PET were strongly associated with subsequent seizure control. Pathologic findings, however, did not correlate with degree of PET hypometabolism or subsequent outcome. These data demonstrate that in patients judged to have temporal lobe epilepsy, the presence of temporal lobe hypometabolism is associated with a positive outcome after ipsilateral temporal lobectomy.

As aggressive neurosurgery and adjuvant therapy have become standard care for most patients with primary central nervous system (CNS) tumors, limitations of posttreatment neuroimaging techniques have become more apparent. Interpretation of computed cranial tomography (CT) and magnetic resonance imaging (MRI) in patients with brain tumors is complicated by changes related to surgery, corticosteroids, radiation, and chemotherapy. We investigated the role of 18F-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (FDG-PET) in these difficult diagnostic situations by obtaining FDG-PET scans in 5 patients following temporal lobectomy for epilepsy, in 5 patients with recurrent anaplastic gliomas before and after corticosteroid therapy, and in 5 patients after the development of histologically confirmed radionecrosis. We also obtained postoperative FDG-PET scans in 32 consecutive patients undergoing initial resection of a primary brain tumor. Our results indicate that glucose uptake as detected by FDG-PET scanning with [18F]fluorodeoxyglucose is not increased in the postoperative period; is not affected by steroid therapy; and accurately predicts early recurrence of tumor, supplementing other predictors of tumor behavior, including extent of resection, histological diagnosis, and postoperative CT. Thus PET using [18F]fluorodeoxyglucose can contribute to the optimum management of patients with primary brain tumors.

Summary:Purpose: Interictal ['XF]fluorodeoxyglucose (FDG) positron emission tomography (PET) reveals regional hypometabolism in 60-80% of patients with mesial temporal lobe epilepsy (MTLE). The extent of hypometabolism generally extends beyond the epileptogenic zone. The pathophysiology underlying this widespread change is unknown. This study evaluated the relation between hippocampal neuronal loss and hypometabolism in patients with MTLE.Methods: Forty-three patients with MTLE after anterior temporal lobectomy were included. Pathology demonstrated mesial temporal sclerosis (n = 41) or endfolium sclerosis (n = 2). Interictal FDG-PET scans were graded by visual analysis on a scale ranging from normal (grade 1) to severe (grade 5) hypometabolism. Neuronal counting was performed in the subiculum, hippocampal subfields, and dentate granular cell layer (DG). Neuronal density of patients was compared with that of seven autopsy controls. Data were compared by using Student's t tests and Kruskal-Wallis one-way analysis of variance (ANOVA).Results: Significant neuronal loss in CAI through CA4 and DG was found in patients compared with controls. Neuronal density in the subiculum, CAI, CA4, and DG did not correlate with severity of hypometabolism. However, patients with abnormal FDG-PET had higher neuronal density in CA2 and CA3 versus patients with normal studies.Conclusions: This study supports a previous observation that degree of FDG-PET hypometabolism does not parallel severity of hippocampal neuronal loss in MTLE. Key Words: FDG-PET-Mesial temporal lobe epilepsy-Mesial temporal sclerosis-Hippocampal neuronal density.Interictal [ '8F]fluorodeoxyglucose positron emission tomography (FDG-PET) demonstrates hypometabolism involving, but not restricted to, the epileptogenic zone in 60-90% of patients with mesial temporal lobe epilepsy (MTLE; 1,2). The pathophysiology of this finding is unknown. Hippocampal atrophy and FDG-PET hypometabolism have been shown to be reliable predictors of outcome after anterior temporal lobectomy (ATL; 3-5). Several investigators have found a significant correlation between hippocampal volume on magnetic resonance imaging (MRI) and severity of hippocampal cell loss in the resected tissue (6-8). Conflicting results were obtained when hippocampal volume was correlated with FDG-PET hypometabolism in patients with MTLE Accepted Aprii 20, 1998. Address correspondence and reprint requests to Dr. N. Foldvary at The Cleveland Clinic Foundation, Section of Epilepsy and Sleep Disorders, Department of Neurology, 9500 Euclid Avenue, S-5 I , Cleveland, OH 44195, U.S.A. (9,lO). In addition, Engel et al. ( 1 1) found no relation between degree of hypometabolism and frequency of interictal discharges during PET by using scalp, sphenoidal, and depth electrode recordings, suggesting that hypometabolism is unrelated to epileptiform activity. Henry et al. (12) found no correlation between severity of hypometabolism measured quantitatively and hippocampal neuronal density in 40 patients with TLE. Further to eval...