Cerebral metabolic topography in unilateral temporal lobe epilepsy z E. Rubin, MD, PhD; V. Dhawan, PhD; J.R. Moeller, PhD; S. Takikawa, MD; D.R. Labar, MD, PhD; N. Schaul, MD; W.B. Barr, PhD; and D. Eidelberg, MD zyxw Article abstract--Objectiue: Fluorodeoxyglucose positron emission tomography (FDG-PET) studies of temporal lobe epilepsy (TLE) generally report interictal hypometabolism in the vicinity of the seizure focus. Yet, other evidence sug- gests that interictal metabolic abnormalities might extend to remote brain areas. We used FDG-PET to evaluate metabolism in selected regions distant from the focus in TLE. Subjects: Twenty adult patients with medically in- tractable TLE were selected by criteria favoring a unilateral mesiobasal temporal focus. Structural imaging in this sample was normal except for medial temporal sclerosis in zyxwv 13 patients. Twenty normal volunteers were controls. De- sign: PET imaging was performed interictally. Regional glucose metabolism normalized by global metabolism was ana- lyzed using zyxwvutsrqp t tests and correlation analysis. Results: Ipsilateral to the seizure focus, metabolism was depressed com- pared with normal in the temporal pole zyxwvut @ = 0.001), but relatively elevated in the mesiobasal region @ = 0.005). Con- tralateral to the focus, metabolism was elevated in lateral temporal cortex @ = 0.0003) and mesiobasal regions @ = 0.0001). Metabolic correlation between ipsilateral and contralateral mesiobasal regions was similar in normal subjects (r = 0.74) and patients (r = 0.68). In contrast, correlations were abnormal between temporal poles and other temporal lobe subregions, both ipsilateral and contralateral to the seizure focus. Conclusions: Relative to normal values, both el- evations and depressions of metabolism exist interictally in TLE. Such abnormalities, and accompanying changes in interregional correlations, may have wide spatial distribution. These findings are atypical among PET studies but are consistent with other physiologic, anatomic, and neuropsychological investigations of TLE. NEUROLOGY 1995;45:2212-2223 The pathophysiology of temporal lobe epilepsy (TLE) involves long-term modification of neuronal connections both within the temporal lobe and be- tween the temporal lobe and other parts of the brain. Persistent abnormalities are evident within the epileptic temporal lobe in terms of cell number, axon pathways, and synaptic These cellular changes appear related to larger-scale ictal and interictal abnormalities of the diseased tempo- ral lobe seen in EEG activity, cerebral metabolism and blood flow, and neuropsychological f ~ n c t i o n . ~ Less impressive evidence so far has been found for persistently altered function in the epileptic brain beyond the seizure focus. Abnormal electrical activ- ity originating in the focus obviously affects remote areas acutely during seizure generalization. The separate and clinically important issue of whether the transmission of such abnormal activity between the focus and recipient regions may lead to pro- longed alterations in remote areas has received only preliminary attention. The most specific evi- dence for such distant effects in TLE comes from neuropsychological studies. Reports by Milner,6 Novelly e t a1,6 and Takahashi et a17 suggest that in unilateral TLE, the interictal function of the tem- poral lobe contralateral to the focus is impaired. In- terictal performance of frontal lobe tasks also wors- ens in the presence of a temporal lobe focus.8These studies found that such neuropsychological deficits may improve following effective excision of the tem- poral focus, raising the possibility of both re- versible and irreversible alterations in neural cir- cuits that include the seizure focus. Fluorodeoxyglucose positron emission tomo- graphic (FDG-PET) studies also support the pres- ence of functional abnormalities in TLE beyond the seizure focus. Numerous PET studies have re- ported interictal hypometabolism in TLE not only in the vicinity of the electrographically defined seizure focus, but also more widely within the af- fected temporal lobe and in nontemporal regions of the same hemisphere (see Henry et al,9 for exam- ple). Areas of evident hypometabolism tend to ex- tend further than any evident anatomic abnormal- ity; this is particularly true of medial temporal sclerosis (MTS), the lesion most characteristically From the Department of Biological Psychiatry (Drs. Rubin and Moeller), Columbia University/New York State Psychiatric Institute, New York, Ny, the Department of Neurology (Drs. Dhawan, Takikawa, and Eidelberg), North Shore University HospitaUCornell University Medical College, Manhasset, Ny, the Department of Neurology (Dr. Labar), New York HospitaYCornell University Medical College, New York, Ny, and Long Island Jewish Hospital (Drs. Schaul and Barr), New Hyde Park, zyxwvutsr NY. Supported in part by The Epilepsy Foundation of America and by NIMH Grant T32-MH15144 Received November 16, 1994. Accepted in final form March 28,1995. Address correspondence and reprint requests to Dr. D. Eidelberg, Department of Neurology, North Shore University Hospital, 300 Community Drive, Manhasset, NY 11030. zyxwvutsrq 2212 NEUROLOGY 45 December 1996