Abstract:
Through the effective combination of instrumentation, tracer
kinetic principles, and radiopharmaceuticals, positron computed
tomography (PET) allows for the analytic, noninvasive measurement of
local tissue physiology in humans. A large number of studies have
already been performed in patients with epilepsy using
18F-fluorodeoxyglucose (FDG) to measure local cerebral glucose
utilization. In patients with complex partial epilepsy who are
candidates for surgery, hypometabolic zones have been seen consistently
(70%) in the interictal state. These areas of hypometabolism have been
related to electroencephalographic findings, surgical pathology, and
clinical symptomatology. The complex anatomical and pathophysiological
investigation of these hypometabolic zones is discussed. Ictal studies
of patients with partial seizures have demonstrated a much more variable
metabolic pattern which usually consists of hypermetabolism relative to
baseline or interictal studies. Generalized epilepsy produced by
electroconvulsive shock and petit mal epilepsy have been studied using
FDG to estimate glucose metabolism. These studies demonstrated
hypermetabolism in the ictal state, relative to interictal or postictal
scans, but with a more generalized pattern than ictal studies of partial
seizures. Methodological problems in the study of epilepsy with PET are
discussed in detail. The investigation of interictal hypometabolism
through animal models of epilepsy and quantitative autoradiography is
described as a means to understand the human PET results. The impact and
future direction of PET studies in epileptic populations will probably
employ the use of behavioral, pharmacological, and electrophysiological
maneuvers to provide more specific details about the fundamental
pathophysiological mechanisms of specific aspects of epilepsy. These
techniques may allow for a truly pathophysiological classification
system for the common and unusual types of epilepsy, and through this
classification system improve the therapeutic and prognostic clinical
approach to patients