Positron emission tomography in generalized seizures

Abstract

We used 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) to study nine patients with clinical absence or generalized seizures. One patient had only absence seizures, two had only generalized tonic-clonic seizures, and six had both seizure types. Interictal scans in eight failed to reveal focal or lateralized hypometabolism. No apparent abnormalities were noted. Two patients had PET scans after isotope injection during hyperventilation-induced generalized spike-wave discharges. Diffusely increased metabolic rates were found in one compared with an interictal scan, and in another compared with control values. Another patient had FDG injected during absence status: EEG showed generalized spike-wave discharges (during which she was unresponsive) intermixed with slow activity accompanied by confusion. Metabolic rates were decreased, compared with the interictal scan, throughout both cortical and subcortical structures. Interictal PET did not detect specific anatomic regions responsible for absence seizure onset in any patient, but the results of the ictal scans did suggest that pathophysiologic differences exist between absence status and single absence attacks.

Hemodynamic and Metabolic Aspects of Photosensitive Epilepsy Revealed by Functional Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy

“…Sperling and Skolnick ( 5 ) observed widespread decreases (less in frontal, more in parietal lobes) in "'xenon-measured CBF during sustained ictal theta and spike-wave activities in a single patient with generalized epilepsy. Theodore et al (2) observed diffusely decreased CMRGlc with PET scanning in an unresponsive patient during absence status with generalized spike-wave discharges. Other ictal studies in humans all showed increased CBF and CMRGlc.…”

“…In the interictal periods, these investigations showed a normal cerebral metabolic rate for glucose (CMRGlc) (1)(2)(3), and during ictal episodes of various types showed both increased and decreased CMRGlc and cerebral blood flow (CBF) (1-7). Thus these data suggest that further investigations in the human generalized epilepsies might advance the understanding of their pathophysiologies.…”

“…Atypical absences and absence status demonstrated a global decrease (5-35%) or no change (2,3). These studies were limited in time resolution by the 30 to 45-min uptake period (heavily weighted to the first 10-15 min) of the tracer isotope in which both ictal and interictal periods were often admixed, presumably with averaging of metabolic effects (22,35).…”

Brain Mechanisms of Altered Consciousness in Generalised Seizures

“…Attempts to define neural changes associated with the electro-clinical manifestation of absences seizures using neuroimaging techniques have generated controversial data. Some studies have shown a global ictal increase in cerebral metabolism or blood flow [29,33,35], others have detected spatially limited changes [5,11]. Typical absence seizures can often show fluctuation in EEG patterns, with non-fixed focal abnormalities [19].…”

The American Epilepsy Society: An Historic Perspective on 50 Years of Advances in Research

“…Subsequent studies showed that metabolic activity was increased in the epileptogenic brain region during partial seizures (53), whereas metabolic activity for glucose increased diffusely and bilaterally during absence seizures (54). The use of fluorodeoxyglucose (FDG-PET) reliably identifies temporal lobe epileptogenic foci, and abnormalities predict the outcome of temporal lobectomy (55).…”