Metabolic Correlates of the Ictal-Interictal Continuum: FDG-PET During Continuous EEG

Abstract

Background Ictal-interictal continuum (IIC) continuous EEG (cEEG) patterns including periodic discharges and rhythmic delta activity are associated with poor outcome and in the appropriate clinical context, IIC patterns may represent “electroclinical” status epilepticus (SE). To clarify the significance of IIC patterns and their relationship to “electrographic” SE, we investigated FDG-PET imaging as a complementary metabolic biomarker of SE among patients with IIC patterns. Methods A single-center prospective clinical database was ascertained for patients undergoing FDG-PET during cEEG. Following MRI-PET co-registration, the maximum standardized uptake value in cortical and subcortical regions was compared to contralateral homologous and cerebellar regions. Consensus cEEG review and clinical rating of etiology and treatment response were performed retrospectively with blinding. Electrographic SE was classified as discrete seizures without interictal recovery or >3-Hz rhythmic IIC patterns. Electroclinical SE was classified as IIC patterns with electrographic and clinical response to anticonvulsants; clonic activity; or persistent post-ictal encephalopathy. Results Eighteen hospitalized subjects underwent FDG-PET during contemporaneous IIC patterns attributed to structural lesions (44 %), neuroinflammatory/neuroinfectious disease (39 %), or epilepsy (11 %). FDG-PET hypermetabolism was common (61 %) and predicted electrographic or electroclinical SE (sensitivity 79 % [95 % CI 53–93 %] and specificity 100 % [95 % CI 51–100 %]; p = 0.01). Excluding electrographic SE, hypermetabolism also predicted electroclinical SE (sensitivity 80 % [95 % CI 44–94 %] and specificity 100 % [95 % CI 51–100 %]; p = 0.01). Conclusions In hospitalized patients with IIC EEG patterns, FDG-PET hypermetabolism is common and is a candidate metabolic biomarker of electrographic SE or electroclinical SE.

Electroencephalographic Periodic Discharges and Frequency-Dependent Brain Tissue Hypoxia in Acute Brain Injury

“…3 A recent case series suggests that brain tissue hypermetabolism may be seen on positron emission tomography scanning in patients with IIC. 45 Magnetic resonance imaging studies have revealed vasogenic and cytotoxic edema in some patients with PDs that are similar to those seen in patients with seizures. 46 Functional magnetic resonance imaging in patients with idiopathic generalized epilepsy has revealed increased CBF associated with elevated cerebral metabolic rate of oxygen consumption during interictal epileptiform discharges.…”

WONOEP appraisal: Imaging biomarkers in epilepsy

“…In a series of 18 patients with possible or probable SE based solely on EEG criteria, FDG-PET hypermetabolism correctly classified those in status with 80% sensitivity and 100% specificity, supporting the use of PET as an orthogonal biomarker of SE. 11 Figure 3 provides examples of an equivocal EEG pattern with co-localized FDG-PET hypermetabolism that resolved with anticonvulsant treatment, and an EEG pattern suggestive of SE with occipital hypometabolism in a patient with Creutzfeldt-Jakob disease who did not respond clinically to anticonvulsant drug treatment. This indicates that FDG-PET can be a biomarker of SE.…”

Epileptiform abnormalities predict delayed cerebral ischemia in subarachnoid hemorrhage

“…Indirect observations indicate that LPDs increase local cerebral blood flow and cause focal hypermetabolism on PET imaging and microdialysis recordings of lactate/pyruvate ratios (Theodore et al 1983; Pohlmann-Eden et al 1996; Struck et al 2016; Vespa et al 2016). These studies suggest that, like CSDs, abnormal neural activity is metabolically taxing.…”