Investigation of Cerebral O-(2-[18F]Fluoroethyl)-L-Tyrosine Uptake in Rat Epilepsy Models.

PURPOSE: A recent study reported on high, longer lasting and finally reversible cerebral uptake of O-(2-[18F]fluoroethyl)-L-tyrosine ([18F]FET) induced by epileptic activity. Therefore, we examined cerebral [18F]FET uptake in two chemically induced rat epilepsy models and in patients with focal epilepsy to further investigate whether this phenomenon represents a major pitfall in brain tumor diagnostics and whether [18F]FET may be a potential marker to localize epileptic foci. PROCEDURES: Five rats underwent kainic acid titration to exhibit 3 to 3.5 h of class IV-V motor seizures (status epilepticus, SE). Rats underwent 4× [18F]FET PET and 4× MRI on the following 25 days. Six rats underwent kindling with pentylenetetrazol (PTZ) 3 to 8×/week over 10 weeks, and hence, seizures increased from class I to class IV. [18F]FET PET and MRI were performed regularly on days with and without seizures. Four rats served as healthy controls. Additionally, five patients with focal epilepsy underwent [18F]FET PET within 12 days after the last documented seizure. RESULTS: No abnormalities in [18F]FET PET or MRI were detected in the kindling model. The SE model showed significantly decreased [18F]FET uptake 3 days after SE in all examined brain regions, and especially in the amygdala region, which normalized within 2 weeks. Corresponding signal alterations in T2-weighted MRI were noted in the amygdala and hippocampus, which recovered 24 days post-SE. No abnormality of cerebral [18F]FET uptake was noted in the epilepsy patients. CONCLUSIONS: There was no evidence for increased cerebral [18F]FET uptake after epileptic seizures neither in the rat models nor in patients. The SE model even showed decreased [18F]FET uptake throughout the brain. We conclude that epileptic seizures per se do not cause a longer lasting increased [18F]FET accumulation and are unlikely to be a major cause of pitfall for brain tumor diagnostics.

Divergent metabolic substrate utilization in brain during epileptogenesis precedes chronic hypometabolism.

Alterations in metabolism during epileptogenesis may be a therapy target. Recently, an increase in amino acid transport into the brain was proposed to play a role in epileptogenesis. We aimed to characterize alterations of substrate utilization during epileptogenesis and in chronic epilepsy. The lithium-pilocarpine post status epilepticus (SE) rat model was used. We performed longitudinal O-(2-[(18)F]fluoroethyl)-l-tyrosine (18F-FET) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) and calculated 18F-FET volume of distribution (Vt) and 18F-FDG uptake. Correlation analyses were performed with translocator protein-PET defined neuroinflammation from previously acquired data. We found reduced 18F-FET Vt at 48 h after SE (amygdala: -30.2%, p = 0.014), whereas 18F-FDG showed increased glucose uptake 4 and 24 h after SE (hippocampus: + 43.6% and +42.5%, respectively; p < 0.001) returning to baseline levels thereafter. In chronic epileptic animals, we found a reduction in 18F-FET and 18F-FDG in the hippocampus. No correlation was found for 18F-FET or 18F-FDG to microglial activation at seven days post SE. Whereas metabolic alterations do not reflect higher metabolism associated to activated microglia, they might be partially driven by chronic neuronal loss. However, both metabolisms diverge during early epileptogenesis, pointing to amino acid turnover as a possible biomarker and/or therapeutic target for epileptogenesis.

Neurobehavioral problems in children with early-onset epilepsy: A population-based study.

PURPOSE: Neurobehavioral problems (i.e., cognitive impairment/behavior problems) are a major challenge in childhood epilepsy. Yet there are limited data in children with early-onset epilepsy (CWEOE; onset ≤4 years), the period in which the incidence of childhood epilepsy is highest. This study aimed to determine the prevalence, spectrum, and risk factors for neurobehavioral problems CWEOE. METHODS: This prospective, population-based, case-controlled study identified children with newly diagnosed early-onset epilepsy in South East Scotland using active multisource capture-recapture surveillance (May 2013 - June 2015). The CWEOE and controls completed an age-appropriate neurobehavioral assessment battery across seven domains: general cognitive ability (GCA), adaptive behavior, externalizing, internalizing, executive functioning, social functioning, and Autism Spectrum Disorder (ASD) risk. RESULTS: Fifty-nine CWEOE were identified with an ascertainment of 98% (95% confidence interval [CI] 94, 103). Forty-six (78% [95% CI 65.9, 86.6]) CWEOE (27 male, median age 25.5, range 1-59, months) and 37 controls (18 male, median age 31.5, range 3-59, months) consented for study entry. The CWEOE were similar to controls in gender, age, prematurity, and family history of psychopathology, but not socioeconomic status (Fisher's exact test [FET] < .001). Neurobehavioral assessments were carried out a median of 2.97 (Interquartile range [IQR] 1.51-4.95) months post epilepsy diagnosis. More CWEOE (63% [95% CI 48.6, 75.5]) had neurobehavioral problems compared with controls (27% [95% CI 15.4, 43.0]); p < 0.01. This observation was independent of socioeconomic status. Multidimensional problems were prevalent in CWEOE with 43% having two or more different domain-level problems; GCA impairment, adaptive behavior, internalizing, social functioning, and ASD risk were particularly marked. Risk factors varied by domain. DISCUSSION: This novel study using comprehensive psychometric assessments found that neurobehavioral problems in CWEOE were detectable, common, and multidimensional. The degree of cooccurrence implies that problems are the norm, and multidimensional screening should be considered at epilepsy onset. The findings could aid policy development on health and educational provision in CWEOE.

Epileptic Activity Increases Cerebral Amino Acid Transport Assessed by 18F-Fluoroethyl-l-Tyrosine Amino Acid PET: A Potential Brain Tumor Mimic.

O-(2-18F-fluoroethyl)-l-tyrosine (18F-FET) PET is a well-established method increasingly used for diagnosis, treatment planning, and monitoring in gliomas. Epileptic activity, frequently occurring in glioma patients, can influence MRI findings. Whether seizures also affect 18F-FET PET imaging is currently unknown. The aim of this retrospective analysis was to investigate the brain amino acid metabolism during epileptic seizures by 18F-FET PET and to elucidate the pathophysiologic background. METHODS: Ten patients with 11 episodes of serial seizures or status epilepticus, who underwent MRI and 18F-FET PET, were studied. The main diagnosis was glioma World Health Organization grade II-IV (n = 8); 2 patients suffered from nonneoplastic diseases. Immunohistochemical assessment of LAT1/LAT2/CD98 amino acid transporters was performed in seizure-affected cortex (n = 2) and compared with glioma tissues (n = 3). RESULTS: All patients exhibited increased seizure-associated strict gyral 18F-FET uptake, which was reversible in follow-up studies or negative shortly before and without any histologic or clinical signs of tumor recurrence. 18F-FET uptake corresponded to structural MRI changes, compatible with cortical vasogenic and cytotoxic edema, partial contrast enhancement, and hyperperfusion. Patients with prolonged postictal symptoms lasting up to 8 wk displayed intensive and widespread (≥ 1 lobe) cortical 18F-FET uptake. LAT1/LAT2/CD98 was strongly expressed in neurons and endothelium of seizure-affected brains and less in reactive astrocytosis. CONCLUSION: Seizure activity, in particular status epilepticus, increases cerebral amino acid transport with a strict gyral 18F-FET uptake pattern. Such periictal pseudoprogression represents a potential pitfall of 18F-FET PET and may mimic brain tumor. Our data also indicate a seizure-induced upregulation of neuronal, endothelial, and less astroglial LAT1/LAT2/CD98 amino acid transporter expression.

A comprehensive electrographic and behavioral analysis of generalized tonic-clonic seizures of GEPR-9s.

This study records noise-free intracerebral EEG of the genetically epilepsy prone rat (GEPR-9), along with behavioral correlates, during a seizure on unanesthetized freely behaving unrestrained animals. The GEPR-9 exhibits acoustically triggered generalized tonic-clonic seizures, and often times the EEG, recorded with conventional techniques, has resulted in data with imbedded movement artifact. For noise-free video-EEG recordings, we used a previously developed system that consists of a head connector with a FET preamplifier and battery, signal conditioning device (5000x gain, 1 Hz-100 Hz filters), A/D converter and video/PC-PC/video computer boards for recording image data. Each animal was implanted with three monopolar/referential electrodes chosen among the following areas: cortex, inferior colliculus, reticular formation and caudal medulla. The video-EEG data were quite similar for all recorded animals: (1) basal desynchronized EEG before sound stimulus; (2) increase in EEG frequency after stimulus and before seizure onset; (3) high-amplitude polyspikes during massive myoclonic thrusts with or without a very fast running episode; (4) an electrodecremental response during tonic extension; (5) wave and spike complex during forelimb and hindlimb tonic rigidity and posttonic clonus; (6) low-amplitude EEG during postictal depression. Time sequenced spectral analysis also highlights the epileptiform EEG pattern during seizure with high reproducibility between animals. While testing seizure naive GEPR-9s, there was a clear evolution from modest epileptiform EEG activity on the first acoustic stimulation to progressively higher amplitude, duration and frequency epileptiform EEG activity throughout seizure repetition.