Abstracts

Rationale: Positron emission tomography (PET) with 18-Fluorodeoxyglucose (18F-FDG) is an established sensitive technique to identify the functional deficit zone in patients with epilepsy and is widely used interictally in presurgical evaluation of refractory epilepsy. Few reports of ictal FDG-PET are available in the literature and most cases described were either incidental (when seizures happen following tracer injection) or planned PET scans in patients with very frequent seizures or status epilepticus. We report feasibility and utility of ictal FDG-PET scans in patients with refractory epilepsy who were admitted for presurgical assessment to the epilepsy monitoring unit in a hospital with active nuclear medicine department. Methods: Ictal PET imaging was planned and performed in four patients (two males and two females, ages 7-33) with refractory epilepsy. All patients had video-EEG monitoring for hours to days prior to injection and for 45-90 minutes following injection of FDG. Visual analysis of the PET scans was done as well as quantified analysis using NeuroQ software. The clinical characteristics of the four patients, details of interictal and ictal EEG, neuroimaging and PET findings were reviewed and analyzed. Results: One child had symptomatic generalized epilepsy with different seizures types including focal seizures and double cortex on brain MRI. Her PET scan showed the "double cortex" sign or subcortical band hypermetabolism with uptake asymmetry and findings were concordant with the EEG ictal abnormalities as well as the ictal SPECT pattern (Single Photon Emission Tomography). The three adults patients had unremarkable brain MRIs. The two young men had infrequent partial seizures and underwent ictal PET scans as well as interictal studies for comparison. Findings on ictal PET scans were concordant with electrographic seizure onset and evolution. The fourth patient had a cluster of cyclic simple partial seizures consisting of asymmetrical or unilateral right eyelid twitches or blinking but normal 3 Tesla brain MRI. Her ictal PET revealed ipsilateral temporal hypermetabolism by quantitative analysis that was not evident on visual inspection. Conclusions: Ictal PET is feasible in appropriate settings when there is good coordination between the epilepsy unit and the nuclear medicine department. Ictal PET findings were concordant with the EEG especially in the non lesional epilepsy cases when specific quantifying techniques such as NeuroQ were used for images analysis. Planned ictal PET imaging was proven to be useful and valuable even in patients with infrequent partial seizures. Future evaluations mostly studies on a larger sample of patients with direct comparison to ictal SPECT are needed. Funding: None