A 13-year-old boy, with no relevant medical history, presented with a recent onset of epilepsy. He initially had several generalized seizures which were treated with antiepileptic drugs. He continued having continuous partial epileptic attacks with dyskinesia of the tongue and mouth.

MRI showed hyperintense lesions on fluid-attenuated inversion recovery (FLAIR) images in the left precentral gyrus and medial frontal gyrus (a, yellow arrows). To localize the seizure onset, an ictal brain FDG PET was performed, which showed intense uptake in the left precentral gyrus (b, blue arrow), corresponding with the motor cortex of the tongue and jaw. There was also a focus of high metabolism in the left frontal lobe and the putamen (b, orange arrow) as well as in the right cerebellum (b, red arrow) because of seizure propagation and crossed cerebellar hypermetabolism. There was diffuse hypometabolism in the remaining cortex in the context of a functional deficit zone. Coregistration of the images (c) shows correspondence of the focal hypermetabolism with the hyperintense lesions on FLAIR images. A biopsy of the lesion in the left frontal lobe showed a gangliocytoma. Because of the localization in eloquent cortex, a resection was not possible and treatment started with radiotherapy.

FDG PET is usually used for evaluation of brain metabolism interictally, but during epilepsia partialis continua, ictal FDG PET can be a valuable imaging tool since it can not only depict the functional deficit zone but also show the ictal onset zone [1–4].

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