Thalamic activation and cortical deactivation during typical absence status monitored using [¹⁸F]FDG-PET: A case report

Ictal EEG showing continuous generalized 2–3Hz spike/multiple spike slow wave activity, with a predominance over the anterior areas; the patient appeared confused, slow, drowsy.

Axial and sagittal [¹⁸F]FDG-PET images obtained during the absence state (A) and in the intercritical state (B). Images were spatially normalised into the Montreal Neurological Institute (MNI) space using SPM2 (Wellcome Department of Imaging Neuroscience, UK, London). The images represent regional [¹⁸F]FDG concentration values normalised to those measured in the whole brain (globals). In (C) and (D) are reported the areas of relative hypermetabolism (red) and of relative hypometabolism (blue) obtained by the subtraction of normalised PET images (absence state–intercritical state) and superimposed on 3D-T1 MRI axial and sagittal images obtained in a volunteer in the MNI space. L=left side; R=right side; the percentage thresholds for increase and decrease were arbitrary settled at +25% and −20%, respectively. White arrows: relative increase; blue arrows: relative decrease. During the absence state the cerebral glucose metabolism appears relatively increased in the thalamus and cerebellar vermis and relatively decreased in the fronto-parietal and posterior cingulate cortices.