Rasmussen encephalitis (RE) is a severe epileptic and inflammatory encephalopathy of unknown etiology, responsible for focal neurological signs and cognitive decline. The current leading hypothesis suggests a sequence of immune reactions induced by an indeterminate factor. This sequence is thought to be responsible for the production of autoantibody-mediated central nervous system degeneration. However, these autoantibodies are not specific to the disease and not all patients present with them. We report the case of a 4-year-old girl suffering from RE displaying some atypical features such as fast evolution and seizures of left parietal onset refractory to several antiepileptics, intravenous immunoglobulins, and corticosteroids. Serum autoantibodies directed against voltage-gated potassium channels (VGKC) were evidenced at 739 pM, a finding never previously reported in children. This screening was performed because of an increased signal in the temporolimbic areas on brain magnetic resonance imaging, which was similar to what is observed during limbic encephalitis. The patient experienced epilepsia partialis continua with progressive right hemiplegia and aphasia. She underwent left hemispherotomy at the age of 5.5 years after which she became seizure free with great cognitive improvement. First described in adults, VGKC autoantibodies have been recently described in children with various neurological manifestations. The implication of VGKC autoantibodies in RE is a new observation and opens up new physiopathological and therapeutic avenues of investigation.
Nonconvulsive status epilepticus (NCSE) is clinically difficult to diagnose, especially in old patients without epilepsy, and requires electroencephalography (EEG) for diagnosis. Its incidence among elderly patients with confusion of unknown origin (CUO) remains undetermined.
Intermittent photic stimulation is performed during an EEG to evoke photoparoxysmal response. When they appear triggered by low-frequency stimulation in children, they are suggestive of rare diagnosis, that is, neuronal ceroid lipofuscinosis. Among adults, their significance is less well understood. Low-frequency (<5 Hz) intermittent photic stimulation was performed over a period of 5 years during adult standard EEG. This retrospective study included all patients exhibiting low-frequency photoparoxysmal response. Five cases were identified. Three of them presented with active epilepsy (two progressive myoclonus epilepsy, one unclassifiable), two had visual deficiency, and three had dementia. The etiologies were MELAS (two), Creutzfeldt-Jakob disease (one), Kufs disease (one), and remained undetermined for one patient. In all patients, low-frequency photoparoxysmal response was observed years or months before the final diagnoses have been reached. Low-frequency photoparoxysmal response, classically associated with childhood progressive myoclonus epilepsy, seems to have a wider etiological spectrum in adult population. Moreover, this neurophysiological feature could be present before the final diagnosis in most cases. Systematically testing low frequencies during intermittent photic stimulation even during adult EEG seems warranted, particularly in a context of severe progressive neurologic deterioration.
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