FLAIR fornix hyperintensity in VGKC-related autoimmune encephalitis

Excerpt

A 52-year-old man presented with progressive fatigue, drowsiness, weight loss, and memory impairment associated with left-sided temporal lobe seizures. Brain MRI revealed increased bilateral FLAIR signal in the hippocampus, amygdala, mammillary bodies, hypothalamus and fornix (Figs. 1, 2). Blood analysis showed normal CRP, TSH, vitamin B1 and B12 levels. Routine immunological screening, and HIV and syphilis serology were negative. Anti-voltage-gated potassium channel (VGKC) antibodies were positive (463 pmol/l; normal range 0–100 pmol/l), in the absence of antiganglioside antibodies, NMDA/TPO/GAD antibodies and other paraneoplastic antibodies. CSF analysis showed oligoclonal bands in the absence of other abnormalities. Brain FDG-PET revealed bilateral frontal, parietal and temporal hypometabolism (all equally involved). Whole-body FDG-PET, thoraco-abdominal–pelvic CT and testicular echography were normal. Oral antiepileptic treatment (valproic acid 500 mg bid) led to seizure freedom. Important clinical improvement after corticosteroid treatment (60 mg od for 1 month, followed by tapering during 3 months) was seen, in the presence of persistent MRI abnormalities (although increased signal became less severe) 4 months later. After 1 year of follow-up, no clinical relapse occurred, and thoraco-abdominal–pelvic CT and whole-body FDG-PET remained normal. A diagnosis of VGKC-related autoimmune, probably non-paraneoplastic, encephalitis was made.

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