[Ictal electroencephalography (EEG) activity and cerebral blood flow dynamics as potential pathological indicators: a case of anti-leucine-rich glioma-inactivated 1 protein (LGI1) encephalitis].

A 29 year-old, right-handed woman was admitted to our hospital due to her headache with fever elevation lasting for two months followed by a prolonged loss of awareness with an involuntary movement in her left hand and mouth. This movement appeared very frequently, and the duration was very short, so called "faciobrachial dystonic seizures (FBDS)". Some of FBDS were followed by prolonged loss of awareness. Brain MRI fluid attenuated inversion recovery (FLAIR) image revealed high intensity lesion in the left mesial temporal lobe. Arterial spin labeling (ASL) image indicated hyper perfusion in this lesion and also the lateral temporal region. No ictal electroencephalography (EEG) change was observed before the onset of FBDS. FBDS was often followed by focal impaired awareness seizure (FIAS) in which ictal EEG showed rhythmic alpha activity arising from left mid-temporal region. This EEG seizure pattern was clearly visible in the time-frequency analysis. Given these clinical findings, along with an evidence of serum anti-leucine-rich glioma-inactivated 1 (LGI1) antibody positive, she was diagnosed with anti-LGI1 encephalitis. Immunotherapy (methylpredonisolone and intravenous immunoglobulin) with a multiple anti-epileptic drugs therapy (lacosamide, perampanel, and lamotrigine) was highly responsible to her symptoms. Although the high intensity lesion in FLAIR image still remained after the treatment, findings of ASL and EEG showed clear correlation to her cognitive function and seizures, respectively. Temporal change in ASL imaging suggested that the hyper perfusion in ASL during the acute stage could be provided by inflammation of the encephalitis its self and also the seizures activities (FBDS and FIAS). The pathophysiological indication of anti-LGI1 encephalitis was limited in terms of the therapeutic strategy, however, our findings collectively suggested that the combination analysis of EEG activity and cerebral blood flow dynamics (ASL) could be the potential candidate.