LAUSR

BACKGROUND The core manifestations of leucine-rich-glioma-inactivated-1 (LGI1) autoantibody-mediated encephalitis are limbic encephalitis and faciobrachial dystonic seizures (FBDSs). Agrypnia excitata (AE) is a rare syndrome characterized by sleep-wake cycle disruption, autonomic hyperactivation, and episodes of oneiric stupor (OS). Only a few diseases are known to present with AE. An autoimmune etiology must be considered when accompanied by neuromyotonia (NM). We report a case of anti-LGI1 encephalitis presenting with AE. METHODS Detailed clinical, video-polysomnographic, laboratory, radiological, and long-term follow-up assessments were performed. RESULTS A previously healthy 58-year-old man was referred for a rapidly progressive change in mental status, characterized by persistent drowsiness and confusion, accompanied by frequent episodes of unconscious gestures ranging from simple stereotyped movements to more complex actions mimicking various daily activities. Other symptoms included tachycardia, hyperhidrosis, mild hyponatremia, rare FBDSs, and a single generalized tonic-clonic seizure, but no NM. Prolonged video-polysomnography excluded epileptic activity and showed continuous monomorphic slowing of background activity not consistent with a regular wakefulness or sleep state. A brain magnetic resonance imaging scan was unremarkable. Brain fluorodeoxyglucose positron emission tomography revealed hypermetabolism of the hippocampi, amygdala, and basal ganglia. Anti-LGI1 antibodies were detected in the cerebrospinal fluid. The sleep disorder resolved progressively after starting immunotherapy. CONCLUSIONS AE can be a dominant, treatable manifestation of anti-LGI1 encephalitis. OS episodes are a useful clinical feature for establishing diagnostic suspicion and could provide a window to understanding the mechanisms behind some movement disorders in autoimmune encephalitis.