To increase awareness among clinicians about the atypical presentations of IgLON5 encephalitis, which can mimic other neurological conditions

Anti-IgLON5 disease is a rare neurological disorder characterized by heterogeneous clinical manifestations including sleep disorders, gait instability, bulbar dysfunction, ocular symptoms, movement disorders, and cognitive impairment. Initial presentation with headaches followed by clinical seizures and non-convulsive status epilepticus is an unusual presentation of this disease. 

We present a 74-year-old female who was initially admitted with pneumonia and treated with intravenous antibiotics. Neurology was consulted for one week history of right sided temporal headaches without migrainous features and new onset left facial contractions. Exam revealed perseveration, right gaze preference, left sided partial neglect, and left facial dyskinesia. Computed tomography of the head was unremarkable.  Lumbar puncture was consistent with elevated protein without pleocytosis (Protein 83mg/dl, WBC 2 cell/ µL).  Continuous electroencephalography (cEEG) revealed right hemispheric continuous lateralized periodic discharges at 1- 1.5 Hz and 3 discrete clinical seizures involving right arm automatisms.  In addition, intermittent left facial and arm dyskinetic movements were seen without clear EEG correlation. Patient was managed with Keppra, Vimpat and Phenytoin. Brain Magnetic resonance imaging demonstrated increased FLAIR and DWI gyriform changes in right temporoparietal region and right mesial temporal lobe. Given the high clinical suspicion of autoimmune encephalitis and APE2 score of 12, intravenous methylprednisolone was administered for 5 days with rapid improvement in EEG and remarkable neurological recovery.  She was later found to have a positive serum autoimmune encephalitis panel for IgLON5 Ab.

This case illustrates that IgLON5 encephalitis can present atypically with headache as an initial symptom. Significant symptom relief can be achieved with prompt intervention, highlighting the importance of early recognition in managing this rare disorder.