Autoimmune encephalitis: the clinical evolution as a key to the diagnosis

Anti-N-methyl D-aspartate receptor (NMDAR) encephalitis is a devastating disease, that despite being increasingly diagnosed, there are no consensus guidelines for the optimal management. A previously healthy 3-year-old-boy brought to the emergency department due to seizures. Neurological examination was normal, and electroencephalogram (EEG) suggested focal epilepsy. Anticonvulsive medication was initiated. He progressively lost age-appropriate language skills, presented behavioural changes and psychiatric symptoms. Neurological examination at that time revealed symmetric gross motor weakness of the lower limbs. Brain and spinal cord MRI and cerebrospinal fluid were normal. Repeated EEG showed global lentification. Steroid therapy was initiated for the suspicion of autoimmune encephalitis, later confirmed as NMDAR encephalitis. He became clinically improved after 10 days of treatment but only returned to his baseline after 3 months of disease onset. The authors emphasised the variable course of the disease and possible late response to treatment.