Anti-N-methyl D-aspartate receptor encephalitis (NMDARE) is an autoimmune disease characterized by subacute onset of neurologic and psychiatric symptoms including cognitive dysfunction, seizures, and movement disorders. Unlike adults, children tend to present with neurological symptoms before the onset of psychiatric symptoms. Prior infection is suggested as an etiology for the development of NMDARE, and there is a lower frequency of paraneoplastic etiology in children than adults. Although epilepsia partialis continua (EPC) and isolated dyskinesias are rare mono-symptomatic presentations of NMDARE, it is important to consider neuroinflammatory disease in the pediatric patient with new-onset isolated abnormal movements.

A 6-year-old male presented to our tertiary care children’s hospital with first lifetime generalized tonic-clonic seizure, and two days later he developed abnormal right upper extremity movements. On examination he was noted to have near-continuous right wrist choreoathetosis while awake with maintained awareness, along with right shoulder twitching and right-sided orofacial movements. This movement continued during sleep and continuous EEG showed persistent left posterior focal slowing, as well as abundant notched spiking concerning for EPC. Magnetic resonance imaging of the brain was normal. He was started on anti-seizure medication and frequency of movements decreased. Two weeks later, the patient developed irritability, insomnia, and language regression. Cerebrospinal fluid (CSF) studies were significant for protein 36, glucose 47, WBC 19, and was positive for NMDAR antibody with titer of 1:32. Serum anti-streptolysin O antibody was positive with titer of 1:2. Oncologic screening was negative for tumor. He was treated with high-dose steroids, IVIg, and rituximab. He remains on anti-seizure medication and follow-up EEG after discharge normalized.