First Reported Case Of Anti-N-Methyl D-Aspartate Receptor Encephalitis In A Child With Crossed Cerebellar Diaschisis And Extreme Delta Brush

Abstract Background Neuroimaging is an important step in the diagnostic workup of patients with suspected autoimmune encephalitis. Conventional MRI reveals abnormalities roughly half of the time. Functional neuroimaging, including FDG-PET scans, have an increased ability to detect changes in neuronal activity and have superior efficacy at correlating clinical course in NMDARe as well. Case History A five-year old patient was consulted for hemiparesis, catatonic features, perioral-facial dyskinesias, and subclinical status epilepticus. Initial brain MRI scans were unremarkable, but 18fluorodeoxyglucose-positron emission tomography (FDG-PET) showed global left cerebral hemisphere hypermetabolism in a crossed cerebro-cerebellar diaschisis distribution. Electroencephalography (EEG) revealed extreme delta brush pattern (EDB), characteristic for NMDARe, with blood and csf anti-NMDAR autoantibodies. Prompt treatment was initiated. In eight weeks, the serum autoantibody concentration was non-detectable, FDG-PET and EEG returned to normal, and conventional MRI scan had begun to show mild, faint signal in the right fronto-parietal cortex without any clinical correlate. At discharge, he had residual mild executive functioning deficits including poor problem solving, impulsivity and inattention which slowly improved with outpatient rehabilitative services. Conclusions NMDARe can be challenging to diagnose when sophisticated neuroimaging tools are not readily available. EEG pattern suggested NMDARe weeks prior to conventional MRI scans showed any, albeit non-specific, abnormalities. This is the first reported case, to our knowledge, of NMDARe with crossed cerebellar diaschisis and EDB. Functional neuroimaging modalities that infer neuronal activity/metabolism (BOLD sequence or FDG-PET) or perfusion (ASL) may detect upstream pathological features of NMDARe prior to typical diagnostic algorithms.