Transient extreme spindles in a young child with anti-NMDAR encephalitis: A case report.

Anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis is a type of immune-mediated encephalitis, which is a new category of treatment-responsive paraneoplastic encephalitis. In patients with this disease, electroencephalography (EEG) shows non-specific findings, but recently, a unique EEG pattern, named the extreme delta brush, was detected in 40% of adult patients and was suggested to be specific to this type of encephalitis. Here, we describe a two-year-old boy with anti-NMDAR encephalitis, who presented with speech arrest and disturbances of gait and cognition several weeks after developing febrile convulsions. In the early stages of the disease, EEG showed 14-16 Hz, continuous, fast waves characterized by a high amplitude (200-500 µV), very diffuse spreading, and a sharp morphology, during light sleep only, which was compatible with extreme spindles. As the patient's symptoms worsened, this finding was replaced by rhythmic, diffuse, high-voltage, slow waves. Immediately after immunomodulatory therapies, including intravenous methylprednisolone and immunoglobulin, his clinical manifestations and EEG abnormalities appeared to improve. We propose that although the extreme spindle is a non-specific finding of this type of encephalitis, early EEG monitoring might be necessary to detect not only the extreme delta brush pattern, but also non-specific findings, including extreme spindles, which would aid early diagnosis and treatment.