A case report and literature review of severe anti-NMDAR encephalitis with predominant caudate nucleus involvement in a child

Background: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune encephalitis with diverse imaging manifestations. Isolated involvement of the caudate nucleus is rare and can be easily misdiagnosed, especially in the early stages when inflammatory symptoms are not apparent. This report describes a pediatric case of severe anti-NMDAR encephalitis with predominant involvement of the caudate nucleus. Case presentation: A 15-year-old male initially presented with stroke-like episodes, misdiagnosed as cerebral infarction. Subsequently, he developed seizures, recurrent low-grade fever, psychiatric symptoms, involuntary orofacial movements, autonomic dysfunction, loss of speech, and inability to perform activities of daily living. Brain MRI revealed a lesion in the left caudate nucleus. The diagnosis was confirmed by positive serum and cerebrospinal fluid anti-NMDAR IgG antibodies. Targeted positron emission tomography (PET) using ¹⁸ F-fluorodeoxyglucose ( ¹⁸ F-FDG) and the ¹⁸ F-DPA-714 tracer for the 18kDa translocator protein (TSPO) identified a core inflammatory area and extensive regions of neuronal dysfunction. The patient's condition gradually improved following immunotherapy and symptomatic treatment. Conclusion: This case provides valuable insights into the pathogenesis of anti-NMDAR encephalitis, particularly its selective involvement of specific brain regions such as the caudate nucleus. The unique imaging features compel us to explore mechanisms beyond the traditional model of direct antibody-mediated pathogenicity.