Case report: anti-NMDAR encephalitis with cerebellar ataxia as the initial manifestation

Among autoimmune encephalitis (AE), anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is the most common type. In patients with anti-NMDAR encephalitis, psychiatric and cognitive symptoms were often observed as the initial manifestations, whereas cerebellar ataxia was rarely reported. We report the case of a 22-year-old male patient who initially presented with cerebellar ataxia and was eventually diagnosed with anti-NMDAR encephalitis on the basis of positive results for anti-NMDAR antibodies in the cerebrospinal fluid. After combined therapy with intravenous immunoglobulin, methylprednisolone, and rituximab and subsequent rehabilitation, the patient’s symptoms were gradually alleviated. This case highlights the atypical presentation of anti-NMDAR encephalitis with cerebellar ataxia as the initial symptom, which is rare. Granule cell dysfunction, due to the wide distribution of GluN1 subunits, may disrupt the signaling to Purkinje cells, resulting in ataxia. Early recognition and treatment with immunotherapy, followed by rehabilitation, are crucial for improving patient outcomes, especially in cases with atypical presentations.