A 50-year-old Chinese womanexperienced sudden left lower limb weakness and episodic orofacial motor movements 4 months before admission. Three months after onset, she noticed worsening weakness in her left lower limb but could still walk. Subsequently, she developed involuntary left limb movements, memory loss, and unclear speech. She had a history of diabetes but no reported family neurological disorders. Neurological examination unveiled cognitive impairment, evidenced by a Mini-Mental State Examination score of 17 and a Montreal Cognitive Assessment score of 6, alongside dysarthria, grade 4 weakness in the left lower limb, increased muscle tone in the left limbs, and left limb ataxia. Multiple brain magnetic resonance images (MRI) revealed an isolated diffusion-weighted imaging (DWI) high signal in the right precentral gyrus, demonstrating an increasing lesion size as the disease progressed (Figure 1 and Figure 2). The cerebrospinal fluid (CSF) analysis revealed a mild elevation in protein at 58.5 mg/dL (normal range, 15-45 mg/dL), normal leukocyte and glucose levels, and negative cytology results. Blood and CSF antibody measurements included tests for antineuronal immunoglobulin G antibodies against intracellular serum antigens (Amphiphysin,