Ataxia-Parkinsonism in a Patient With Double-Positive Anti-Hu and Anti-NMDAR Antibodies

Movement disorders may be a core feature of autoimmune brain disorders, including paraneoplastic neurological syndromes. A 73-year-old white male presents with memory impairment, gait instability, dysphagia, and severe dysarthria progressing over 1.5 years. He recently developed behavior and sleep disturbances. His cognitive assessment showed time disorientation, short-term memory impairment with preserved retrieval, and pseudobulbar affect. The remainder of the neurological exam showed seborrhea, facio-cervical dystonia, a right positive palmomental reflex, fragmented pursuit eye movements, dysarthria, minor right pyramidal signs, bilateral asymmetric limb ataxia and symmetric akinetic parkinsonism. He was wheelchair-bound, capable of only a few short steps with help. MRI depicted generalized cortico-subcortical atrophy with temporal predominance. He was positive for antibodies anti-Hu in serum (1:10 000) and CSF (1:100), as antibodies anti-NMDAR in serum (1:320) and CSF (1:10). The patient had no clinical improvement after a therapeutical trial with 1 g intravenous methylprednisolone. Additional workup for occult neoplasia was positive for prostatic adenocarcinoma. He remains stable 2.5 years after disease onset.