The underlying causes of eye movement disorders and ataxia.

This case report describes a 54-year-old Chinese woman with progressive gait instability, speech slowing, and cerebellar ataxia. Initial symptoms included mild bradykinesia and frequent backward falls. Neurological evaluation revealed supranuclear gaze palsy, hyporeflexia, and cerebellar dysfunction (SARA 26/40). Differential diagnoses included MSA, SCA, and PD. Genetic testing excluded SCA, while advanced imaging ruled out other disorders. The patient met criteria for probable PSP-C, a rare PSP subtype marked by cerebellar ataxia. [18F]PM-PBB3 tau PET imaging demonstrated abnormal tau accumulation in the striatum, thalamus, midbrain, and pons, consistent with PSP-C neuropathology. This case underscores the diagnostic utility of tau PET in distinguishing PSP-C from overlapping conditions and provides novel imaging evidence in an Asian cohort. Findings highlight the potential of noninvasive tau-targeted imaging for early detection and management of PSP-C.