Concomitant progressive supranuclear palsy and multiple system atrophy: A rare case report of tauopathy and synucleinopathy interface.

Progressive supranuclear palsy (PSP) and multiple system atrophy (MSA) are neurodegenerative disorders characterized by parkinsonian symptoms. PSP typically presents with supranuclear gaze palsy, postural instability, and subcortical dementia, while dysautonomia and cerebellar signs are hallmark features of MSA. We report the case of a 77-year-old male patient with a four-year history of progressive parkinsonian symptoms that have shown poor response to treatment. His clinical manifestations included bradykinesia, rigidity, swallowing difficulties, urinary frequency, nocturia, downward gaze palsy, hypometric saccades, and finger-nose dysmetria. Examination revealed increased tone in both upper extremities, more pronounced on the right side, along with bradykinesia, slow hand movements, and bilateral decrement in finger tapping. Brain magnetic resonance imaging (MRI) revealed mixed MRI findings consistent with atypical parkinsonian syndrome, showing signs of MSA-C with pontocerebellar atrophy and the "hot cross bun" sign, as well as PSP with midbrain atrophy (hummingbird sign) and tegmental hypersignal.