Progressive Supranuclear Palsy Unmasked After Post-COVID-19 Functional Decline in an Elderly Patient: A Diagnostic Challenge.

Progressive supranuclear palsy (PSP) is a rare neurodegenerative tauopathy characterized by early postural instability, vertical supranuclear gaze palsy, axial rigidity, and poor response to levodopa therapy. Diagnosis remains challenging, particularly in the early stages, because of overlap with other Parkinsonian syndromes. We report the case of an 83-year-old woman who developed progressive gait instability, severe functional decline, dysphagia, and marked weight loss following a mild SARS-CoV-2 infection. Extensive investigations initially excluded metabolic, infectious, neoplastic, and structural causes. Neurological examination revealed axial and limb bradykinesia, hypomimia, hypophonia, apraxia, severe postural instability, and vertical gaze limitation. Oculomotor assessment also documented square wave jerks and eyelid opening apraxia. Levodopa therapy was ineffective. Brain MRI demonstrated marked midbrain atrophy with relative preservation of pontine volume, producing the characteristic hummingbird sign and Mickey Mouse sign. DAT-SPECT showed bilateral putaminal dopaminergic deficit, supporting a degenerative Parkinsonian syndrome. A diagnosis of probable PSP was established according to Movement Disorder Society criteria, clinical presentation, absence of levodopa responsiveness, and supportive imaging findings. This case highlights the diagnostic complexity of PSP when nonspecific systemic manifestations precede neurological deterioration and emphasizes the value of integrating clinical assessment with structural and functional neuroimaging.