A Case of Pathologically Confirmed Corticobasal Degeneration Initially Presenting as Progressive Supranuclear Palsy Syndrome

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) overlap clinically with parkinsonism or extrapyramidal signs and pathologically with tauopathy. Asymmetric parkinsonism and cortical dysfunctions are classical features of CBD. However, symmetric parkinsonism, frequent falls, and supranuclear gaze palsy are key features of PSP. Despite biochemically classified as 4R tauopathies, tufted astrocytes of PSP and astrocytic plaque of CBD show pathologically important differences. Herein, we report a 68-year-old man with pathologically confirmed CBD. He was clinically suspected to have PSP because of progressive gait disturbances, frequent falls, and vertical saccade limitation. Neurological examination performed at age 71 revealed symmetrical bradykinesia, axial rigidity, and postural instability with worsening of early existing symptoms. Magnetic resonance imaging of the brain taken at age 70 detected midbrain and left frontotemporal atrophy and right middle cerebral artery infarction. Left frontotemporoparietal hypometabolism and asymmetrically decreased fluoro-propyl-carbomethoxy-iodophenyl-tropane uptake in the basal ganglia were observed. The autopsy was performed at the time of his death (at age 72), which revealed severe pallor of the substantia nigra and mildly hypopigmented locus ceruleus. AT8 immunohistochemistry and Gallyas staining revealed tau-positive neuronal and glial inclusions, astrocytic plaques, ballooned neurons, and numerous threads in both gray and white matter. No abnormal inclusions were revealed by beta-amyloid, α-synuclein and TDP-43 immunohistochemistry. In our case, cerebral infarction, periventricular and deep white matter ischemic changes, and midbrain atrophy were likely to produce PSP–CBD overlapping symptoms. However, our patient was finally confirmed to have CBD based on pathological findings such as astrocytic plaques.