First described in the 1960s, corticobasal degeneration is also known as cortical-basal ganglionic degeneration. It typically comes on as an asymmetric parkinsonian syndrome, most often in the sixth decade or later. Long considered a rare disorder, the description of additional cases and case series in recent years has widened the clinical spectrum.
Cortical manifestations of corticobasal degeneration include not only dementia and alien limb sign, but also apraxia and cortical sensory loss. The basal ganglionic component includes parkinsonism and limb dystonia. There may be postural tremor and a focal reflex myoclonus. Dementia may be the presenting sign. Not all patients exhibit the "alien limb" sign throughout the clinical course.
Two sets of diagnostic criteria derived from clinical case series are summarized in Table 1. Proposed research diagnostic criteria are listed in Table 2.
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