Comparison of apraxia in corticobasal degeneration and progressive supranuclear palsy

Objective: To describe ideomotor apraxia in patients with corticobasal degeneration and those with progressive supranuclear palsy, two parkinsonian disorders that are often misdiagnosed due to the overlap in their clinical features, and to determine whether systematic apraxia testing is useful for differential diagnosis. Method: Fourteen patients fulfilling National Institute of Neurological Disorders and Stroke-Society for Progressive Supranuclear Palsy clinical criteria for progressive supranuclear palsy, 13 patients fulfilling modified Lang criteria for corticobasal degeneration, and 12 normal healthy control subjects were given the Test of Oral and Limb Apraxia, which was scored according to the Florida Apraxia Battery for occurrence of various types of apraxic errors. Results: Both patients with progressive supranuclear palsy and corticobasal degeneration committed a greater number of apraxic errors than normal healthy control subjects on both transitive and intransitive tasks (p < 0.001 in both cases), but apraxia was much more severe in patients with corticobasal degeneration than progressive supranuclear palsy (p < 0.001). The index of apraxia severity, in combination with the assessment of the two key features of progressive supranuclear palsy (falls and vertical gaze palsy), correctly classified all patients. Conclusions: Patients with corticobasal degeneration show more severe ideomotor apraxia than patients with progressive supranuclear palsy, and systematic assessment of ideomotor apraxia facilitates the differential diagnosis between patients with progressive supranuclear palsy and those with corticobasal degeneration.