PROGRESSIVE APRAXIA IN CLINICALLY DISCORDANT MONOZYGOTIC TWINS

Objective: To determine disease concordancy in the first identical twi n with corticobasal degeneration. The patients were 63-year-old, eryth rocyte antigen-confirmed monozygotic male twins who were clinically di scordant for progressive apraxia caused by corticobasal degeneration. Interventions: Neuropsychologic and kinesiologic testing, magnetic res onance imaging, and positron emission tomographic measurements of cere bral metabolic rate for glucose. Results: The affected twin had lower neuropsychologic and kinesiologic test scores than did his brother, pa rticularly on tests sensitive to right- compared with left-hemisphere function; widespread cerebral atrophy, worst in right parietotemporal cortices; and reduced whole-brain cerebral metabolic rate for glucose, worst in right posterior cortices. The clinically asymptomatic twin h ad normal neuropsychologic and kinesiologic test scores but performed more poorly on tests sensitive to left- compared with right-hemisphere function; had no abnormalities on magnetic resonance imaging; and had left temporoparietal as well as mild whole-brain hypometabolism. Conc lusions: Corticobasal degeneration may remain clinically discordant in identical twins after 7 years. Positron emission tomography and neuro psychologic findings suggest the possibility of a preclinical stage of corticobasal degeneration. There is generalized cortical atrophy in p atients with corticobasal degeneration in addition to focal atrophy.