Progressive apraxia in clinically discordant monozygotic twins
R. J. Caselli, E. M. Reiman, D. Timmann, G. E. Stelmach, M. A. Lawson, D. Osborne, S. B. Moore and M. J. Cevette
Section of Neurology, Mayo Clinic, Scottsdale (Ariz), USA.
OBJECTIVE: To determine disease concordancy in the first identical twin
with corticobasal degeneration. The patients were 63-year-old, erythrocyte
antigen-confirmed monozygotic male twins who were clinically discordant for
progressive apraxia caused by corticobasal degeneration. INTERVENTIONS:
Neuropsychologic and kinesiologic testing, magnetic resonance imaging, and
positron emission tomographic measurements of cerebral metabolic rate for
glucose. RESULTS: The affected twin had lower neuropsychologic and
kinesiologic test scores than did his brother, particularly 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 had 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. CONCLUSIONS: Corticobasal degeneration may
remain clinically discordant in identical twins after 7 years. Positron
emission tomography and neuropsychologic findings suggest the possibility
of a preclinical stage of corticobasal degeneration. There is generalized
cortical atrophy in patients with corticobasal degeneration in addition to
focal atrophy.