Retest effects and cognitive decline in longitudinal follow-up of patientswith early HD

Objective: To assess the natural progression of cognitive impairment in Hun tington's disease (HD) and to reveal factors that may mask this: progressio n. Background: Although numerous cross-sectional studies reported cognitive deterioration at different stages of the disease, progressive cognitive de terioration has been, up to now, difficult to demonstrate in neuropsycholog ical longitudinal studies. Methods: The authors assessed 22 patients in ear ly stages of HD at yearly intervals for 2 to 4 years (average, 31.2 +/- 10 months), using a comprehensive neuropsychological battery based on the Core Assessment Program for Intracerebral Transplantation in Huntington's Disea se (CAPIT-HD). Results: The authors observed a significant decline in diffe rent cognitive functions over time: these involved primarily attention and executive functions but also involved language comprehension, and visuospat ial immediate memory. Episodic memory impairment that tvas already present at the time of enrollment did not show significant decline. The authors fou nd a significant retest effect at the second assessment in many tasks. Conc lusion: Many attention and executive tasks adequately assess the progressio n of the disease at an early stage. For other functions, the overlapping of retest effects and disease progression may confuse the results. High inter individual and intraindividual variability seem to be hallmarks of the dise ase.