Cognitive executive function in dystonia

Dystonia is a movement disorder considered to result from basal ganglia dysfunction. The aim of this study was to investigate the functional significance of frontal hyperactivity demonstrated in dystonia in imaging studies by examining executive function and working memory, in which the prefrontal cortex is known to be involved. We assessed 10 patients with idiopathic dystonia and 12 age- and IQ-matched normal controls. All subjects completed tests of first letter, category, and alternating category word fluency, the Wisconsin Card Sorting Test, the Stroop Colour Word Naming Test, the Missing Digit Test of working memory, a test of random number generation, a test requiring generation of self-ordered random number sequences, the Paced Serial Addition Test, a test of conditional associative learning, and finger tapping and peg insertion under unimanual, bimanual, and dual task conditions. The patients with dystonia did not differ significantly from controls on any measures of executive function or working memory used other than category word fluency and the extent of decline in tapping with one hand under dual task conditions when simultaneously inserting pegs with the other hand. For this small sample, the results suggest that unlike other movement disorders associated with fronto-striatal dysfunction such as Parkinson's disease or Huntington's disease, dystonia was not associated with deficits on the tests of executive function or working memory used. A more detailed investigation of cognitive function in a larger sample of patients is required.