Tourette's syndrome in monozygotic twins. Relationship of tic severity to neuropsychological function
C. Randolph, T. M. Hyde, J. M. Gold, T. E. Goldberg and D. R. Weinberger
Clinical Brain Disorders Branch, National Institute of Mental Health, Bethesda, Md.
OBJECTIVE--To determine whether there is a relationship between tic
severity and neuropsychological function in Tourette's syndrome (TS).
DESIGN--The study employed a case-control series involving monozygotic twin
pairs, divided into more severe and less severe groups based on tic
severity and tested with a neuropsychological battery of tests.
SETTING--Twin pairs were recruited nationwide and evaluated in the National
Institute of Mental Health Neuropsychiatric Research Hospital.
PATIENTS--Twelve twin pairs (mean age, 10.5 years; range, 8 to 16 years) in
which at least one member met criteria for a diagnosis of TS.
RESULTS--Global neuropsychological performance was significantly worse in
the twins with more severe tic symptoms, with significant differences
emerging on individual tests of attention, visuospatial perception, and
motor function. In each twin pair, the twin with more severe tics had
poorer global neuropsychological function. CONCLUSIONS--The results suggest
that the nongenetic factors that influence tic severity in TS exert a
similar effect on neuropsychological function, and that these two clinical
manifestations of TS may share a common pathophysiologic state.
