Movement Disorders zyxwvutsrqponm Vol. 11, No. 6, zyxwvutsrqpon 1996,. pp. 6834% zyxwvutsrqpon Q zyxwvutsrqpon 1996 Movement Disorder Society Abnormal Sensorimotor Integration in Writer’s Cramp: Study of Contingent Negative Variation Akio Ikeda, Hiroshi Shibasaki, “Ryuji Kaji, Kiyohito Terada, Takashi Nagamine, Manabu Honda, “Toshiaki Hamano, and *Jun Kimura Department$ zyxwvutsrqp of Brain Pathophysiology and *Neurology, Kyoto University School of Medicine Kyoto, Japan Summary: To investigate the pathophysiology of idio- pathic focal dystonia, we recorded contingent negative variation (CNV) as a physiological index of sensorimotor integration in 14 right-handed patients with writer’s cramp and compared it with normative data. CNV was recorded in the S2 choice reaction time paradigm: Two kinds of auditory S2 (Go or No-Go) were given 2 s after the auditory Sl, and the subject reacted only to the Go signal by extending the wrist. In normal subjects, the late CNV amplitude had no difference at Cz between left- and right-hand tasks and was symmetric without significant amplitude laterality irrespective of the side of hand move- ment. In patients with writer’s cramp, the late CNV am- plitude at Cz was relatively larger for the left-hand task than the right-hand task (p < 0.03), and a significant am- plitude laterality of the late CNV (larger on the right) was present especially at the central area for the right-hand task (p < 0.03). Since the late CNV is known to be gen- erated, at least in part, from primary and supplementary motor cortices, the significant laterality of the late CNV seen with the right-hand task in patients with writer’s cramp might represent functional abnormality of motor cortices possibly as the result of basal ganglia function. Key Words: Writer’s crampIdiopathic focal dystonia- Contingent negative variation. Dystonia is defined as a motor syndrome charac- terized by abnormal movements and postures pro- duced by prolonged, excessive muscle contractions that distort a certain body part into typical postures (1). When it occurs in adult life, it is usually con- fined to the site of initial involvement like oroman- dibular dystonia, spasmodic torticollis, and writer’s cramp (idiopathic focal dystonia). In symptomatic dystonia, lesions are often found in the basal gan- glia. Although previous observations in idiopathic dystonia patients suggested abnormality of the brainstem and spinal inhibitory networks (2,3), these findings may be secondary to abnormal de- scending commands from the rostra1 structures. It is assumed that the primary abnormality in patients with idiopathic focal dystonia is in the basal ganglia and that it disrupts the thalamic input to the frontal _ _ _ ~ _ ~ ~ ~ _ ~ Received June 20, 1995, and in revised form January 22, 1996. Accepted February 19, 1996. Address correspondence and reprint requests to Dr. A. Ikeda at Department of Brain Pathophysiology, Kyoto University School of Medicine, Shogoin, Sakyo-ku, Kyoto, 606, Japan. cortex and ultimately to the motor cortex (4). It was pointed out that dystonic posturing is very similar to that seen in patients with seizures involving the supplementary motor area (SMA) (5). This fact is compatible with the concept that the SMA is a ma- jor cortical target of the basal ganglia output (6). Therefore, the mechanism of dystonia has been dis- cussed in relation to the basal ganglia as well as the SMA (4). Contingent negative variation (CNV) is one of the event-related potentials first reported by Walter et al. (7). It is a slow negative cortical potential occur- ring between two successive stimuli only when the two stimuli are associated with or contingent to each other. Previous investigations suggested that the CNV represents cognition, expectancy, prepa- ration, estimation, and voluntary motor control (8). Therefore, it might reflect the neuronal activity nec- essary for sensorimotor integration or association in planning or execution of externally triggered, vol- untary movements. Recent animal experiments demonstrated “behaviorally contingent activity” in 683