Cortical pattern of complex but not simple movements is affected in writer’s cramp: A parametric event-related fMRI study

ObjectivePatients with writer’s cramp (WC) were studied for differences in cortical activation during movements likely to induce WC (complex movements) and movements which rarely lead to dystonia (simple movements).MethodsEleven WC patients (10 F, 1 M, mean age 41.5 ± (SD)7.2 years) and eleven age matched controls were examined for Blood oxygenation-level dependent (BOLD) 1.5 T fMRI. The complex task consisted of writing a single letter or random drawing using an especially adapted joystick with the line of trajectory visualized or hidden. The simple task consisted of self-initiated fingers flexion/extension using the affected hand.ResultsUnlike the controls, WC patients performing complex movements exhibited a lower BOLD signal in the primary sensorimotor cortex and in the posterior parietal cortex bilaterally. A hypoactivation was also observed in the right secondary somatosensory area, in the right anterior insula and in the left premotor cortex (p < 0.05 corrected). No significant inter-group differences were found for simple movements.ConclusionsAlthough WC patients’ complex movements during fMRI were never associated with dystonic cramp, they exhibited an abnormally low cortical activity. This phenomenon was not observed in simple movements and was unrelated to the character of handwriting or to visual feedback.SignificanceOur results support the dualistic behavior in the sensorimotor system in WC.

► The sensorimotor network in writer’s cramp shows dualistic behavior during simple and complex movements. ► The aberrant cortical pattern during complex movements was independent of the character of graphic expression or the visual feedback. ► Parametric fMRI design using kinematic parameters of writing is necessary for compensation of the inter-individual variability of hand movements.