The sensory consequences of repetitive strain injury in musicians: focal dystonia of the hand 1

Abstract

Some individuals with repetitive strain injury (RSI) develop focal dystonia of the hand (FD_h), a disorder of motor control manifested in a specific context during skilled, hand movements. This descriptive study was designed to determine if musicians with FD_h had reduced tactile discrimination. Ten healthy adults and ten patients with FD_h participated in the study. From the standardized Sensory Integration and Praxis Test, five subtests were selected to measure tactile discrimination. The Paired Wilcoxon Test was used to analyze, meaningful, planned pairwise differences by side and by group. The two groups performed similarly on the three tests measuring tactile motor perception (Finger Identification, Localization and Kinesthesia). However, those with FD_h performed significantly worse than the healthy comparison group on two tactile perceptual tasks: (1) Graphesthesia, right affected (P < 0.003) and left unaffected (P < 0.005); and (2) Manual Form Perception (stereognosis) on the right affected (P < 0.002) and left unaffected (P < 0.002). It is possible that the somatosensory differences as measured by tactile discrimination tasks represent some degradation of the hand representation following prolonged, repetitive, near simultaneous sensory stimulation of adjacent digits. Tactile discrimination should be tested in patients with RSI to detect potential risks for developing FD_h. Effective treatment of patients with RSI including FD_h may need to target the somatosensory deficits in order to restore stress-free motor movements.