"Motor" impairment in Asperger syndrome: evidence for a deficit in proprioception

Motor impairment has frequently been described in Asperger syndrome (AS), a pervasive developmental disorder included in the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV). Previous research focusing on this motor dysfunction has yielded inconsistent results, and the "clumsiness" observed clinically remains poorly defined. To clarify further the issue of motor impairment, we compared a group of 10 children and young adults who met DSM-IV criteria for AS with a control group with no neurological impairment. Subjects were matched on age, sex, socioeconomic status, and Verbal IQ. A broad battery of motoric tests was administered. Subjects with AS were found to perform more poorly than controls on tests of apraxia, one-leg balance with eyes closed, tandem gait, and repetitive finger-thumb apposition. No significant differences were found on tests of finger tapping, grooved pegboard, trail making, or visual-motor integration. The pattern of impairments suggests that a proprioceptive deficit may underlie the incoordination observed in AS and that these individuals may be overreliant on visual input to maintain balance and position in space.