Slowed down: response time deficits in well-recovered subjects with incomplete spinal cord injury

Abstract

OBJECTIVE: To quantify remaining motor deficits in well-recovered subjects with incomplete spinal cord injury. DESIGN: Case-control study. SETTING: Spinal cord injury center of a university hospital. PARTICIPANTS: Out of a volunteer sample, we recruited 15 subjects with incomplete paraplegia (mean age, 50y; 67% men; neurologic level from T4 to L4; mean time since injury, 6.3y) and close-to-normal walking pattern. They were compared with 15 age- and sex-matched controls. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Response time and its 4 subparts, processing time, conduction time, motor time, and movement time. These were assessed with an electromyogram-supported lower-limb response time task and single-pulse transcranial magnetic stimulation to measure the motor-evoked potential latency of the M. tibialis anterior. In addition, participants were tested for lower-extremity muscle strength, gait capacity, visual acuity, and upper-extremity response time. RESULTS: Well-recovered subjects with incomplete paraplegia still suffered from deficits in conduction and movement time, whereas their processing and motor times were essentially normal. In addition, these patients showed delayed movement times of the upper limb, even if their injury was located in the thoracic or lumbar region. CONCLUSIONS: Well-recovered patients with incomplete paraplegia still experience difficulties with quick and accurate movements. Furthermore, combining transcranial magnetic stimulation, electromyogram, and a response time task proved useful for investigating deficits in executing fast and accurate movements.