Richard Brannegan1, Russell Bartt. 1. Division of Neurology, John H Stroger Hospital of Cook County, Chicago, IL 60612, USA. richard.brannegan@hektoen.org
Abstract
OBJECTIVE: To determine how often the second lumbrical motor potential is present when the abductor pollicis brevis (APB) motor potential is absent in severe carpal tunnel syndrome (CTS). DESIGN: Prospective study of consecutive patients with severe CTS and an absent motor potential from the APB. SETTING: Single-center public hospital-based electromyography lab. PARTICIPANTS: Patients with a clinical diagnosis of CTS who had an absent median sensory response and an absent median motor response to APB on routine nerve conduction testing. Twenty-two hands of 19 patients were examined. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Presence and distal latency of motor potential to the second lumbrical. RESULTS: The second lumbrical potential was present in 17 hands (77%). The distal motor latency to the second lumbrical was prolonged in all (mean, 9.1ms; normative value, <4.1ms). CONCLUSIONS: Second lumbrical recordings improve localization in many patients with severe CTS when routine median sensory and motor conduction studies produce no potentials.
OBJECTIVE: To determine how often the second lumbrical motor potential is present when the abductor pollicis brevis (APB) motor potential is absent in severe carpal tunnel syndrome (CTS). DESIGN: Prospective study of consecutive patients with severe CTS and an absent motor potential from the APB. SETTING: Single-center public hospital-based electromyography lab. PARTICIPANTS: Patients with a clinical diagnosis of CTS who had an absent median sensory response and an absent median motor response to APB on routine nerve conduction testing. Twenty-two hands of 19 patients were examined. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Presence and distal latency of motor potential to the second lumbrical. RESULTS: The second lumbrical potential was present in 17 hands (77%). The distal motor latency to the second lumbrical was prolonged in all (mean, 9.1ms; normative value, <4.1ms). CONCLUSIONS: Second lumbrical recordings improve localization in many patients with severe CTS when routine median sensory and motor conduction studies produce no potentials.