Electrodiagnostic changes of the lower limbs in subjects with chronic complete cervical spinal cord injury

Objective: To assess the electrodiagnostic changes in the lower limbs as me asured by nerve conduction studies (NCSs) and electromyography in individua ls with chronic complete tetraplegia, Design: Prospective testing of NCS and electromyography. Setting: Model spinal cord injury rehabilitation center. Participants: Twenty-five individuals with chronic complete tetraplegia wit hout risk factors for peripheral neuropathy or other lower motoneuron disor ders. Interventions: Nerve conduction parameters recorded from the peroneal, tibi al, and sural nerves, and compared with normal values. The presence of spon taneous activity (SA), including fibrillation and positive sharp waves, rec orded in 5 muscle groups-2 proximal (vastus medialis, iliopsoas), 2 distal (tibialis anterior, medial gastrocnemius), and L4 lumbar paraspinals. Analy sis to see if the presence of SA correlated with the distance of the muscle from the spinal cord or with spasticity (measured by the modified Ashworth scale). Main Outcome Measures: Nerve conduction latencies and velocities; motor and sensory conduction latencies; compound muscle action potential (CMAP) and sensory nerve action potential amplitudes; spontaneous potentials: fibrilla tion and positive sharp waves; and spasticity. Results: NCS responses were obtained at a decreased frequency relative to a ble-bodied subjects. Statistically significant results in comparison to nor mal means included a diminished sural amplitude, and diminished peroneal an d tibial CMAP and nerve conduction velocity (p <.0001). SA was recorded in at least I of the muscles tested in 92% of subjects, with 72% having SA in more than 1 of the muscles tested affected. A significant difference was se en for SA in the medial gastrocnemius as compared with the iliopsoas (p =.0 39). No correlation was noted in terms of SA with degree of spasticity. Conclusion: A statistically significant difference in NCS responses in the lower limbs in chronic tetraplegia was found relative to normal control val ues. However, only the frequency of responses elicited and the decreased CM AP of the peroneal nerve are clinically significant. SA was present in many of the lower extremity muscles in the subjects. Predominantly axonal chang es were evident in individuals with chronic complete tetraplegia.