SERIAL RECORDING OF SOMATOSENSORY AND MYOELECTRIC MOTOR EVOKED-POTENTIALS - ROLE IN ASSESSING FUNCTIONAL RECOVERY AFTER GRADED SPINAL-CORD INJURY IN THE RAT

Accurate functional outcome measures are essential in assessing therap eutic interventions after experimental spinal cord injury (SCI). We ex amined the hypothesis that serial recording of somatosensory (SSEP) an d myoelectric motor evoked potentials (mMEPs) would provide complement ary information to standard methods of behavioral analysis in a rat mo del of SCI and would allow objective discrimination of functional reco very in sensory and motor tracts. Clip compression injury of varying s everity (sham, 23 g, 34 g, 56 g) and transections were performed at T1 in adult rats. SSEPs were recorded from the right sensorimotor cortex (SMC) after stimulation of the contralateral hind paw; mMEPs were rec orded from the paraspinal, quadriceps, and the tibialis anterior muscl es after anodal stimulation of the SMC. The inclined plane and Tarlov techniques were used to assess clinical neurological function. All out come measures were assessed weekly prior to and up to 6 weeks followin g injury. Changes in clinical neurological function as assessed by the inclined plane and Tarlov methods varied with increasing injury sever ity (R = -0.72 and R = -0.73, respectively). SSEP latency was strongly correlated with injury severity (R = 0.92) and with clinical behavior al scores (R = -0.93 for inclined plane). The tibialis anterior mMEP c orrelated significantly, though weakly, with changes in inclined plane (R = 0.49) and Tarlov scores (R = 0.41). Although the mMEPs were sens itive to the presence of SCI, these recordings did not discriminate be tween severities of injury. We conclude that serial recording of SSEPs but not myoelectric MEPs correlates closely with the extent and tempo ral course of clinical neurological recovery after graded SCI in the r at.