Motor Power Differences Within the First Two Weeks Post-SCI in Cervical Spinal Cord-Injured Quadriplegic Subjects

Abstract

The purpose of this study was to confirm the clinical impression that motor power significantly changed within the first 2 weeks after a spinal cord injury (SCI) and to determine the time for motor power assessment within the first 2 weeks post injury that best correlated with motor power determined 6 months post-SCI. Our hypothesis was that within the first 2 weeks postinjury, the manual muscle test (MMT) scores would change significantly from the ≤ 24 h examination and that the post-24 h evaluations of strength would have a higher correlation with the 6 month measure of motor outcome than the evaluation of strength performed ≤ 24 h after SCI. The biceps, extensor carpi radialis, triceps, flexor digitorum profundus, and interosseous muscle strength was measured in 40 subjects using the MMT (muscles graded 0/5 to 5/5) at ≤ 24h, 72 h, 1 week, 2 weeks, 3 months, and 6 months post-SCI. Upper extremity motor index scores (MIS) obtained at the four testing periods within 2 weeks of injury were analyzed using a Friedman analysis of variance with Duncan's post-hoc tests to identify significant differences. Separate analyses were performed on subgroupings of the total sample based on the strength of the most rostral key muscle having less than antigravity strength. There were three groups evaluated: initial MMT 0/5 (n = 22), initial MMT 1–1.5/5 (n = 17), and initial MMT 2–2.5/5 (n = 13). Significant differences were found between the ≤ 24 h and the 2 week assessments for MIS as well as for MMT grades of 0/5 and 1–1.5/5 (p < 0.05). For all analyses, the 72 h and the 1 week MIS and MMT values were similar (p > 0.05), as were the 1 week and 2 week values. The 72 h MIS differed from the 2 week MIS (p < 0.05). Spearman analyses were performed correlating strength assessments (MIS and MMT values) in the first 2 weeks postinjury with 6 month assessments. Results indicated that assessments performed after 24 h were more highly correlated with 6 month outcome than were strength determinations within 24 h of injury. These results support the hypothesis that there are significant changes in motor power within the first 2 weeks post-SCI. The 72 h and 1 week periods are similar and represent the earliest and best times to evaluate strength for research and prognostic purposes.