LAUSR

There is a paucity of data comparing the demographics, mechanism of injury, and outcomes of upper versus lower cervical spinal cord injuries (cSCI). The study objective was to define different clinical manifestations of cSCI. Data were collected prospectively through centers of the North American Clinical Trials Network (NACTN). Data was collected on 470 patients (21% women, mean age 50 years). Cervical vertebral level was analyzed as an ordinal variable to determine a natural demarcation to classify upper versus lower cSCI. For continuous variable analysis, falls were associated with C3 more than C4 vertebral level injuries (60% vs. 42%) (p=0.0126), while motor vehicle accidents (MVA) were associated with C4 more than C3 (40% vs. 29%) (p=0.0962). Motor ISNSCI scores also demonstrated a natural demarcation between C3 and C4, with C3 having higher median ASIA motor scores (40 [4 - 73] vs. 11 [3 - 59], p= 0.0227). There were no differences when comparing C2 to C3 nor C4 to C5. Given the significant differences seen between C3 and C4, but not C2 and C3 nor C4 and C5, upper cSCI was designated as C1-C3, and lower cSCI was designated as C4-C7. Compared to a lower cSCI, patients with an upper cSCI were more likely to have a fall as their mechanism of injury (54% vs. 36%, p= 0.0072). Patients with an ASIA C cSCI were likely to have an upper cervical injury: 23% vs. 11% (p= 0.0226). Additionally, patients with an upper cSCI were more likely to have diabetes prior to injury, 37% vs. 22% respectively (p= 0.0084). Lower cSCI were more likely injured through sports (19% vs. 8%, p= 0.0171) and present with ASIA A (42% vs. 25%, p= 0.0186) neurological grade. Patients with lower cSCI were also significantly more likely to have complications such as shock, pulmonary embolism, and pleural effusion. In conclusion, there appears to be a natural demarcation of injury type between C3 and C4. Upper cSCI (C1-C3) was more associated with falls and diabetes, whereas lower cSCI (C4-C7) was more associated with sports, worse ASIA scores, and more complications. Further research will be needed to understand the mechanistic and biological differences between these two groups and whether different treatments may be appropriate for each of these groups.