Space Available for the Cervical Spinal Cord of Asymptomatic Adult Nigerians

OBJECTIVE The space available for the spinal cord (SAC) is a measure of spinal cord functional reserve and may vary in different societies. The objective of this study is to measure normal SAC at each subaxial cervical disc level of asymptomatic adult Nigerians and to compare obtained values with published studies worldwide. METHODS This is a prospective, cross-sectional study using magnetic resonance imaging facility at Memfys Hospital Enugu, from 2012 to 2013. Disc level measurement of midsagittal spinal canal and cord of randomly selected 102 consenting asymptomatic adults, 21 to 50 years. Literature search of related studies worldwide was used to compare with the current study. Analysis was done using inferential and descriptive statistics. RESULTS Average SAC values were 4.9±1.4 mm (C3/4), 4.5±1.2 mm (C4/5), 4.6±1.4 mm (C5/6), and 4.9±1.2 mm (C6/7). In 21-30 years group, SAC was 5.4±0.6 mm(C3/4), 4.9±0.6 mm(C4/5), 4.9±0.6 mm(C5/6), and 5.1±0.5 mm(C6/7). In 31-40 years group, SAC was 5.4±0.5 mm(C3/4), 4.6±0.5 mm (C4/5), 4.9±0.6 mm (C5/6), and 5.3±0.6 mm (C6/7); but among 41-50 years group, SAC was 3.8±0.6 mm (C3/4), 3.9±0.6 mm (C4/5), 3.6±0.6 mm (C5/6), and 4.3±0.6 mm (C6/7). In females SAC was 4.9±1.3 mm(C3/4), 4.5±1.2 mm(C4/5), 4.6±1.2 mm(C5/6), and 4.8±1.1 mm (C6/7). In males, SAC was 4.9±1.4 mm(C3/4), 4.6±1.2 mm(C4/5), 4.5±1.5 mm(C5/6), and 5.1±1.3 mm(C6/7). From analysis of variance, impact of age on SAC was 0.118 (p=0.001) while gender had 0.078 (p=0.223). SAC at each level has positive correlation of 0.6 to 0.7 with adjacent levels (p<0.0001). Comparing this result with studies worldwide, our population has lower SAC values than others. CONCLUSION C4/5 and C5/6 are narrowest subaxial cervical spine levels and probably explain preponderance of C4/5 and C5/6 cord injury. There may be higher incidence of congenital canal stenosis predisposing to worse outcome following cervical spine injury or degenerative diseases in this study population. This is different from European series but similar to Japanese.