Journal of Experimental and Clinical Anatomy

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 18  |  Issue : 1  |  Page : 38--42

A study of magnetic resonance imaging-derived cervical spinal cord dimensions in young adult Nigerians: Clinical relevance


Chika Anele Ndubuisi1, Kelechi Onyenekeya Ndukuba2, Samuel Chinonyerem Ohaegbulam2, Tobechi Nwankwo Mbadugha2, Moses Osaodion Inojie2, Anthony Jude Edeh3,  
1 Department of Neurosurgery, Memfys Hospital; Department of Surgery, College of Medicine, Enugu State University of Science and Technology, Enugu, Nigeria
2 Department of Neurosurgery, Memfys Hospital, Enugu, Nigeria
3 Department of Surgery, College of Medicine, Enugu State University of Science and Technology, Enugu, Nigeria

Correspondence Address:
Dr. Chika Anele Ndubuisi
Memfys Hospital for Neurosurgery, KM 2 Enugu-Onitsha Expressway, P. O. Box 2292, Enugu
Nigeria

Abstract

INTRODUCTION: Knowledge of cervical cord dimensions is important in making diagnosis of pathological conditions of the spinal cord. This study used magnetic resonance imaging to determine the normal dimensions of the cervical spinal cord in young adult Nigerians and the influence of age and sex on these dimensions. METHODS: A prospective study of 100 healthy asymptomatic individuals (50 males and 50 females) aged 21–40 years was carried out at Memfys Hospital, Enugu, Nigeria. Disc-level axial T1-weighted 0.35T magnetic resonance images of anteroposterior dimensions (APDs) and transverse dimensions (TDs) were obtained from C2/C3 to C7/T1 in millimeters. Approximate cord area (ACA) was calculated as the product of APD and TD. Test of significance for age- and sex-adjusted dimensions was determined. RESULTS: TD increased from C2/3 (12.2 ± 1.0 mm) to peak at C5/6 level (13.4 ± 1.2 mm) before dropping to 11.6 ± 1.4 mm (C7/T1). APD decreased from 8.1 ± 0.6 mm (C2/3) to 6.9 ± 0.7 mm (C7/T1). ACA also increased from 98.7 ± 11.7 mm2 (C2/3) to peak value of 103.3 ± 14.6 mm2 (C5/6), but dropped to 80.0 ± 14.3 mm2 (C7/T1). In general, there was no significant gender-based difference in values of the cord dimensions except in TD at C2/3 (0.036). ANOVA revealed a significant difference in age-adjusted values of TD (0.022) and AP (0.042) at C5/6. Only TD values had significant variability at C5/6 level when individuals in the age group of 36–40 years were compared to those <30 years old. CONCLUSION: TD and ACA give more representative values of cervical spinal cord size and should be utilized clinically in the assessment of these dimensions. The C5/6 has the highest cervical spinal cord dimension. Sex-adjusted dimensions generally did not show statistically significant difference. There is subtle but significant reduction in TD of cervical spinal cord at C5/6 level toward the age of 40 years.



How to cite this article:
Ndubuisi CA, Ndukuba KO, Ohaegbulam SC, Mbadugha TN, Inojie MO, Edeh AJ. A study of magnetic resonance imaging-derived cervical spinal cord dimensions in young adult Nigerians: Clinical relevance.J Exp Clin Anat 2019;18:38-42


How to cite this URL:
Ndubuisi CA, Ndukuba KO, Ohaegbulam SC, Mbadugha TN, Inojie MO, Edeh AJ. A study of magnetic resonance imaging-derived cervical spinal cord dimensions in young adult Nigerians: Clinical relevance. J Exp Clin Anat [serial online] 2019 [cited 2021 Jan 16 ];18:38-42
Available from: https://www.jecajournal.org/text.asp?2019/18/1/38/271866


Full Text



 Introduction



The knowledge of the dimensions of cervical spinal cord is important clinically in evaluating some of the pathological conditions of the cord (Frostell et al., 2016). Previously, in the literature, the spinal cord measurements were based on autopsy studies and these measurements could have been biased by the challenge of exclusion of patients with intrinsic cord pathology. In addition, it has been argued that technique-dependent errors may have also affected the reliability of autopsy-derived measurements of the spinal cord (Sherman et al., 1990). However, the advent of magnetic resonance imaging (MRI) has helped overcome these challenges. MRI is the diagnostic modality of choice in evaluating the spinal cord (Presciutti et al., 2009; Aebli et al., 2013) and has revolutionized the management of spinal cord pathologies (Yu and Williams, 2006). MRI is currently the only imaging modality that can reliably be used by the clinicians to investigate the spinal cord without a need for autopsy and open surgery. There is, therefore, a need to evaluate spinal cord morphometry using MRI-derived dimensions as this may help the clinicians to understand the radiological anatomy of the spinal cord much better and improve the diagnostic yield of some structural pathologies of the spinal cord including degenerative diseases of the spinal cord. MRI-derived spinal cord dimensions have also been demonstrated to show high interobserver reliability (Rüegg et al., 2015s clinician to accurately measure functionally relevant spinal canal and spinal cord dimensions in various planes (Ulbrich et al., 2014). There is, therefore, a need to use this imaging modality to derive the cord dimension for this study population. Furthermore, there is a paucity of publications that assessed the influence of factors such as age and sex on the dimensions of the spinal cord segments in young otherwise healthy adults, especially in the study population. This study used MRI to determine the normal dimensions of cervical spinal cord in young adult Nigerians and assessed the influence of age and sex on these dimensions.

 Methods



This was a prospective, cross-sectional study carried out at Memfys Hospital, Enugu, a tertiary hospital for neurosurgery, in South-East Nigeria. The study period extended from April 2013 to March 2016. One hundred apparently healthy adults without symptoms referable to the cervical spine were selected. These were matched equally for age and sex. The age range of individuals selected ranged from 21 to 40 years. This age range was carefully selected to exclude the pediatric age group and individuals who have significantly predisposition to degenerative spine disease. The study excluded non-Nigerians and individuals with previous history of trauma or whiplash injury, symptoms referable to the cervical spine, congenital deformities that may suggest predisposition to canal stenosis such as spinal bifida, and previous cervical spine infection or surgeries. All patients signed informed consent before participating in the study. The BASDA (BTI 0.35 MRI System, Shenzhen Basda Medical apparatus Co., Ltd., China) was used to obtain T1Wi MRI images using the standard protocol. T2-weighted (T2Wi) images were also obtained to help in excluding any cervical spinal cord pathology that would not be apparent from the T1Wi scan. After the midsagittal T1Wi was acquired, disc-level axial T1-weighted MR images were obtained from C2/C3 to C7/T1. The anteroposterior dimensions (APDs) and transverse dimensions (TDs) were taken at each level from the axial images. Measurements were in millimeters [Figure 1]. Approximate cord area (ACA) was calculated as the product of APD and TD. Analysis was done using descriptive and inferential statistics including t-tests and ANOVA, assisted by SPSS version 16 (SPSS Inc. SPSS for Windows, Version 16.0, Chicago, Illinois, USA). Test of significance for age- and sex-adjusted dimensions was determined. P < 0.05 was considered statistically significant. Ethical approval was obtained for the study.{Figure 1}

 Results



The mean age was 29.2 years. The mean TD increased from C2/3 (12.2 ± 1.0 mm) to C5/6 level (13.4 ± 1.2 mm) where it attained the peak value before the TD dropped again at C6/7 (12.9 ± 1.3 mm) and C7/T1 levels (11.6 ± 1.4 mm) [Table 1]. The mean APDs were 8.1 ± 0.6 mm (C2/3), 7.9 ± 0.6 mm (C3/4), 7.8 ± 0.7 mm (C4/5), 7.7 ± 0.8 mm (C5/6), 7.3 ± 0.7 mm (C6/7), and 6.9 ± 0.7 mm (C7/T1) [Table 1]. The mean ACA also increased from 98.7 ± 11.7 mm 2 (C2/3) to peak value of 103.3 ± 14.6 mm 2 (C5/6), but dropped again to 80.0 ± 14.3 mm 2 (C7/T1) [Table 1]. The mean ACA, TD, and APD values in males and females are compared in [Table 2]. There was a significant difference in the TD obtained between genders at C2/3 level. The age-adjusted values of the APD, TD, and ACA among the different age groups are analyzed in [Table 3]. ANOVA revealed a significant difference in the age-adjusted values at C5/6 level for TD (0.022) and AP (0.042), as well as C7/T1 for TD and ACA [Table 3]. However, when the segments with significant age-adjusted differences in values were subjected to Bonferroni multiple comparison analysis, only the TD revealed a significant effect of variability with age at C5/6 level between asymptomatic individuals in the age group of 36–40 years when compared to those <30 years old [Table 4].{Table 1}{Table 2}{Table 3}{Table 4}

 Discussion



This study is important to the study environment because there is paucity of studies that have assessed the normal cervical spinal cord dimension using magnetic resonance imaging. Hence, most anatomical and clinical references rely on data generated from other study population of different races.

The normal range of the cervical spinal cord dimension across the different segments of the spinal cord, age groups, and gender was the emphasis of this study. This was the major reason for the choice of the age range used in this study. Unlike other studies that extended analysis across all the age groups (Sherman et al., 1990; Rüegg et al., 2015), individuals within the age range of 20–40 years were used in the current study because the spinal cord dimensions would have developed fully to the adult size, and within this age group, there will not be significant spinal cord atrophy and other spinal cord diseases (Ishikawa et al., 2003). The ACA, TD, and APD did not show much significant difference in dimensions across most of the segments of the spinal cord. Clinically, the implication of this finding is that adults in the study population do not need separate gender- or age-based normal range values for the evaluation of the spinal cord morphometry for structural lesions. This will also make radiological interpretation of cervical spine MRI investigations less cumbersome. It should, however, be noted that while there may not be significant difference in cervical spinal cord dimension between genders (Sherman et al., 1990), studies carried out among other populations in other parts of the world observed significant effect of gender on the spinal cord dimension (Ishikawa et al., 2003; Kato et al., 2012; Ulbrich et al., 2014; Papinutto et al., 2015). This may suggest that racial differences exist in the spinal cord morphometry, and data from other populations should be interpreted cautiously for individuals from other races, especially at the early stages of spinal cord atrophy.

At C5/6 level, in this study, however, the age group of 36–40 years had a significant drop in the TD of the spinal cord when compared to those in the third decade of life. This may suggest that subtle cord atrophy begins to manifest in the cervical spinal cord, especially at the C5/6 level as healthy asymptomatic individuals approach the latter half of the fourth decade of life. Some studies (Ishikawa et al., 2003; Kato et al., 2012) had demonstrated a trend toward reduction in cord dimension, especially in the older age groups. Furthermore, the significant difference observed in the TD at C5/6 and C7/T1 between individuals in the age subgroup of 20–35 years and those >35 years in this study may be a reflection of the hand usefulness, especially the thumb and other finger activities. Many daily activities among the younger age groups are phone and computer dependent, and as a result, the functional activities involving the fingers should reflect on the segmental nerve size and spinal cord dimension. Subaxial cervical spinal cord dimension may have a relationship with an individual's hand dexterity, especially as age advances. In a separate study, Freund et al., 2014, had also observed that, in patients with spinal cord injury, the extent of impairment of function correlates with the extent of spinal cord atrophy at the corresponding vertebral levels.

In this study, the AP dimension failed to clearly demonstrate the expected focal increase in size expected around the zone of origin of the brachial plexus. On the other hand, the TD as anatomically expected peaked at C5/6 level before it gradually dropped toward the C7/T1 level. This is because the cervical spinal cord enlargement from the effect of brachial plexus is mostly along the axial plane (Sherman et al., 1990). The midsagittal dimension of the cervical cord has been documented in a previous study not to show much significant variation across the different segments (Sherman et al., 1990). On the other hand, the TD across different segments showed significant variations. Therefore, the TD has more influence on the segmental variations of the cervical spinal cord dimension when compared with the midsagittal dimension and may be more reliable in anthropometry of the cervical spinal cord.

In this study, the ACA was, therefore, derived from both the midsagittal and the TDs as a single representative value of the cervical spinal cord size at each segment. Clinically, the authors believe that because this representative value of ACA accommodated both the midsagittal and the TDs of the cervical spinal cord, it will improve the reliability of the measurements obtained at each segment of the cervical spinal cord.

This study has many other clinical applications. The knowledge of the normal range of each segment of the cervical spinal cord will help in early diagnosis of some clinical conditions including degenerative spinal cord diseases caused by young juvenile diabetes, some stages of multiple sclerosis, amyotrophic lateral sclerosis, severe combined degenerative disease of the cord, and cord atrophy from other conditions including spinal cord injury. The extent of spinal cord atrophy as obtained from serial MRI-based measurements has been found to correlate strongly with the extent of disability. Therefore, these serial measurements of cervical spinal cord dimensions in these patients with early clinical cervical cord degenerative diseases may be clinically relevant tool for monitoring disease progression.

However, the authors recommend using at least two of the parameters, preferably the ACA and the TD of the cervical spinal cord when making a clinical diagnosis as these are more reliable in clinical evaluation of the spinal cord.

Furthermore, prior knowledge of the previous values of MRI- derived spinal cord dimension in healthy young adults may help in the diagnosis of early symptomatic intramedullary space-occupying lesion of the cervical spinal cord, when symptoms are still at early stage and signal abnormalities have not been observed in a subsequent MRI (Moghaddamand Bhatt, 2018). In such instance, serial MRI scans may reveal increase in size of the segment of the spinal cord affected by the lesion, especially in low-grade gliomas where such lesions may not take contrast following neuroimaging investigations.

Finally, this study will help determine the normal range of cervical spinal cord dimensions in the Nigerian study population. However, further studies need to be carried out among extended populationswith spinal cord pathologies and other degenerative spine diseases.

 Conclusion



The transverse diameter and the ACA give more representative values of the cord size in the cervical spine. The C5/6 level has the biggest dimension of the cervical spinal cord. The sex-adjusted dimensions did not show any statistically significant difference. There is significant reduction in the TD of the cervical spinal cord at C5/6 level toward the age of 40 years.[12]

Acknowledgment

We would like to acknowledge the management of Memfys Hospital for supporting the study and also Ashraf Adeol, the radiographer, who assisted with the MRI images.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Aebli N., Rüegg T.B., Wicki A.G., Petrou N., Krebs J. (2013). Predicting the risk and severity of acute spinal cord injury after a minor trauma to the cervical spine. Spine J 13:597-604.
2Freund P, Weiskopf N, Ward NS, Hutton C, Gall A, Ciccarelli O, Craggs M, Friston K, Thompson AJ. (2011). Disability, atrophy and cortical reorganization following spinal cord injury. Brain 134 (Pt 6):1610-22.
3Frostell A., Hakim R., Thelin E.P., Mattsson P., Svensson M. (2016). A review of the segmental diameter of the healthy human spinal cord. Front Neurol 7:238.
4Ishikawa M., Matsumoto M., Fujimura Y., Chiba K., Toyama Y. (2003). Changes of cervical spinal cord and cervical spinal canal with age in asymptomatic subjects. Spinal Cord 41:159-63.
5Kato F., Yukawa Y., Suda K., Yamagata M., Ueta T. (2012). Normal morphology, age-related changes and abnormal findings of the cervical spine. Part II: Magnetic resonance imaging of over 1,200 asymptomatic subjects. Eur Spine J 21:1499-507.
6Moghaddam S.M., Bhatt A.A. (2018). Location, length, and enhancement: systematic approach to differentiating intramedullary spinal cord lesions. Insights Imaging 9 (4):511-26.
7Papinutto N., Schlaeger R., Panara V., Zhu A.H., Caverzasi E., Stern W.A. (2015). Age, gender and normalization covariates for spinal cord gray matter and total cross-sectional areas at cervical and thoracic levels: A 2D phase sensitive inversion recovery imaging study. PLoS ONE 10 (3):e0118576. doi: 10.1371/journal.pone. 0118576.
8Presciutti S.M., DeLuca P., Marchetto P., Wilsey J.T., Shaffrey C., Vaccaro A.R. (2009). Mean subaxial space available for the cord index as a novel method of measuring cervical spine geometry to predict the chronic stinger syndrome in American football players. J Neurosurg Spine 11:264-71.
9Rüegg T.B., Wicki A.G., Aebli N., Wisianowsky C., Krebs J. (2015). The diagnostic value of magnetic resonance imaging measurements for assessing cervical spinal canal stenosis. J Neurosurg Spine 22:230-6.
10Sherman J.L., Nassaux P.Y., Citrin C. M. (1990). Measurements of the normal cervical spinal cord on MR imaging. Am J Neuroradiol 11:369-72.
11Ulbrich E.J., Schraner C., Boesch C., Hodler J., Busato A., Anderson S.E. (2014). Normative MR cervical spinal canal dimensions. Radiology 271 (1):172-82.
12Yu W., Williams S. (2006). Spinal imaging: Radiographs, computed tomography, and magnetic resonance imaging. In: Spinak JM, Connolly PJ, editors. Orthopaedic Knowledge Update Spine. 3rd ed. American Academy of Orthopaedic Surgeons 6: p. 57-67.