Predicting the risk and severity of acute spinal cord injury after a minor trauma to the cervical spine.

BACKGROUND CONTEXT: Acute spinal cord injury (SCI) after a minor trauma to the cervical spine has been reported in patients without preceding neurologic symptoms. Spinal canal stenosis may be the reason for the discrepancy between the severity of the injury and that of the trauma. The spinal canal to vertebral body ratio is often used to assess canal stenosis on conventional radiographs. However, the ratio does not appraise soft-tissue stenosis and canal narrowing at the level of the intervertebral disc. Parameters measured on magnetic resonance (MR) images may thus be more meaningful. The relevance of MR image parameters for predicting the risk and severity of acute SCI in patients after a minor trauma to the cervical spine has not yet been established.

PURPOSE: To investigate MR image parameters of the cervical spine in patients suffering from acute SCI after a minor trauma to the cervical spine. To investigate the use of these parameters for predicting the risk and severity of acute cervical SCI after a minor trauma to the cervical spine.

STUDY DESIGN/

SETTING

Retrospective radiological study of consecutive patients.

PATIENT SAMPLE: Fifty-two patients suffering from acute cervical SCI and 131 patients showing no neurologic deficits after a minor trauma to the cervical spine.

OUTCOME MEASURES: On sagittal MR images: vertebral body diameter, midvertebral canal diameter, disc-level canal diameter, and spinal cord diameter. On lateral conventional radiographs: vertebral body diameter and midvertebral canal diameter.

METHODS

Conventional lateral radiographs and sagittal T2-weighted MR images of the cervical spine (C3-C7) were analyzed. The following calculations were performed using measurements from MR images: the spinal canal to vertebral body ratio, the space available for the cord, and the canal-to-cord ratio. Using measurements from conventional radiographs, the spinal canal to vertebral body ratio was determined. Receiver-operating curves were calculated for evaluating the classification accuracy of the different parameters for predicting the risk, severity, and course of SCI.

RESULTS

All investigated MR image parameters in the SCI group were significantly (p<.001) smaller compared with the control group. However, there was no significant (p>.9) difference in any parameter among the different American Spinal Injury Association impairment score groups. A cutoff value of 8.0 mm for the minimal sagittal disc-level canal diameter yielded the largest positive predictive value and likelihood ratio for predicting SCI.

CONCLUSIONS

Patients at risk of acute SCI after a minor trauma to the cervical spine can be identified by applying a disc-level canal diameter cutoff value (measured on MR images) of 8 mm. Additional factors to the radiological characteristics of the spinal canal affect the severity of acute SCI after a minor trauma to the cervical spine.