MR diffusion tensor imaging of the spinal cord: can it help in early detection of cervical spondylotic myelopathy and assessment of its severity?

A meta-analysis of the role of diffusion tensor imaging in cervical spinal cord compression

BACKGROUND AND PURPOSE

At present, the role of diffusion tensor imaging (DTI) remains controversial. This study aimed to confirm the role of DTI by comparing the differences in fractional anisotropy (FA) values between patients with cervical spinal cord compression (CSCC) and healthy individuals.

METHODS

A systematic and comprehensive literature search was conducted using the Web of Science, Embase, PubMed, and Cochrane Library databases to compare the mean FA values of patients with CSCC and healthy controls across all compression levels in the cervical spinal cord. Essential data from the literature, such as demographic information, imaging parameters, and DTI analysis method, were extracted. Fixed- or random-effect models based on I² heterogeneity were applied to the pooled and subgroup analyses.

RESULTS

Ten studies containing 445 patients and 197 healthy volunteers were eligible. The pooled results demonstrated a decrease in mean FA values across all compression levels in the experiment group compared to those in healthy controls (standardized mean difference = -1.54; 95% confidence interval = [-1.95, -1.14]; p < .001). Meta-regression revealed that the scanner field strength and DTI analysis method had a significant effect on heterogeneity.

CONCLUSIONS

Our results show that FA values in the spinal cord decline in patients with CSCC, thus confirming the crucial role of DTI in CSCC.

Clinical and Research MRI Techniques for Assessing Spinal Cord Integrity in Degenerative Cervical Myelopathy-A Scoping Review

BACKGROUND

Degenerative cervical myelopathy (DCM) manifests as the primary cause of spinal cord dysfunction and is non-traumatic, chronic and progressive in nature. Decompressive surgery is typically utilised to halt further disability and neurological dysfunction. The limitations of current diagnostic options surrounding assessment and prognostic potential render DCM still largely a clinical diagnosis.

AIMS

To outline the limitations of current diagnostic techniques, present evidence behind novel quantitative MRI (qMRI) techniques for assessing spinal cord integrity in DCM and suggest future directions.

METHOD

Articles published up to November 2021 were retrieved from Medline, EMBASE and EBM using key search terms: spinal cord, spine, neck, MRI, magnetic resonance imaging, qMRI, T1, T2, T2*, R2*, DTI, diffusion tensor imaging, MT, magnetisation transfer, SWI, susceptibility weighted imaging, BOLD, blood oxygen level dependent, fMRI, functional magnetic resonance imaging, functional MRI, MRS, magnetic resonance spectroscopy.

RESULTS

A total of 2057 articles were retrieved with 68 articles included for analysis. The search yielded 2 articles on Quantitative T1 mapping which suggested higher T1 values in spinal cord of moderate-severe DCM; 43 articles on DTI which indicated a strong correlation of fractional anisotropy and modified Japanese Orthopaedic Association scores; 15 articles on fMRI (BOLD) which demonstrated positive correlation of functional connectivity and volume of activation of various connections in the brain with post-surgical recovery; 6 articles on MRS which suggested that Choline/N-acetylaspartate (Cho/NAA) ratio presents the best correlation with DCM severity; and 4 articles on MT which revealed a preliminary negative correlation of magnetisation transfer ratio with DCM severity. Notably, most studies were of low sample size with short timeframes within 6 months.

CONCLUSIONS

Further longitudinal studies with higher sample sizes and longer time horizons are necessary to determine the full prognostic capacity of qMRI in DCM.

The Role of Diffusion Tensor Tractography in Assessment of Spondylotic Myelopathy

Introduction

Cervical spondylotic myelopathy (CSM) describes a neurological deficit related to the spinal cord due to the changes in the facet joints and discs of the cervical spine as a result of degeneration. Diagnosis is mainly dependent on imaging. Diffusion tensor tractography (DTT), being a non-invasive technique, shows better sensitivity when compared to the conventional T2WI sequence in the early detection of cervical spondylotic myelopathy (CSM). The objective was to determine the diagnostic accuracy of the apparent diffusion coefficient (ADC) in predicting high T2 signals in CSM.

Methods

A prospective observational study was done on 47 subjects aged between 25 and 70 years, referred to the department of radiology with clinical and imaging evidence of CSM in a tertiary care institute in Chennai. Nurick classification system was used to assess severity clinically. Diffusion-weighted imaging and DTT were done with 1.5 Tesla MRI. The primary outcome variable was a high T2 signal. Mean fractional anisotropy (FA) at the stenotic level and ADC value at a stenotic level were considered explanatory variables. The sensitivity, specificity, predictive values, and diagnostic accuracy of the screening test with the decided cut-off values along with their 95% CI were presented. P-value <0.05 was considered statistically significant. SPSS version 22 (IBM Inc., Armonk, New York) was used for statistical analysis.

Results

The mean age was 48.26 ± 10.28 years. The majority (72.34%) were males, the majority (42.55%) had a Nurick score of two, and 25.53% had a Nurick score of one. Twenty-six (55.32%) reported a high T2 signal, 36 (76.60%) had elevated ADC, and 11 (23.40 %) had no elevated ADC. There was a statistically significant difference in mean FA and ADC values across groups categorized as non-stenotic level and stenotic level (p-value <0.05). The ADC value had a moderately high sensitivity (76.92%) and low specificity (23.81%) in predicting high T2 signals with a diagnostic accuracy of 53.19%.

Conclusion

DTI parameters at stenotic level (ADC and FA values) in patients with cervical spondylosis help in the early detection of cervical cord compressive myelopathy prior to the appearance of T2 signal changes in conventional MRI, thereby improving clinical outcome and patient management.