Role of MRI Diffusion Tensor Imaging in Early Diagnosis of Cervical Spondylotic Myelopathy (CSM)

Background and Purpose

Cervical spondylotic myelopathy (CSM) is a common degenerative disorder of the cervical spine and is considered as the most common cause of spinal cord dysfunction in older individuals worldwide. Assessing the severity of the disease objectively remains a challenge and there is still remaining controversy in terms of the optimal timing and indications for surgical intervention. The conventional MRI is the gold standard for radiographic evaluation of the spinal cord; however, it cannot assess the underlying microstructural deficits of the spinal cord and it has a limited application in determining prognosis and recovery of the disease [1]. We sought to assess the utility of MR diffusion tensor imaging as an imaging technique in clinically suggested CSM patients by obtaining the microstructural parameters (Fractional anisotropy; FA and apparent diffusion coefficient; ADC) in the cervical spinal cord segments.

Patient & methods

our study was a prospective cross-sectional study including 40 patients with clinical manifestations of cervical spondylotic myelopathy. The patients were sorted according to the European myelopathy score into three categories as follows: grade 1 (with mild symptoms), grade 2 (with moderate symptoms) and grade 3 (with severe symptoms). All the patients were investigated with a 1.5 T MRI unit acquiring conventional MRI and DTI sequences. FA and ADC values at each spinal segment from C2/C3 to C6/C7 were generated and measured using manual drawing of multiple ROIs within the cervical cord in the sagittal and axial combined anatomical and color-coded images. For each of these cases, the patient’s age, gender, DTI parameters at each spinal segment level, maximum compression level, conventional T2WI characteristics and EMS score were recorded, analyzed and compared.

Results

The study included 23 females (57.5%) and 17 males (42.5%). Their age ranged from 30 to 72 years with a mean age of 47.3 ± 9.79 years.

The study revealed a significant difference in the mean FA and ADC values between stenotic and non-stenotic segments of the cervical spinal cord. There was a significant correlation between the European myelopathy score and DTI parameters (FA and ADC). FA and ADC values performed better in recognizing myelopathic changes in patients who were classified as grade 1 according to EMS compared to conventional MRI T2WI which performed very poorly in recognizing myelopathy changes in the same patients, therefore DTI indices were more sensitive in the detection of CSM patients compared to conventional MRI especially in early myelopathic stages. T2 weighted images were highly significant in recognizing myelopathy changes in patients who were classified as grade 3 according to EMS. The CSM patients had significant FA decrease and ADC increase at the most compressed part of the cervical spinal cord and there was a significant correlation between the number of patients who had myelopathic changes by DTI parameters and the severity of disease. The FA sensitivity and specificity in recognition of myelopathic changes were 73.5% and 83.3% respectively and the ADC sensitivity and specificity were 100% and 70.6% respectively.

Conclusion

In conclusion, diffusion tensor imaging enhances the efficacy and accuracy of MRI in the diagnosis of cervical spondylotic myelopathy. Therefore, it can be used as a non-invasive modality for detection of the spondylotic myelopathy changes in the early stages helping to decide the appropriate timing of decompression surgery before attaining the irreversible chronic changes.

Abbreviations

ADC: Apparent diffusion coefficient; CSM: Cervical spondylotic myelopathy; DTI: Diffusion tensor imaging; FA: Fractional Anisotropy; EMS: European myelopathy score