Rationale and Objectives
Cervical disc degeneration can result in nerve root compression and severe symptoms that significantly impair the patient’s quality of life. The purpose of this study is to investigate multiple diffusion metrics changes in the diffusion tensor imaging (DTI) of cervical nerve roots and their relationship with the clinical severity of patients with cervical disc herniation.
Materials and Methods
High directional DTI of the cervical nerve roots was performed in 18 symptomatic patients and 10 healthy volunteers with a 3.0-T magnetic resonance system after a routine cervical disc scanning. The fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated from the DTI data and compared between the affected and unaffected sides in the same patient and between healthy volunteers and symptomatic patients. The correlation between the side-to-side diffusion metric differences and the clinical International Standards for Neurological Classification of Spinal Cord Injury scores was analyzed.
Results
C5–C8 nerve roots were clearly delineated with DTI. The FA, MD, AD, and RD of compressed nerve roots were 0.31 ± 0.091, 2.06 ± 0.536, 2.69 ± 0.657, and 1.75 ± 0.510 mm 2 /s, respectively. Compared to the unaffected side or healthy volunteers, the nerve roots of the affected side showed decreased FA ( P < .022) and increased MD ( P < .035), AD ( P < .047), and RD ( P < .012). The clinical International Standards for Neurological Classification of Spinal Cord Injury scores of the patients were negatively correlated with MD ( r = −0.57, P = .002), AD ( r = −0.451, P = .021), and RD ( r = −0.564, P = .003) but not with FA ( r = 0.004, P = .984).
Conclusions
DTI can potentially be used to assess microstructural abnormalities in the cervical nerve roots in patients with disc herniation.
Diffusion tensor imaging (DTI) based on magnetic resonance (MR) imaging (MRI) can provide valuable information about tissue microstructure changes by applying a motion probing gradient in some directions for the in vivo monitoring of the potentially restricted, random microscopic motion of water molecules in tissues . The amount of nonrandom water diffusion that results from microstructural damage within diseased tissues can be quantified using DTI data . Diffusion tensor tractography (DTT), which is generated from the reconstruction and analysis of the data obtained by DTI, can be used to follow the orientation of nerve fibers and thereby trace specific neural pathways .
Previously, DTT has been widely applied in the central nerve system (i.e., brain and spinal cord) and less commonly in peripheral nerves such as the sciatic, median, radial, and ulnar nerves . The results of previous studies showed that DTI with fiber tracking might provide information and depict abnormalities beyond the resolution of conventional anatomic MR techniques. Quantitative DTI indices, such as the fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values, have been reported to be abnormal in areas that may appear normal in structural MR images . Recently, DTT examination of the lumbar nerves or sacral plexus was successfully achieved in healthy volunteers (HVs) and patients with disc herniation . The results indicated that the compressed nerve roots have a decreased FA value and increased diffusivities, which may reflect microstructural changes of the compressed nerves in patients with disc herniation before conventional MRI. Comparatively, cervical disc degeneration can result in cervical nerve root compression early and can easily induce severe symptoms that significantly impair the quality of life of patients. However, as far as we know, the usefulness of DTI in evaluation of the compressed cervical nerve roots has not been investigated previously.
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Materials and methods
Subjects
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MR Acquisition
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Data Processing and Analysis
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Statistical Analysis
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Ethical Aspects
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Results
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Table 1
Fractional Anisotropy (FA), Mean Diffusivity (MD), Axial Diffusivity (AD), and Radial Diffusivity (RD) Measured in Healthy volunteers and Symptomatic Patients
Healthy Volunteers Patients Left Root Right Root Difference ∗ Compressed Root Contralateral Root Difference † FA 0.367 ± 0.083 0.356 ± 0.075 0.011 ± 0.058 0.292 ± 0.110 0.343 ± 0.100 −0.051 ± 0.160 ‡ MD ( × 10 3 mm 2 /sec) 1.916 ± 0.611 1.944 ± 0.544 0.028 ± 0.471 2.070 ± 0.655 1.813 ± 0.520 0.257 ± 0.340 ‡ AD ( × 10 3 mm 2 /sec) 2.620 ± 0.698 2.623 ± 0.673 0.003 ± 0.590 2.666 ± 0.800 2.470 ± 0.730 0.195 ± 0.478 ‡ RD ( × 10 3 mm 2 /sec) 1.543 ± 0.518 1.623 ± 0.565 0.080 ± 0.430 1.767 ± 0.628 1.484 ± 0.456 0.282 ± 0.339 ‡
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Discussion
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