Specific microstructural changes of the cervical spinal cord in syringomyelia estimated by diffusion tensor imaging

Abstract

The microstructure of the spinal cord in syringomyelia has not been well studied. The aim of this study was to evaluate the microstructure of the cervical cord in patients with syringomyelia using diffusion tensor imaging (DTI) and to investigate the association between DTI parameters and the size of the syrinx cavity. Thirty patients with syringomyelia and 11 age-matched controls were included in this study. DTI and T1/T2-weighted MRI were used to estimate spinal microstructure. The patients were divided into a clinical symptom group (group A) and a non-clinical symptom group (group B) according to ASIA assessments. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values (mm²/s) were measured and compared between patients and controls. Correlation between FA/ADC and the size of the syrinx cavity was examined with a bivariate analysis. FA values were lower (P < 0.000) and ADC values were higher (P < 0.000) compared to the controls at the level of all syrinxes examined in patients with syringomyelia; both FA values and ADC values reached normal values either above or below the syrinx levels (all P > 0.05). FA values and ADC values at all cervical levels were not significantly different either in controls or outside of the syrinx (all P > 0.05). FA values of group A was significantly lower than those of group B (P < 0.000). There was a negative association between FA values and the size of syrinx cavity, and a positive association between ADC values and the size of syrinx cavity (FA: P < 0.05, ADC: P < 0.05). The microstructure of the cervical spinal cord is different across all patients with syringomyelia. DTI is a promising tool for estimating quantitative pathological characteristics that are not visible with general MRI.

Figure 1

(A) MRI image at sagittal plane on T2W, (B) the ratio as index of syrinx dimension which was calculated by maximal syrinx diameter (S)/spinal cord diameter (C) at the same location on T2W axial. (C) Location map and measurement of DTI parameters on sagittal plane. (D–F) Measurement of DTI parameters on transverse plane.

Figure 2

(a–c) FA values (mean ± SEM) at all cervical levels in controls, outside the area of the visible syrinx and the area of the visible syrinx, respectively.

Figure 3

(a–c) ADC values (mm²/s: mean ± SEM) at all cervical levels in controls, outside the area of the visible syrinx and the area of the visible syrinx, respectively.

Figure 4

The association between size of syrinx cavity and FA values at C5 (a) and C6 (b) was negative. However, about ADC values (mm²/s) the association was positive (c,d).

Figure 5

The differences of DTI parameters among patients with clinical symptom, patients without clinical symptom and normal controls. (a) The difference of FA values (mean + SD), (b) the difference of ADC values (mean + SD).