Potential impairment of spinal cord around the apical vertebral level in hyperkyphotic patients: findings from diffusion tensor imaging

Purpose To evaluate the neuronal metrics/microstructure of the spinal cord around apical region in patients with hyperkyphosis using diffusion tensor imaging (DTI). Methods Thirty-seven patients with hyperkyphosis aged 45.5 +/- 19.6 years old who underwent 3.0 T magnetic resonance imaging (MRI) examination with DTI sequence were prospectively enrolled from July 2022 to July 2023. Patients were divided into three groups according to spinal cord/ cerebrospinal fluid (CSF) architecture on sagittal-T2 MRI of the thoracic apex (the axial spinal cord classification): Group A-circular cord with visible CSF, Group B-circular cord without visible CSF at apical dorsal, and Group C-spinal cord deformed without intervening CSF. The fractional anisotropy (FA) values acquired from DTI were compared among different groups. Correlations between DTI parameters and global kyphosis (GK)/sagittal deformity angular ratio (sagittal DAR) were evaluated using Pearson correlation coefficients. Results In all patients, FA values were significantly lower at apical level as compared with those at one level above or below the apex (0.548 +/- 0.070 vs. 0.627 +/- 0.056 versus 0.624 +/- 0.039, P < 0.001). At the apical level, FA values were significantly lower in Group C than those in Group B (0.501 +/- 0.052 vs. 0.598 +/- 0.061, P < 0.001) and Group A (0.501 +/- 0.052 vs. 0.597 +/- 0.019, P < 0.001). Moreover, FA values were significantly lower in symptomatic group than those in non-symptomatic group (0.498 +/- 0.049 v. 0.578 +/- 0.065, P < 0.001). Pearson correlation analysis showed that GK (r(2) = 0.3945, P < 0.001) and sagittal DAR (r(2) = 0.3079, P < 0.001) were significantly correlation with FA values at apical level. Conclusion In patients with hyperkyphosis, the FA of spinal cord at apical level was associated with the neuronal metrics/microstructure of the spinal cord. Furthermore, the DTI parameter of FA at apical level was associated with GK and sagittal DAR.