Value of diffusion tensor imaging and tractography in unilateral lumbar disc prolapse

Abstract

Abstract Background Conventional MR imaging is not enough for evaluation of symptomatic foraminal stenosis, because there is high incidence of false-positive results in asymptomatic elderly patients. Conventional MR cannot quantitatively assess the severity of the nerve lesion. DTI is a non-invasive way to effectively trace the nerve fiber bundle and quantitatively evaluate the nerve injury. DTI with fiber tracking may describe abnormalities beyond the resolution of conventional MR techniques. The aim of this work was to compare between the mean values of diffusion parameters such as fractional anisotropy and apparent diffusion coefficient of the compressed lumbar spinal nerve roots and of the contralateral normal nerve roots. Correlate these parameters with the severity of neurological symptoms. This is a prospective study that was conducted on 50 patients with symptomatic unilateral posterolateral lumbar disc prolapse at a university hospital. They were investigated with diffusion tensor imaging with tractography on a 1.5-T MR. The changes in the mean fractional anisotropy and apparent diffusion coefficient values of the compressed nerves and the relationship between these changes and the severity of the neurological side effects using Japanese Orthopedic Association score and visual analogue scale were investigated. Results The mean fractional anisotropy values were significantly lower (p ≤ 0.001), and mean apparent diffusion coefficient values were significantly higher (p ≤ 0.001) in compressed nerves than in contralateral intact nerves. There were strong correlations between the DTI parameters and the severity of the neurological symptoms as assessed using the Japanese Orthopedic Association score and the visual analogue scale. Conclusion In patients with lumbar disc prolapse, radicular diffusion parameters are affected in the compressed roots in comparison to the healthy roots and this affection is correlated with the degree of prolapse and with the severity of neurological symptoms. DTI with fiber tracking provide clinically relevant information and describe abnormalities beyond the resolution of conventional MR techniques.

Keywords

• Lumbar disc prolapse
• Diffusion tensor imaging
• Fiber tractography
• Fractional anisotropy (FA)
• Apparent diffusion coefficient (ADC)
• The Japanese Orthopedic Association (JOA) score