Investigations on the correlation of corticospinal tract with muscular strength using diffusion tensor imaging and functional MR imaging technique

Objective To investigate the effects of corticospinal tract (CST) injury on muscular strength of the extremities in patients with cerebral infarction and tumor. Methods Using diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) techniques in addition combinning DTI with functional MR imaging (fMRI), the localization diagnosis of CST injury induced by cerebral infarction and tumor was made meanwhile the effect of CST injury on muscular strength was observed. 40 cases with acute cerebral infarction (ACI) (onset time 72 h) and 113 cases with cerebral tumor received MRI and diffusion weighted imaging (DWI) examinations. A part of them received enhanced MRI and fMRI examinations. All the data of DTI were collected then DTT was performed and bilateral CST were reconstructed meanwhile the correlative analysis between pathological chang in ill side of CST and its effect on muscular strength of the extremities was done. Results (1) The fractional anisotropy value (FA value) of the infarction area was (0.336±0.065), but the FA value of bilaterally normal white matter in the contralateral hemisphere was (0.705±0.069). The FA value in infarct area of white matter was significant lower than that in normal hemisphere (paired test, t = 15.823, P 0.001). (2) DTT showed that the CST of patients with acute cerebral infarctionand tumor were compression, displacement, translocation, and partial break. (3) The diminution rate of muscular strength in patients with cerebral infarction (infarction group) was 67.50% (27/40) but in patients with cerebral tumor (tumor group) was 16.81% (19/113), all of whom in both groups had injury of CST and the difference between two groups was significant (χ2 = 36.096, P 0.001). (4) The diminution rate of muscular strength in patients with infarction or tumor who had CST injury of posterior crus internal capsule was 72.72% (16/22) in infarction group and 25.93% (7/27) in tumor group, respectively. Otherwise, it was 78.57% (11/14) and 4.35% (1/23) if the CST injury imvolved brain stem (including pons and medulla), respectively. The difference between two groups was significant (χ2 = 10.661, χ2 = 21.879; P 0.05 or P 0.01). (5) fMRI showed that among 15 patients 4 cases had translocation, 3 cases had morphologic change, 2 cases had reduction in motor-activated area of ill hemisphere, and other cases were normal. Conclusion The injuries of CST in patients with cerebral infarction are much more serious than those in cerebral tumor so that the effects on movement and muscular strength of the extremities are more evident. Based on the combination of DTI with fMRI the origin, run, and function of white matter tract are able to observe. This technique might provide useful information for the doctor to carry out purposive treatments which can improve the ability of self-recovery of the neurofiber tracts after injure caused by ischemia lesion. It has a specified value for us to perform the research on the functional evaluation of regenerative neurofibers.