BACKGROUND: Ischemic stroke is often followed by the abnormalities of neurons and corticospinal tract, which can lead to corresponding clinical symptoms and signs. Recently, with the continuous perfection of high-field MRI instrument, it becomes possible to assess and investigate the cortical function and structural reconstruction following stroke by using MRI and diffusion tensor imaging (DTI). OBJECTIVE: To observe the cortical motor function and changes of corticospinal tracts by using MRI and DTI in the patients with ischemic stroke at acute period, compare with the normal subjects, and assess the damage of corticospinal tract and muscle strength. DESIGN: A case-control observation. SETTING: Department of Medical Imaging, Fuzhou General Hospital of Nanjing Military Area Command of Chinese PLA. PARTICIPANTS: Nine inpatients (5 males and 4 females) with injury of motor function induced by acute ischemic stroke were selected from Fuzhou General Hospital of Nanjing Military Area Command of Chinese PLA between August and December in 2005, they aged 16-87 years with an average of 51 years old, and those with obvious conscious disturbances and severe cognitive disorders were excluded. At the same time, nine healthy right-handed physical examinees matched by age and gender with the patients were also selected, and they all had no nervous disease, epilepsy, mental diseases, cerebrovascular abnormalities and injury history, etc. All the subjects were informed with the detected items and agreed to participate in. METHODS: All the 9 patients with ischemic stroke at acute period and 9 healthy subjects were examined with MRI and DTI. ① A block-based design was used in the MRI, the passive finger-to-finger exercise was used as the stimulative task, and the static condition was taken as the baseline task. The GE 1.5T MRI system was used, all the data were processed after off-line, and analyzed with the SPM2 software, the association between the activated area and local anatomy of brain was observed. ② The DTI image was processed with the dTV.II.R1 software part of the anisotropic image and color anisotropic image were shown, and the three-dimensional white matter image of bilateral corticospinal tracts of the patients were reconstructed.③ The muscle strength of the affected hand of the stroke patients was judged with the Brunnstorm standard. MAIN OUTCOME MEASURES: The manifestations of MRI, DTI and corticospinal tracts of the 9 stroke patients were mainly observed. RESULTS: All the 9 stroke patients and 9 healthy subjects were involved in the analysis of results. ① Results of MRI examination: The handed exercise of the healthy subjects mainly activated contralateral sensorimotor cortex, posterior parietal cortex and bilateral supplementary motor areas. For the exercise of ipsilateral hand of 7 stroke patients, contralateral sensorimotor cortex was weakly activated, but ipsilateral posterial parietal cortex was obviously activated, and the activation of cerebrum was observed in 3 of them. For the other two patients, bilateral sensorimotor cortexes were activated during the exercise of ipsilateral hand, and the ipsilateral activated area was greater than the controlateral one. The exercise of contralateral hand activated contralateral sensorimotor cortex, posterior parietal cortex and contralateral supplementary motor area, and no obvious ipsilateral activated area was observed. ② Results of DTI examination: The anisotropic values of the infarcted area were obviously lower than those of the contralateral part (t=4.570, P < 0.01). the anisotropic value of the infarcted area were obviously was obviously correlated with bilateral muscle strength (t=0.888, P < 0.05). ③ Results of the examination for corticospinal tracts: The reconstruction of bilateral corticospinal tracts, contralateral anatomic form were generally identical with those of normal subjects, the consistency of each continuous form from anterior central gyrus downward to internal capsule to bridge of varolius and bulbus medullae. Because of the involvement of infarcted area to different extent, ipsilateral corticospinal tract was manifested by the interruption of succession and loss of consistency of anatomic structural form. The severity for the injury of corticospinal tract was markedly correlated with the muscle strength of the ipsilateral hand (r=0.888, P < 0.05). CONCLUSION: ① The MRI manifestations of stroke patients during the exercise of affected hand are different from those of normal subjects, suggesting that there is compensation and reconstruction of brain function. ② DTI examination is good for the judgement of the correlation between the damaged severity of infarction and muscle strength. ③ The damaged severity of corticospinal tracts is correlated with muscle strength, and it can be used to judge the prognosis of rehabilitative treatment.
