Dynamic Structural and Functional Reorganizations Following Motor Stroke

Abstract

Background The combined effects of bilateral corticospinal tract (CST) reorganization and interhemispheric functional connectivity (FC) reorganization on motor recovery of upper and lower limbs after stroke remain unknown. Material/Methods A total of 34 patients underwent magnetic resonance imaging (MRI) examination at weeks 1, 4, and 12 after stroke, with a control group of 34 healthy subjects receiving 1 MRI examination. Interhemispheric FC in the somatomotor network (SMN) was calculated using the resting-state functional MRI (rs-fMRI). Fractional anisotropy (FA) of bilateral CST was recorded as a measure of reorganization obtained from diffusion tensor imaging (DTI). After intergroup comparisons, multiple linear regression analysis was used to explore the effects of altered FA and interhemispheric FC on motor recovery. Results Interhemispheric FC restoration mostly occurred within 4 weeks after stroke, and FA in ipsilesional remained CST consistently elevated within 12 weeks. Multivariate linear regression analysis showed that the increase in both interhemispheric FC and ipsilesional CST-FA were significantly correlated with greater motor recovery from week 1 to week 4 following stroke. Moreover, only increased FA of ipsilesional CST was significantly correlated with greater motor recovery during weeks 4 to 12 after stroke compared to interhemispheric FC. Conclusions Our results show dynamic structural and functional reorganizations following motor stroke, and structure reorganization may be more related to motor recovery at the late subacute phase. These results may play a role in guiding neurological rehabilitation.

Diffusion Tensor Imaging as a Prognostic Tool for Recovery in Acute and Hyperacute Stroke

“…Furthermore, FA within PLIC in the acute phase was significantly correlated with clinical outcome at 90 days in peripheral infarcts, whereas no significant association was found for basal ganglia infarcts. Similarly, Xia and colleagues [ 33 ] reported a decline in FA values in the ipsilesional CST during the first week poststroke and then longitudinal increase over the next 12 weeks. Again, significant associations with clinical outcome were found after the acute phase.…”

“…Three studies included additional imaging modalities, i.e., resting-state functional MRI (rs-fMRI) [ 26 , 32 , 33 ]. With regards to additional neurophysiological measures, only one study examined the functional integrity of the pyramidal tract using transcranial magnetic stimulation (TMS) [ 34 ].…”

“…One study does did provide information regarding field strength [ 30 ]. With regards to the number of directions, three studies used 6 directions (two in 1.5 T [ 34 , 35 ] and one in 3.0 T [ 36 ]), eight studies used 12 directions (four in 1.5 T [ 37 , 38 , 39 ] and four in 3.0 T [ 40 , 41 , 42 , 43 ]), three studies used 15 directions (two in 1.5 T [ 44 , 45 ] and one in 3.0 T [ 23 ]), three studies used 16 directions (one in 1.5 T [ 46 ] and two in 3.0 T [ 24 , 47 ]), one study in 1.5 T used 20 directions [ 31 ], one study in 3.0 T used 25 directions [ 48 ], eight studies used 30 directions (two in 1.5 T [ 49 , 50 ] and six in 3.0 T [ 18 , 29 , 33 , 51 , 52 , 53 ]), three studies in 1.5 T used 32 directions [ 54 , 55 , 56 ], one study in 3.0 T used 55 directions [ 57 ], and seven studies in 3.0 T used 64 directions [ 25 , 26 , 27 , 32 , 58 , 59 , 60 ]). Six studies did not provide information regarding diffusion directions.…”

Efficacy and Safety of Vagus Nerve Stimulation on Upper Limb Motor Recovery After Stroke. A Systematic Review and Meta-Analysis

“…This study found an average increase of 6.9 points in the Fugl-Meyer scale after 15 days of therapy, which increased to 7.7 points 4 weeks after therapy and was significantly greater than the change observed in the sham group. Given that most of the cortical reorganization processes are expected to occur during the sub-acute phase post stroke (56), this may be the optimal window of recovery to be modulated by the implementation of VNS in combination with physical therapy, however, future clinical studies with larger sample sizes will be necessary to confirm whether earlier administration of this intervention is associated with greater improvement in motor function.…”

Resting-state functional connectivity for determining outcomes in upper extremity function after stroke: A functional near-infrared spectroscopy study

“…Resting-state brain networks during stroke recovery were initially assessed using functional magnetic resonance imaging (fMRI). According to studies on resting-state fMRI, stroke patients have different modes of functional connectivity compared with healthy people, and abnormal dynamic functional connectivity is associated with post-stroke motor recovery (4,(9)(10)(11). Although fMRI is the gold standard for measuring cortical activity, it has some drawbacks, such as restricted monitoring environments, acoustic scanner noises, subject head immobilization, and high cost (12).…”