Changes of the corticospinal tract in the unaffected hemisphere in stroke patients: A diffusion tensor imaging study

Comparative study of vestibular projection pathway connectivity in cerebellar injury patients and healthy adults

Objective

Cerebellar injury can not only cause gait and postural instability, nystagmus, and vertigo but also affect the vestibular system. However, changes in connectivity regarding the vestibular projection pathway after cerebellar injury have not yet been reported. Therefore, in the current study, we investigated differences in the connectivity of the vestibular projection pathway after cerebellar injury using diffusion tensor imaging (DTI) tractography.

Methods

We recruited four stroke patients with cerebellar injury. Neural connectivity in the vestibular nucleus (VN) of the pons and medulla oblongata in patients with cerebellar injury was measured using DTI. Connectivity was defined as the incidence of connection between the VN on the pons and medulla oblongata and target brain regions such as the cerebellum, thalamus, parieto-insular vestibular cortex (PIVC), and parietal lobe.

Results

At thresholds of 10 and 30, there was lower connectivity in the ipsilateral hemisphere between the VN at the medullar level and thalamus in the patients than in healthy adults. At a threshold of 1 and 10, the patient group showed lower VN connectivity with the PIVC than healthy adults. At a threshold of 1, VN connectivity with the parietal lobe in the contralateral hemisphere was lower in the patients than in healthy adults. Additionally, at a threshold of 30, VN connectivity at the pons level with the cerebellum was lower in healthy adults than in the patients.

Conclusion

Cerebellar injury seems to be associated with decreased vestibular projection pathway connectivity, especially in the ipsilateral thalamus, PIVC, and contralateral parietal lobe.

The effect of walnut rolling training on hand function and corticospinal tract

Background

We investigated the effect of the walnut rolling training for two weeks on the hand function and corticospinal tract (CST) in normal subjects.

Methods

Seventeen right-handed normal subjects performed walnut rolling training with their non-dominant (left) hand, with the right hand defined as the control side. The walnut rolling training was performed three times daily, for 30 minutes at a time, over two weeks. The Purdue Pegboard Test (PPT), tip pinch and grip strength (GS) were used evaluate the change of hand function, and diffusion tensor tractography (DTT) evaluated change of the CST and transcallosal fibers for the hand motor somatotopy.

Results

All of the clinical scores in terms of PPT, tip pinch and GS increased significantly in the post-training (PPT: 16.59±1.09, tip pinch: 5.03±2.18, GS: 40.61±10.99) in the left hand compared with pre-training (PPT: 14.94±1.36, tip pinch: 3.66±1.44, GS: 33.58±11.08) (P<0.05). By contrast, the clinical scores for the right hand did not differ significantly between pre- (PPT: 16.25±1.98, tip pinch: 5.75±2.26, GS: 37.58±14.61) and post-training (PPT: 16.97±1.67, tip pinch: 5.66±2.31, GS: 37.82±14.25). The fiber numbers (FN) of the right CST increased significantly in post-training DTT (2,123.05±529.07) compared with pre-training DTT (1,734.73±581.84) (P<0.05), whereas fractional anisotropy (FA) (pre-training: 0.50±0.02, post-training: 0.51±0.01) did not change significantly. Neither FA nor FN of the left CST and transcallosal fibers changed significantly from pre- (FA: 0.44±0.02, FN: 1,871.15±636.36) to post-training DTTs (FA: 0.45±0.03, FN: 1,823.84±701.14).

Conclusions

We demonstrated improvement of hand function and facilitation of the contralateral CST by walnut rolling training in normal subjects. Our results suggest that walnut rolling training can be used for improvement of hand function and facilitation of the contralateral CST.

Evaluation of Diffusional Kurtosis Imaging in Sub-acute Ischemic Stroke: Comparison with Rehabilitation Treatment Effect

Stroke is a serious worldwide medical condition that causes neurological function disability. Diffusional kurtosis imaging, which measures the non-Gaussianity of water diffusion, has been demonstrated to be a sensitive biomarker in many neuro-pathologies. This study explores the relationship between neural function recovery and transformation of the ischemic lesion and/or corticospinal tract during the sub-acute phase after stroke by using diffusional kurtosis imaging. We performed a prospective study of function recovery and K metrics of 43 patients with sub-acute ischemic stroke in the middle cerebral artery territory. The effect of rehabilitation treatment was evaluated using both the Fugl-Meyer motor function score and modified Barthel index score at post-treatment compared with admission, and patients were allocated to two groups: good and poor rehabilitation effect (GRE and PRE). Metrics of diffusional kurtosis imaging within ischemic lesion and along the corticospinal tract were acquired, respectively. All three relative axial diffusional kurtoses (rKas) along the corticospinal tract in the GRE group ( n = 21) were significantly larger than those of the PRE group ( n = 22), including rKa in the posterior limb of internal capsule, rKa in the cerebral peduncle, and rKa in the basal part of the pons ( p = 0.014, 0.005, and 0.021, respectively). This multi-parametric magnetic resonance imaging study showed that diffusional kurtosis imaging has the potential to complement existing stroke imaging techniques and revealed its own advantages in elucidating the possible biophysical mechanism of functional restoration underlying ischemic stroke.

Proliferation of Bilateral Nerve Fibers Following Thalamic Infarction Contributes to Neurological Function Recovery: A Diffusion Tensor Imaging (DTI) Study

BACKGROUND The aim of this study was to investigate the reorganization in ipsilesional and contralesional thalamic radiation fibers after unilateral focal thalamic stroke in sensory disturbance patients. MATERIAL AND METHODS We recruited 12 patients with acute unilateral thalamic infarction and sensory disturbance and 12 healthy age- and sex-matched controls. All patients underwent diffusion tensor imaging (DTI) and were assessed with National Institutes of Health stroke scale (NIHSS), Barthel index (BI), and paragraph 8 of NIHSS (NIHSS8) at 1 week (W1), 4 weeks (W4), 3 months (M3), and 6 months (M6) after thalamic infraction. The relationship between FA changes and the clinical scores changes were then examined. RESULTS NIHSS and NIHSS8 scores decreased while BI scores increased gradually from W1 to M6 in patients, but not in controls. FA values of the patients gradually increased in ipsilesional and contralesional thalamic radiation fibers from W1 to M6. In addition, the FA values in patients were significantly higher at M3 and M6 compared to W1. No significant changes were observed in the controls. Regarding the relationship between FA changes and the clinical scores changes, the FA increases were negatively correlated with NIHSS and NIHSS8 decrease while FA increases were positively correlated with BI increases. CONCLUSIONS Our results indicate that reorganization occurred after unilateral focal thalamic infarct not only in ipsilesional, but also in contralesional thalamic radiation fibers in patients with sensory disturbance. In addition, the results suggested that the reorganization can support and promote stroke restoration.

Corticospinal tract diffusion properties and robotic visually guided reaching in children with hemiparetic cerebral palsy

Perinatal stroke is the leading cause of hemiparetic cerebral palsy (CP), resulting in life-long disability. In this study, we examined the relationship between robotic upper extremity motor impairment and corticospinal tract (CST) diffusion properties. Thirty-three children with unilateral perinatal ischemic stroke (17 arterial, 16 venous) and hemiparesis were recruited from a population-based research cohort. Bilateral CSTs were defined using diffusion tensor imaging (DTI) and four diffusion metrics were quantified: fractional anisotropy (FA), mean (MD), radial (RD), and axial (AD) diffusivities. Participants completed a visually guided reaching task using the KINARM robot to define 10 movement parameters including movement time and maximum speed. Twenty-six typically developing children underwent the same evaluations. Partial correlations assessed the relationship between robotic reaching and CST diffusion parameters. All diffusion properties of the lesioned CST differed from controls in the arterial group, whereas only FA was reduced in the venous group. Non-lesioned CST diffusion measures were similar between stroke groups and controls. Both stroke groups demonstrated impaired reaching performance. Multiple reaching parameters of the affected limb correlated with lesioned CST diffusion properties. Lower FA and higher MD were associated with greater movement time. Few correlations were observed between non-lesioned CST diffusion and unaffected limb function though FA was associated with reaction time (R = -0.39, p < .01). Diffusion properties of the lesioned CST are altered after perinatal stroke, the degree of which correlates with specific elements of visually guided reaching performance, suggesting specific relevance of CST structural connectivity to clinical motor function in hemiparetic children.

Dominance of the Unaffected Hemisphere Motor Network and Its Role in the Behavior of Chronic Stroke Survivors

Balance of motor network activity between the two brain hemispheres after stroke is crucial for functional recovery. Several studies have extensively studied the role of the affected brain hemisphere to better understand changes in motor network activity following stroke. Very few studies have examined the role of the unaffected brain hemisphere and confirmed the test-retest reliability of connectivity measures on unaffected hemisphere. We recorded blood oxygenation level dependent functional magnetic resonance imaging (fMRI) signals from nine stroke survivors with hemiparesis of the left or right hand. Participants performed a motor execution task with affected hand, unaffected hand, and both hands simultaneously. Participants returned for a repeat fMRI scan 1 week later. Using dynamic causal modeling (DCM), we evaluated effective connectivity among three motor areas: the primary motor area (M1), the premotor cortex (PMC) and the supplementary motor area for the affected and unaffected hemispheres separately. Five participants' manual motor ability was assessed by Fugl-Meyer Motor Assessment scores and root-mean square error of participants' tracking ability during a robot-assisted game. We found (i) that the task performance with the affected hand resulted in strengthening of the connectivity pattern for unaffected hemisphere, (ii) an identical network of the unaffected hemisphere when participants performed the task with their unaffected hand, and (iii) the pattern of directional connectivity observed in the affected hemisphere was identical for tasks using the affected hand only or both hands. Furthermore, paired t-test comparison found no significant differences in connectivity strength for any path when compared with one-week follow-up. Brain-behavior linear correlation analysis showed that the connectivity patterns in the unaffected hemisphere more accurately reflected the behavioral conditions than the connectivity patterns in the affected hemisphere. Above findings enrich our knowledge of unaffected brain hemisphere following stroke, which further strengthens our neurobiological understanding of stroke-affected brain and can help to effectively identify and apply stroke-treatments.

Microstructural changes of the whole brain in patients with comitant strabismus: evidence from a diffusion tensor imaging study

OBJECTIVE

The aim of this study was to investigate the fractional anisotropy (FA) and mean diffusivity (MD) using a diffusion tensor imaging technique and whole-brain voxel-based analysis in patients with comitant strabismus.

PATIENTS AND METHODS

A total of 19 (nine males and ten females) patients with comitant strabismus and 19 age-, sex-, and education-matched healthy controls (HCs) underwent magnetic resonance imaging examination. Imaging data were analyzed using two-sample t-tests to identify group differences in FA and MD values. Patients with comitant strabismus were distinguishable from HCs by receiver operating characteristic curves.

RESULTS

Compared with HCs, patients with comitant strabismus exhibited significantly decreased FA values in the brain regions of the left superior temporal gyrus and increased values in the bilateral medial frontal gyrus, right globus pallidus/brainstem, and bilateral precuneus. Meanwhile, MD value was significantly reduced in the brain regions of the bilateral cerebellum posterior lobe and left middle frontal gyrus but increased in the brain regions of the right middle frontal gyrus and left anterior cingulate.

CONCLUSION

These results suggest significant brain abnormalities in comitant strabismus, which may underlie the pathologic mechanisms of fusion defects and ocular motility disorders in patients with comitant strabismus.