Search

Background: Low-frequency rTMS can induce upregulation of excitability in the contralateral hemisphere by interhemispheric interaction. Objective: The aim of this study was to compare the effects of interhemispheric modulation on hemodynamic changes after applying low-frequency rTMS over the anatomical hand knob (HK) and the hand motor hotspot (hMHS) in the dominant motor cortex. Methods: Ten healthy right-handed participants without a history of neurological or psychiatric symptoms (five males; 29.8±2.8 years) participated in this single-blind, randomized, cross-over study. rTMS was applied under three conditions over the dominant (left) hemisphere for 20 minutes: 1) 1 Hz rTMS stimulation on the HK (HK-rTMS), 2) 1 Hz rTMS stimulation on the hMHS (hMHS-rTMS), and 3) sham stimulation (Sham-rTMS). For all participants, functional near-infrared spectroscopy (fNIRS) was applied for measurement of cerebral oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) concentration over the non-dominant (right) hemisphere during a serial reaction time task (SRTT) with the non-dominant (left) hand before and after each condition. Results: The average coordinates of the hMHS (x = – 39.60 mm, y = – 17.11 mm, z = 66.40 mm) were anterior and lateral to the HK (x = – 36.72 mm, y = – 28.87 mm, z = 56.41 mm). In fNIRS time-series analysis, the integral value of oxyHb was significantly increased over the motor cortical region of the non-dominant hemisphere after the hMHS-rTMS compared with Sham-rTMS. The HK-rTMS also showed slight increment of oxyHb concentration but without statistical significance. The SPM group analysis showed greater magnitude of the activity in hMHS-rTMS than that of HK-rTMS after stimulation (p

Background and purpose Various clinical and neuroimaging predictive factors have been identified for the recovery of upper extremity (UE) motor function after stroke. However, few studies have addressed factors related to the recovery of lower extremity (LE) motor function after stroke or performed direct comparisons of UE and LE motor recovery in the same set of patients. In this study, predictive factors for UE and LE motor recovery after stroke were investigated using clinical and neuroimaging characteristics. Methods Forty-two subacute ischaemic stroke patients underwent structural and functional magnetic resonance imaging data acquisition and cognitive/behavioral assessments using the Fugl-Meyer assessment, the National Institutes of Health Stroke Scale (NIHSS) and the Mini-Mental State Examination (MMSE) 2 weeks after stroke onset. Neuroimaging factors, including corticospinal tract (CST) fractional anisotropy, lesion volume, CST lesion load and interhemispheric homotopic functional connectivity, were extracted. The outcome of motor function was assessed by Fugl-Meyer assessment scores 3 months after onset. Results Early clinical and neuroimaging factors for predicting motor recovery were noticeably different for UE and LE. UE motor function recovery was related to age, NIHSS, MMSE, CST lesion load, lesion volume, ipsilesional CST integrity and interhemispheric homotopic functional connectivity. In contrast, LE motor recovery was related to ipsilesional and contralesional CST integrity and MMSE. Specifically, LE recovery showed a strong relationship to the preservation of cognitive function compared with motor impairment. Conclusions Our results indicate that different mechanisms underlie UE and LE motor recovery after stroke. LE motor recovery seems to be more intensively modulated by cognitive functions than UE.

Repetitive transcranial magnetic stimulation (rTMS) is used to modulate neuronal excitability of the human brain. Distant effects on contralateral corticomotor excitability can be exerted by interhemispheric modulation by low-frequency rTMS on ipsilateral hemisphere. To modulate corticospinal excitability, accurate determination of the stimulation site is important to maximize the effects of rTMS. In the present study, we investigated the difference in the distant effect of 1 Hz rTMS with respect to inducing functional improvement in the non-dominant hand by inhibiting the dominant hemisphere depending on cortical target areas. Ten healthy right-handed volunteers without any neurological disorders were enrolled. The anatomical hand knob (HK) identified from individual magnetic resonance imaging and the transcranial magnetic stimulation (TMS) induced hand motor hotspot (hMHS) by recording motor evoked potentials (MEPs) in the contralateral first dorsal interosseous muscle were determined. All participants underwent three conditions of 1 Hz rTMS on left hemisphere intervention; rTMS application over the HK, rTMS application over the hMHS, and sham-rTMS. Before and after each intervention, all participants undergone motor function assessments with their left hand. The cortical mapping showed that the hMHS was located anteriorly and laterally compared to the HK. Motor function tests showed the most significant improvements after the hMHS stimulation. When we compared the distant effects of target site on corticospinal excitability and motor behavior, delivering 1 Hz rTMS to the hMHS was more effective than delivering it to the HK for improving corticomotor excitability, motor skill, and dexterity. These results suggest that TMS-induced hMHS is an optimal target area to induce distant effect of low-frequency rTMS in motor function.

Noninvasive brain stimulation (NBS), such as repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS), has been used in stroke patients with motor impairment. NBS can help recovery from brain damage by modulating cortical excitability. However, the efficacy of NBS varies among individuals. To obtain insights of responsiveness to the efficacy of NBS, we investigated characteristic changes of the motor network in responders and nonresponders of NBS over the primary motor cortex (M1). A total of 21 patients with subacute stroke (13 males, mean age 59.6±11.5 years) received NBS in the same manner: 1 Hz rTMS on the contralesional M1 and anodal tDCS on the ipsilesional M1. Participants were classified into responders and nonresponders based on the functional improvement of the affected upper extremity after applying NBS. Twelve age-matched healthy controls (8 males, mean age 56.1±14.3 years) were also recruited. Motor networks were constructed using resting-state functional magnetic resonance imaging. M1 intrahemispheric connectivity, interhemispheric connectivity, and network efficiency were measured to investigate differences in network characteristics between groups. The motor network characteristics were found to differ between both groups. Specifically, M1 intrahemispheric connectivity in responders showed a noticeable imbalance between affected and unaffected hemispheres, which was markedly restored after NBS. The responders also showed greater interhemispheric connectivity and higher efficiency of the motor network than the nonresponders. These results may provide insight on patient-specific NBS treatment based on the brain network characteristics in neurorehabilitation of patients with stroke. This trial is registered with trial registration number NCT03390192.

The aim of this preliminary study was to investigate the potential of serum brain-derived neurotrophic factor (BDNF) as a biomarker in poststroke depressive mood in subacute stroke patients. Thirty-eight subacute stroke patients were recruited in this study. All participants underwent the standard rehabilitation program that included 2 h of physical therapy daily and 1 h of occupational therapy five days a week. The rehabilitation period lasted two weeks during the subacute stroke phase. We measured the serum BDNF, proBDNF, and matrix metalloproteinase-9 before and one and two weeks after the standard rehabilitation program. In addition, all participants were assessed using the Geriatric Depression Scale-Short Form (GDS-SF) for depressive mood at three time points. Pearson correlation analysis was performed to determine the relationship between serum BDNF levels and the GDS-SF. The GDS-SF showed significant improvement during the standard rehabilitation program period (p < 0.05). The GDS-SF was significantly correlated with serum BDNF levels at each time point (p < 0.05). These results suggest that serum BDNF may be used as a biomarker for depressive mood in subacute stroke patients. However, further studies with larger study populations are needed to clarify these results.

Most previous stroke studies have been performed in heterogeneous patient populations. Moreover, the brain network might demonstrate different recovery dynamics according to lesion location. In this study, we investigated variation in motor network alterations according to lesion location. Forty patients with subcortical ischemic stroke were enrolled. Patients were divided into two groups: 21 patients with supratentorial stroke (STS) and 19 patients with infratentorial stroke (ITS). All patients underwent resting-state functional magnetic resonance imaging and behavioral assessment at 2 weeks and 3 months poststroke. Twenty-four healthy subjects participated as a control group. To compare altered connectivity between groups, measures used in previous studies to evaluate interhemispheric balance and global network reorganization were investigated and the relationship between network measures and motor functions were examined. Cortico-cerebellar connectivity was also extracted to investigate its relationship with interhemispheric connectivity. In the STS group, measures related to interhemispheric balance were disrupted compared to the control group 2 weeks poststroke, while this was not found in the ITS group. During recovery, measures related to global network reorganization in the STS group and measures related to interhemispheric balance in the ITS group demonstrated significant changes, respectively. Moreover, motor functions were correlated with altered network measures in both groups. There was an interactive relationship between cortico-cerebellar and interhemispheric cortical connectivity only in the ITS group. Different changes in the motor network were observed depending on the location of stroke lesions. These results might originate from differences in the interactions between cortico-cerebellar and interhemispheric connectivity.