Despite the methodologic differences, several common features can be identified based on the reviewed studies. Clinical improvements occurred even late after injury, after subjects were deemed to have reached a recovery plateau. This clinical improvement was accompanied by cortical reorganization that depended on the type of intervention as well as other factors. This review also suggests direction for future research studies.

C erebral autoregulation (CA) is essential to maintain a constant cerebral blood flow (CBF) in the context of changes in cerebral perfusion pressure.1 Assessment of CA reflects cerebrovascular function and has been used widely in hypertension studies and other clinical settings. 2,3 Quantitative assessment of CA is challenged by the methods used for CBF measurement. Modern imaging modalities such as single-photon emission computed tomography, positron emission tomography, perfusion computed tomography, and MRI are difficult to be applied for CBF measurement in clinical studies of CA because of the cumbersome experimental conditions, the limitations of using radioactive isotopes (single-photon emission computed tomography and positron emission tomography), or other imaging contrast agents (computed tomography and MRI) for repeated measurements. 4 Recently, transcranial Doppler (TCD) has been used to assess CA because of its bedside availability, noninvasiveness, and high temporal resolution in measuring changes in cerebral blood flow velocity (CBFV) in the basal cerebral arteries. 5 However, because the diameter of the insonated vessels cannot be measured directly using TCD, the validity of using this technique to assess CA is based on a fundamental assumption that changes in CBFV represent changes in volumetric CBF, that is, by assuming that the diameter of basal cerebral arteries does not change significantly in the face of changes in blood pressure. 5 For its importance, this assumption has been evaluated repeatedly by using a variety of imaging modalities to measure CBF and to compare with TCD measurement of CBFV during changes in arterial pressure. 6,7 However, the findings so far are inconsistent. [8][9][10] One of the major limitations of these studies is that CBF and CBFV often were not measured simultaneously or were measured with different temporal and spatial resolutions, thus making it difficult or even impossible for direct comparisons between CBF and CBFV Abstract-The validity of using transcranial Doppler measurement of cerebral blood flow velocity (CBFV) to assess cerebral autoregulation (CA) still is a concern. This study measured CBFV in the middle cerebral artery using transcranial Doppler and volumetric cerebral blood flow (CBF) in the internal carotid artery (ICA) using color-coded duplex ultrasonography to assess CA during steady-state changes in mean arterial pressure (MAP 7 However, this study was conducted only in 7 patients with cerebrovascular diseases under surgical conditions, and these observations need to be confirmed.Color-coded duplex ultrasonography (CDUS) is a noninvasively bedside available technology that has been used to measure volumetric CBF in the ICA.12,13 Similar to TCD, CDUS also has high temporal resolution.14 In addition, changes in CBF in the ICA most likely reflect those in the MCA and anterior cerebral artery, which are the major branches of ICA.In this study, we simultaneously measured changes in CBFV in the MCA and ICA and CBF in the ICA to assess CA during stepw...

Objective To extend the applicability of the Wolf Motor Function test (WMFT) to describe the residual functional abilities of moderate-to-severely affected stroke patients. The WMFT is a motor function test for mild to moderate upper extremity weakness in stroke patients, but it has not been routinely used for evaluation of more severe hemiparetic stroke patients due to its numerical characteristics. Design Data was collected as part of two double-blind sham controlled randomized interventional studies, the Transcranial Direct Current Stimulation (tDCS) in Chronic Stroke Recovery and tDCS Enhanced Stroke Recovery and Cortical Reorganization. Stroke patients were evaluated with the upper-extremity Fugl-Meyer (UFM) and the WMFT in the same setting prior to treatment. Setting University inpatient rehabilitation and outpatient clinic. Participants 32 stroke patients with moderate-to-severe hemiparesis enrolled in the tDCS in Chronic Stroke Recovery and tDCS Enhanced Stroke Recovery and Cortical Reorganization studies. Intervention Not applicable. Main Outcome Measures WMFT scores were calculated using 1) median performance times, 2) new calculation using the mean rate of performance. We compared the distribution of values from the two methods and examined the WMFT-UFM correlation for the traditional and the new calculation. Results WMFT rate values were more evenly distributed across their range than median WMFT time scores. The association between the WMFT rate and UFM was as good as the association between the median WMFT time scores and UFM (Spearman rs 0.84 vs −0.79). Conclusions The new WMFT mean rate of performance is valid and a more sensitive measure in describing the functional activities of the moderate to severely affected upper extremity of stroke subjects and avoids the pitfalls of the median WMFT time calculations.

Abstract. Transcranial direct current stimulation (tDCS) of the human sensorimotor cortex during physical rehabilitation induces plasticity in the injured brain that improves motor performance. Bi-hemispheric tDCS is a noninvasive technique that modulates cortical activation by delivering weak current through a pair of anodal-cathodal (excitation-suppression) electrodes, placed on the scalp and centered over the primary motor cortex of each hemisphere. To quantify tDCS-induced plasticity during motor performance, sensorimotor cortical activity was mapped during an event-related, wrist flexion task by functional near-infrared spectroscopy (fNIRS) before, during, and after applying both possible bi-hemispheric tDCS montages in eight healthy adults. Additionally, torque applied to a lever device during isometric wrist flexion and surface electromyography measurements of major muscle group activity in both arms were acquired concurrently with fNIRS. This multiparameter approach found that hemispheric suppression contralateral to wrist flexion changed resting-state connectivity from intra-hemispheric to inter-hemispheric and increased flexion speed (p < 0.05). Conversely, exciting this hemisphere increased opposing muscle output resulting in a decrease in speed but an increase in accuracy (p < 0.05 for both). The findings of this work suggest that tDCS with fNIRS and concurrent multimotor measurements can provide insights into how neuroplasticity changes muscle output, which could find future use in guiding motor rehabilitation. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Key pointsr Cerebral autoregulation (CA) is a key mechanism to protect brain perfusion in the face of changes in arterial blood pressure, but little is known about individual variability of CA and its relationship to the presence of brain white matter hyperintensity (WMH) in older adults, a type of white matter lesion related to cerebral small vessel disease (SVD).r This study demonstrated the presence of large individual variability of CA in healthy older adults during vasoactive drug-induced changes in arterial pressure assessed at the internal carotid and vertebral arteries. We also observed, unexpectedly, that it was the 'over-' rather than the 'less-reactive' CA measured at the vertebral artery that was associated with WMH severity.r These findings challenge the traditional concept of CA and suggest that the presence of cerebral SVD, manifested as WMH, is associated with posterior brain hypoperfusion during acute increase in arterial pressure.Abstract This study measured the individual variability of static cerebral autoregulation (CA) and determined its associations with brain white matter hyperintensity (WMH) in older adults. Twenty-seven healthy older adults (13 females, 66 ± 6 years) underwent assessment of CA during steady-state changes in mean arterial pressure (MAP) induced by intravenous infusion of sodium nitroprusside (SNP) and phenylephrine. Cerebral blood flow (CBF) was measured using colour-coded duplex ultrasonography at the internal carotid (ICA) and vertebral arteries (VA). CA was quantified by a linear regression slope (CA slope) between percentage changes in cerebrovascular resistance (CVR = MAP/CBF) and MAP relative to baseline values. Periventricular and deep WMH volumes were measured with T2-weighted magnetic resonance imaging. MAP was reduced by −11 ± 7% during SNP, and increased by 21 ± 8% during phenylephrine infusion. CA demonstrated large individual variability with the CA slopes ranging from 0.37 to 2.20 at the ICA and from 0.17 to 3.18 at the VA; no differences in CA were found between the ICA and VA. CA slopes measured at the VA had positive correlations with the total and periventricular WMH volume (r = 0.55 and 0.59, P < 0.01). Collectively, these findings demonstrated the presence of large individual variability of CA in older adults, and that, when measured in the posterior cerebral circulation, it is the higher rather than lower CA reactivity that is associated with WMH severity.

Functional magnetic resonance imaging (fMRI) of brain function is used in neurorehabilitation to gain insight into the mechanisms of neural recovery following neurological injuries such as stroke. The behavioral paradigms involving the use of force motor tasks utilized in the scanner often lack the ability to control details of motor performance. They are often limited by subjectiveness, lack of repeatability, and complexity that may exclude evaluation of patients with poor function. In this paper we describe a novel MR compatible wrist device that is capable of measuring isometric forces generated at the hand and joint moments along wrist flexion-extension and wrist ulnarradial deviation axes. Joint moments measured by the system can be visually displayed to the individual and used during target matching block or event related paradigms. Through a small set of pilot testing both inside and outside the MR environment, we have found that the force tracking tasks and performance in the scanner are reproducible, and that high quality force and moment recordings can be made during fMRI studies without compromising the fMRI images. Furthermore, the device recordings are extremely sensitive making it possible for individuals with poor hand and wrist function to be tested. NIH Public Access

No abstract

Neuroimaging techniques provide information on the neural substrates underlying functional recovery after stroke, the number one cause of long-term disability. Despite the methodological difficulties, they promise to offer insight into the mechanisms by which therapeutic interventions can modulate human cortical plasticity. This information should lead to the development of new, targeted interventions to maximize recovery.