Non-affected Hemispheres Research Articles

Resting-state EEG as Biomarker of Maladaptive Motor Function and Depressive Profile in Stroke Patients.

Objective: Investigate the relationship between resting-state EEG-measured brain oscillations and clinical and demographic measures in Stroke patients. Methods: We performed a cross-sectional analysis of a cohort study (DEFINE cohort), Stroke arm, with 85 patients, considering demographic, clinical, and stroke characteristics. Resting-state EEG relative power from delta, theta, alpha, and beta oscillations were measured from the central region. Multivariate regression models were used for both affected and non-affected hemispheres. Results: Motor function was negatively associated with Delta and Theta oscillations, while positively associated with Alpha oscillations (both hemispheres). Similarly, cognition levels measured were negatively associated with Delta activity. Depression levels were negatively associated with Alpha activity specifically in the affected hemisphere, while positively associated with Beta activity in both hemispheres. Regarding pain measures, no significant association was observed, while CPM measure showed a positive association with Alpha activity in the non-affected hemisphere. Finally, we found that theta/alpha ratio was negatively associated with motor function and CPM scores. Conclusion: The results lead us to propose a framework for brain oscillations in stroke, whereas Delta and Beta would represent disrupted mal-adaptive brain plasticity and Theta and Alpha would represent compensatory and functional brain oscillations for motor and sensory deficits in stroke, respectively.

Common Mutation in the HFE Gene Modifies Recovery After Intracerebral Hemorrhage.

Intracerebral hemorrhage (ICH) is characterized by bleeding into the brain parenchyma. During an ICH, iron released from the breakdown of hemoglobin creates a cytotoxic environment in the brain through increased oxidative stress. Interestingly, the loss of iron homeostasis is associated with the pathological process of other neurological diseases. However, we have previously shown that the H63D mutation in the homeostatic iron regulatory (HFE) gene, prevalent in 28% of the White population in the United States, acts as a disease modifier by limiting oxidative stress. The following study aims to examine the effects of the murine homolog, H67D HFE, on ICH. An autologous blood infusion model was utilized to create an ICH in the right striatum of H67D and wild-type mice. The motor recovery of each animal was assessed by rotarod. Neurodegeneration was measured using fluorojade-B and mitochondrial damage was assessed by immunofluorescent numbers of CytC+ (cytochrome C) neurons and CytC+ astrocytes. Finally, the molecular antioxidant response to ICH was quantified by measuring Nrf2 (nuclear factor-erythroid 2 related factor), GPX4 (glutathione peroxidase 4), and FTH1 (H-ferritin) levels in the ICH-affected and nonaffected hemispheres via immunoblotting. At 3 days post-ICH, H67D mice demonstrated enhanced performance on rotarod compared with wild-type animals despite no differences in lesion size. Additionally, H67D mice displayed higher levels of Nrf2, GPX4, and FTH1 in the ICH-affected hemisphere; however, these levels were not different in the contralateral, non-ICH-affected hemisphere. Furthermore, H67D mice showed decreased degenerated neurons, CytC+ Neurons, and CytC+ astrocytes in the perihematomal area. Our data suggest that the H67D mutation induces a robust antioxidant response 3 days following ICH through Nrf2, GPX4, and FTH1 activation. This activation could explain the decrease in degenerated neurons, CytC+ neurons, and CytC+ astrocytes in the perihematomal region, leading to the improved motor recovery. Based on this study, further investigation into the mechanisms of this neuroprotective response and the effects of the H63D HFE mutation in a population of patients with ICH is warranted.

Chronic hyperglycemia before acute ischemic stroke impairs the bilateral cerebrovascular response to exercise during the subacute recovery period.

Background and PurposeChronic hyperglycemia contributes to cerebrovascular dysfunction by damaging blood vessels. Poor glucose control has been tied to impairments in cerebral blood flow, which may be particularly detrimental for people recovering from major cerebrovascular events such as acute ischemic stroke. In this secondary analysis, we explore for the first time the connection between chronic hyperglycemia before acute stroke and the cerebrovascular response (CVR) to exercise 3 and 6 month into the subacute recovery period.MethodsWe recorded middle cerebral artery velocity (MCAv) using transcranial Doppler ultrasound bilaterally at rest and during moderate‐intensity exercise in stroke patients at 3 (n = 19) and 6 (n = 12) months post‐stroke. We calculated CVR as the difference between MCAv during steady‐state exercise and resting MCAv. We obtained hemoglobin A1c levels (HbA1c; a measure of blood glucose over the prior 3 months) from the electronic medical record (EMR) and divided participants by HbA1c greater or less than 7%.ResultsParticipants with high HbA1c (>7%) at the time of acute stroke had significantly lower CVR to exercise for both the stroke‐affected (p = .009) and non‐affected (p = .007) hemispheres at 3 months post‐stroke. These differences remained significant at 6 months post‐stroke (stroke‐affected, p = .008; non‐affected, p = .016).ConclusionsPatients with chronic hyperglycemia before acute ischemic stroke demonstrated impaired cerebrovascular function during exercise months into the subacute recovery period. These findings highlight the importance of maintaining tight glucose control to reduce morbidity and improve recovery post‐stroke and could have implications for understanding cerebrovascular pathophysiology.

Cerebral Blood Flow Response During Bolus Normal Saline Infusion After Ischemic Stroke

Goals: We quantified cerebral blood flow response to a 500 cc bolus of 0.9%% normal saline (NS) within 96 hours of acute ischemic stroke (AIS) using diffuse correlation spectroscopy (DCS). Materials and Methods: Subjects with AIS in the anterior, middle, or posterior cerebral artery territory were enrolled within 96 hours of symptom onset. DCS measured relative cerebral blood flow (rCBF) in the bilateral frontal lobes for 15 minutes at rest (baseline), during a 30-minute infusion of 500 cc NS (bolus), and for 15 minutes after completion (post-bolus). Mean rCBF for each time period was calculated for individual subjects and median rCBF for the population was compared between time periods. Linear regression was used to evaluate for associations between rCBF and clinical features. Results: Among 57 subjects, median rCBF (IQR) increased relative to baseline in the ipsilesional hemisphere by 17% (−2.0%, 43.1%), P< 0.001, and in the contralesional hemisphere by 13.3% (−4.3%, 36.0%), P < .004. No significant associations were found between ipsilesional changes in rCBF and age, race, infarct size, infarct location, presence of large vessel stenosis, NIH stroke scale, or symptom duration. Conclusion: A 500 cc bolus of .9% NS produced a measurable increase in rCBF in both the affected and nonaffected hemispheres. Clinical features did not predict rCBF response.

Abstract WMP37: Assessment of Intracranial Atherosclerotic Stenosis Using 4D Flow MRI Derived Hemodynamic Biomarkers

Introduction: Despite medical management, 12% of patients with intracranial atherosclerotic disease (ICAD) experience recurrent stroke. Degree of stenosis, the current standard for risk stratification, does not reflect the hemodynamic significance of the lesion. We hypothesized that 4D flow MRI derived parameters including flow rate (FR) and peak velocity (PV) in major cerebral arteries, as well as the pressure drop (PD) in the atherosclerotic stenosis (AS) could be new imaging biomarkers for the hemodynamic impact of AS on local and global cerebrovascular flow redistribution. Methods: Intracranial dual- venc 4D flow MRI and time-of-flight (TOF) MRA were acquired in 23 controls and 13 ICAD patients at 3T (Fig. 1a). AS was graded as moderate (50-69%) and severe (70-99%) based on TOF MRA. 4D flow MRI data was corrected for phase offsets and noise and subsequently processed using an automated analysis tool (Fig. 1b-f). At each analysis plane (Fig.1e), the lumen region was determined from the TOF MRA (registered with 4D flow MRI), and area, PV and FR were calculated. The PD in AS was estimated from the Bernoulli equation using PV and area at AS and the area proximal to the AS. PV and FR ratios between left and right hemispheres for controls and affected to nonaffected hemispheres for patients were also calculated. Results: The PV ratio was significantly different (ranked sum test, p=0.003, Fig. 1g) between control and patient cohorts while FR ratio was similar (p=0.5). In addition, there was a significant correlation between PD in AS and PV ratio for the patient cohort (Spearman correlation, r=0.64, p=0.03, Fig. 1h). Conclusions: In this pilot study, we demonstrated the feasibility of two 4D flow MRI derived hemodynamic parameters, peak velocity and pressure drop, for the characterization of the impacts of ICAD on local and global cerebral flow distribution. Future studies are warranted to assess the prognostic value of these parameters for improved ICAD risk stratification.

Somatotopic organization of corticospinal/corticobulbar motor tracts in controls and patients with tumours: A combined fMRI-DTI study.

ObjectivesTo investigate the relative somatotopic organization of the motor corticospinal/corticobulbar foot, hand, lip and tongue fascicles by combining fMRI with DTI and to examine the influence of subjacent intrinsic tumours on these fascicles.MethodsThe study was approved by the local ethics committee. Seven male and three female volunteers (median age: 35 years) and one female and eight male patients with brain tumours (median age: 37 years) were scanned on a 1.5-T MRI scanner. fMRI data, analysed using SPM5, identified the motor task-driven fMRI grey matter activations of the hand, foot, lips and tongue as seed regions for probabilistic tractography. The relationship between the components of the CST was assessed and the distances between them were measured. A statistical comparison was performed comparing these distances in the group of healthy hemispheres with those of the group of non-affected hemispheres and healthy hemispheres.ResultsHand fascicles were identified in all subjects (38/38, 100%), followed by foot (32/38, 84%), lip (31/38, 81%) and tongue fascicles (28/38, 74%). At superior levels, the hand fascicles were anterolateral to the foot fascicles in 77–93% of healthy hemispheres (HH), in 50–71% of non-affected patients' hemispheres (pH) and in 67–89% of affected PH. At inferior levels, the hand fascicles were either anteromedial in 46–45% of HH or anterior in 75% of non-affected PH and in 67–83% of affected PH. Tongue and lip fascicles overlapped in 25–45% of HH, in 10–20% of non-affected PH and in 15–25% of affected PH. No significant difference was found between the group of affected hemispheres and that of healthy and non-affected hemispheres.ConclusionThe somatotopy of the hand fascicles in relation to the foot fascicles was anterolateral in patients and volunteers at superior levels but anteromedial in volunteers and mostly anterior in patients at inferior levels. The lip and tongue fascicles generally overlapped. Intracranial tumours displaced the motor fascicles without affecting their relative somatotopy.

A high-resolution computational localization method for transcranial magnetic stimulation mapping

BackgroundTranscranial magnetic stimulation (TMS) is used for the mapping of brain motor functions. The complexity of the brain deters determining the exact localization of the stimulation site using simplified methods (e.g., the region below the center of the TMS coil) or conventional computational approaches. ObjectiveThis study aimed to present a high-precision localization method for a specific motor area by synthesizing computed non-uniform current distributions in the brain for multiple sessions of TMS. MethodsPeritumoral mapping by TMS was conducted on patients who had intra-axial brain neoplasms located within or close to the motor speech area. The electric field induced by TMS was computed using realistic head models constructed from magnetic resonance images of patients. A post-processing method was implemented to determine a TMS hotspot by combining the computed electric fields for the coil orientations and positions that delivered high motor-evoked potentials during peritumoral mapping. The method was compared to the stimulation site localized via intraoperative direct brain stimulation and navigated TMS. ResultsFour main results were obtained: 1) the dependence of the computed hotspot area on the number of peritumoral measurements was evaluated; 2) the estimated localization of the hand motor area in eight non-affected hemispheres was in good agreement with the position of a so-called “hand-knob”; 3) the estimated hotspot areas were not sensitive to variations in tissue conductivity; and 4) the hand motor areas estimated by this proposal and direct electric stimulation (DES) were in good agreement in the ipsilateral hemisphere of four glioma patients. Conclusion(s)The TMS localization method was validated by well-known positions of the “hand-knob” in brains for the non-affected hemisphere, and by a hotspot localized via DES during awake craniotomy for the tumor-containing hemisphere.

Is Dynamic Cerebral Autoregulation Bilaterally Impaired after Unilateral Acute Ischemic Stroke?

Whether dynamic cerebral autoregulation (dCA) is impaired focally in the affected hemisphere or bilaterally in both the affected and nonaffected hemispheres after ischemic stroke remains controversial. We therefore investigated the pattern of dCA in acute ischemic stroke patients with different subtypes. Sixty acute ischemic stroke patients with unilateral anterior circulation infarct [30 with large artery atherosclerosis (LAA), 13 with small vessel disease (SVD), and 17 with coexisting LAA and SVD] and 16 healthy controls were enrolled. Spontaneous arterial blood pressure and cerebral blood flow velocity fluctuations in both bilateral middle cerebral arteries using transcranial Doppler were recorded over 10 minutes. Transfer function analysis was applied to obtain autoregulatory parameters, autoregulation index (ARI), phase difference (PD), and gain. PD was significantly lower on both the ipsilateral and contralateral sides in the LAA group (ipsilateral, 30.74 degrees; contralateral, 29.17 degrees) and the coexisting LAA and SVD group (20.23 degrees; 13.10 degrees) than that in healthy controls (left side, 51.66 degrees; right side, 58.48 degrees) (all P < .05), but there were no significant differences between the 2 sides when compared with each other in all groups. However, in the coexisting LAA and SVD group, phase on both sides was significantly lower when compared with that in the LAA and SVD groups, respectively. The results of ARI were consistent with the findings in PD. The results indicate that dCA is bilaterally impaired in acute ischemic patients with LAA, and the coexisting SVD may aggravate the bilateral impairment of dCA.

Imaging increased glutamate in children with Sturge–Weber syndrome: Association with epilepsy severity

BackgroundSturge–Weber syndrome (SWS) is strongly associated with epilepsy. Brain tissue studies have suggested that epileptic activity in SWS is driven by glutamatergic synaptic activity. Here, we used proton magnetic resonance spectroscopic imaging (MRSI) to test if glutamate (GLU) concentrations are increased in the affected hemisphere and if such increases are associated with severity of epilepsy in children with SWS. We also studied the metabolic correlates of MRSI abnormalities, using glucose positron emission tomography (PET) imaging. Methods3T MRI and glucose PET were performed in 10 children (age: 7–78 months) with unilateral SWS and a history of epilepsy. MRSI data were acquired from the affected (ipsilateral) and non-affected (contralateral) hemispheres. GLU, N-acetyl-aspartate (NAA) and creatine (Cr) were quantified in multiple voxels; GLU/Cr and NAA/Cr ratios were calculated and compared to seizure frequency as well as glucose PET findings. ResultsThe highest GLU/Cr ratios were found in the affected hemisphere in all children except one with severe atrophy. The maximum ipsilateral/contralateral GLU/Cr ratios ranged between 1.0 and 2.5 (mean: 1.6). Mean ipsilateral/contralateral GLU/Cr ratios were highest in the youngest children and showed a strong positive correlation with clinical seizure frequency scores assessed at the time of the scan (r=0.88, p=0.001) and also at follow-up (up to 1 year, r=0.80, p=0.009). GLU increases in the affected hemisphere coincided with areas showing current or previous increases of glucose metabolism on PET in 5 children. NAA/Cr ratios showed no association with clinical seizure frequency. ConclusionsIncreased glutamate concentrations in the affected hemisphere, measured by MRSI, are common in young children with unilateral SWS and are associated with frequent seizures. The findings lend support to the role of excess glutamate in SWS-associated epilepsy.

Assessment of quantitative corticospinal tract diffusion changes in patients affected by subcortical gliomas using common available navigation software

ObjectiveThe aim of this study is to analyze the quantitative DTI parameters of the CST in patients suffering from subcortical gliomas affecting the CST using generally available navigation software. MethodsA retrospective study was conducted on 22 subjects with diagnosis of primary cerebral glioma and preoperative motor deficits. Exclusion criteria were: involvement of motor cortex, lesion involving both hemispheres, previous surgical treatment. All patients were studied using magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI) sequences. Volume, fractional anisotropy (FA) and mean diffusivity value (MD) of the entire CSTs were estimated. Moreover, distance from midline, diameters, FA and MD were calculated on axial images at the point of minimal distance between tumor and CST. Statistical analysis was performed. ResultsThere was a statistically significant difference of CST volume between affected and non-affected hemispheres (p<0.01). Mean overall/local FA, overall/local MD and sagittal diameter of CST were also significantly different between the two sides (p<0.05). Correlation tests resulted positive between the shift of CST and overall/local MD. Moreover there is significance between CST volume of tumor hemisphere and preoperative duration of motor deficits (p<0.05). ConclusionThe present study has demonstrated for the first time a significant difference of DTI based quantitative parameters of the CST between a tumor affected and a non-affected hemisphere in patients with a corresponding motor deficit. This preliminary data suggests a correlation between DTI based integrity of CST and its function.

Evaluation of 4D vascular flow and tissue perfusion in cerebral arteriovenous malformations: influence of Spetzler-Martin grade, clinical presentation, and AVM risk factors.

The role of intracranial hemodynamics in the pathophysiology and risk stratification of brain AVMs remains poorly understood. The purpose of this study was to assess the influence of Spetzler-Martin grade, clinical history, and risk factors on vascular flow and tissue perfusion in cerebral AVMs. 4D flow and perfusion MR imaging was performed in 17 patients with AVMs. Peak velocity and blood flow were quantified in AVM feeding and contralateral arteries, draining veins, and the straight sinus. Regional perfusion ratios (CBF, CBV, and MTT) were calculated between affected and nonaffected hemispheres. Regarding flow parameters, high-grade AVMs (Spetzler-Martin grade of >2) demonstrated significantly increased peak velocity and blood flow in the major feeding arteries (P < .001 and P = .004) and straight sinus (P = .003 and P = .012) and increased venous draining flow (P = .001). The Spetzler-Martin grade significantly correlated with cumulative feeding artery flow (r = 0.85, P < .001) and draining vein flow (r = 0.80, P < .001). Regarding perfusion parameters, perinidal CBF and CBV ratios were significantly lower (P < .001) compared with the remote ratios and correlated negatively with cumulative feeding artery flow (r = -0.60, P = .014 and r = -0.55, P = .026) and draining vein flow (r = -0.60, P = .013 and r = -0.56, P = .025). Multiple regression analysis revealed no significant association of AVM flow or perfusion parameters with clinical presentation (rupture and seizure history) and AVM risk factors. Macrovascular flow was significantly associated with increasing Spetzler-Martin grade and correlated with perinidal microvascular perfusion in cerebral AVMs. Future longitudinal studies are needed to evaluate the potential of comprehensive cerebral flow and perfusion MR imaging for AVM risk stratification.

Structural and resting-state brain connectivity of motor networks after stroke.

Focal ischemic brain lesions primarily affect circumscribed brain regions and fiber tracts resulting in acute neurological deficits. Secondary damage because of apoptosis, inflammation, diaschisis, and neurodegeneration, however, can also affect remote brain areas and may result in a more widespread perturbation of entire functional networks even in the nonischemic hemisphere. Such network-wide effects may play a role in the development of poststroke cognitive impairment and may impose limits on functional recovery. Assessing the total effect of all these mechanisms onto the damaged and recovering brain may be clinically useful for better outcome prediction and identification of therapeutic targets because some of those processes (diaschisis and inflammation) are in principle reversible and the strengthening of alternative pathways by targeted intervention may promote recovery. From a practical clinical point of view, imaging methods which can be performed on clinical MRI scanners and do not require active patient participation are ideal candidates to perform such assessments. This topical review thus focuses on diffusion tensor imaging (DTI) MRI and resting-state functional MRI (RS-fMRI) as the most promising methods to this regard (Table). We briefly introduce the physiological background of each method and review current evidence for assessing connectivity in the context of motor recovery. View this table: Table. Comparison of Resting-State fMRI and Diffusion Tensor Imaging ### Principles of DTI Diffusion-based MRI methods are techniques that are sensitive to signals originating from freely moving water molecules in the tissue. Unrestricted movement in all 3 spatial directions results in isotropic diffusion. In the healthy human brain, highly organized white matter pathways consisting of tightly packed axons present a barrier to isotropic diffusion. This diffusion anisotropy is characterized by the preferential diffusion of water molecules parallel to the long axis of the fiber bundles with restricted diffusion perpendicular to the long axis.1 During DTI acquisitions, pairs of balanced diffusion-sensitizing field gradients are applied …

Topographic sleep EEG changes in the acute and chronic stage of hemispheric stroke.

After stroke, the injured brain undergoes extensive reorganization and reconnection. Sleep may play a role in synaptic plasticity underlying stroke recovery. To test this hypothesis, we investigated topographic sleep electroencephalographic characteristics, as a measure of brain reorganization, in the acute and chronic stages after hemispheric stroke. We studied eight patients with unilateral stroke in the supply territory of the middle cerebral artery and eight matched controls. All subjects underwent a detailed clinical examination including assessment of stroke severity, sleep habits and disturbances, anxiety and depression, and high-density electroencephalogram examination with 128 electrodes during sleep. The recordings were performed within 10 days after stroke in all patients, and in six patients also 3 months later. During sleep, we found higher slow-wave and theta activity over the affected hemisphere in the infarct area in the acute and chronic stage of stroke. Slow-wave, theta activity and spindle frequency range power over the affected hemisphere were lower in comparison to the non-affected side in a peri-infarct area in the patients' group, which persisted over time. Conversely, in wakefulness, only an increase of delta, theta activity and a slowing of alpha activity over the infarct area were found. Sleep slow-wave activity correlated with stroke severity and outcome. Stroke might have differential effects on the generation of delta activity in wakefulness and sleep slow waves (1-8 Hz). Sleep electroencephalogram changes over both the affected and non-affected hemispheres reflect the acute dysfunction caused by stroke and the plastic changes underlying its recovery. Moreover, these changes correlate with stroke severity and outcome.

Near Infrared Spectroscopy for the Detection of Desaturations in Vulnerable Ischemic Brain Tissue

There is uncertainty whether bilateral near infrared spectroscopy (NIRS) can be used for monitoring of patients with acute stroke. The NIRS responsiveness to systemic and stroke-related changes was studied overnight by assessing the effects of brief peripheral arterial oxygenation and mean arterial pressure alterations in the affected versus nonaffected hemisphere in 9 patients with acute stroke. Significantly more NIRS drops were registered in the affected compared with the nonaffected hemisphere (477 drops versus 184, P<0.001). In the affected hemispheres, nearly all peripheral arterial oxygenation drops (n=128; 96%) were detected by NIRS; in the nonaffected hemispheres only 23% (n=30; P=0.17). Only a few mean arterial pressure drops were followed by a significant NIRS drop. This was however significantly different between both hemispheres (32% versus 13%, P=0.01). This pilot study found good responsiveness of NIRS signal to systemic and stroke-related changes at the bedside but requires confirmation in a larger sample.

Leptomeningeal collateral and cerebral hemodynamics in patients with ICA and MCA steno-occlusion

<title/>Objectives: The purpose of our study was to evaluate the correlation between fluid-attenuated inversion recovery (FLAIR) images of hyperintense vessel (HV), a representative of leptomeningeal vessels (LMVs), and cerebral vascular hemodynamic status in patients with steno-occlusive disease of the internal carotid artery (ICA) and middle cerebral artery (MCA).Methods: Sixty-eight patients with unilateral ICA or MCA stenosis or occlusion were enrolled. Correlations between hyperintense vessel (HV) on FLAIR images and hemodynamic status measured by quantitative single-photon emission computed tomography data were evaluated in four groups: affected (A) and non-affected (B) hemispheres in HV-positive patients, and affected (C) and non-affected (D) hemispheres in HV-negative patients.Results: The presence of HV was most frequently seen on affected hemispheres in patients with MCA and ICA occlusions. HV was significantly higher in the anterior communicating artery (AcomA) (−), posterior communicating artery (PcomA) (−) group than in other groups, which included either or both AcomA and PcomA (P = 0·008). The presence of HV had a significant correlation with transdural anastomosis (P = 0·046) and LMV (P = 1·64×10−9). No significant difference was observed in resting regional cerebral blood flow among the four groups. Vascular reserve in group A was significantly less compared to other groups (P = 0·021).Conclusions: HV is related to the hemisphere with severe ICA and MCA steno-occlusion when the circle of Willis is insufficient. The HV-positive hemisphere on the steno-occlusive side shows a lower vascular reserve than that in the contralateral hemisphere or HV-negative hemispheres.

Aberrant Cortical Functionality and Somatosensory Deficits After Stroke

Damage and/or disconnection of the primary somatosensory cortex (SI) after stroke leads to deficits in touch perception. We used magnetoencephalography to test whether specific patterns of functionality of the somatosensory cortex are associated with different degrees of postacute somatosensory deficit. Nineteen postacute unilateral stroke patients suffering different degrees of somatosensory deficit (six nonexistent, six moderate, and seven severe) and eight aged-matched controls underwent high-resolution MRI and whole-head magnetoencephalography recordings of somatosensory-evoked fields and of spontaneous slow oscillatory activity. Amplitude of SI activation after tactile stimulation in the affected and nonaffected hemispheres and delta dipole density (DDD) in the postcentral areas were estimated and compared across the four groups. Severe postacute somatosensory deficit was accompanied, in all cases, with absence of SI responses to stimulation in the affected hand and a significant asymmetry in postcentral DDD toward the affected hemisphere. Patients with moderate sensory loss showed asymmetry in their postcentral DDD (four cases toward the affected hemisphere and two toward the unaffected) but no atypical amplitudes in SI activation. Recordings in stroke patients without somatosensory deficit did not differ from those obtained in controls for SI amplitude or postcentral DDD. In stroke patients, amplitude of SI responses and postcentral DDD show a negative correlation. Lack of activation of SI cortex after stimulation of the affected hand and spontaneous slow oscillatory activity in postcentral areas are neurophysiological correlates of somatosensory deficit in the postacute phase of stroke.

Bilateral and unilateral movement training on upper limb function in chronic stroke patients: A TMS study

The use of activity-dependent interventions has shown some success in promoting recovery of upper limb function in chronic stroke patients. This study compared the neurophysiological and behavioural changes associated with two such rehabilitation protocols: unilateral and bilateral movement training. Twelve chronic stroke patients were randomly assigned to the two training protocols involving six daily practice sessions. Each session consisted of 50 trials of a dowel placement task performed either with both impaired and unimpaired arm moving synchronously (bilateral training group) or with only the impaired arm moving (unilateral training). Kinematic measurements of upper limb movements were made in four unilateral test trials performed prior to and following each practice session. Functional assessments of the impaired upper limb and neurophysiological assessments, using transcranial magnetic stimulation (TMS), of the affected and non-affected cortical hemispheres were made prior to and following the intervention sessions. Individuals receiving bilateral training showed a reduction in movement time of the impaired limb and increased upper limb functional ability compared to individuals receiving unilateral training. In some patients changes to upper limb function were associated with changes to the cortical representation of a target muscle in the non-affected hemisphere. Overall, these findings suggest that a short-term bilateral training intervention may be effective in facilitating upper limb motor function in chronic stroke patients.

Human cortical dysplasia and epilepsy: an ontogenetic hypothesis based on volumetric MRI and NeuN neuronal density and size measurements.

In epilepsy patients with cortical dysplasia (CD), this study determined the probable ontogenetic timing of pathogenesis based on the number, location and appearance of neurons. Magnetic resonance imaging (MRI) determined gray and white matter volumes of affected and non-affected cerebral hemispheres, and gray and white matter neuronal-nuclear protein (NeuN) densities and sizes were assessed in epilepsy surgery patients (0.2-38 years) with CD (n = 25) and non-CD etiologies (n = 14), and compared with autopsy cases (n = 13; 0-33 years). Pathology group, seizure type and age at surgery were compared against MRI and NeuN data. CD patients demonstrated increased MRI cerebral (3%) and gray matter (8%) volumes of the affected compared with non-affected cerebral hemisphere, and increased layer 1 (131%), upper cortical (9-23%) and white matter (28-77%) NeuN densities compared with autopsy cases. Non-CD cases showed decreased cerebral volumes of the affected hemisphere (14-18%) without changes in NeuN densities. Compared with autopsy cases, in CD and non-CD patients, cortical neurons were hypertrophied. Patients with a history of infantile spasms had a 40% increase in the size of layer 1 neurons compared with cases without spasms. By age, regardless of pathology group, there were logarithmic increases in MRI cerebral and white matter volumes, logarithmic increases in the size of lower gray and superficial white matter neurons, and logarithmic decreases in gray and white matter neuronal densities. These results support the concept that there were more neurons than expected in layer 1, gray, and white matter of CD patients compared with non-CD and autopsy cases. In addition, the location and appearance of neurons are consistent with the hypothesis that CD is the consequence of abnormalities occurring late in corticoneurogenesis that involve excessive neurogenesis with retention of pre-plate cells in the molecular layer and subplate regions.

Neurophysiological and behavioural adaptations to a bilateral training intervention in individuals following stroke.

To examine the neurophysiological and behavioural adaptations to a bilateral training protocol in individuals with hemiparesis due to stroke. Subjects performed daily practice sessions of three specific upper limb tasks over a four-week period. Performance of the tasks was recorded on video for later analysis over the duration of the study. For the first week of the training period the tasks were practised with the impaired upper limb. Only then, with a random start day between 8 and 13, the tasks were practised using a bilateral training protocol. Functional assessments of the affected upper limb and neurophysiological investigations of contra- and ipsilateral pathways from the affected and nonaffected cortical hemispheres were completed prior to the start of the intervention, at the end of the unimanual practice period, and at the conclusion of the bimanual practice period. Six individuals between one month and four years post stroke. Unimanual and bimanual training protocols. Task performance with the affected limb only; motor impairment of the affected upper limb; ipsi- and contralateral corticospinal pathway excitability. Baseline task performance varied markedly between subjects. Most individuals demonstrated little, if any, additional beneficial effect of bimanual practice on task performance. Results of neurophysiological investigations were inconsistent between subjects. Short-term bilateral training following unilateral training may have limited effectiveness in enhancing upper limb motor performance in acute and chronic individuals poststroke. The neural mechanisms associated with bilateral activation therapies remain uncertain.

Serial Changes in Static and Dynamic Cerebral Autoregulation after Acute Ischaemic Stroke

Background: The longitudinal changes in static and dynamic cerebral autoregulation (CA) following acute ischaemic stroke are unknown and were assessed in this study. Methods: Fifty-four ischaemic stroke patients were studied within 96 h of ischaemic stroke and again 7–14 days later, using transcranial Doppler techniques to measure CA. Results were compared to an age-, sex- and blood pressure (BP)-matched control group. Static BP pressor stimulus was produced by thigh cuff inflation and dynamic stimulus by rapid thigh cuff release. Results: Dynamic, but not static, CA was globally impaired at initial (mean dynamic CA index 3.9 ± 3.1 vs. 6.2 ± 2.3, p < 0.005) and follow-up studies (dynamic CA 3.9 ± 2.8 vs. 6.2 ± 2.3, p < 0.01) in stroke patients compared to controls. Static CA was similar in stroke patients and controls and was unchanged during follow-up. Conclusions: Dynamic, but not static, CA is impaired after acute ischaemic stroke and remains abnormal for at least 1–2 weeks post ictus. These changes are present in both the affected and non-affected hemispheres and are unrelated to previous antihypertensive treatment, baseline BP levels or BP changes after stroke, age or stroke type.