Remote depressions of cerebral metabolism in hemiparetic stroke: Topography and relation to motor and somatosensory functions

Enhanced Motor Recovery After Stroke With Combined Cortical Stimulation and Rehabilitative Training Is Dependent on Infarct Location

BACKGROUND

Cortical electrical stimulation of the motor cortex in combination with rehabilitative training (CS/RT) has been shown to enhance motor recovery in animal models of focal cortical stroke, yet in clinical trials, the effects are much less robust. The variability of stroke location in human patient populations that include both cortical and subcortical brain regions may contribute to the failure to find consistent effects clinically.

OBJECTIVE

This study sought to determine whether infarct location influences the enhanced motor recovery previously observed in response to CS/RT. The efficacy of CS/RT to promote improvements in motor function was examined in 2 different rat models of stroke that varied the amount and location of cortical and subcortical damage.

METHODS

Ischemic infarctions were induced by injecting the vasoconstricting peptide endothelin-1 either (1) onto the middle cerebral artery (MCA) producing damage to the frontal cortex and lateral striatum or (2) into a subcortical region producing damage to the posterior thalamus and internal capsule (subcortical capsular ischemic injury [SCII]). Daily CS/RT or RT alone was then given for 20 days, during which time performance on a skilled reaching task was assessed.

RESULTS

Animals with MCA occlusion infarctions exhibited enhanced improvements on a skilled reaching task in response to CS/RT relative to RT alone. No such enhancement was observed in animals with SCII infarctions across the 20 days of treatment.

CONCLUSIONS

The efficacy of CS for enhancing motor recovery after stroke may depend in part on the extent and location of the ischemic infarct.

Training-induced modifications of corticospinal reactivity in severely affected stroke survivors

When permitted access to the appropriate forms of rehabilitation, many severely affected stroke survivors demonstrate a capacity for upper limb functional recovery well in excess of that formerly considered possible. Yet, the mechanisms through which improvements in arm function occur in such profoundly impaired individuals remain poorly understood. An exploratory study was undertaken to investigate the capacity for brain plasticity and functional adaptation, in response to 12-h training of reaching using the SMART Arm device, in a group of severely affected stroke survivors with chronic upper limb paresis. Twenty-eight stroke survivors were enroled. Eleven healthy adults provided normative data. To assess the integrity of ipsilateral and contralateral corticospinal pathways, transcranial magnetic stimulation was applied to evoke responses in triceps brachii during an elbow extension task. When present, contralateral motor-evoked potentials (MEPs) were delayed and reduced in amplitude compared to those obtained in healthy adults. Following training, contralateral responses were more prevalent and their average onset latency was reduced. There were no reliable changes in ipsilateral MEPs. Stroke survivors who exhibited contralateral MEPs prior to training achieved higher levels of arm function and exhibited greater improvements in performance than those who did not initially exhibit contralateral responses. Furthermore, decreases in the onset latency of contralateral MEPs were positively related to improvements in arm function. Our findings demonstrate that when severely impaired stroke survivors are provided with an appropriate rehabilitation modality, modifications of corticospinal reactivity occur in association with sustained improvements in upper limb function.

Cerebellar apparent diffusion coefficient changes in patients with supratentorial ischemic stroke

OBJECTIVES

To evaluate apparent diffusion coefficient (ADC) in cerebellar subregions in patients with stroke.

MATERIALS AND METHODS

The total counts and ADCs were bilaterally measured on cerebellar white matter, gray matters of medial (G1), intermediate (G2), and lateral zones (G3) on SPECT and ADC maps from 20 patients with supratentorial ischemic stroke within the first 48 h and on day 8 after onset. ADCs were also obtained from 15 age-matched controls.

RESULTS

Within 48 h, the ADCs were significantly increased bilaterally in the G3, and tended to be increased bilaterally in the white matter and G1, and contralateral G2 compared with controls. On day 8, the ADCs were significantly increased in all contralateral cerebellar subregions and in ipsilateral G1 and G2, and tended to be increased in ipsilateral G3. The ADC value was significantly higher in contralateral than in ipsilateral white matter on day 8. The interhemispheric asymmetry indices (AIs) of ADC and SPECT were significantly associated with each other in G2 and G3 within 48 h, but not on day 8. The AIs of ADC and SPECT were significantly related to each other in the G3 within 48 h and on day 8.

CONCLUSIONS

Supratentorial ischemic stroke may cause mild cerebellar vasogenic edema.

Safety of 6-Hz Primed Low-Frequency rTMS in Stroke

Background. Suppression of activity in the contralesional motor cortex may promote recovery of function after stroke. Furthermore, the known depressant effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) can be increased and prolonged by preceding it with 6-Hz priming stimulation. Objective. The authors explored the safety of 6-Hz primed low-frequency rTMS in 10 patients with ischemic stroke. Methods. Priming consisted of 10 minutes of 6-Hz rTMS applied to the contralesional hemisphere at 90% of resting motor threshold delivered in 2 trains/min with 5 s/train and 25-second intervals between trains. Low-frequency rTMS consisted of an additional 10 minutes of 1-Hz rTMS at 90% of resting motor threshold without interruption. Possible adverse effects were assessed with the National Institutes of Health Stroke Scale (NIHSS), the Wechsler Adult Intelligence Scale—Third Edition (WAIS-III), the Hopkins Verbal Learning Test—Revised (HVLT-R), the Beck Depression Inventory—Second Edition (BDI-II), a finger movement tracking test, and individual self-assessments. Pretest, treatment, and posttest occurred on the first day with follow-up tests on the next 5 weekdays. Results. There were no seizures and no impairment of NIHSS, WAIS-III, or BDI-II scores. Transient impairment occurred on the HVLT-R. Transient tiredness was common. Occasional reports of headache, neck pain, increased sleep, reduced sleep, nausea, and anxiety occurred. Conclusion. Because there were no major adverse effects, the authors concluded that the treatment was safe for the individuals in this study and that further investigation is now warranted to examine efficacy and safety of serial treatments of 6-Hz primed low-frequency rTMS.

Post-lesional cerebral reorganisation: evidence from functional neuroimaging and transcranial magnetic stimulation

Reorganisation of cerebral representations has been hypothesised to underlie the recovery from ischaemic brain infarction. The mechanisms can be investigated non-invasively in the human brain using functional neuroimaging and transcranial magnetic stimulation (TMS). Functional neuroimaging showed that reorganisation is a dynamic process beginning after stroke manifestation. In the acute stage, the mismatch between a large perfusion deficit and a smaller area with impaired water diffusion signifies the brain tissue that potentially enables recovery subsequent to early reperfusion as in thrombolysis. Single-pulse TMS showed that the integrity of the cortico-spinal tract system was critical for motor recovery within the first four weeks, irrespective of a concomitant affection of the somatosensory system. Follow-up studies over several months revealed that ischaemia results in atrophy of brain tissue adjacent to and of brain areas remote from the infarct lesion. In patients with hemiparetic stroke activation of premotor cortical areas in both cerebral hemispheres was found to underlie recovery of finger movements with the affected hand. Paired-pulse TMS showed regression of perilesional inhibition as well as intracortical disinhibition of the motor cortex contralateral to the infarction as mechanisms related to recovery. Training strategies can employ post-lesional brain plasticity resulting in enhanced perilesional activations and modulation of large-scale bihemispheric circuits.

Practical and Theoretical Considerations in Designing Rehabilitation Trials

This is a descriptive article outlining issues in the development and implementation of a multisite randomized rehabilitation trial for brain injury treatment. The goal of this article is to present practical and theoretical considerations in designing and conducting multicenter rehabilitation trials. Practical issues discussed include (a) treatment setting, (b) patient accessibility in determining the research question of interest, as well as inclusion and exclusion criteria, (c) research protocol development in the context of rehabilitation standard of care, and (d) protocol treatments in the context of realistic cost-benefits analysis. Rehabilitation theory is discussed as playing an important role designing the specifics of the protocol interventions. The Defense and Veterans Brain Injury Center Veterans Health Administration cognitive-didactic versus functional-experiential study methodology is used for illustrative purposes. This study evaluated 2 alternative approaches to treatment: one focusing on underlying cognitive processes and the second on errorless learning in everyday functional situations. Lessons learned over the course of completing the treatment trial are discussed.

Gender-specific Differences of Hypometabolism in mTLE: Implication for Cognitive Impairments

PURPOSE

To determine gender differences of hypometabolism and their implications for cognitive impairment in patients with medically refractory mesial temporal lobe epilepsy (mTLE).

METHODS

Regional cerebral glucose metabolism (rCMRGlu) was studied in 42 patients (21 male, 21 female) with either left- or right-sided mTLE (22 left, 20 right) and in 12 gender- and age-matched healthy controls during resting wakefulness and in 12 sex- and age-matched healthy controls. Clinical characteristics were balanced across the patient subgroups. All patients were subjected to neuropsychological assessment: 41 patients had histologic changes of definite or probable hippocampal sclerosis.

RESULTS

Data analysis based on pixel-by-pixel comparisons and on a laterality index of regions of interest (ROIs) showed significant depressions of the mean rCMRGlu extending beyond the mesiotemporal region and temporolateral cortex to extratemporal regions including the frontoorbital and insular cortex in mTLE patients. Extramesiotemporal hypometabolism prevailed in the male patients. Metabolic asymmetry in temporal and frontal regions was related to performance in the Trail-Making Test and WAIS-R subitems.

CONCLUSIONS

Our data showed a gender-specific predominance of extramesiotemporal hypometabolism in male patients with mTLE related to abnormalities of temporal and frontal lobe functions.

Quantitative EEG patterns following unilateral stroke: a study in chronic stage

The aim of this study was to investigate the EEG power spectra obtained during rest and mental processing in chronic stroke patients. Seventeen patients with stabilized unilateral cerebral ischemia, grouped according to the side of lesion, underwent quantitative EEG recordings during rest and attentive/cognitive tasks. EEG spectral values were compared with those of 11 healthy subjects. Patients displayed different EEG patterns from controls, under rest condition: patients with left hemispheric lesion were characterized by a preserved alpha and beta band "reactivity," with a lack of significant changes in slow band components. In patients with right hemisphere lesion, no significant changes of the slow and fast band activities were evident during each task. These findings indicate that different EEG patterns of activation characterize stroke patients with left and right hemispheric damage.

Longitudinal study of motor recovery after stroke: recruitment and focusing of brain activation

BACKGROUND AND PURPOSE

The goal of this study was to characterize cortical reorganization after stroke and its relation with the site of the stroke-induced lesion and degree of motor recovery using functional MRI (fMRI).

METHODS

Fourteen stroke patients with an affected upper limb were studied longitudinally. Three fMRI sessions were performed over a period of 1 to 6 months after stroke. Upper limb recovery, Wallerian degeneration of the pyramidal tract, and responses to transcranial magnetic stimulation were assessed.

RESULTS

Two main patterns of cortical reorganization were found. Pattern 1 was focusing, in which, after initial recruitment of additional ipsilateral and contralateral areas, activation gradually developed toward a pattern of activation restricted to the contralateral sensorimotor cortex in 9 patients. Five patients were found to have pattern 2, persistent recruitment, in which there was an initial and sustained recruitment of ipsilateral activity. Occurrence of recruitment or focusing seemed to depend mainly on whether the primary motor cortex (M1) was lesioned; persistent recruitment was observed in 3 of 4 patients with M1 injury, and focusing was seen in 8 of 10 patients with spared M1. These patterns had no relation to the degree of recovery; in particular, focusing did not imply recovery. However, there was a clear relation between the degree of recovery and the degree of Wallerian degeneration.

CONCLUSIONS

These results suggest that ipsilateral recruitment after stroke corresponds to a compensatory corticocortical process related to the lesion of the contralateral M1 and that the process of compensatory recruitment will persist if M1 is lesioned; otherwise, it will be transient.

Localization of arm representation in the corona radiata and internal capsule in the non-human primate

Localization of the corticofugal projection in the corona radiata (CR) and internal capsule (IC) can assist in evaluating a patient's residual motor capacity following subtotal brain damage and predicting their potential for functional restitution. To advance our understanding of the organization of the corticofugal projection in this critical brain region, we studied the trajectories of the projection arising from six different cortical arm representations in rhesus monkeys. They included the arm representation of the primary (M1), ventral lateral pre- (LPMCv), dorsolateral pre- (LPMCd), supplementary (M2), rostral cingulate (M3) and caudal cingulate (M4) motor cortices. In the CR, each pathway was segregated as medial motor area fibres arched over the caudate and lateral motor area fibres arched over the putamen. In the IC, the individual corticofugal pathways were found to be widespread, topographically organized and partially overlapping. At superior levels of the IC, the corticofugal projection from the arm representation of M3 coursed through the middle and posterior portion of the anterior limb (ICa). The projection from M2 passed through the posterior portion of the ICa and the genu (ICg). The projection from LPMCv travelled through the genu and anterior portion of the posterior limb (ICp). The projection from LPMCd occupied the anterior portion of the ICp. The projection from M4 descended through the mid-portion of the ICp. Fibres from M1 also travelled in the ICp, positioned immediately posterior to the M4 projection. As each fibre system progressed inferiorly within the IC, all fibres shifted posteriorly to occupy the ICp. Within the ICp, the projections from M3, M2, LPMCv, LPMCd, M4 and M1 maintained their anterior to posterior orientation, respectively. M2, LPMCd and LPMCv fibres overlapped extensively, as did fibres from M4 and M1. Our data suggest that CR and superior capsular lesions may correlate with more favourable levels of functional recovery due to the widespread nature of arm representation. In contrast, the extensive overlap and comparatively condensed organization of arm representation at inferior capsular levels suggest that lesions seated inferiorly are likely to correlate with poorer levels of recovery of upper limb movement. Based on the relative density of corticospinal neurones associated with the motor areas studied, our findings also suggest that motor deficit severity is likely to increase as a lesion occupies progressively more posterior regions of the IC.

Cerebral networks in sensorimotor disturbances

Increasing evidence suggests that the human brain employs multiple, interconnected brain areas for information processing and control of behavior, including the performance of laboratory tasks. Brain diseases are expected to affect these networks directly by interference and indirectly as a consequence of deficit compensation. Covariance analyses applied to functional brain imaging data open the opportunity to study neural networks and their disease-related changes in the human brain. Here, we review our analytic approach based on principal component analysis (PCA) to address such questions. We will discuss its methodological foundations and applications in patients with sensorimotor disorders. We will show that PCA in combination with, both, hypothesis-driven testing and correlation statistics provides a powerful tool for elucidating disease-related abnormalities and postlesional reorganization of neural networks in the human brain.

Neuromagnetic integrated methods tracking human brain mechanisms of sensorimotor areas 'plastic' reorganisation

The potential for reorganization in the adult brain has been largely underestimated in the past and we are just beginning to understand the organisational principles involved in functional recovery. A bulk of experimental evidences have been accumulated in support of the hypothesis that neuronal aggregates adjacent to a lesion in the cortical brain areas can be progressively vicarious to the function of the damaged neurones. Such a reorganisation, if occurring in the affected hemisphere of a patient with a monohemispheric lesion, should significantly modify the interhemispheric symmetry of somatotopic organisation of the sensorimotor cortices, both in terms of absolute surfaces and number of "recruited" neurons, as well as of spatial coordinates. In fact, a roughly symmetrical organisation of sensorimotor - particularly for the hand contorl - in the right and left hemisphere has been observed in healthy humans by different methods of functional brain imaging, including fMRI, TMS, MEG, HD-EEG. Not uniform results about the functional brain activity related to sensory, motor and cognitive functions in normal and diseased subjects are often due to differences in the experimental paradigm designed as well as in the spatial and temporal resolution of the neuroimaging techniques used. The multi-modal integration of data obtained with several neuroimaging techniques allowed a coherent modelling of human brain higher functions. Functional magnetic resonance imaging (fMRI) provided fine spatial details (millimetres) of the brain responses, which were compared with the cortical maps of the motor output to different body districts obtained with transcranial magnetic stimulation (TMS). Magnetoencephalography (MEG) ability to study sensorimotor areas by analysing cortical magnetic fields, is also complementary to the motor cortex topographical mapping provided by TMS. MEG high temporal resolution allows to detect relatively restricted functional neuronal pools activated during cerebral processing of external stimuli. Moreover, these brain responses can be investigated with magnetoencephalography (MEG) and high density electroencephalography (EEG) techniques, with elevated time resolution (ms). With respect to the high resolution EEG technique, the MEG technique allowed a more precise localisation of the sites of neural activity buried into the cortical sulci, but was unable to detect the response of the crown of the cortical giri and of the frontal-mesial cortex (including the supplementary motor area), because of its poor sensitivity to radially oriented dipoles. The integration of functional and anatomical information provide cues on the relationship between brain activity and anatomic sites where this takes place, allowing the characterisation of the physiological activity of the cortical brain layers as well as to study the plastic reorganisation of the brain in different pathological conditions following stroke, limb amputation, spinal cord injury, hemisperectomy.

Temporal lobe epilepsy with sensory aura: interictal glucose hypometabolism

Patients with mesial temporal lobe epilepsy (mTLE) exhibit marked depressions of the regional cerebral glucose metabolism (rCMRGlu) in the mesiotemporal region. We hypothesised that patients with temporal lobe epilepsy (TLE) who have a bilateral somatosensory or acoustic ( = temporolateral/SII-) aura can be differentiated from mTLE by rCMRGlu depressions primarily involving temporo-perisylvian locations. We therefore used this ictal semiology as a clinical criterion to define a subgroup of such patients and measured the rCMRGlu in 16 patients with TLE as evident from interictal and ictal EEG-video monitoring. Clinically, they presented with medically refractory complex partial seizures and were subjected to presurgical evaluation. The pattern of the interictal rCMRGlu in the TLE patients was different from that observed in patients with mTLE and showed significant depressions ipsilateral to the epileptic focus in mesial temporal and lateral temporal regions but spared the thalamus. The neocortical metabolic depressions were spatially more extended in right than in left TLE patients. Magnetic resonance images (MRI) were either normal (n = 5) or revealed unilateral or bilateral hippocampal atrophy/sclerosis (n = 7), or temporal or extratemporal focal cortical dysplasia (n = 4). The selected TLE patients presented here comprise a heterogeneous group showing most pronounced metabolic depressions in the lateral temporal cortex. Thus, our data suggest that non-invasive metabolic imaging can assist in identifying the neocortical symptomatogenic zone in putative temporo-perisylvian lobe epilepsy.

The role of diaschisis in stroke recovery

BACKGROUND AND PURPOSE

Recovery from hemiparesis after stroke has been shown to involve reorganization in motor and premotor cortical areas. However, whether poststroke recovery also depends on changes in remote brain structures, ie, diaschisis, is as yet unresolved. To address this question, we studied regional cerebral blood flow in 7 patients (mean+/-SD age, 54+/-8 years) after their first hemiparetic stroke.

METHODS

We analyzed imaging data voxel by voxel using a principal component analysis by which coherent changes in functional networks could be disclosed. Performance was assessed by a motor score and by the finger movement rate during the regional cerebral blood flow measurements.

RESULTS

The patients had recovered (P<0. 001) from severe hemiparesis after on average 6 months and were able to perform sequential finger movements with the recovered hand. Regional cerebral blood flow at rest differentiated patients and controls (P<0.05) by a network that was affected by the stroke lesion. During blindfolded performance of sequential finger movements, patients were differentiated from controls (P<0.05) by a recovery-related network and a movement-control network. These networks were spatially incongruent, involving motor, sensory, and visual cortex of both cerebral hemispheres, the basal ganglia, thalamus, and cerebellum. The lesion-affected and recovery-related networks overlapped in the contralesional thalamus and extrastriate occipital cortex.

CONCLUSIONS

Motor recovery after hemiparetic brain infarction is subserved by brain structures in locations remote from the stroke lesion. The topographic overlap of the lesion-affected and recovery-related networks suggests that diaschisis may play a critical role in stroke recovery.

Extrarolandic origin of spike and myoclonus activity in epilepsia partialis continua: a magnetoencephalographic and positron emission tomography study

The dipole sources of interictal spike activity were localized and the myoclonus activity back-averaged by combined magnetoencephalography and surface electromyographic measurements in a child who had epilepsia partialis continua without a structural brain lesion. Dipole sources were matched with metabolic information obtained from interictal 5-fluoro-D-glucose positron emission tomography (PET) and superimposed onto high-resolution magnetic resonance images. Dipole sources of interictal epileptic discharges clustered within the inferior parietal cortex, which also showed a regional hypermetabolism on PET scans. The dipole sources of reafferent activity following myocloni in the postcentral gyrus were associated with a local hypometabolism Although there was no obvious phase relationship between interictal spikes and myoclonic jerks, the myocloni were initiated from within the interictal spike area in the extrarolandic cortex. The data demonstrate that motor symptoms may be a remote effect of epileptic activity within functional brain circuits.

Cerebellar hypometabolism in focal epilepsy is related to age of onset and drug intoxication

PURPOSE

We wished to investigate the cerebellar depression of regional cerebral glucose metabolism (rCMRGlu) in patients with focal epilepsy.

METHOD

In 170 consecutive patients with medically refractory, focal epilepsy the rCMRGlu was measured in cerebellum and brain.

RESULTS

rCMRGlu was markedly decreased in both cerebellar hemispheres and slightly in brain. The cerebellum to brain rCMRGlu ratio was significantly decreased in patients with seizure manifestation in infancy, but was normal due to a progressive decrease in brain rCMRGlu in later age. A subgroup of patients with focal epilepsy involving the frontal lobe had a reduced cerebellum/brain rCMRGlu ratio, whereas in patients with mesiotemporal lobe epilepsy (MTLE), the rCMRGlu was decreased to the same degree in cerebellum and brain. The difference in the cerebellum/brain rCMRGlu ratio between the two groups was accounted for by the younger age of the patients with focal epilepsy involving the frontal lobe, however. In another subgroup of patients with a documented history of critical drug intoxications, the cerebellar rCMRGlu was severely decreased, resulting in a significantly reduced cerebellum/brain rCMRGlu ratio.

CONCLUSION

Our retrospective study suggests that the cerebellum is particularly vulnerable in infancy to ongoing epileptic activity and high dosage of antiepileptic drugs (AEDs).

Thalamic metbolism and corticospinal tract integrity determine motor recovery in stroke

We studied the role of remote metabolic depressions and pyramidal tract involvement regarding motor recovery following a first hemiparetic ischemic stroke. In 23 patients the regional cerebral glucose metabolism (rCMRGlu) was measured with positron emission tomography and the location and spatial extent of the stroke lesions were assessed by magnetic resonance imaging. Motor impairment during the acute and chronic stages (4 weeks after stroke) was determined by a motor score and recordings of magnetic evoked motor potentials. Twelve patients recovered significantly, whereas 11 patients retained a disabling hemiparesis. In contrast to patients with good motor recovery, rCMRGlu was severely depressed in the thalamus on the lesion side in patients with poor motor recovery. This patient group also showed more severe damage to the pyramidal tract on magnetic resonance images and a more pronounced reduction of the magnetic evoked motor potential amplitude. Neither the size of the stroke lesions nor the spatial extent of the lesional and remote rCMRGlu depressions outside the thalamus correlated with the thalamic hypometabolism and the improvement of the motor score. We conclude that preservation both of parts of the pyramidal tract and of the thalamic circuitry is a major determinant for the quality of hand motor recovery following acute brain ischemia in the adult.

Cerebral network underlying unilateral motor neglect: evidence from positron emission tomography

In 4 male patients (age range 50-73 years) with unilateral motor hemineglect as a sequelae of circumscribed cerebral infarction, depressions of the regional cerebral glucose metabolism (rCMRGlu) were mapped to identify the metabolically affected cerebral structures. Motor neglect was defined according to Castaigne by lack of spontaneous and pain-induced motor activity on one side of the body in the absence of paresis, pyramidal signs, and sensory loss. The depressions of the rCMRGlu as determined by positron emission tomography (PET) were found to exceed the areas of structural damage but to be restricted to the affected cerebral hemisphere. Significant mean rCMRGlu depressions followed a focal pattern involving the premotor, prefrontal, parietal and cingulate cortex, as well as the thalamus. In correspondence to the lack of significant mean rCMRGlu depressions in primary sensorimotor cortex, basal ganglia, and cerebellum the cortico-spinal pathway was spared as indicated by preserved magnetic evoked motor potentials. Our data provide evidence suggesting that motor hemineglect is a disturbance in a cerebral network of higher order cortical areas subserving motor activity in the presence of an intact motor cortical output system.