Effects of Bracing in Adult With Scoliosis: A Retrospective Study.

OBJECTIVE: To assess the effectiveness of bracing in adult with scoliosis. DESIGN: Retrospective cohort study. SETTING: Outpatients followed in 2 tertiary care hospitals. PARTICIPANTS: Adults (N=38) with nonoperated progressive idiopathic or degenerative scoliosis treated by custom-molded lumbar-sacral orthoses, with a minimum follow-up time of 10 years before bracing and 5 years after bracing. Progression was defined as a variation in Cobb angle ≥10° between the first and the last radiograph before bracing. The brace was prescribed to be worn for a minimum of 6h/d. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Rate of progression of the Cobb angle before and after bracing measured on upright 3-ft full-spine radiographs. RESULTS: At the moment of bracing, the mean age was 61.3±8.2 years, and the mean Cobb angle was 49.6°±17.7°. The mean follow-up time was 22.0±11.1 years before bracing and 8.7±3.3 years after bracing. For both types of scoliosis, the rate of progression decreased from 1.28°±.79°/y before to .21°±.43°/y after bracing (P<.0001). For degenerative and idiopathic scoliosis, it dropped from 1.47°±.83°/y before to .24°±.43°/y after bracing (P<.0001) and .70°±.06°/y before to .24°±.43°/y after bracing (P=.03), respectively. CONCLUSIONS: For the first time, to our knowledge, this study suggests that underarm bracing may be effective in slowing down the rate of progression in adult scoliosis. Further prospective studies are needed to confirm these results.

Changes in spinal inhibitory networks induced by furosemide in humans.

During neural development in animals, GABAergic and glycinergic neurons are first excitatory, and then become inhibitory in the mature state. This developmental shift is due mainly to strong expression of the cation-chloride K-Cl cotransporter 2 (KCC2) and down-regulation of Na-K-Cl cotransporter 1 (NKCC1) during maturation. The down-regulation of co-transporter KCC2 after spinal cord transection in animals leads to the depolarising (excitatory) action of GABA and glycine and thus results in a reduction of inhibitory synaptic efficiency. Furosemide, a loop diuretic, has been shown to selectively and reversibly block inhibitory postsynaptic potentials without affecting excitatory postsynaptic potentials in animal spinal neurons. Moreover, this diuretic has been also demonstrated to block the cation-chloride co-transporters. Here, we used furosemide to demonstrate changes in spinal inhibitory networks in healthy human subjects. Non-invasive electrophysiological techniques were used to assess presynaptic inhibition, postsynaptic inhibition and the efficacy of synaptic transmission between muscle afferent terminals and soleus motoneurons in the spinal cord. Orally administered furosemide, at doses commonly used in the clinic (40 mg), significantly reduced spinal inhibitory interneuronal activity for at least 70 min from intake compared to control experiments in the same subjects while no changes were observed in the efficacy of synaptic transmission between muscle afferent terminals and soleus motoneurons. The reduction of inhibition was dose-dependent. Our results provide indirect evidence that reversible changes in the cation-chloride transport system induce modulations of inhibitory neuronal activity at spinal cord level in humans.

Anodal transcranial direct current stimulation of the motor cortex induces opposite modulation of reciprocal inhibition in wrist extensor and flexor.

Transcranial direct current stimulation (tDCS) is used as a noninvasive tool to modulate brain excitability in humans. Recently, several studies have demonstrated that tDCS applied over the motor cortex also modulates spinal neural network excitability and therefore can be used to explore the corticospinal control acting on spinal neurons. Previously, we showed that reciprocal inhibition directed to wrist flexor motoneurons is enhanced during contralateral anodal tDCS, but it is likely that the corticospinal control acting on spinal networks controlling wrist flexors and extensors is not similar. The primary aim of the study was to explore the effects of anodal tDCS on reciprocal inhibition directed to wrist extensor motoneurons. To further examine the supraspinal control acting on the reciprocal inhibition between wrist flexors and extensors, we also explored the effects of the tDCS applied to the ipsilateral hand motor area. In healthy volunteers, we tested the effects induced by sham and anodal tDCS on reciprocal inhibition pathways innervating wrist muscles. Reciprocal inhibition directed from flexor to extensor muscles and the reverse situation, i.e., reciprocal inhibition, directed from extensors to flexors were studied in parallel with the H reflex technique. Our main finding was that contralateral anodal tDCS induces opposing effects on reciprocal inhibition: it decreases reciprocal inhibition directed from flexors to extensors, but it increases reciprocal inhibition directed from extensors to flexors. The functional result of these opposite effects on reciprocal inhibition seems to favor wrist extension excitability, suggesting an asymmetric descending control onto the interneurons that mediate reciprocal inhibition.

[Neurologic disabilities after road traffic accidents]. / Le handicap neurologique après accidents du trafic.

Car crashes lead to central nervous system damages inducing mainly either locomotor and bladder in case of spinal injury or cognitive impairment after brain injury. Recently the way of management of locomotor disability changes a lot due to economical, philosophical reasons and scientific progress. A better understanding of mechanisms of ladder dysfunctions after spinal lesions lead to introduce new therapeutics solution in these patients which significantly reduce mortality and morbidity. Cognitive impairments following traumatic brain injury are now better characterised and their management becomes more efficient.

The use of a tool requires its incorporation into the movement: evidence from stick-pointing in apraxia.

When using a tool, the agent has to control the movement of this implement to perform an efficient action. While perceptual assimilation of a tool has been shown to occur during its use, the incorporation of an implement into the control of movements has received little attention. Here, we investigated the relation between the ability to integrate an object into motor coordination, and tool use. Apraxic patients impaired for familiar tool use were asked to point at targets located at various distances using either their finger, or two sticks of different lengths (23 and 53 cm). Left-brain damaged patients without apraxia participated as controls. Movement kinematics were analysed, with a particular focus on the working point (WP) of the action, defined as the tip of the finger or stick. Control patients produced movements with similar kinematic characteristics in all conditions, and were slightly less accurate with the sticks than with their finger. In contrast, more than half of the apraxics (6/10) showed various degrees of impairment when pointing with the sticks, manifested by deviant and inefficient motor strategies and abnormally large errors. In light of previous work in motor control and kinematics, it is argued that this reflects a deficit in anticipatively controlling a WP located in the stick, that is, in integrating the stick into the movement. We propose that this impairment might be related to dysfunction of the processes involved in dynamic body representation, which needs to be extended to include the tool to be used. Future directions are discussed to further characterize the relation between object incorporation and tool use, and its relevance for understanding apraxia and the neural bases of tool use.

Intrathecal baclofen infusion for ambulant children with cerebral palsy.

This study assessed the effects of continuous intrathecal infusion of baclofen on the gait of ambulant children with cerebral palsy. Details, collected retrospectively before and after pump implantation, included Gillette Functional Assessment Questionnaire score, use of walking aids, Ashworth Scale score, and joint angle at which the stretch reflex was triggered. Twenty-one ambulant children and young adults with cerebral palsy were included. Their mean age was 11 years and 10 months (standard deviation, 4 years and 10 months; range, 6-22 years). The mean length of treatment was 25.8 months (range, 5-75 months). After treatment, the lower-limb Ashworth score decreased by 1.4 points (standard deviation, 0.52), and the Gillette Functional Assessment Questionnaire score increased significantly, from 5.04 (standard deviation, 2.08) to 6.09 (standard deviation, 2.05) (P < 0.05). Seven children were able to use less supportive walking aids. Continuous intrathecal baclofen infusion appears to decrease spasticity and improve the gait capacity of children with cerebral palsy. Prospective, controlled studies are necessary to prove the functional effect of intrathecal baclofen infusion.

Relevance of botulinum toxin injection and nerve block of rectus femoris to kinematic and functional parameters of stiff knee gait in hemiplegic adults.

Stiff knee gait (SKG) is common in hemiplegic patients. The main focus of treatment is rectus femoris (RF) spasticity. The aims of this study were to evaluate the effect of botulinum toxin injection (BTI) in the RF muscle on peak knee flexion during swing phase and its quantitative and functional impact on gait. We also wished to evaluate the correlation between the effects of nerve block and BTI on peak knee flexion. 10 adult hemiplegic subjects (>6 months post stroke or traumatic brain injury) with SKG and inappropriate RF EMG activity during mid-swing phase were included. 3D gait analysis, clinical and functional assessments (Timed Up and Go test, 10 m walk test, 6 min walk test and the time taken to ascend and descend a flight of stairs) were performed initially, 30 min after anaesthetic block of the RF nerve and one month post BTI. After BTI, there was a significant increase in knee flexion (8 degrees average) and a tendency towards improvement in gait and functional parameters. The effect of the nerve block on peak knee flexion was significantly correlated with the effect of BTI (11 degrees average increase in peak knee flexion after nerve block). We challenge the relevance of RF nerve blocks in this population when EMG and kinematic data are available. Our results indicate that BTI is an effective treatment for SKG in adult hemiplegic subjects, with a significant increase in peak knee flexion, no reduction in hip flexion and a tendency towards functional improvements.

Furosemide Unmasks Inhibitory Dysfunction after Spinal Cord Injury in Humans: Implications for Spasticity.

Spasticity after spinal cord injury has considerable quality of life implications, impacts on rehabilitation efforts and necessitates long-term multi-disciplinary pharmacological and non-pharmacological management. The potassium chloride co-transporter (KCC2) plays a central role in intracellular chloride homeostasis and the inhibitory function of mature neurons. Animal studies consistently have demonstrated a downregulation of KCC2 activity after spinal cord transection, causing a shift from the inhibitory action of gamma-aminobutyric acid and glycine to an excitatory effect. Furosemide, a recognized KCC2 antagonist in animals, blocks the formation of inhibitory post-synaptic potentials in spinal motoneurons without affecting excitatory post-synaptic potentials. Based on observations in animals studies, we hypothesized that furosemide may be used to unmask KCC2 downregulation after spinal cord injury in humans, which contributes to reflex hyperexcitability. We have shown previously that furosemide reduces both pre-synaptic and post-synaptic inhibition in healthy subjects without altering monosynaptic excitatory transmission. These findings provide evidence that furosemide may be used in humans to evaluate inhibitory synapses in the spinal cord. In this present study, we show that furosemide fails to modulate both pre- and post-synaptic inhibitions relayed to soleus spinal motor neurons in persons with spinal cord injury. The lack of furosemide effect after spinal cord injury suggests KCC2 dysfunction in humans, resulting in reduced inhibitory synaptic transmission in spinal neurons. Our findings suggest that KCC2 dysfunction may be an important etiological factor in hyperreflexia after spinal cord injury. These observations may pave the way to novel therapeutic strategies against spasticity centered on chloride homeostasis.

An accelerometry-based comparison of 2 robotic assistive devices for treadmill training of gait.

OBJECTIVE: Two commercial robotic devices, the Gait Trainer (GT) and the Lokomat (LOKO), assist task-oriented practice of walking. The gait patterns induced by these motor-driven devices have not been characterized and compared. METHODS: A healthy participant chose the most comfortable gait pattern on each device and for treadmill (TM) walking at 1, 2 (maximum for the GT), and 3 km/h and over ground at similar speeds. A system of accelerometers on the thighs and feet allowed the calculation of spatiotemporal features and accelerations during the gait cycle. RESULTS: At the 1 and 2 km/h speed settings, single-limb stance times were prolonged on the devices compared with overground walking. Differences on the LOKO were decreased by adjusting the hip and knee angles and step length. At the 3 km/h setting, the LOKO approximated the participant's overground parameters. Irregular accelerations and decelerations from toe-off to heel contact were induced by the devices, especially at slower speeds. CONCLUSIONS: The LOKO and GT impose mechanical constraints that may alter leg accelerations-decelerations during stance and swing phases, as well as stance duration, especially at their slower speed settings, that are not found during TM and overground walking. The potential impact of these perturbations on training to improve gait needs further study.

Assessing of imagined and real expanded Timed Up and Go tests in patients with chronic stroke: A case-control study.

OBJECTIVE: To assess temporal congruence (the difference in performance-time and time to imagine) between the sub-tasks of the Expanded Timed Up and Go (ETUG) and imagined ETUG (iETUG) tests in patients with hemiparesis following unilateral hemispheric stroke, and to compare the results with those for with healthy subjects. DESIGN: Case-controlled study. Subject/patients: Twenty patients with chronic stroke and 20 healthy subjects. METHODS: TUG, ETUG and iETUG test performance times were recorded for all participants. Temporal congruence was calculated with the following formula: (ETUG-iETUG)/[(ETUG+iETUG)/2]*100. RESULTS: Patients' performances were slower than those of healthy subjects for all 5 sub-tasks of the TUG, ETUG and iETUG tests. However, there was no significant difference in temporal congruence between healthy subjects and patients. Intragroup analysis showed significant differences between the executed and the imagined conditions for both groups for the "walking", "turn around" and "sitting" phases (healthy subjects p = 0.01, p = 0.03, p = 0.03, and patients p = 0.01, p = 0.003, p = 0.003, respectively). CONCLUSION: Temporal congruence was similar for healthy subjects and patients for all sub-tasks of the ETUG test. Moreover, temporal congruence was reduced for the same sub-tasks of the ETUG test in patients and healthy subjects. This suggests that the motor imagery involved the same cerebral structures in both groups, probably including the cerebellum, since it was intact in all patients.

Evaluating the Effect of Cognitive Dysfunction on Mental Imagery in Patients with Stroke Using Temporal Congruence and the Imagined 'Timed Up and Go' Test (iTUG).

BACKGROUND: Motor imagery (MI) capacity may be altered following stroke. MI is evaluated by measuring temporal congruence between the timed performance of an imagined and an executed task. Temporal congruence between imagined and physical gait-related activities has not been evaluated following stroke. Moreover, the effect of cognitive dysfunction on temporal congruence is not known. OBJECTIVE: To assess temporal congruence between the Timed Up and Go test (TUG) and the imagined TUG (iTUG) tests in patients with stroke and to investigate the role played by cognitive dysfunctions in changes in temporal congruence. METHODS: TUG and iTUG performance were recorded and compared in twenty patients with chronic stroke and 20 controls. Cognitive function was measured using the Montreal Cognitive Assessment (MOCA), the Frontal Assessment Battery at Bedside (FAB) and the Bells Test. RESULTS: The temporal congruence of the patients with stroke was significantly altered compared to the controls, indicating a loss of MI capacity (respectively 45.11 ±35.11 vs 24.36 ±17.91, p = 0.02). Furthermore, iTUG test results were positively correlated with pathological scores on the Bells Test (r = 0.085, p = 0.013), likely suggesting that impairment of attention was a contributing factor. CONCLUSION: These results highlight the importance of evaluating potential attention disorder in patients with stroke to optimise the use of MI for rehabilitation and recovery. However further study is needed to determine how MI should be used in the case of cognitive dysfunction.

Reliability and validity of bilateral thigh and foot accelerometry measures of walking in healthy and hemiparetic subjects.

OBJECTIVE: Measures of walking ability in large clinical trials are usually limited to a timed short-distance walk and the distance walked in a fixed time. A new integrated system of 5 accelerometers was tested for reliability and compared to a footswitch system to determine if the accelerometers offered a practical option for the acquisition of spatiotemporal gait parameters. METHODS: Leg accelerations and decelerations were defined in relation to simultaneous kinematic and electromyographic data acquired from a healthy subject. Eight healthy adults and 6 independent ambulators with hemiparetic stroke walked 15 m at 2 different speeds wearing both the accelerometers and footswitches. Twelve healthy subjects walked at 5 different speeds repeated 3 times on each of 2 days wearing the accelerometers. Walking speed, cadence, stride length, and single- and double-limb support, swing, and stance times were calculated. RESULTS: No differences (t test, P > 0.2) were found between footswitch and accelerometer variables when comparing all left or right legs in healthy subjects and all paretic or unaffected legs in stroke subjects. A 2-way nested ANOVA model (speed, left and right legs, trial, and session) with the accelerometers at walking speeds from 0.5 to 1.8 m/s revealed high reproducibility of all measures. CONCLUSIONS: The accelerometry system provided reliable and valid spatiotemporal measures of gait for the upper range of speeds likely to be targeted for rehabilitation interventions in ambulatory subjects.

Human treadmill walking needs attention.

BACKGROUND: The aim of the study was to assess the attentional requirements of steady state treadmill walking in human subjects using a dual task paradigm. The extent of decrement of a secondary (cognitive) RT task provides a measure of the attentional resources required to maintain performance of the primary (locomotor) task. Varying the level of difficulty of the reaction time (RT) task is used to verify the priority of allocation of attentional resources. METHODS: 11 healthy adult subjects were required to walk while simultaneously performing a RT task. Participants were instructed to bite a pressure transducer placed in the mouth as quickly as possible in response to an unpredictable electrical stimulation applied on the back of the neck. Each subject was tested under five different experimental conditions: simple RT task alone and while walking, recognition RT task alone and while walking, walking alone. A foot switch system composed of a pressure sensitive sensor was placed under the heel and forefoot of each foot to determine the gait cycle duration. RESULTS: Gait cycle duration was unchanged (p > 0.05) by the addition of the RT task. Regardless of the level of difficulty of the RT task, the RTs were longer during treadmill walking than in sitting conditions (p < 0.01) indicating that an increased amount of resources are required for the maintainance of walking performance on a treadmill at a steady state. No interaction (p > 0.05) was found between the attentional demand of the walking task and the decrement of performance found in the RT task under varying levels of difficulty. This finding suggests that the healthy subjects prioritized the control of walking at the expense of cognitive performance. CONCLUSION: We conclude that treadmill walking in young adults is not a purely automatic task. The methodology and outcome measures used in this study provide an assessment of the attentional resources required by walking on the treadmill at a steady state.

Central analgesic effect of ketoprofen in humans: electrophysiological evidence for a supraspinal mechanism in a double-blind and cross-over study.

The aims of this study were: (1) to test the hypothesis of a central analgesic effect of the aspirin-like drug ketoprofen and (2) to attempt to differentiate between a spinal and a supraspinal mechanism in this possible central action. The threshold of the nociceptive flexion reflex from the biceps femoris muscle elicited by sural nerve stimulation was studied before and after a double-blind, cross-over and randomized intravenous injection of ketoprofen (100 mg in 5 ml saline) and saline (5 ml) in 2 groups of volunteers. The first one was composed of 10 normal subjects while the second consisted of 8 paraplegic patients with complete spinal section of traumatic origin. In normal subjects, ketoprofen injection resulted in a rapid and significant increase (+68%) of the threshold of the nociceptive reflex, while saline injection produced a slow increase of only 17% of this threshold. In contrast, in paraplegic patients, neither ketoprofen nor saline produced any significant change in the nociceptive reflex threshold. A supraspinal involvement in the central analgesic effect of this drug is discussed.

Cortical reorganization allows for motor recovery after crossed cerebrocerebellar atrophy.

The authors report the case of a 33-year-old woman who exhibited, at the age of 17, a left-sided hemiplegia, which was followed by good motor recovery, though with a permanent deficit in fine finger movements. She had a widespread loss of neural tissue in the right hemisphere (crossed cerebrocerebellar atrophy), including (1) marked atrophy and thinning of the precentral and postcentral gyri; (2) widespread deep white matter destruction, including the corticospinal tract; and (3) crossed cerebellar atrophy. Except over the supplementary motor area (SMA), transcranial magnetic stimulation did not elicit motor evoked potentials in the affected hand. Nevertheless, during opening and closing of the affected hand, functional magnetic resonance imaging showed an activation of the lesioned primary sensorimotor cortex (SMC), as well as of the intact SMA and the parietal areas, but not of the ipsilateral motor areas. The authors speculate that recovery was achieved by a motor command generated in the SMC and the parietal cortex, passing through corticospinal axons originating in the SMA.

Transcranial direct-current stimulation reduced the excitability of diaphragmatic corticospinal pathways whatever the polarity used.

We investigated effects of transcranial direct-current stimulation (tDCS) on the diaphragmatic corticospinal pathways in healthy human. Anodal, cathodal, and sham tDCS were randomly applied upon the left diaphragmatic motor cortex in twelve healthy right-handed men. Corticospinal pathways excitability was assessed by means of transcranial magnetic stimulation (TMS) elicited motor-evoked-potential (MEP). For each tDCS condition, MEPs were recorded before (Pre) tDCS then after 10 min (Post1, at tDCS discontinuation in the anodal and cathodal sessions) and 20 min (Post2). As result, both anodal and cathodal tDCS significantly decreased MEP amplitude of the right hemidiaphragm at both Post1 and Post2, versus Pre. MEP amplitude was unchanged versus Pre during the sham condition. The effects of cathodal and anodal tDCS applied to the diaphragm motor cortex differ from those observed during tDCS of the limb motor cortex. These differences may be related to specific characteristics of the diaphragmatic corticospinal pathways as well as to the diaphragm's functional peculiarities compared with the limb muscles.

Botulinum toxin effect on voluntary and stretch reflex-related torque produced by the quadriceps: an isokinetic pilot study.

BACKGROUND: An understanding of the mechanical effects of botulinum toxin type A (BoNT A) on spastic and voluntary muscle contraction may help predict functional responders. OBJECTIVE: To compare the effect of BoNT A on the voluntary and stretch reflex-related torques produced by activation of the rectus femoris (RF). METHODS: This was a prospective open study where 15 incomplete spinal cord injury patients, impaired by a stiff-knee gait, with RF hyperactivity in mid-swing quantified by formal gait analysis (GA), were assessed before and after RF BoNT A injection (Botox, 200 UI). MAIN OUTCOME MEASURES: Included isokinetic peak torque (and angle at peak torque) at 0° (supine) and 90° (seated) during passive stretch (10 deg/s, 90 deg/s, and 150 deg/s), and voluntary contraction (60 deg/s) of the quadriceps. Secondary measures included impairment by Modified Tardieu Scale (MTS), peak knee flexion and spatial-temporal data by GA, activity (6-minute walking test, timed stair climbing), and discomfort (Verbal Rating Scale). RESULTS: Voluntary torque decreased (-16%; P = .0004) but with only a trend toward a decrease in stretch reflex-related torque. The angle at spastic torque increased at 90 deg/s (+5°; P = .03), whereas MTS, peak knee flexion (+4°; P = .01), spatial-temporal data, timed stair climbing test (25%; P = .02), and discomfort were significantly improved. CONCLUSION: BoNT A appeared to delay the stretch-reflex angle at peak torque, whereas the voluntary torque decreased. After strict patient selection, BoNT A injection into the RF muscle led to improvements in impairment, activity, and discomfort.

Walking velocity and lower limb coordination in hemiparesis.

BACKGROUND/OBJECTIVE: Gait training at fast speed has been suggested as an efficient rehabilitation method in hemiparesis. We investigated whether maximal speed walking might positively impact inter-segmental coordination in hemiparetic subjects. METHODS: We measured thigh-shank and shank-foot coordination in the sagittal plane during gait at preferred (P) and maximal (M) speed using the continuous relative phase (CRP), in 20 healthy and 27 hemiparetic subjects. We calculated the root-mean square (CRP(RMS)) and its variability (CRP(SD)) over each phase of the gait cycle. A small CRP(RMS) indicates in-phasing, i.e. high level of synchronization between two segments along the gait cycle. A small CRP(SD) indicates high stability of the inter-segmental coordination across gait cycles. RESULTS: Increase from preferred to maximal speed was 57% in healthy and 49% in hemiparetic subjects (difference NS). In healthy subjects, the main change was shank-foot in-phasing at stance (CRP(Shank-Foot/RMS), P, 98±10; M, 67±12, p<0.001). In hemiparetic subjects, we also found shank-foot in-phasing at late stance bilaterally (non-paretic CRP(Shank-Foot/RMS), P, 37±9; M, 29±8, p<0.001; paretic CRP(Shank-Foot/RMS), P, 38±13; M, 32±12, p<0.001), and thigh-shank in-phasing at mid-stance in the non-paretic limb (CRP(Thigh-Shank/RMS), P, 57±9; M, 49±9, p<0.001). CRP(Thigh-Shank) variability diminished in the paretic limb (CRP(Thigh-Shank/SD), P, 18.3±6.3; M, 16.1±5.2, p<0.001). CONCLUSION: During gait velocity increase in hemiparesis, there is improvement of thigh-shank coordination stability in the paretic limb and of shank-foot synchronization at late stance bilaterally, which optimizes the propulsive phase similarly to healthy subjects. These findings may add incentive for rehabilitation clinicians to explore maximal velocity gait training in hemiparesis.

Affected and unaffected quantitative aspects of grip force control in hemiparetic patients after stroke.

Adequate grip force modulation is critical to manual dexterity and often impaired in hemiparetic stroke patients. Previous studies in hemiparetic patients suggest that aspects of grip force control may be differently affected by the lesion. We developed a visuomotor power grip force-tracking task allowing quantification of tracking error, force variability and release duration. We investigated force control in 24 chronic stroke patients with varying severity of hemiparesis and in healthy control subjects. Force tracking was performed at 10, 20, and 30% maximal voluntary contraction (MVC). Control subjects were also tested at absolute force levels similar to those of the patients. Patients tracking with their paretic hand at similar relative (%MVC) grip force levels showed increased error, force variability and release duration, but surprisingly, there was no difference in tracking error or variability between patients and control subjects performing at similar absolute force levels. Furthermore, patients improved their tracking performance across repeated blocks similar to control subjects. Release duration, however, was increased (also in the non-paretic hand), was force-independent and did not correlate with MVC strength. Of the three performance measures, only release duration explained some of the variance in arm and hand function (Frenchay Arm Test score), independent of MVC strength. The findings show (i) that hemiparetic stroke patients preserve the ability to modulate (generate and maintain) power grip force within their limited force range and (ii) that MVC grip strength and duration of grip release are differently affected and are two complementary predictors of arm function after stroke.

Wallerian degeneration in lateral cervical spinal cord detected with diffusion tensor imaging in four chronic stroke patients.

BACKGROUND AND PURPOSE: wallerian degeneration (WD) in descending motor tracts after stroke is described at the level of the internal capsule and the brainstem. We investigated whether diffusion tensor imaging (DTI) can detect degeneration in the lateral cervical spinal cord after stroke. METHODS: DTI at 1.5 T of the cervical spinal cord was performed in 4 chronic hemiparetic patients after ischemic stroke. Stroke lesions included the corticospinal tract. DTI was also performed in 12 healthy controls. Diffusion parameters were obtained for left and right (i) half and (ii) lateral spinal cord extending from C2 to C7. RESULTS: relative fractional anisotropy (FA) in the lateral tracts on the affected side compared with the unaffected side (left/right) was reduced in stroke patients as compared with controls (P= .007). FA was lowest in patients with severe upper limb hemiparesis. Relative apparent diffusion coefficient in the lateral tracts was increased in the patients (P= .03). CONCLUSIONS: this study provides preliminary evidence that DTI at 1.5 T can be used for identification and quantification of WD in the lateral cervical spinal cord in stroke patients. This may prove useful for prognosis of motor outcome after stroke.