Symptoms and Central Sensory Integration in People With Chronic mTBI: Clinical Implications.

INTRODUCTION: Balance deficits in people with chronic mild traumatic brain injury (mTBI; ≥3 months post-mTBI), thought to relate to central sensory integration deficits, are subtle and often difficult to detect. The purpose of this study was to determine the sensitivity of the instrumented modified clinical test of sensory integration for balance (mCTSIB) in identifying such balance deficits in people with symptomatic, chronic mTBI and to establish the associations between balance and mTBI symptom scores in the chronic mTBI group. METHODS: The Institutional Review Board approved these study methods. Forty-one people with chronic mTBI and balance complaints and 53 healthy controls performed the mCTSIB (eyes open/closed on firm/foam surfaces; EoFi, EcFi, EoFo, and EcFo) with a wearable sensor on their waist to quantify sway area (m2/s4). Sensory reweighting variables were calculated for the firm and foam stance conditions. A stopwatch provided the clinical outcome for the mCTSIB (time). Each participant completed the Neurobehavioral Symptom Inventory (NSI), which quantifies mTBI-related symptoms and provides a total score, as well as sub-scores on affective, cognitive, somatic, and vestibular domains. RESULTS: The mTBI group reported significantly higher symptom scores across each NSI sub-score (all Ps < .001). The mTBI group had a significantly larger sway area than the control group across all mCTSIB conditions and the mTBI group had significantly higher sensory reweighting scores compared to the control group on both the firm (P = .01) and foam (P = .04) surfaces. Within the mTBI group, the NSI vestibular score significantly related to the mCTSIB sway area EcFi (r = 0.38; P = .02), sway area EcFo (r = 0.43; P = .006), sensory reweighting firm (r = 0.33; P = .04), and sensory reweighting foam (r = 0.38; P = .02). The average sway area across the 4 mCTSIB conditions was significantly (area under the curve: 0.77; P < .001) better at differentiating groups than the mCTSIB clinical total score. The average sway area across the 4 mCTSIB conditions had a sensitivity of 73% and a specificity of 71%. The clinical mCTSIB outcome scores were not different between groups. CONCLUSION: People with chronic mTBI appear to have central sensory integration deficits detectable by instrumented measures of postural assessment. These findings suggest that central sensory integration should be targeted in rehabilitation for people with chronic mTBI.

Use of Wearable Sensors to Assess the Effects of Performing a Cognitive Task on Sensory Integration of Balance in Healthy Individuals.

This study investigated the effects of performing a cognitive task on the sensory integration of balance in healthy individuals. Ten subjects (five F/five M; 21.5 ± 2.17 years; 69.9 ± 3.4 inches; 155.6 ± 26.1 lbs; Caucasian), without known balance issues, performed the modified Clinical Test of Sensory Interaction of Balance (mCTSIB) with and without a cognitive task. The cognitive task involved counting down in threes from a randomly assigned number between 95 and 100. Postural sway area and postural sway jerk were assessed through the use of inertial sensors placed around the subjects' lower lumbar region. Each subject performed four trials for the four conditions of the mCTSIB: eyes open firm (EOFirm), eyes closed firm (ECFirm), eyes open foam (EOFoam), and eyes closed foam (ECFoam). We tested the effect of performing a cognitive task on the sensory integration of balance. We hypothesized that sensory cognitive interaction would be more apparent for more complex conditions and would be better assessed with postural sway jerk compared to postural sway area measure. With the addition of a cognitive task for the mCTSIB: (1) postural sway area increased in the baseline condition, i.e., EOFirm (p < 0.05), but did not increase in the most difficult condition, i.e., ECFoam; (2) postural sway jerk increased in all conditions of the mCTSIB (p < 0.05); (3) cognitive performance did not deteriorate across conditions of the mCTSIB. Postural sway jerk was shown to be a more sensitive measure in detecting the effect of a cognitive task on sensory integration for postural control. Overall, inertial sensors can be used to reliably assess postural sway differences related to sensory−cognitive integration.

Gait and Balance Changes with Investigational Peripheral Nerve Cell Therapy during Deep Brain Stimulation in People with Parkinson's Disease.

BACKGROUND: The efficacy of deep brain stimulation (DBS) and dopaminergic therapy is known to decrease over time. Hence, a new investigational approach combines implanting autologous injury-activated peripheral nerve grafts (APNG) at the time of bilateral DBS surgery to the globus pallidus interna. OBJECTIVES: In a study where APNG was unilaterally implanted into the substantia nigra, we explored the effects on clinical gait and balance assessments over two years in 14 individuals with Parkinson's disease. METHODS: Computerized gait and balance evaluations were performed without medication, and stimulation was in the off state for at least 12 h to best assess the role of APNG implantation alone. We hypothesized that APNG might improve gait and balance deficits associated with PD. RESULTS: While people with a degenerative movement disorder typically worsen with time, none of the gait parameters significantly changed across visits in this 24 month study. The postural stability item in the UPDRS did not worsen from baseline to the 24-month follow-up. However, we measured gait and balance improvements in the two most affected individuals, who had moderate PD. In these two individuals, we observed an increase in gait velocity and step length that persisted over 6 and 24 months. CONCLUSIONS: Participants did not show worsening of gait and balance performance in the off therapy state two years after surgery, while the two most severely affected participants showed improved performance. Further studies may better address the long-term maintanenace of these results.

Cerebellar White Matter Damage Is Associated With Postural Sway Deficits in People With Multiple Sclerosis.

OBJECTIVE: To assess how postural sway deficits during eyes open and closed relate to the integrity of cerebellar peduncles in individuals with multiple sclerosis (MS). DESIGN: Cross-sectional study. SETTING: Laboratory based setting. PARTICIPANTS: Twenty-nine adults with MS (Expanded Disability Status Scale: 2-4) and 15 adults without MS were recruited (N=44). Inclusion criteria for all participants were ability to maintain balance independently by standing on toes for 3 seconds, and no known biomechanical conditions affecting balance. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Postural sway using body-worn, inertial sensors during quiet standing, integrity of cerebellar peduncles quantified using diffusion-tensor imaging and clinical assessment scales for ataxia and balance. RESULTS: Radial diffusivity of the inferior cerebellar peduncle was related to postural sway measures during both eyes open and closed. In contrast, radial diffusivity of the superior cerebellar peduncle was related to postural sway only in stance with eyes open. CONCLUSIONS: The inferior cerebellar peduncle, which carries somatosensory information to the cerebellum, contributes to control of standing balance with or without visual inputs, consistent with the high dependence on somatosensory information for posture. The superior cerebellar peduncle, which carries cortical information to the cerebellum, contributes to control of standing posture only when vision is available. Radial diffusivity of the inferior cerebellar peduncle was related to reactive balance control, whereas radial diffusivity of the superior cerebellar peduncle was related to the kinetic component of the ataxia rating scale.

Inertial Sensor-Based Assessment of Central Sensory Integration for Balance After Mild Traumatic Brain Injury.

Introduction: Optimal balance control requires a complex integration of sensory information from the visual, vestibular, and proprioceptive systems. The goal of this study is to determine if the instrumented modified Clinical Test of Sensory Integration and Balance (mCTSIB) was impaired acutely after mild traumatic brain injury (mTBI) when postural sway under varying sensory conditions was measured with a wearable inertial sensor. Materials and Methods: Postural sway was assessed in athletes who had sustained a mTBI within the past 2-3 d (n = 38) and control athletes (n = 81). Postural sway was quantified with a wearable inertial sensor (Opal; APDM, Inc.) during four varying sensory conditions of quiet stance: (1) eyes open (EO) firm surface, (2) eyes closed (EC) firm surface, (3) eyes open (EO) foam surface, and (4) eyes closed (EC) foam surface. Sensory reweighting deficits were computed by comparing the postural sway area in eyes closed versus eyes open conditions for firm and foam condition. Results: Postural sway was higher for mTBI compared with the control group during three of the four conditions of instrumented mCTSIB (EO firm, EC firm, and EC foam; p < 0.05). Sensory reweighting deficits were evident for mTBI individuals compared with control group on foam surface (EC firm vs EO firm; p < 0.05) and not on firm surface (EC firm vs EO firm; p = 0.63). Conclusions: The results from this study highlight the importance of detecting postural sway deficits during sensorimotor integration in mild TBI individuals.

Instrumented Test of Sensory Integration for Balance: A Validation Study.

BACKGROUND AND PURPOSE: Abnormal postural sway is associated with an increase in risk of falls but is difficult for clinicians to accurately quantify without access to laboratory equipment. Instrumenting clinical outcome measures using body-worn movement monitors is a low-cost alternative. This is the first study to compare the modified Clinical Test of Sensory Integration for Balance (i-mCTSIB) to the laboratory test of the Sensory Organization Test (SOT) with dynamic posturography in a group of participants with Parkinson's disease (PD) and subtle balance limitations. The purpose of this study was to (1) determine the concurrent validity of the i-mCTSIB with the SOT (6 and 4 conditions) and (2) compare the i-mCTSIB and the SOT to differentiate between individuals with and without recent falls within the previous 6 months. METHODS: This cross-sectional study examined 26 participants with idiopathic PD who had a Motor Unified Parkinson's Disease Rating Scale score of 32.7 (13.5) out of 108. RESULTS: The composite and conditions 1 and 4 of the i-mCTSIB and SOT scores were significantly correlated: composite scores r = -0.64 (P ≤ .001), C1 r = -0.43 (P = .03), C3 r = -0.60 (P ≤ .01), and C4 r = -0.54 (P ≤ .001). A significant difference was observed in mean i-mCTSIB composite scores between fallers and nonfallers (P = .04). In contrast, the SOT composite was not significantly different between fallers and nonfallers (P = 0.31). DISCUSSION: The results suggest that the i-mCTSIB may be a valid and clinically meaningful measure of sensory organization in persons with PD, even those with mild postural instability as measured by the median Hoehn and Yahr score (2.0). Future research should evaluate predictive validity of the i-mCTSIB for prospective falls. CONCLUSION: The instrumented mCTSIB with portable, body-worn movement allows clinicians to quantify abnormal postural sway without the ceiling effects of clinical balance testing or the expense and importability of force plate technology in the SOT. Instrumenting mCTSIB may also distinguish between fallers and nonfallers.

Validity of the Instrumented Push and Release Test to Quantify Postural Responses in Persons With Multiple Sclerosis.

OBJECTIVE: To test the validity of wearable inertial sensors to provide objective measures of postural stepping responses to the push and release clinical test in people with multiple sclerosis. DESIGN: Cross-sectional study. SETTING: University medical center balance disorder laboratory. PARTICIPANTS: Total sample N=73; persons with multiple sclerosis (PwMS) n=52; healthy controls n=21. MAIN OUTCOME MEASURES: Stepping latency, time and number of steps required to reach stability, and initial step length were calculated using 3 inertial measurement units placed on participants' lumbar spine and feet. RESULTS: Correlations between inertial sensor measures and measures obtained from the laboratory-based systems were moderate to strong and statistically significant for all variables: time to release (r=.992), latency (r=.655), time to stability (r=.847), time of first heel strike (r=.665), number of steps (r=.825), and first step length (r=.592). Compared with healthy controls, PwMS demonstrated a longer time to stability and required a larger number of steps to reach stability. CONCLUSIONS: The instrumented push and release test is a valid measure of postural responses in PwMS and could be used as a clinical outcome measures for patient care decisions or for clinical trials aimed at improving postural control in PwMS.

Corpus Callosum Structural Integrity Is Associated With Postural Control Improvement in Persons With Multiple Sclerosis Who Have Minimal Disability.

BACKGROUND: Improvement of postural control in persons with multiple sclerosis (PwMS) is an important target for neurorehabilitation. Although PwMS are able to improve postural performance with training, the neural underpinnings of these improvements are poorly understood. OBJECTIVE: To understand the neural underpinnings of postural motor learning in PwMS. METHODS: Supraspinal white matter structural connectivity in PwMS was correlated with improvements in postural performance (balancing on an oscillating surface over 25 trials) and retention of improvements (24 hours later). RESULTS: Improvement in postural performance was directly correlated to microstructural integrity of white matter tracts, measured as radial diffusivity, in the corpus callosum, posterior parieto-sensorimotor fibers and the brainstem in PwMS. Within the corpus callosum, the genu and midbody (fibers connecting the prefrontal and primary motor cortices, respectively) were most strongly correlated to improvements in postural control. Twenty-four-hour retention was not correlated to radial diffusivity. CONCLUSION: PwMS who exhibited poorer white matter tract integrity connecting the cortical hemispheres via the corpus callosum showed the most difficulty learning to control balance on an unstable surface. Prediction of improvements in postural control through training (ie, motor learning) via structural imaging of the brain may allow for identification of individuals who are particularly well suited for postural rehabilitation interventions.

Trunk Muscle Coordination During Upward and Downward Reaching in Stroke Survivors.

In this study, we investigated deficits in coordination of trunk muscle modes involved in the stabilization of the trunk's trajectory for reaching upward and downward beyond functional arm length. Trunk muscle activity from 10 stroke survivors (8 men, 2 women; 64.1 ± 10.5 years old) and 9 healthy control subjects (7 men, 2 women; 59.3 ± 9.3 years old) was analyzed. Coordination of trunk muscle modes to stabilize the trunk trajectory was investigated using the uncontrolled manifold (UCM) analysis. The UCM analysis decomposes the variability of muscle modes into good and bad variability. The good variability does not affect the control of trunk motion, whereas the bad variability does. In stroke survivors, deficits in the ability to flexibly combine trunk muscle modes was associated with reduced ability to minimize those combinations of trunk muscle modes that led to an error in trunk trajectory (bad variability), and this had a greater effect on reaching upward. This reduced coordination of trunk muscle modes during reaching was correlated with a clinical measure of trunk impairment.

Postural Motor Learning Deficits in People With MS in Spatial but Not Temporal Control of Center of Mass.

BACKGROUND: Multiple sclerosis (MS) is associated with balance deficits resulting in falls and impaired mobility. Although rehabilitation has been recommended to address these balance deficits, the extent to which people with MS can learn and retain improvements in postural responses is unknown. AIM: To determine the ability of people with MS to improve postural control with surface perturbation training. METHODS: A total of 24 patients with mild MS and 14 age-matched controls underwent postural control training with a set pattern of continuous, forward-backward, sinusoidal, and surface translations provided by a force platform. Postural control was then tested the following day for retention. The primary outcome measures were the relative phase and center-of-mass (CoM) gain between the body CoM and the platform motion. RESULTS: People with MS demonstrated similar improvements in acquiring and retaining changes in the temporal control of the CoM despite significant deficits in postural motor performance at the baseline. Both MS and control groups learned to anticipate the pattern of forward-backward perturbations, so body CoM shifted from a phase-lag (age-matched controls [CS] = -7.1 ± 1.3; MS = -12.9 ± 1.0) toward a phase-lead (CS = -0.7 ± 1.8; MS = -6.1 ± 1.4) relationship with the surface oscillations. However, MS patients were not able to retain the changes in the spatial control of the CoM acquired during training. CONCLUSIONS: People with MS have the capacity to improve use of a feed-forward postural strategy with practice and retain the learned behavior for temporal not spatial control of CoM, despite their significant postural response impairments.

Relationship of diminished interjoint coordination after stroke to hand path consistency.

Differences between 12 left-brain (LCVA, 65.4 ± 11.7 years old) and 10 right-brain (RCVA, 61 ± 12.1 years old) chronic stroke survivors and 10 age-matched control adults in coordinating specific joint motions of the arm to stabilize hand path when reaching to a central target were investigated in this study. The importance of coordinating joints to stabilize hand path was tested by comparing results from uncontrolled manifold (UCM) analysis performed on experimental data versus simulated data where the covariation (coordination) between particular joint motions was removed from the original data set. UCM analysis allowed estimation of the joint configuration variance magnitude that led to hand path variability (V ORT), where the extent of increase in V ORT after removing a joint's covariation indicated how well coordinated its motion actually was with those of the other joints. The more strongly coordinated a joint was with other joints, the greater effect removal of its covariance should have on indices of hand path stability. For the paretic arm of stroke survivors, simulated removal of a joint's covariation, mainly that of shoulder with elbow and wrist, led to less change in the magnitude of V ORT compared to the same arm of control subjects. These findings confirm a reduced ability of the motion of proximal joint from paretic arm to combine flexibly with motions of the distal joints to stabilize hand path.

Trunk Muscle Coordination During Upward and Downward Reaching in Stroke Survivors.

In this study, we investigated deficits in coordination of trunk muscle modes involved in the stabilization of the trunk's trajectory for reaching upward and downward beyond functional arm length. Trunk muscle activity from 10 stroke survivors (8 men, 2 women; 64.1 ± 10.5 years old) and 9 healthy control subjects (7 men, 2 women; 59.3 ± 9.3 years old) was analyzed. Coordination of trunk muscle modes to stabilize the trunk trajectory was investigated using the uncontrolled manifold (UCM) analysis. The UCM analysis decomposes the variability of muscle modes into good and bad variability. The good variability does not affect the control of trunk motion, whereas the bad variability does. In stroke survivors, deficits in the ability to flexibly combine trunk muscle modes was associated with reduced ability to minimize those combinations of trunk muscle modes that led to an error in trunk trajectory (bad variability), and this had a greater effect on reaching upward. This reduced coordination of trunk muscle modes during reaching was correlated with a clinical measure of trunk impairment.

Timing variability of reach trajectories in left versus right hemisphere stroke.

This study investigated trajectory timing variability in right and left stroke survivors and healthy controls when reaching to a centrally located target under a fixed target condition or when the target could suddenly change position after reach onset. Trajectory timing variability was investigated with a novel method based on dynamic programming that identifies the steps required to time warp one trial's acceleration time series to match that of a reference trial. Greater trajectory timing variability of both hand and joint motions was found for the paretic arm of stroke survivors compared to their non-paretic arm or either arm of controls. Overall, the non-paretic left arm of the LCVA group and the left arm of controls had higher timing variability than the non-paretic right arm of the RCVA group and right arm of controls. The shoulder and elbow joint warping costs were consistent predictors of the hand's warping cost for both left and right arms only in the LCVA group, whereas the relationship between joint and hand warping costs was relatively weak in control subjects and less consistent across arms in the RCVA group. These results suggest that the left hemisphere may be more involved in trajectory timing, although the results may be confounded by skill differences between the arms in these right hand dominant participants. On the other hand, arm differences did not appear to be related to differences in targeting error. The paretic left arm of the RCVA exhibited greater trajectory timing variability than the paretic right arm of the LCVA group. This difference was highly correlated with the level of impairment of the arms. Generally, the effect of target uncertainty resulted in slightly greater trajectory timing variability for all participants. The results are discussed in light of previous studies of hemispheric differences in the control of reaching, in particular, left hemisphere specialization for temporal control of reaching movements.

Motor abundance contributes to resolving multiple kinematic task constraints.

This study investigated the use of motor abundance during the transport and placing of objects that required either precise or minimal orientation to the target. Analyses across repetitions of the structure of joint configuration variance relative to the position and orientation constraints were performed using the Uncontrolled Manifold (UCM) approach. Results indicated that the orientation constraint did not affect stability of the hand's spatial path. Orientation was weakly stabilized during the late transport phase independent of the orientation constraint, indicating no default synergy stabilizing orientation. Stabilization of orientation for conditions most requiring it for successful insertion of the object was present primarily during the adjustment phase. The results support the hypothesis that a major advantage of a control scheme that utilizes motor abundance is the ability to resolve multiple task constraints simultaneously without undue interference among them.