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.

A map of evidence using transcranial direct current stimulation (tDCS) to improve cognition in adults with traumatic brain injury (TBI)

Introduction

Cognition impairments often occur after a traumatic brain injury and occur at higher rates in military members. Cognitive symptoms impair daily function, including balance and life quality, years after the TBI. Current treatments to regain cognitive function after TBI, including medications and cognitive rehabilitation, have shown limited effectiveness. Transcranial direct current stimulation (tDCS) is a low-cost, non-invasive brain stimulation intervention that improves cognitive function in healthy adults and people with neuropsychologic diagnoses beyond current interventions. Despite the available evidence of the effectiveness of tDCS in improving cognition generally, only two small TBI trials have been conducted based on the most recent systematic review of tDCS effectiveness for cognition following neurological impairment. We found no tDCS studies that addressed TBI-related balance impairments.

Methods

A scoping review using a peer-reviewed search of eight databases was completed in July 2022. Two assessors completed a multi-step review and completed data extraction on included studies using a priori items recommended in tDCS and TBI research guidelines.

Results

A total of 399 results were reviewed for inclusion and 12 met the criteria and had data extracted from them by two assessors using Google Forms. Consensus on combined data results included a third assessor when needed. No studies using tDCS for cognition-related balance were found.

Discussion

Guidelines and technology measures increase the identification of brain differences that alter tDCS effects on cognition. People with mild-severe and acute-chronic TBI tolerated and benefited from tDCS. TBI-related cognition is understudied, and systematic research that incorporates recommended data elements is needed to advance tDCS interventions to improve cognition after TBI weeks to years after injury.

Inertial Sensor-Based Assessment of Static Balance in Athletes with Chronic Ankle Instability

The Balance Error Scoring System (BESS), a subjective examiner-based assessment, is often employed to assess postural balance in individuals with chronic ankle instability (CAI); however, inertial sensors may enhance the detection of balance deficits. This study aimed to compare the BESS results between the CAI and healthy groups using conventional BESS scores and inertial sensor data. The BESS test (six conditions: double-leg, single-leg, and tandem stances on firm and foam surfaces, respectively) was performed for the CAI (n = 16) and healthy control (n = 16) groups with inertial sensors mounted on the sacrum and anterior shank. The BESS score was calculated visually by the examiner by counting postural sway as an error based on the recorded video. The root mean square for resultant acceleration (RMS_acc) in the anteroposterior, mediolateral, and vertical directions was calculated from each inertial sensor affixed to the sacral and shank surfaces during the BESS test. The mixed-effects analysis of variance and unpaired t-test were used to assess the effects of group and condition on the BESS scores and RMS_acc. No significant between-group differences were found in the RMS_acc of the sacral and shank surfaces, and the BESS scores (P > 0.05), except for the total BESS score in the foam condition (CAI: 14.4 ± 3.7, control: 11.7 ± 3.4; P = 0.039). Significant main effects of the conditions were found with respect to the BESS scores and RMS_acc for the sacral and anterior shank (P < 0.05). The BESS test with inertial sensors can detect differences in the BESS conditions for athletes with CAI. However, our method could not detect any differences between the CAI and healthy groups.

Do sensorimotor control properties mediate sway in people with chronic balance complaints following mTBI?

BACKGROUND

Up to 40% of mild traumatic brain injuries (mTBI) can result in chronic unresolved symptoms, such as balance impairment, that persist beyond three months. Sensorimotor control, the collective coordination and regulation of both sensory and motor components of the postural control system, may underlie balance deficits in chronic mTBI. The aim of this study was to determine if the relationship between severity of impairment in chronic (> 3 months) mTBI and poorer balance performance was mediated by sensorimotor integration measures.

METHODS

Data were collected from 61 healthy controls and 58 mTBI participants suffering persistent balance problems. Participants completed questionnaires (Dizziness Handicap Inventory (DHI), Neurobehavioral Symptom Inventory (NSI), and Sports Concussion Assessment Tool Symptom Questionnaire (SCAT2)) and performed instrumented postural sway assessments and a test of Central Sensory Motor Integration (CSMI). Exploratory Factor Analysis was used to reduce the variables used within the mediation models to constructs of impairment (Impairment Severity - based on questionnaires), balance (Sway Dispersion - based on instrumented postural sway measures), and sensorimotor control (Sensory Weighting, Motor Activation and Time Delay - based on parameters from CSMI tests). Mediation analyses used path analysis to estimate the direct effect (between impairment and balance) and indirect (mediating) effects (from sensorimotor control).

RESULTS

Two out of three sensorimotor integration factors (Motor Activation and Time Delay) mediated the relationship between Impairment Severity and Sway Dispersion, however, there was no mediating effect of Sensory Weighting.

SIGNIFICANCE

These findings have clinical implications since rehabilitation of balance commonly focuses on sensory cues. Our findings indicate the importance of Motor Activation and Time Delay, and thus a focus on strategies to improve factors related to these constructs throughout the rehabilitative process (i.e., level of muscular contractions to control joint torques; response time to stimuli/perturbations) may improve a patient's balance control.