BACKGROUND: Little is known on the peripheral and central sensory contributions to persistent dizziness and imbalance following mild traumatic brain injury (mTBI). OBJECTIVE: To identify peripheral vestibular, central integrative, and oculomotor causes for chronic symptoms following mTBI. METHODS: Individuals with chronic mTBI symptoms and healthy controls (HC) completed a battery of oculomotor, peripheral vestibular and instrumented posturography evaluations and rated subjective symptoms on validated questionnaires. We defined abnormal oculomotor, peripheral vestibular, and central sensory integration for balance measures among mTBI participants as falling outside a 10-percentile cutoff determined from HC data. A X-squared test associated the proportion of normal and abnormal responses in each group. Partial Spearman’s rank correlations evaluated the relationships between chronic symptoms and measures of oculomotor, peripheral vestibular, and central function for balance control. RESULTS: The mTBI group (n = 58) had more abnormal measures of central sensory integration for balance than the HC (n = 61) group (mTBI: 41% –61%; HC: 10%, p’s < 0.001), but no differences on oculomotor and peripheral vestibular function (p > 0.113). Symptom severities were negatively correlated with central sensory integration for balance scores (p’s < 0.048). CONCLUSIONS: Ongoing balance complaints in people with chronic mTBI are explained more by central sensory integration dysfunction rather than peripheral vestibular or oculomotor dysfunction.

Imbalance is common following mild Traumatic Brain Injury (mTBI) and can persist months after the initial injury. To determine if mTBI subjects with chronic imbalance differed from healthy age- and sex-matched controls (HCs) we used both the Central SensoriMotor Integration (CSMI) test, which evaluates sensory integration, time delay, and motor activation properties and the standard Sensory Organization Test (SOT). Four CSMI conditions evoked center-of-mass sway in response to: surface tilts with eyes closed (SS/EC), surface tilts with eyes open viewing a fixed visual surround (SS/EO), visual surround tilts with eyes open standing on a fixed surface (VS/EO), and combined surface and visual tilts with eyes open (SS+VS/EO). The mTBI participants relied significantly more on visual cues during the VS/EO condition compared to HCs but had similar reliance on combinations of vestibular, visual, and proprioceptive cues for balance during SS/EC, SS/EO, and SS+VS/EO conditions. The mTBI participants had significantly longer time delays across all conditions and significantly decreased motor activation relative to HCs across conditions that included surface-tilt stimuli with a sizeable subgroup having a prominent increase in time delay coupled with reduced motor activation while demonstrating no vestibular sensory weighting deficits. Decreased motor activation compensates for increased time delay to maintain stability of the balance system but has the adverse consequence that sensitivity to both internal (e.g., sensory noise) and external disturbances is increased. Consistent with this increased sensitivity, SOT results for mTBI subjects showed increased sway across all SOT conditions relative to HCs with about 45% of mTBI subjects classified as having an “Aphysiologic” pattern based on published criteria. Thus, CSMI results provided a plausible physiological explanation for the aphysiologic SOT pattern. Overall results suggest that rehabilitation that focuses solely on sensory systems may be incomplete and may benefit from therapy aimed at enhancing rapid and vigorous responses to balance perturbations.

Baseline concussion assessments are advocated to provide an objective preinjury point of comparison for determining the extent of postconcussion neurological deficits and to assist with return-to-activity decision making. Many factors, including testing environment, proctor availability, and testing group size, can influence test accuracy and validity; however, it is unknown how self-reported fatigue affects test scores. To investigate the influence of self-reported fatigue and patient sex on baseline concussion assessment scores. Cross-sectional study; Level of evidence, 3. Participants included 494 healthy Division I college student-athletes (221 women, 273 men; mean ± SD age, 20.0 ± 1.3 years). During preseason baseline testing, participants were asked to rate their fatigue on a scale from 0 to 100 based on how they normally feel and function each day (0, completely exhausted; 100, completely awake and alert). Each participant then completed a multimodal baseline concussion assessment, including a graded symptom checklist (number of symptoms endorsed and total symptom severity score), Standardized Assessment of Concussion (SAC), Balance Error Scoring System (BESS), and CNS Vital Signs computerized neurocognitive testing. Multiple linear regressions tested whether self-reported fatigue and sex predicted baseline concussion examination scores. Athletes with higher self-reported fatigue levels (ß = –0.014, P < .01) and female athletes (ß = –0.216, P < .01) reported more total symptoms. Being male (ß = 0.856, P < .01) increased the likelihood of endorsing zero symptoms versus any symptoms by a factor of 2.40. Women also had significantly higher SAC scores (ß = 0.569, P < .001), BESS scores (ß = –2.747, P < .001), and CNS Vital Signs summary scores (ß = 4.506, P < .001). SAC, BESS, and CNS Vital Signs scores were not predicted by fatigue level (P > .05). Female athletes and fatigued athletes endorsed more symptoms and higher symptom severity at baseline. Using total symptom endorsement and total symptom severity scores as part of the postinjury management is a common practice. The current data suggest that levels of reported exhaustion can influence concussion assessment scores meant to represent a healthy baseline and likely would interfere with postinjury assessment scores.

Our purpose was to determine concussion mechanism and activity differences among three cohorts of football players: youth, high school, and college. Participants in this prospective cohort study were youth (ages 5–14 years, 118 teams, 310 team-seasons), high school (96 teams, 184 team-seasons), and college (34 teams, 71 team-seasons) football players. Athletic trainers collected athlete-exposure (AE) and concussion data during the 2012–2014 seasons. Injury mechanism referred to the object that made contact with the concussed player, resulting in the concussion. Injury activity referred to the type of football-specific activity that the player was involved in when the concussion was sustained. Injury proportion ratios (IPR) compared distributions of concussion mechanisms and activities among age levels. A total of 1429 concussions were reported over 1,981,284 AE across all levels (Rate: 0.72/1000AE). Overall, most concussions were caused by player contact (84.7%). During games, a greater proportion of youth football concussions (14.7%) were caused by surface contact than high school (7.3%, IPR = 2.02; 95% confidence interval [CI]: 1.10–3.72) and college (7.1%, IPR = 2.07, 95% CI: 1.02–4.23) football. Compared with college football concussions (90.2%), a smaller proportion of youth (80.0%, IPR = 0.89, 95% CI: 0.79–0.99) and high school (83.2%, IPR = 0.92, 95% CI: 0.86–0.99) football concussions were caused by player contact. A greater proportion of game youth football concussions (42.1%) occurred while an individual was being tackled than occurred in high school (23.2%, IPR = 1.81, 95% CI: 1.34–2.45) and college (23.0%, IPR = 1.83, 95% CI: 1.29–2.62) football. Findings were similar during practices. Compared with college football game concussions (15.8%), a smaller proportion of youth (6.3%, IPR = 0.40, 95% CI: 0.17–0.93) and high school (9.5%, IPR = 0.60, 95% CI: 0.38–0.95) football game concussions occurred while an individual was being blocked. Concussion mechanism and activity differences should be considered when developing concussion prevention and sport-safety methods specific to different age levels, in order to maximize effectiveness.