Postural control deficits identify lingering post-concussion neurological deficits

Abstract

Concussion, or mild traumatic brain injury, incidence rates have reached epidemic levels and impaired postural control is a cardinal symptom. The purpose of this review is to provide an overview of the linear and non-linear assessments of post-concussion postural control. The current acute evaluation for concussion utilizes the subjective balance error scoring system (BESS) to assess postural control. While the sensitivity of the overall test battery is high, the sensitivity of the BESS is unacceptably low and, with repeat administration, is unable to accurately identify recovery. Sophisticated measures of postural control, utilizing traditional linear assessments, have identified impairments in postural control well beyond BESS recovery. Both assessments of quiet stance and gait have identified lingering impairments for at least 1 month post-concussion. Recently, the application of non-linear metrics to concussion recovery have begun to receive limited attention with the most commonly utilized metric being approximate entropy (ApEn). ApEn, most commonly in the medial-lateral plane, has successfully identified impaired postural control in the acute post-concussion timeframe even when linear assessments of instrumented measures are equivalent to healthy pre-injury values; unfortunately these studies have not gone beyond the acute phase of recovery. One study has identified lingering deficits in postural control, utilizing Shannon and Renyi entropy metrics, which persist at least through clinical recovery and return to participation. Finally, limited evidence from two studies suggest that individuals with a previous history of a single concussion, even months or years prior, may display altered ApEn metrics. Overall, non-linear metrics provide a fertile area for future study to further the understanding of postural control impairments acutely post-concussion and address the current challenge of sensitive identification of recovery.

Decreased Anticipatory Postural Adjustments During Gait Initiation Acutely Postconcussion

“…25, 43 The results of this study seek to further clarify and specify these disruptions. The preparatory component of the GI motor task is believed to be modulated by the supplementary motor area while the locomotor component is regulated by the primary motor cortex.…”

“…These findings are consistent with a conservative postural control strategy identified both acutely and chronically post-concussion. 21, 25, 40–42 …”

“…Impaired postural control is a cardinal sign of concussion; 25 however, there has been limited investigation of dynamic postural control and specifically the dynamically challenging ability to plan, initiate, and execute a step effectively. Therefore, the purpose of this study was to investigate impairments in dynamic postural control during the transitional motor task of GI in individuals acutely post-concussion.…”

Altered dynamic postural control during gait termination following concussion

“…[17] Gait performance is highly consistent in healthy college-aged recreational and student-athletes. [18] Specifically, changes in gait parameters (e.g., velocity, stride length) are most pronounced up to age 10, after which there are minimal changes in gait pattern. [17] Unlike quiet standing, unobstructed gait is less reliant on sensory feedback as both supraspinal planning (motor cortex and pyramidal tract) and central pattern generators are largely responsible for feedforward control.…”

Comparison of psychological response between concussion and musculoskeletal injury in collegiate athletes.

“…The current concussion RTP protocol is based on “passing” balance and cognitive tests as well as self-reporting asymptomatic; however, lingering neurobiological deficits beyond RTP are routinely reported in the literature (Buckley, Oldham, & Caccese, 2016; McCrea, Prichep, Powell, Chabot, & Barr, 2010; McCrory et al, 2013). Typically, these deficits are assessed individually per task (e.g., identified cognitive deficits); however, the influence of psychological response on physical or cognitive outcomes has received limited consideration.…”