Scott C. Livingston

Differential Rates of Recovery After Acute Sport-related Concussion: Electrophysiologic, Symptomatic, and Neurocognitive Indices

Purpose To determine if motor evoked potentials (MEPs), postconcussion signs and symptoms, and neurocognitive functions follow a similar recovery pattern after concussion. Methods Nine collegiate athletes with acute concussion (>24 hours after injury) participated in this retrospective time series design. Transcranial magnetic stimulation was applied over the motor cortex, and MEPs were recorded from the contralateral upper extremity. Self-reported symptoms were evaluated using the Head Injury Scale, and the Concussion Resolution Index was used to assess neurocognitive function. All measures were repeated on days 3, 5, and 10 after injury. Results Composite scores on the Head Injury Scale were significantly higher on day 1 after injury (F3,51 = 15.3; P = 0.0001). Processing speed on the Concussion Resolution Index was slower on days 1, 3, and 5 compared with that on day 10 (F3,24 = 6.75; P = 0.0002). Median MEP latencies were significantly longer on day 10 compared with day 1 after concussion (t8 = −2.69; P = 0.03). Ulnar MEP amplitudes were significantly smaller on day 3 after concussion compared with day 5 (t8 = −3.48; P = 0.008). Conclusions Acutely concussed collegiate athletes demonstrate changes in MEPs, which persist for up to 10 days after injury and do not follow the same recovery pattern as symptoms and neuropsychological test performance. The apparent differential rates of recovery most likely indicate different pathophysiological processes occurring in the immediate postconcussion period.

A preliminary investigation of motor evoked potential abnormalities following sport-related concussion

Background: Assessment of concussion is primarily based on self-reported symptoms, neurological examination and neuropsychological testing. The neurophysiologic sequelae and the integrity of the corticomotor pathways could be obtained by evaluating motor evoked potentials (MEPs). Objectives: To compare MEPs obtained through transcranial magnetic stimulation (TMS) in acutely concussed and non-concussed collegiate athletes. Methods: Eighteen collegiate athletes (12 males, six females, aged 20.4 ± 1.3 years) including nine subjects with acute concussion (≤24 hours) matched to nine control subjects. TMS was applied over the motor cortex and MEP responses were recorded from the contralateral upper extremity. MEP thresholds (%), latencies (milliseconds per metre) and amplitudes were assessed. Central motor conduction time (CMCT) was calculated from MEP, M response and F wave latencies. Testing was performed on days 1, 3, 5 and 10 post-concussion. Results: Ulnar MEP amplitudes were significantly different between post-concussion days 3 and 5 (F3,48 = 3.13, p = 0.041) with smaller amplitudes recorded on day 3 (0.28 ± 0.10 ms m−1). Median MEP latencies were significantly longer (F3,48 = 4.53, p = 0.023) 10 days post-concussion (27.1 ± 1.4 ms m−1) compared to day 1 (25.7 ± 1.5 ms m−1). No significant differences for motor thresholds or CMCTs were observed (p > 0.05). Conclusion: MEP abnormalities among acutely concussed collegiate athletes provide direct electrophysiologic evidence for the immediate effects of concussion.

Visual perturbation impacts upright postural stability in athletes with an acute concussion

ABSTRACT Objective: The impact that visual perturbation has on upright postural stability in an athlete with a concussion has not been established. The present study aimed to characterize the influence that visual perturbation stimuli have on upright balance among athletes with acute concussions. Design: A 2X2X2 repeated measure designed was used. Method: The present study examined the influence visual perturbation has on individuals suffering from an acute concussion. Fourteen participants (7 with a concussion and 7 matched controls) underwent various balance assessments with and without visual perturbation. Results: Overall, athletes with acute concussions demonstrated impairments in balance 24–48 hours following a concussion. However, when assessed using a visual perturbation task, athletes with acute concussions demonstrated improved balance, while control subjects did not show any significant changes during the same visual perturbation task. Conclusion: An athlete’s ability to disregard visual perturbation stimuli is imperative for successful participation in sports. Due to the observed alterations in balance when given a visual perturbation task, it is suggested that athletes with acute concussions place more attention on the balance task and may disregard other less meaningful tasks.

Differentiating Concussion From Intracranial Pathology in Athletes

Clinical Scenario: A cerebral concussion is a traumatically induced transient disturbance of brain function characterized by a complex pathophysiologic process and is classified as a subset of mild traumatic brain injury. The occurrence of intracranial lesions after sport-related head injury is relatively uncommon, but the possibility of serious intracranial injury (ICI) should be included in the differential diagnosis. ICIs are potentially life threatening and necessitate urgent medical management; therefore, prompt recognition and evaluation are critical to proper medical management. One of the primary objectives of the initial evaluation is to determine if the concussed athlete has an acute traumatic ICI. Athletic trainers must be able promptly recognize clinical signs and symptoms that will enable them to accurately differentiate between a concussion (ie, a closed head injury not associated with significant ICI) and an ICI. The identification of predictors of intracranial lesions is, however, relatively broad. Focused Clinical Question: Which clinical examination findings (ie, clinical signs and symptoms) indicate possible intracranial pathology in individuals with acute closed head injuries?

Visual Cortices and their Impact on Sport-Related Concussion: A Review

Visual Cortices and their Impact on Sport-Related Concussion: A Review The human visual cortex is a complex anatomical system which involves inputs and outputs from multiple areas of the brain including both the ventral and dorsal visual pathways. These visual areas and pathways may be altered following a concussion (a subtype of mild traumatic brain injury or TBI) as a result of topdown processing in the brain. Theoretical models for changes occurring in the visual pathways derived from primate research can be applied to the visual cortex in humans following concussions. The purposes of this review article are to: (1) provide an overview of the two anatomical pathways of the human visual system, (2) describe the implications for the differential effects of brain injury in the dorsal and ventral visual pathways of individuals who have sustained a mild TBI, and (3) explain how frontal cortex function or dysfunction modulates both perception and action which take place in posterior parts of the brain.