Principle Investigator: Christopher D. Ingersoll, PhD
Institution: University of Virginia, Charlottesville, VA
Title: Motor Evoked Potential Abnormalities Following Acute Concussion Among High School and Collegiate Athletes: Relationship to Post-Concussive Symptoms, Neuropsychological Test Scores, and Balance Error Scores.
Abstract: A transcranial magnetic stimulation (TMS) technique for recording motor evoked potentials (MEP) in concussed athletes will be examined. MEPs provide critical information about the excitability or inhibition of the primary motor cortex and the integrity of the descending motor pathways. MEP abnormalities in subjects with mild to severe head injuries have been reported but have not been evaluated in athletes with mild head injuries. Investigation of MEPs in a sports-related concussion population will increase our understanding of the pathophysiology of concussive injuries and will assist in the assessment and management of such injuries. The purposes of this study are to (1) examine MEPs in acutely concussed athletes and correlate these abnormalities to self-reported symptoms, neuropsychological test (NPT) performance, and balance error scores on a functional balance task, and (2) evaluate the impact of visual input and controlled mental activity on MEPs following concussion We hypothesize that (1) recently concussed athletes will demonstrate MEPs abnormalities over 1 to 15 days following injury, (2) self-reported symptoms, neuropsychological test scores, and balance error scores will be strongly correlated with MEP abnormalities, and (3) concussed subjects will demonstrate differences in MEPs under different visual input and mental activity conditions (at rest and during a functional balance task). A repeated measures design will be used to address the primary aims of this study. A 2 x 4 x 6 repeated measures design (group by visual/mental activity condition by time) will be used to address the secondary aim of the study. The dependent variables are motor thresholds, MEP latencies and amplitudes, central motor conduction time, concussion symptoms, NPT scores, and scores on a functional balance task. Symptoms will be recorded using a Head Injury Scale (HIS); balance will be assessed using the Balance Error Scoring System (BESS); the Concussion Resolution Index (CRI) will be used for neuropsychological assessment. TMS will be applied over the motor cortex with responses recorded in 2 distal upper limb muscles. Subjects will be tested under 4 different visual/controlled mental activity conditions; Serial testing will be conducted 1, 3, 5, 10, and 15 days following concussive injury. A multiple linear regression model will be used to determine the strength of correlation between MEPs and HIS, CRI and BESS scores; a two-way repeated measures MANOVA (a priori significance level P< .05) will be used to compare visual/mental activity conditions, with individual univariate ANOVAs and simple main effects testing used in the post hoc analyses.