CURRENT RESEARCH INVOLVING THE SATA:



Len TK, Neary JP. (2011). Cerebrovascular pathophysiology following mild traumatic brain injury. Clinical Physiology and Functional Imaging 31(2): 85 - 93. DOI: 10.1111/j.1475-097X.2010.00990.x

Mild traumatic brain injury (mTBI) or sport-induced concussion has recently become a prominent concern not only in the athletic setting (i.e. sports venue) but also in the general population. The majority of research to date has aimed at understanding the neurological and neuropsychological outcomes of injury as well as return-to-play guidelines. Remaining relatively unexamined has been the pathophysiological aspect of mTBI. Recent technological advances including transcranial Doppler ultrasound and near infrared spectroscopy have allowed researchers to examine the systemic effects of mTBI from rest to exercise, and during both asymptomatic and symptomatic conditions. In this review, we focus on the
current research available from both human and experimental (animal) studies surrounding the pathophysiology of mTBI. First, the quest for a unified definition of mTBI, its historical development and implications for future research is discussed. Finally, the impact of mTBI on the control and regulation of cerebral blood flow, cerebrovascular reactivity, cerebral oxygenation and neuroautonomic cardiovascular regulation, all of which may be compromised with mTBI, is discussed.

Len TK, Neary JP, Asmundson GJG, Goodman DG, Bjornson B, Bhambhani YN. (2011). Cerebrovascular reactivity impairment following sport-induced concussion. Medicine & Science in Sports & Exercise. DOI: 10.1249/MSS.0b013e3182249539

PURPOSE:: This study evaluated cerebrovascular reactivity (CVR) following a sport-induced concussion, also referred to as mild traumatic brain injury (mTBI), by monitoring middle cerebral artery blood velocity (vMCA) with transcranial Doppler ultrasonography (TCD) and simultaneous end-tidal carbon dioxide (PETCO2) measurements. METHODS:: Thirty-one athletes (16 - 25 years old) participated in this study. The participants were divided into two groups - healthy (n = 21) and mTBI (n = 10). Participants in the mTBI group suffered a mTBI within the last seven days (x¯ = 4.5 ± 1.1 days). Outcome measures included vMCA and PETCO2 in response to breath-holding (5 × 20 seconds, 40 seconds rest) and hyperventilation (5 × 20 seconds, 40 seconds rest). RESULTS:: Resting vMCA values between groups were not significantly different. Percentage change of vMCA was significantly different following the recovery period of the second hyperventilation (P = 0.034). mTBI subjects failed to return to resting levels following each breath-hold. End-tidal CO2 changes mirrored the vMCA changes. CONCLUSION:: These data suggest that normal CVR responses may be disrupted in the days immediately following occurrence of mTBI. Transcranial Doppler ultrasonography combined with expired gas measurements provides a useful method for assessing CVR impairment following mTBI. Further research, including serial monitoring following mTBI and analysis of CVR response to exercise, is warranted before any firm conclusions can be drawn.

 

Len TK, Neary JP. (2012). Autonomic dysregulation following mild traumatic brain injury. In KS Baker & NC Edwards (eds.), Brain injuries: New research. Hauppage, NY: Nova Publishing.

With upwards of 4 million sport-related head injuries occurring annually in the United States alone, mild traumatic brain injury (mTBI) is quickly becoming a primary concern in the medical community. Researchers have developed a sound understanding of the neurochemical and psychological aspects of mTBI but these areas are only one aspect of the injury needing consideration. As such, current return-to-play guidelines agree that the underlying physiological mechanisms of mTBI are not yet fully understood and warrant further investigation. Research into the area of mild traumatic brain injuries has evolved exponentially over the last two decades and as the understanding of these injuries develops, so do new ideas and concepts surrounding them. To date, the majority of research has been completed using the severe traumatic brain injury model. However, with the development of non-invasive monitoring technologies, researchers are quickly redefining the methods used to investigate mTBI. Technologies including transcranial Doppler, near-infrared spectroscopy, ballistocardiography, seismocardiography, and fMRI are now commonly being used in mTBI research. Persisting autonomic cardiovascular dysregulation following mTBI has been observed in athletes after suffering mTBI. It is known that the autonomic nervous system and the cardiovascular system become uncoupled following acute brain injury. This disconnect results in manifestations of altered heart rate variability and may possibly affect cerebral autoregulatory processes as well. This chapter will provide information surrounding autonomic dysfunction and its relationship with mTBI. Implications for future research and possible monitoring methods will also be discussed.