Faculty Bibliography

OBJECTIVES: Traumatic brain injury (TBI) has high morbidity and mortality in both civilian and military populations. Blast and other mechanisms of TBI damage the brain by causing neurons to disconnect and atrophy. Such traumatic axonal injury can lead to persistent vegetative and minimally conscious states (VS and MCS), for which limited treatment options exist, including physical, occupational, speech, and cognitive therapies. More than 60 000 patients have received vagus nerve stimulation (VNS) for epilepsy and depression. In addition to decreased seizure frequency and severity, patients report enhanced mood, reduced daytime sleepiness independent of seizure control, increased slow wave sleep, and improved cognition, memory, and quality of life. Early stimulation of the vagus nerve accelerates the rate and extent of behavioral and cognitive recovery after fluid percussion brain injury in rats. METHODS: We recently obtained Food and Drug Administration (FDA) approval for a pilot prospective randomized crossover trial to demonstrate objective improvement in clinical outcome by placement of a vagus nerve stimulator in patients who are recovering from severe TBI. Our hypothesis is that stimulation of the vagus nerve results in increased cerebral blood flow and metabolism in the forebrain, thalamus, and reticular formation, which promotes arousal and improved consciousness, thereby improving outcome after TBI resulting in MCS or VS. DISCUSSION: If this study demonstrates that VNS can safely and positively impact outcome, then a larger randomized prospective crossover trial will be proposed.

Abstract Long-term mortality is increased after mild traumatic brain injury (mTBI). Central cardiovascular-autonomic dysregulation resulting from subtle, trauma-induced brain lesions might contribute to cardiovascular events and fatalities. We investigated whether there is cardiovascular-autonomic dysregulation after mTBI. In 20 mTBI patients (37+/-13 years, 5-43 months post-injury) and 20 healthy persons (26+/-9 years), we monitored respiration, RR intervals (RRI), blood pressures (BP), while supine and upon standing. We calculated the root mean square successive RRI differences (RMSSD) reflecting cardiovagal modulation, the ratio of maximal and minimal RRIs around the 30th and 15th RRI upon standing (30:15 ratio) reflecting baroreflex sensitivity (BRS), spectral powers of parasympathetic high-frequency (HF: 0.15-0.5 Hz) RRI oscillations, of mainly sympathetic low-frequency (LF: 0.04-0.15 Hz) RRI oscillations, of sympathetic LF-BP oscillations, RRI-LF/HF-ratios reflecting sympathovagal balance, and the gain between BP and RRI oscillations as additional BRS index (BRS(gain)). We compared supine and standing parameters of patients and controls (repeated measures analysis of variance; significance: p<0.05). While supine, patients had lower RRIs (874.2+/-157.8 vs. 1024.3+/-165.4 ms), RMSSDs (30.1+/-23.6 vs. 56.3+/-31.4 ms), RRI-HF powers (298.1+/-309.8 vs. 1507.2+/-1591.4 ms(2)), and BRS(gain) (8.1+/-4.4 vs. 12.5+/-8.1 ms.mmHg(-1)), but higher RRI-LF/HF-ratios (3.0+/-1.9 vs. 1.2+/-0.7) than controls. Upon standing, RMSSDs and RRI-HF-powers decreased significantly in controls, but not in patients; patients had lower RRI-30:15-ratios (1.3+/-0.3 vs. 1.6+/-0.3) and RRI-LF-powers (2450.0+/-2110.3 vs. 4805.9+/-3453.5 ms(2)) than controls. While supine, mTBI patients had reduced cardiovagal modulation and BRS. Upon standing, their BRS was still reduced, and patients did not withdraw parasympathetic or augment sympathetic modulation adequately. Impaired autonomic modulation probably contributes to cardiovascular irregularities post-mTBI

Rehabilitation following traumatic brain injury (TBI) is best provided by an interdisciplinary team of health care providers that takes advantage of the unique skills of multiple specialists, as well as their combined strengths that address problems that cut across disciplines. The setting where rehabilitation is provided is determined by the medical stability of patients, their ability to tolerate intensive therapies, and their likelihood of community reintegration within a reasonable period of time. Successful rehabilitation requires prompt recognition and treatment of TBI-related medical, cognitive, and behavioral problems to promote recovery and enhance community reintegration, using a combination of rehabilitation modalities and medications