Sex Differences in Sleep Architecture After Traumatic Brain Injury: Potential Implications on Short-Term Episodic Memory and Recovery

Sleep-wake disturbances (SWDs) are common after TBI and often extend into the chronic phase of recovery. Such disturbances in sleep can lead to deficits in executive functioning, attention, and memory consolidation, which may ultimately impact the recovery process. We examined whether SWDs post-TBI were associated with morbidity during the post-acute period. Particular attention was placed on the impact of sleep architecture on learning and memory. Because women are more likely to report SWDs, we examined sex as a biological variable. We also examined subjective quality of life, depression, and disability levels. Data were retrospectively analyzed for 57 TBI patients who underwent an overnight polysomnography. Medical records were reviewed to determine cognitive and functional status during the period of the sleep evaluation. Consideration was given to medications, owing to the fact that a high number of these are likely to have secondary influences on sleep characteristics. Women showed higher levels of disability and reported more depression and lower quality of life. A sex-dependent disruption in sleep architecture was observed, with women having lower percent time in REM sleep. An association between percent time in REM and better episodic memory scores was found. Melatonin utilization had a positive impact on REM duration. Improvements in understanding the impact of sleep-wake disturbances on post-TBI outcome will aid in defining targeted interventions for this population. Findings from this study support the hypothesis that decreases in REM sleep may contribute to chronic disability and underlie the importance of considering sex differences when addressing sleep.

Sleep-wake disturbances in supra-and infratentorial stroke: an analysis of post-acute sleep architecture and apnea

BACKGROUND AND PURPOSE

Sleep-wake disturbances (SWD) are common following stroke, and often extend into the post-acute to chronic periods of recovery. Of particular interest to recovery is a reduction in rapid eye movement (REM) sleep, as we know REM sleep to be important for learning and memory. While there is a breadth of evidence linking SWD and stroke, much less work has been done to identify and determine if differences in sleep architecture and apnea severity are dependent on stroke infarct topographies.

METHODS

A retrospective chart review was conducted of 48 ischemic stroke patients having underwent a full, overnight polysomnography (PSG). All patients were over 30 days post-injury (post-acute) at the time of the PSG. Patients were divided into supra- and infratentorial infarct topography groups based on available medical and imaging records. In addition to sleep study record review, cognitive and outcome measures were examined.

RESULTS

Results showed that patients with infratentorial stroke had poorer sleep efficiency, decreased REM sleep, and higher apnea hypopnea index (AHI) than those with supratentorial injuries. Longer continuous REM periods were correlated with higher verbal learning/memory scores, higher levels of positive affect, and lower levels of emotional/behavioral dyscontrol. Neither age nor AHI were significantly correlated with the amount or duration of REM. Slow-wave sleep was significantly reduced across both injury topographies.

CONCLUSIONS

Infratentorial ischemic stroke patients display significant disruptions in sleep architecture and may require close monitoring for SWDs in the post-acute period to maximize outcome potential. REM sleep is particularly affected when compared to supratentorial ischemic stroke.

Obstructive sleep apnea during the chronic stroke recovery period: Comparison between primary haemorrhagic and ischaemic events

The present study retrospectively determined the incidence of obstructive sleep apnea (OSA) after a primary haemorrhagic event compared to an ischaemic stroke during the post-acute recovery period ( x ¯ >3 months). Consideration of medications taken during the sleep evaluation provided additional information on the association between OSA and pathophysiological conditions that may increase the risk of a repeated cardiovascular event. The medical records from 103 patients that underwent a type I fully attended overnight polysomnography as a standard evaluation procedure at a rehabilitation facility were reviewed. Diagnosis of ischaemic or primary haemorrhagic stroke was obtained from a neurological report that was typically confirmed by imaging. Medications taken at the time of the sleep study were documented. Age-adjusted assessment of sleep-disordered breathing revealed a higher incidence of apnea and hypopnea in the ischaemic stroke group (p < 0.005). Patients with ischaemic stroke were also more likely to have severe OSA (p < 0.005). In comparison, a higher percentage of patients with haemorrhagic stroke had an apnea-hypopnea index <5 events/hr (p < 0.005). Those with an ischaemic stroke were taking more lipid lowering agents (p < 0.05). Results suggest that apnea is less prevalent after a haemorrhagic stroke, independent of hypertension, compared to an ischaemic stroke. An increase in predictive values for OSA was observed for indicators of diabetes (p < 0.05). These data indicate that it is relevant to consider stroke type when determining the risk of OSA during the chronic recovery period thus facilitating new strategies for stroke recurrence prevention.

Abstract P204: Stroke Topography Impacts Sleep Architecture in Post-Acute Stroke

Introduction/Objective: Sleep-wake disturbances (SWDs) are common amongst stroke patients; however, little work has been done on the effect of stroke location on sleep architecture. The aim of this study was to investigate the impact of stroke topography on prevalence and severity of SWDs in the post-acute phase of ischemic stroke recovery.

Methods: Ischemic stroke patients (n=55) were assessed for SWDs via overnight attended polysomnography in a post-acute rehabilitation setting. The mean age was 55 ± 1.4 years and mean latency from injury was 106 ± 11 days. Sleep measures included total sleep time (TST), sleep and REM latency, sleep efficiency, percent time in sleep stages, apnea/hypopnea index (AHI), wake after sleep onset (WASO), and arousal index. Patients who did not have at least four hours of TST were excluded. Stroke patients were identified as having supratentorial or infratentorial injuries.

Results: Results showed a significant difference between supratentorial and infratentorial stroke in regards to sleep efficiency, REM sleep, and sleep apnea. Patients with infratentorial stroke (n=15) displayed significantly poorer sleep efficiency (F(1,53)=12.386, p<.001), decreased REM sleep (F(1,53)=5.944), p<.05) and higher AHI (F(1,53)=4.698, p<.05). In addition to displaying a decreased amount of REM, infratentorial stroke patients displayed significantly shorter bouts of REM (F(1,52)=7.482, p<.01). Neither age nor AHI were significantly correlated with the amount or duration of REM (p>.05).

Conclusion: Infratentorial ischemic stroke patients display significant disruptions in sleep and may require close monitoring for sleep-wake disturbances in the post-acute period. REM sleep is particularly effected when compared to supratentorial ischemic stroke.

1129 Sex Dependent Effects on Sleep Architecture After Traumatic Brain Injury: Impact on Outcome

Introduction

Traumatic Brain Injury (TBI) is frequently associated with problems with sleep and diurnal somnolence. After determining if subjective somnolence was associated with sleep disturbances, we investigated if alterations in sleep architecture were associated with cognitive, social and emotional health in a sex dependent manner. For patients receiving positive airway pressure (PAP) treatment, we determined if lack of compliance contributed to cognitive and quality of life issues.

Methods

Adult TBI subjects (n=57) were assessed via overnight polysomnography. Mean age was 41 years and mean TBI chronicity was 2.5 years. Overall level of disability was determined by the Mayo Portland Inventory II. Sleep measures included slow wave sleep (SWS), REM latency, percent time in all sleep stages, apnea/hypopnea index, wake after sleep onset (WASO), and arousal index. Outcome measures were the California Verbal Learning Test (CVLT), Montreal Cognitive Assessment (MoCA), Trails A and B, Beck Depression Inventory, and Neuro-QoL.

Results

No sex effects for reporting somnolence were found. Besides being associated with increased subjective anxiety and stigma, somnolence was associated with increased arousals, decreases in SWS and higher incidence of REM AHI. WASO and number of arousals had a negative impact on the amount of SWS and sleep efficiency. Men spent significantly more time in REM sleep, which was correlated with higher scores on the MoCA and CVLT. Women showed more disability. Longer latencies to SWS were associated with increased CVLT performance. AHI was associated with increases in emotional/behavioral dyscontrol, fatigue and self-reported sleep disturbance. All effects were statistically significant.

Conclusion

Female TBI patients show significant impairments in REM sleep, which may impact learning and memory. Sleep disturbances were associated with poorer cognitive performance and may ultimately affect outcome, as indicated by lower scores on quality of life measures.

Support

Centre for Neuro Skills

1139 Sleep Disturbances In Chronic Stroke Patients: Emotional And Cognitive Impact

Introduction

The objective was to investigate the impact of sleep-wake disturbances (SWD) on cognition and quality of life in the post-acute phase of stroke.

Methods

Adult stroke (n=92) patients were assessed for SWD via overnight polysomnography. The mean age was 52 ± 1 years and mean latency from injury was 117 ± 10 days. Sleep measures included total sleep time (TST), sleep and REM latency, percent time in sleep stages, apnea/hypopnea index (AHI), wake after sleep onset (WASO), and arousal index. The primary cognitive/outcome measures were: Montreal Cognitive Assessment (MoCA), California Verbal Learning Test (CVLT-II), Neuro-QoL and Mayo Portland Adaptability Inventory (MPAI).

Results

Women had lower AHI (F(1,88)=9.360, p&lt;.01), fewer arousals (F(1,90)=4.53, p&lt;.05), and spent significantly more time in SWS (F(1,90)=11.525, p&lt;.001) than men; however, SWS was reduced in both sexes. SWS made up &lt; 3% of TST in 60% of patients and was not correlated with higher AHI. SWDs negatively impacted subjective quality of life (NeuroQOL). Longer latencies to sleep were associated with increased depression (p&lt;.05) and decreased positive affect (p&lt;.01). Increased sleep efficiency led to improved positive affect (p&lt;.05) and decreases in emotional/behavioral dyscontrol (p&lt;.05). Increased time in REM sleep decreased emotional/behavioral dyscontrol (p&lt;.05), while increasing satisfaction with social roles and activities(p&lt;.01). SWDs also negatively impacted cognitive/outcome scores. Increased TST and sleep efficiency led to higher scores on CVLT-II list B and long delay free recall (p&lt;.05), while higher AHI led to poorer performance on long delay and forced choice recognition trials (p&lt;.01). Additionally, non-REM AHI negatively impacted MPAI adjustment scores (F(1,69)=4.036, p&lt;.05).

Conclusion

Male stroke patients displayed significantly more arousals and spent less time in SWS than females. For both sexes, better sleep indicated improved quality of life. Sleep measures were correlated with cognitive/outcome measures. Non-REM AHI significantly predicted outcome at discharge from rehabilitation facility.

Support

 

Prevalence of growth hormone deficiency in middle-age adults recovering from stroke

Objective: The prevalence of chronic growth hormone deficiency (GHD) and its association with other hormonal deficiencies was determined in middle-aged patients post-stroke with and without consideration of body mass index (BMI).Methods: Clinical records were reviewed to determine pituitary function at least 3 months post-stroke. Patients with a history of endocrine anomalies were excluded. GHD was determined by utilizing standard peak GH cutoffs following the glucagon stimulation test. A secondary analysis was conducted with stricter BMI-adjusted cutoffs. The accuracy of IGF-1 in predicting GHD was also examined.Results: GHD was diagnosed in 54% of patients (≥5.0 μg/L), with 32% falling into the severe (≤3 μg/L) category. Patients with GHD had lower levels of FSH, T3, LH, and SHBG. Analyzes of BMI-adjusted GH levels, revealed that 14% of patients were GHD. These patients had higher prolactin. IGF-1 values were not predictive of GHD. Latency to be admitted to post-acute rehabilitation was greater in patients with GHD.Conclusions: Evidence suggests patients with stroke may be at risk for developing GHD. GHD was associated with decreased levels of other hormones. Co-morbidities for stroke and neuroendocrine dysfunction overlap and may have implications for recovery following stroke.

Abstract TP167: Prevalence of Growth Hormone Deficiency in the Chronic Phase of Recovery From Stroke

Introduction: The objective of the current retrospective study was to determine the prevalence of growth hormone deficiency (GHD) in middle-aged patients with ischemic and hemorrhagic stroke who were at least 3 months post-stroke. It was hypothesized a large percentage of patients with stroke would exhibit growth hormone deficiency, as well as, other hormone deficiencies. A secondary objective was to determine if chronic health conditions often associated with stroke were associated with neuroendocrine dysfunction.

Methods: Clinical records from 139 adult patients (from 2009-2017), who were in the post-acute phase of their recovery, were obtained to analyze findings from standard endocrine blood tests. Patients with a pre-stroke history of endocrine anomalies were excluded from the study. Growth hormone was assessed by the glucagon stimulation test (GST).

Results: GHD was identified in 54% of the patients with stroke during the chronic phase of recovery. Patients with GHD took longer to be admitted to post-acute rehabilitation compared to patients with normal GH levels. Patients with GHD also had lower levels of follicle stimulating hormone (FSH), triiodothyronine (T3), luteinizing hormone (LH) and sex hormone binding globulin. Body mass index was higher in patients with GHD.

Conclusions: There is a considerable risk of developing hypopituitarism, particularly GHD, following ischemic or hemorrhagic stroke. In this relatively large sample of middle-aged stroke patients, GHD was associated with decreased levels of T3 and gonadotrophic hormones. Co-morbidities for stroke and neuroendocrine dysfunction overlap and may have implications for recovery following stroke and warrant further investigation.

Abstract TMP47: Sleep and Endocrine Disturbances Are Associated With Poorer Outcomes During the Post-Acute Phase of Stroke Recovery

Introduction: Sleep disturbances, including decreases in slow wave sleep (SWS) are common following stroke. In this study, we sought to identify the implications of decreased slow wave sleep on endocrine function and cognitive/outcome measures in the post-acute phase of stroke recovery.

Methods: Adult stroke patients (n=44) were assessed via overnight polysomnography (PSG). The mean age was 50 ± 1.8 years and mean latency from stroke was 126 ± 16 days. Sleep measures included total sleep time (TST), sleep and REM latency, percent time in sleep stages, apnea/hypopnea index (AHI), wake after sleep onset (WASO), and arousal index. Hormone levels were analyzed within 10 days of PSG. The primary outcome measures were as follows: California Verbal Learning Test (CVLT), Montreal Cognitive Assessment (MoCA), Trails A and B, Mayo Portland Adaptability Inventory (MPAI), and NeuroQOL. Sex differences were also analyzed.

Results: Age and BMI were positively correlated with subjective daytime sleepiness using the Epworth Sleepiness Scale (p<.05); however, while BMI was positively correlated with the arousal index (p<.01), it was not correlated with AHI. TST was negatively correlated with subscales of the MPAI (p<.05). Time spent in SWS was associated with decreases in self reported anxiety, fatigue, and sleep disturbances on the NeuroQOL (p<.01). Increases in SWS were also correlated with higher scores on the MoCA (p<.05). Increases in sex hormone binding globulin (SHBG) were associated with decreases in TST (p<.05) and increased percent WASO (p<.01). Additionally, SHBG was negatively associated with the CVLT list B (p<.05). For men, SHBG is positively associated with the number of repetitions on the CVLT (p<.01). As expected, men had a higher arousal index and higher AHI than women.

Conclusion: Time spent in SWS is associated with better subjective well-being and improved performance on cognitive measures. Hormone levels, especially SHBG, may serve as early biomarkers for sleep disturbances after stroke and are associated with negative performance on some measures of cognition.

The interplay between neuroendocrine and sleep alterations following traumatic brain injury

BACKGROUND

Sleep and endocrine disruptions are prevalent after traumatic brain injury (TBI) and are likely to contribute to morbidity.

OBJECTIVE

To describe the interaction between sleep and hormonal regulation following TBI and elucidate the impact that alterations of these systems have on cognitive responses during the posttraumatic chronic period.

METHODS

Review of preclinical and clinical literature describing long-lasting endocrine dysregulation and sleep alterations following TBI. The bidirectional relationship between sleep and hormones is described. Literature describing co-occurrence between sleep-wake disturbances and hormonal dysregulation will be presented. Review of literature describing cognitive effects of seep and hormones. The cognitive and functional impact of sleep disturbances and hormonal dysregulation is discussed within the context of TBI.

RESULTS/CONCLUSIONS

Sleep and hormonal alterations impact cognitive and functional outcome after TBI. Diagnosis and treatment of these disturbances will impact recovery following TBI and should be considered in the post-acute rehabilitative setting.

National Institute of Neurological Disorders and Stroke and Department of Defense Sport-Related Concussion Common Data Elements Version 1.0 Recommendations

Through a partnership with the National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, and Department of Defense, the development of Sport-Related Concussion (SRC) Common Data Elements (CDEs) was initiated. The aim of this collaboration was to increase the efficiency and effectiveness of clinical research studies and clinical treatment outcomes, increase data quality, facilitate data sharing across studies, reduce study start-up time, more effectively aggregate information into metadata results, and educate new clinical investigators. The SRC CDE Working Group consisted of 32 worldwide experts in concussion from varied fields of related expertise divided into three Subgroups: Acute (<72 h post-concussion), Subacute (3 days-3 months post-concussion) and Persistent/Chronic (>3 months post-concussion). To develop CDEs, the Subgroups reviewed various domains, then selected from, refined, and added to existing CDEs, case report forms and field-tested data elements from national registries and funded research studies. Recommendations were posted to the NINDS CDE Website for Public Review from February 2017 to April 2017. Following an internal Working Group review of recommendations, along with consideration of comments received from the Public Review period, the first iteration (Version 1.0) of the NINDS SRC CDEs was completed in June 2017. The recommendations include Core and Supplemental-Highly Recommended CDEs for cognitive data elements and symptom checklists, as well as other outcomes and end-points (e.g., vestibular, oculomotor, balance, anxiety, depression), and sample case report forms (e.g., injury reporting, demographics, concussion history) for domains typically included in clinical research studies. The NINDS SRC CDEs and supporting documents are publicly available on the NINDS CDE website www.commondataelements.ninds.nih.gov . Widespread use of CDEs by researchers and clinicians will facilitate consistent SRC clinical research and trial design, data sharing, and metadata retrospective analysis.

The influence of post-acute rehabilitation length of stay on traumatic brain injury outcome: a retrospective exploratory study

OBJECTIVE

Data regarding length of stay (LOS) in a rehabilitation programme after traumatic brain injury (TBI) are limited. The goal of this study was to examine the effect of LOS and disability on outcome following TBI.

METHODS

Records from patients in a multidisciplinary rehabilitation programme at least 3 months after TBI were analysed retrospectively to study the influence of LOS on functional outcome at different levels of disability. Functional status was determined by the Mayo-Portland Adaptability Inventory (MPAI) and the Community Integration Questionnaire (CIQ). Patients were further grouped by time since injury of 3-12 months or over 1 year.

RESULTS

Those with a mild and moderate disabilities and over 1 year chronicity showed improvements after 90 days of rehabilitation. Patients with a severe disability and over 1 year chronicity required at least 180 days to show improvements. Moderately and severely disabled patients with an injury chronicity of 3-12 months showed improvements in the MPAI after 90 days. However, further improvement was observed after 180 days in the severely disabled group.

CONCLUSIONS

Results suggest that both, level of disability and injury chronicity, should be considered when determining LOS. Data also show an association between LOS and changes in the MPAI and CIQ.

The Impact of Traumatic Brain Injury on Later Life: Effects on Normal Aging and Neurodegenerative Diseases

The acute and chronic effects of traumatic brain injury (TBI) have been widely described; however, there is limited knowledge on how a TBI sustained during early adulthood or mid-adulthood will influence aging. Epidemiological studies have explored whether TBI poses a risk for dementia and other neurodegenerative diseases associated with aging. We will discuss the influence of TBI and resulting medical comorbidities such as endocrine, sleep, and inflammatory disturbances on age-related gray and white matter changes and cognitive decline. Post mortem studies examining amyloid, tau, and other proteins will be discussed within the context of neurodegenerative diseases and chronic traumatic encephalopathy. The data support the suggestion that pathological changes triggered by an earlier TBI will have an influence on normal aging processes and will interact with neurodegenerative disease processes rather than the development of a specific disease, such as Alzheimer's or Parkinson's. Chronic neurophysiologic change after TBI may have detrimental effects on neurodegenerative disease.

Abstract WP171: Female Sex Hormones and Post Acute Stroke Outcome

Introduction: The protective effects of estrogen are widely known following brain injury and waning female sex hormones such as estrogen and prolactin with age are associated with decline in cognitive performance. In this study, we focus on the relationship between female sex hormones and outcome following stroke, specifically how these hormones affect level of disability and responsiveness to rehabilitation following stroke.

Methods: Sex hormone levels were evaluated in 54 female stroke survivors with a mean latency of 98.8 days (SEM ± 23.06). Age differences in hormone levels and disability were evaluated according to younger (Y; M=39.3, SEM ± 1.5) and older (O; M=58.4, SEM ± 1.2) age categories. Functional ability was assessed with the Disability Rating Scale (DRS), Independent Living Scale (ILS) and the Mayo-Portland Adaptability Inventory 4 (MPAI). All patients underwent post acute rehabilitation.

Results: The Y group had higher levels of estradiol (p<0.05) and prolactin (p<0.05) compared to the O group. Correspondingly, follicle stimulating (FSH) and luteinizing hormones (LH) were higher in the O group (p<0.05). The Y group had lower disability according DRS, ILS activities of daily living (ADL) subscale and MPAII (p<0.05). High levels of prolactin were correlated with better performance in ADL’s (p<0.005). Estradiol correlated with lower disability as measured by MPAI (p<0.005). High values of FSH were associated with lower initiation as assessed by a subscale of the ILS. Analysis of changes in outcome measures before and after rehabilitation showed that both groups benefited equally.

Conclusions: Hormones are predictive of levels of disability and independence in ADL’s. Sex hormone levels in post-stroke patients should be considered for prognostication. In spite of hormonal differences both groups benefit from rehabilitation.

Abstract WP159: Effects of Gender on Sleep Alterations After Stroke

Introduction: Stroke in women tends to lead to greater disabilities and increased likelihood of institutionalization compared to men. We explored if sleep disturbances following stroke are influenced by gender. We also evaluated if levels of thyroid hormone (TSH, T3, T4), which are associated to functional outcome are influenced by gender.

Methods: Sleep was evaluated via polysomnography in stroke 33 patients (men: n=20; women: n=13; M age = 54). Functional outcome was assessed with the Supervision Rating Rating Scale (SRS) and the Mayo-Portland Adaptability Inventory 4 (MPAI). Patients were also evaluated for hormonal alterations. Sleep values were also compared with age-matched published normative data from uninjured adults.

Results: Women performed worse on the MPAI Ability Index and Adjustment index compared to men (p<0.05). Women also showed more disability according the SRS (p<0.05). Ability Index and sleep efficiency was correlated for all (p<0.01). Both male and female stroke patients had a higher percent time in Stage 2 (M: 61.5 and 66.7, respectively) compared to normative data (45.7). Moreover, 88% of stroke survivors did not did not reach Stage 3. Women showed lower sleep efficiency, spent less percent of time in REM and had a higher percent wake after sleep onset compared to normative data. Women also had lower T3 levels compared to men (p<0.01). Incidence of apnea was higher in men compared to women (p<0.05). Men tended to have more central apnea (p=0.08). Men had more spontaneous arousals during sleep and reported more daytime sleepiness compared to women (p<0.05). Accordingly, Epworth scores were correlated with low levels of participation in the MPAI for men (p<0.03). Comparisons to normative data showed that men have a shorter sleep-latency (M: 8.3 vs 15.8).

Conclusions: Whereas apnea is more predominant in men, alterations in sleep architecture appear to be more marked in women. Women also have lower levels of T3. Sleep alterations after stroke are associated with functional deficits. These findings have implications for cognitive processing, as Stage III and REM are important for memory consolidation.

Challenges in Determining the Role of Rest and Exercise in the Management of Mild Traumatic Brain Injury

Current consensus guidelines recommending physical and cognitive rest until a patient is asymptomatic after a sports concussion (ie, a mild traumatic brain injury) are being called into question, particularly for patients who are slower to recover and in light of preclinical and clinical research demonstrating that exercise aids neurorehabilitation. The pathophysiological response to mild traumatic brain injury includes a complex neurometabolic cascade of events resulting in a neurologic energy deficit. It has been proposed that this energy deficit leads to a period of vulnerability during which the brain is at risk for additional injury, explains why early postconcussive symptoms are exacerbated by cognitive and physical exertion, and is used to rationalize absolute rest until all symptoms have resolved. However, at some point, rest might no longer be beneficial and exercise might need to be introduced. At both extremes, excessive exertion and prolonged avoidance of exercise (physical and mental) have negative consequences. Individuals who have experienced a concussion need guidance for avoidance of triggers of severe symptoms and a plan for graduated exercise to promote recovery as well as optimal functioning (physical, educational, and social) during the postconcussion period.

Detection of Growth Hormone Deficiency in Adults with Chronic Traumatic Brain Injury

This study examined the prevalence of growth hormone deficiency (GHD) in patients with traumatic brain injury (TBI) during the post-acute phase of recovery and whether GHD was associated with increased disability, decreased independence, and depression. A secondary objective was to determine the accuracy of insulin-like growth factor-1 (IGF-1) levels in predicting GHD in patients with TBI. Anterior pituitary function was assessed in 235 adult patients with TBI through evaluation of fasting morning hormone levels. GH levels were assessed through provocative testing, specifically the glucagon stimulation test. GHD was diagnosed in a significant number of patients, with 45% falling into the severe GHD (≤3 μg/L) category. IGF-1 levels were not predictive of GHD. Patients with GHD were more disabled and less independent compared with those patients who were not GHD. Those patients with more severe GHD also showed decreased levels of cortisol and testosterone. Symptoms of depression were also more prevalent in this group. In addition, patients with severe GHD had delayed admission to post-acute rehabilitation. This study confirms the high prevalence of GHD in patients with TBI and the necessity to monitor clinical symptoms and perform provocative testing to definitively diagnose GHD.

Recovery of stress response coincides with responsiveness to voluntary exercise after traumatic brain injury

We have recently shown that there is a heightened stress response after a mild traumatic brain injury (TBI) during the first 2 post-injury weeks. This corresponds to the same post-injury period when exercise does not increase brain-derived neurotrophic factor (BDNF) and autonomic dysfunction becomes evident with exercise. Here we determined stress and autonomic responses to voluntary and forced exercise at a post-injury time window when exercise has been found to elicit beneficial effects. Rats underwent a mild fluid percussion injury and were exercised at post-injury days 28-32 and 35-39. Cardiac and temperature autonomic function were evaluated. Hippocampal tissue was obtained immediately after exercise for analysis of BDNF. In contrast to the sub-acute period, corticosterone and adrenocorticotropic hormone responses to exercise were normalized in the TBI group. Irrespective of injury, forced exercise markedly stimulated the corticotrophic axis and did not increase BDNF. BDNF levels were increased with voluntary exercise in all animals. Rats exposed to forced exercise had lower activity levels during periods of non-exercise. This effect was more pronounced in the TBI rats. Cardiac and temperature autonomic responses to delayed exercise also recuperated. Rats with TBI that underwent forced exercise, however, had higher core body temperatures during experimental manipulations, thus suggesting that exposure to a potent stressor facilitates responsiveness to environmental stimulations.

Temperature and heart rate responses to exercise following mild traumatic brain injury

We have previously reported that mild fluid percussion injury (FPI) is associated with a heightening of the hypothalamic-pituitary-adrenal axis response during the first post-injury weeks. This is the same time period when rehabilitative exercise has been strongly suggested to be ineffective. Here, we explored whether cardiac and temperature autonomic function may also be compromised during this early post-injury period. Following an FPI or sham injury, rats were exercised with forced (fRW) or voluntary (vRW) running wheels on post-injury days 0-4 and 7-11. Results indicated that overall activity levels were decreased and circadian rhythm was affected after FPI. Autonomic disruptions became evident when exercise was introduced, and these disruptions were dependent upon the characteristics of exercise. Elevations in heart rate (HR) and core body temperature (CBT) were observed as a response to vRW and fRW. FPI animals had more pronounced increases in HR as a result of vRW. Likewise, increases in HR were observed with fRW in all animals. A strong stress response has recently been associated with fRW exercise. FPI rats exposed to fRW were more responsive to experimental manipulations and had higher a CBT after the FRW session. The results suggest that subacute exercise, particularly if linked to a strong stress response, may be counterproductive. Here we show that cardiac and temperature autonomic function are compromised during the subacute period following a mild TBI.

Differential effects of voluntary and forced exercise on stress responses after traumatic brain injury

Voluntary exercise increases levels of brain-derived neurotrophic factor (BDNF) after traumatic brain injury (TBI) when it occurs during a delayed time window. In contrast, acute post-TBI exercise does not increase BDNF. It is well known that increases in glucocorticoids suppress levels of BDNF. Moreover, recent work from our laboratory showed that there is a heightened stress response after fluid percussion injury (FPI). In order to determine if a heightened stress response is also observed with acute exercise, at post-injury days 0-4 and 7-11, corticosterone (CORT) and adrenocorticotropic hormone (ACTH) release were measured in rats running voluntarily or exposed to two daily 20-min periods of forced running wheel exercise. Forced, but not voluntary exercise, continuously elevated CORT. ACTH levels were initially elevated with forced exercise, but decreased by post-injury day 7 in the control, but not the FPI animals. As previously reported, voluntary exercise did not increase BDNF in the FPI group as it did in the control animals. Forced exercise did not increase levels of BDNF in any group. It did, however, decrease hippocampal glucocorticoid receptors in the control group. The results suggest that exercise regimens with strong stress responses may not be beneficial during the early post-injury period.

Effects of acute restraint-induced stress on glucocorticoid receptors and brain-derived neurotrophic factor after mild traumatic brain injury

We have previously reported that experimental mild traumatic brain injury results in increased sensitivity to stressful events during the first post-injury weeks, as determined by analyzing the hypothalamic-pituitary-adrenal (HPA) axis regulation following restraint-induced stress. This is the same time period when rehabilitative exercise has proven to be ineffective after a mild fluid-percussion injury (FPI). Here we evaluated effects of stress on neuroplasticity. Adult male rats underwent either an FPI or sham injury. Additional rats were only exposed to anesthesia. Rats were exposed to 30 min of restraint stress, followed by tail vein blood collection at post-injury days (PID) 1, 7, and 14. The response to dexamethasone (DEX) was also evaluated. Hippocampal tissue was collected 120 min after stress onset. Brain-derived neurotrophic factor (BDNF) along with glucocorticoid (GR) and mineralocorticoid (MR) receptors was determined by Western blot analysis. Results indicated injury-dependent changes in glucocorticoid and mineralocorticoid receptors that were influenced by the presence of dexamethasone. Control and FPI rats responded differentially to DEX in that GR increases after receiving the lower dose of DEX were longer lasting in the FPI group. A suppression of MR was found at PID 1 in vehicle-treated FPI and Sham groups. Decreases in the precursor form of BDNF were observed in different FPI groups at PIDs 7 and 14. These findings suggest that the increased sensitivity to stressful events during the first post-injury weeks, after a mild FPI, has an impact on hippocampal neuroplasticity.

The pathophysiology of concussions in youth

Mild traumatic brain injury, especially sport-related concussion, is common among young persons. Consequences of transient pathophysiologic dysfunction must be considered in the context of a developing or immature brain, as must the potential for an accumulation of damage with repeated exposure. This review summarizes the underlying neurometabolic cascade of concussion, with emphasis on the young brain in terms of acute pathophysiology, vulnerability, alterations in plasticity and activation, axonal injury, and cumulative risk from chronic, repetitive damage, and discusses their implications in the context of clinical care for the concussed youth, highlighting areas for future investigation.

Heightening of the stress response during the first weeks after a mild traumatic brain injury

The effects of a mild traumatic brain injury range from white matter disruption to affective disorders. We set out to determine the response to restraint-induced stress after a mild fluid-percussion injury (FPI), an experimental model for brain injury. Hypothalamic-pituitary-adrenal (HPA) axis regulation of corticosterone (CORT) and adrenocorticotropic hormone (ACTH) was determined during the first post-injury weeks, which corresponds to the same time period when rehabilitative exercise has been shown to be ineffective after a mild FPI. Adult male rats underwent either an FPI or sham injury. Additional rats were only exposed to anesthesia. HPA regulation was evaluated by measuring the effects of dexamethasone (DEX) treatment on CORT and ACTH. Tail vein blood was collected following 30-min restraint stress, at post-injury days (PID) 1, 7 and 14, prior to (0 min) and at 30, 60, 90 and 120 min after stress onset. Results from these studies indicate that the stress response was significantly more pronounced after FPI in that CORT and ACTH restraint-induced increases were more pronounced and longer lasting compared to controls. DEX suppression of CORT and ACTH was observed in all groups, suggesting that stress hyper-responsiveness after mild FPI is not attributable to reduced sensitivity of CORT feedback regulation. The increased sensitivity to stressful events in the first two post-injury weeks after a mild FPI may have a negative impact on early rehabilitative therapies.

Voluntary exercise or amphetamine treatment, but not the combination, increases hippocampal brain-derived neurotrophic factor and synapsin I following cortical contusion injury in rats

Prior work has shown that d-amphetamine (AMPH) treatment or voluntary exercise improves cognitive functions after traumatic brain injury (TBI). In addition, voluntary exercise increases levels of brain-derived neurotrophic factor (BDNF). The current study was conducted to determine how AMPH and exercise treatments, either alone or in combination, affect molecular events that may underlie recovery following controlled cortical impact (CCI) injury in rats. We also determined if these treatments reduced injury-induced oxidative stress. Following a CCI or sham injury, rats received AMPH (1 mg/kg/day) or saline treatment via an ALZET pump and were housed with or without access to a running wheel for 7 days. CCI rats ran significantly less than sham controls, but exercise level was not altered by drug treatment. On day 7 the hippocampus ipsilateral to injury was harvested and BDNF, synapsin I and phosphorylated (P) -synapsin I proteins were quantified. Exercise or AMPH alone significantly increased BDNF protein in sham and CCI rats, but this effect was lost with the combined treatment. In sham-injured rats synapsin I increased significantly after AMPH or exercise, but did not increase after combined treatment. Synapsin levels, including the P-synapsin/total synapsin ratio, were reduced from sham controls in the saline-treated CCI groups, with or without exercise. AMPH treatment significantly increased the P-synapsin/total synapsin ratio after CCI, an effect that was attenuated by combining AMPH with exercise. Exercise or AMPH treatment alone significantly decreased hippocampal carbonyl groups on oxidized proteins in the CCI rats, compared with saline-treated sedentary counterparts, but this reduction in a marker of oxidative stress was not found with the combination of exercise and AMPH treatment. These results indicate that, whereas exercise or AMPH treatment alone may induce plasticity and reduce oxidative stress after TBI, combining these treatments may cancel each other's therapeutic effects.

Time window for voluntary exercise-induced increases in hippocampal neuroplasticity molecules after traumatic brain injury is severity dependent

We recently found that an exercise-induced increase in hippocampal brain-derived neurotrophic factor (BDNF) is dependent when exercise is initiated after traumatic brain injury (TBI). When voluntary exercise was delayed by 2 weeks after a mild fluid-percussion injury (FPI) in rats, an increase in BDNF and an improvement in behavioral outcome were observed. This suggests that following FPI there is a therapeutic window for the implementation of voluntary exercise. To determine if more severely injured animals require more time after TBI before voluntary exercise can increase neuroplasticity, adult male rats with a moderate lateral FPI or sham injury were housed with or without access to a running wheel from post-injury-day (PID) 0-6, 14-20 or 30-36. Rats with a mild injury only had access to the running wheel from PID 0-6 or 14-20. Rats were sacrificed at PID 7, 21, or 37. BDNF, synapsin I, and cyclic AMP response element binding protein (CREB) were analyzed within the ipsilateral hippocampus. Whereas BDNF levels significantly increased with exercise in the mild FPI rats that were exercised from PID 14 to 20, the moderate FPI rats only showed significant increases in BDNF when exercised from PID 30 to 36. In addition, moderate FPI rats that were allowed to exercise from PID 30 to 36 also exhibited significant increases in synapsin I and CREB. These results indicate that the time window for exercise-induced increases in BDNF, synapsin I, and CREB is dependent on injury severity.

Experience-dependent behavioral plasticity is disturbed following traumatic injury to the immature brain

Traumatic brain injury (TBI) is most prevalent in children and young adults. The long-term effects of pediatric TBI include cognitive and behavioral impairments; however, over time, it is difficult to distinguish individual variability in intellect and behavior from sequelae of early injury. Postnatal day (PND) 19 rats underwent lateral fluid percussion (FP) injury, followed by rearing in either standard (STD) or enriched environment (EE) conditions. The hypothesis was that the traditional enhancement of cognitive functioning following EE rearing would be attenuated when this rearing is preceded by TBI at PND19. Thirty days after injury, Morris water maze (MWM) acquisition and subsequent probe trial retention were used to assess the behavioral effects of injury on experience-dependent plasticity induced by housing in EE at two different time windows. MWM acquisition demonstrated improvements following early EE rearing in both sham and injured animals; however, the degree of improvement was greater for uninjured animals. When EE rearing was delayed for 2 weeks after injury, the injury effect was absent and the effect of rearing even stronger. Memory testing in the early EE groups using a delayed probe trial showed an effect of injury and housing, with the sham EE animals benefiting the most. After the delayed EE, sham EE animals again showed more probe target hits, while FPEE animals did not, demonstrating an enduring memory deficit. These data confirm that early TBI has effects on experience-dependent plasticity resulting in long-term neurobehavioral deficits. In addition, the ability to benefit from environmental stimulation following TBI is dependent upon time after injury.

Voluntary exercise following traumatic brain injury: brain-derived neurotrophic factor upregulation and recovery of function

Voluntary exercise leads to an upregulation of brain-derived neurotrophic factor (BDNF) and associated proteins involved in synaptic function. Activity-induced enhancement of neuroplasticity may be considered for the treatment of traumatic brain injury (TBI). Given that during the first postinjury week the brain is undergoing dynamic restorative processes and energetic changes that may influence the outcome of exercise, we evaluated the effects of acute and delayed exercise following experimental TBI. Male Sprague-Dawley rats underwent either sham or lateral fluid-percussion injury (FPI) and were housed with or without access to a running wheel (RW) from postinjury days 0-6 (acute) or 14-20 (delayed). FPI alone resulted in significantly elevated levels of hippocampal phosphorylated synapsin I and phosphorylated cyclic AMP response element-binding-protein (CREB) at postinjury day 7, of which phosphorylated CREB remained elevated at postinjury day 21. Sham and delayed FPI-RW rats showed increased levels of BDNF, following exercise. Exercise also increased phosphorylated synapsin I and CREB in sham rats. In contrast to shams, the acutely exercised FPI rats failed to show activity-dependent BDNF upregulation and had significant decreases of phosphorylated synapsin I and total CREB. Additional rats were cognitively assessed (learning acquisition and memory) by utilizing the Morris water maze after acute or delayed RW exposure. Shams and delayed FPI-RW animals benefited from exercise, as indicated by a significant decrease in the number of trials to criterion (ability to locate the platform in 7 s or less for four consecutive trials), compared with the delayed FPI-sedentary rats. In contrast, cognitive performance in the acute FPI-RW rats was significantly impaired compared with all the other groups. These results suggest that voluntary exercise can endogenously upregulate BDNF and enhance recovery when it is delayed after TBI. However, when exercise is administered to soon after TBI, the molecular response to exercise is disrupted and recovery may be delayed.

Effects of MK-801 on vicarious trial-and-error and reversal of olfactory discrimination learning in weanling rats

The effects of dizocilpine maleate (MK-801) on vicarious trial-and-error (VTE), and on simultaneous olfactory discrimination learning and its reversal, were observed in weanling rats. The term VTE was used by Tolman (The determiners of behavior at a choice point. Psychol. Rev. 1938;46:318-336), who described it as conflict-like behavior at a choice-point in simultaneous discrimination learning. It takes the form of head movements from one stimulus to the other, and has recently been proposed by Amsel (Hippocampal function in the rat: cognitive mapping or vicarious trial-and-error? Hippocampus, 1993;3:251-256) as related to hippocampal, nonspatial function during this learning. Weanling male rats received systemic MK-801 either 30 min before the onset of olfactory discrimination training and its reversal, or only before its reversal. The MK-801-treated animals needed significantly more sessions to acquire the discrimination and showed significantly fewer VTEs in the acquisition phase of learning. Impaired reversal learning was shown only when MK-801 was administered during the reversal-learning phase, itself, and not when it was administered throughout both phases.

Immediate and long-term effects of neonatal MK-801 treatment on nonspatial learning

These experiments observed the immediate and long-term effects of neonatal treatment with MK-801 on patterned single alternation (PSA), a form of nonspatial, memory-based learning. Rat pups were injected daily on postnatal days (PND) 7-19, with MK-801 (MK+) or the less active isomer of MK-801 (MK-) (0.25 mg/kg), and trained at either PND 22 or 60. Rats treated with MK+ or MK- and trained on PND 22 were significantly impaired in PSA when compared with the saline control. Beyond the learning impairment, MK+ rats showed an overall decreased running speed during training. They also presented an array of abnormal behaviors and significant weight loss. These nonassociative variables were determined for several doses (0.025, 0. 05, 0.1, 0.15, and 0.20 mg/kg) through PND days 22-25. Rats that received the threshold dose for secondary effects (0.025 mg/kg) also showed an overall decrease in running speed, but failed to show a significant nonspatial learning impairment on PSA. The PSA learning impairment was found to be not long lasting; rats trained at PND 60, after neonatally receiving the original high dose of MK-801, did not differ from controls.