Loss of cortisol circadian rhythm in patients with traumatic brain injury: a microdialysis evaluation

The Surgical Stress Response and Anesthesia: A Narrative Review

The human physiological response "to stress" includes all metabolic and hormonal changes produced by a traumatic event at the micro or macro cellular levels. The main goal of the body's first response to trauma is to keep physiological homeostasis. The perioperative non-specific adaptation response can sometimes be detrimental and can produce systemic inflammatory response syndrome (SIRS), characterized by hypermetabolism and hyper catabolism. We performed a narrative review consisting of a description of the surgical stress response's categories of changes (neurohormonal and immunological response) followed by reviewing methods found in published studies to modulate the surgical stress response perioperatively. We described various preoperative measures cited in the literature as lowering the burden of surgical trauma. This article revises the anesthetic drugs and techniques that have an impact on the surgical stress response and proven immune-modulatory effects. We also tried to name present knowledge gaps requiring future research. Our review concludes that proper preoperative measures, adequate general anesthetics, multimodal analgesia, early postoperative mobilization, and early enteral nutrition can decrease the stress response to surgery and ease patient recovery. Anesthetics and analgesics used during the perioperative period may modulate the innate and adaptive immune system and inflammatory system, with a consecutive impact on cancer recurrence and long-term outcomes.

Acute neuroendocrine changes after traumatic brain injury

Introduction

Post-traumatic hypopituitarism (PTHP) is a significant, but often neglected consequence of traumatic brain injury (TBI).

Research question

We aimed to provide a comprehensive overview of epidemiology, pathophysiology, clinical features and diagnostic approaches of PTHP.

Materials and methods

MEDLINE, EMBASE, Cochrane Library and Web of Science were searched. 45 articles of human studies evaluating acute endocrine changes following mild, moderate and severe TBI were selected.

Results

Severity of TBI seems to be the most important risk factor of PTHP. Adrenal insufficiency (AI) was present in 10% of TBI patients (prevalence can be as high as 50% after severe TBI), and hypocortisolemia is a predictor of mortality and long-term hypopituitarism. Suppression of the thyroid axis in 2-33% of TBI patients may be an independent predictor of adverse neurological outcome, as well. 9-36% of patients with severe TBI exhibit decreased function of the somatotrophic axis with a divergent effect on the central nervous system. Arginine-Vasopressin (AVP) deficiency is present in 15-51% of patients, associated with increased mortality and unfavorable outcome. Due to shear and injury of the stalk hyperprolactinemia is relatively common (2-50%), but it bears little clinical significance. Sex hormone levels remain within normal values.

Discussion and conclusion

PTHP occurs frequently after TBI, affecting various axis and determining patients' outcome. However, evidence is scarce regarding exact epidemiology, diagnosis, and effective clinical application of hormone substitution. Future studies are needed to identify patients at-risk, determine the optimal timing for endocrine testing, and refine diagnostic and treatment approaches to improve outcome.

Context is key: glucocorticoid receptor and corticosteroid therapeutics in outcomes after traumatic brain injury

Traumatic brain injury (TBI) is a global health burden, and survivors suffer functional and psychiatric consequences that can persist long after injury. TBI induces a physiological stress response by activating the hypothalamic-pituitary-adrenal (HPA) axis, but the effects of injury on the stress response become more complex in the long term. Clinical and experimental evidence suggests long lasting dysfunction of the stress response after TBI. Additionally, pre- and post-injury stress both have negative impacts on outcome following TBI. This bidirectional relationship between stress and injury impedes recovery and exacerbates TBI-induced psychiatric and cognitive dysfunction. Previous clinical and experimental studies have explored the use of synthetic glucocorticoids as a therapeutic for stress-related TBI outcomes, but these have yielded mixed results. Furthermore, long-term steroid treatment is associated with multiple negative side effects. There is a pressing need for alternative approaches that improve stress functionality after TBI. Glucocorticoid receptor (GR) has been identified as a fundamental link between stress and immune responses, and preclinical evidence suggests GR plays an important role in microglia-mediated outcomes after TBI and other neuroinflammatory conditions. In this review, we will summarize GR-mediated stress dysfunction after TBI, highlighting the role of microglia. We will discuss recent studies which target microglial GR in the context of stress and injury, and we suggest that cell-specific GR interventions may be a promising strategy for long-term TBI pathophysiology.

Circadian Rhythmicity of Vital Signs at Intensive Care Unit Discharge and Outcome of Traumatic Brain Injury

BACKGROUND

Physiological functions with circadian rhythmicity are often disrupted during illness.

OBJECTIVE

To assess the utility of circadian rhythmicity of vital signs in predicting outcome of traumatic brain injury (TBI).

METHODS

A retrospective single-center cohort study of adult intensive care unit (ICU) patients with largely isolated TBI to explore the relationship between the circadian rhythmicity of vital signs during the last 24 hours before ICU discharge and clinical markers of TBI severity and score on the Glasgow Outcome Scale 6 months after injury (GOS-6).

RESULTS

The 130 study participants had a median age of 39.0 years (IQR, 23.0-59.0 years), a median Glasgow Coma Scale score at the scene of 8.0 (IQR, 3.0-13.0), and a median Rotterdam score on computed tomography of the head of 3 (IQR, 3-3), with 105 patients (80.8%) surviving to hospital discharge. Rhythmicity was present for heart rate (30.8% of patients), systolic blood pressure (26.2%), diastolic blood pressure (20.0%), and body temperature (26.9%). Independent predictors of a dichotomized GOS-6 ≥4 were the Rotterdam score (odds ratio [OR], 0.38 [95% CI, 0.18-0.81]; P = .01), Glasgow Coma Scale score at the scene (OR, 1.22 [95% CI, 1.05-1.41]; P = .008), age (OR, 0.95 [95% CI, 0.92-0.98]; P = .003), oxygen saturation <90% in the first 24 hours (OR, 0.19 [95% CI, 0.05-0.73]; P = .02), serum sodium level <130 mmol/L (OR, 0.20 [95% CI, 0.05-0.70]; P = .01), and active intracranial pressure management (OR, 0.16 [95% CI, 0.04-0.62]; P = .008), but not rhythmicity of any vital sign.

CONCLUSION

Circadian rhythmicity of vital signs at ICU discharge is not predictive of GOS-6 in patients with TBI.

Identification of HMGCR, PPGARG and prohibitin as potential druggable targets of dihydrotestosterone for treatment against traumatic brain injury using system pharmacology

BACKGROUND

Traumatic Brain Injury (TBI) has long-term devastating effects for which there is no accurate and effective treatment for inflammation and chronic oxidative stress. As a disease that affects multiple signalling pathways, the search for a drug with a broader spectrum of pharmacological action is of clinical interest. The fact that endocrine disruption (e.g hypogonadism) has been observed in TBI patients suggests that endogenous therapy with testosterone, or its more androgenic derivative, dihydrotestosterone (DHT), may attenuate, at least in part, the TBI-induced inflammation, but the underlying molecular mechanisms by which this occurs are still not completely clear.

AIMS AND METHODS

In this study, the main aim was to investigate proteins that may be related to the pathophysiological mechanism of TBI and also be pharmacological targets of DHT in order to explore a possible therapy with this androgen using network pharmacology.

RESULTS AND CONCLUSIONS

We identified 2.700 proteins related to TBI and 1.567 that are potentially molecular targets of DHT. Functional enrichment analysis showed that steroid (p-value: 2.1-22), lipid metabolism (p-value: 2.8-21) and apoptotic processes (p-value: 5.2-21) are mainly altered in TBI. Furthermore, being mitochondrion an organelle involved on these molecular processes we next identified that out of 32 mitochondrial-related proteins 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR), peroxisome proliferator activated receptor gamma (PPGARG) and prohibitin are those found highly regulated in the network and potential targets of DHT in TBI. In conclusion, the identification of these cellular nodes may prove to be essential as targets of DHT for therapy against post-TBI inflammation.

Saliva cortisol levels and physiological parameter fluctuations in mild traumatic brain injury patients compared to controls

BACKGROUND

Evidence suggests that fluctuations of cortisol and physiological parameters can emerge during the course of mild Traumatic Brain Injury (mTBI).

OBJECTIVE

To investigate fluctuations of cortisol and physiological parametersduring the acute phase of mTBI in hospitalized patients.

METHODS

30 participants (19 patients with mTBI and 11 controls) were examined for saliva cortisol dynamics, heart rate (HR), systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP) and body temperature (BT) fluctuations for four consecutive days. Also, the participants completed the Athens Insomnia Scale and Epworth Sleepiness Scales, in order to check for sleep problems.

RESULTS

Patients showed elevated levels of cortisol relative to controls (peak at 8 am and lowest levels at 12 am), as well as for most physiological parameters. MAP was significantly higher for patients throughout the measurement period, and BT was elevated for patients relative to controls at almost all measurements of the first and second day. Mean HR tended to track at non-significantly higher levels for the mTBI group. Patients' sleepiness and insomnia values (ESS and AIS) were initially significantly higher relative to controls but the difference dissipated by day 4.

CONCLUSION

The increase in absolute values of cortisol and physiological parameters measurements, indicates that in the acute phase of mTBI, a stressful process is activated which may affect sleep quality as well.Supplemental data for this article is available online at at doi: 10.1080/00207454.2021.1951264.

Traumatic Optic Neuropathy Is Associated with Visual Impairment, Neurodegeneration, and Endoplasmic Reticulum Stress in Adolescent Mice

Traumatic brain injury (TBI) results in a number of impairments, often including visual symptoms. In some cases, visual impairments after head trauma are mediated by traumatic injury to the optic nerve, termed traumatic optic neuropathy (TON), which has few effective options for treatment. Using a murine closed-head weight-drop model of head trauma, we previously reported in adult mice that there is relatively selective injury to the optic tract and thalamic/brainstem projections of the visual system. In the current study, we performed blunt head trauma on adolescent C57BL/6 mice and investigated visual impairment in the primary visual system, now including the retina and using behavioral and histologic methods at new time points. After injury, mice displayed evidence of decreased optomotor responses illustrated by decreased optokinetic nystagmus. There did not appear to be a significant change in circadian locomotor behavior patterns, although there was an overall decrease in locomotor behavior in mice with head injury. There was evidence of axonal degeneration of optic nerve fibers with associated retinal ganglion cell death. There was also evidence of astrogliosis and microgliosis in major central targets of optic nerve projections. Further, there was elevated expression of endoplasmic reticulum (ER) stress markers in retinas of injured mice. Visual impairment, histologic markers of gliosis and neurodegeneration, and elevated ER stress marker expression persisted for at least 30 days after injury. The current results extend our previous findings in adult mice into adolescent mice, provide direct evidence of retinal ganglion cell injury after head trauma and suggest that axonal degeneration is associated with elevated ER stress in this model of TON.

Continuous Free Cortisol Profiles in Healthy Men

CONTEXT

In humans, approximately 95% of circulating cortisol is bound to corticosteroid-binding globulin and albumin. It is only the free fraction that is biologically active and can activate signaling pathways via glucocorticoid hormone receptors in cells. Microdialysis is a well-established technique that enables the sampling of molecules in different compartments of the body, including extracellular fluid. This is the first study validating a rapid sampling microdialysis method measuring free cortisol in the subcutaneous and blood compartments of healthy volunteers.

METHODS

Healthy nonsmoking volunteers (42 men, aged 18-24 years; body mass index 18-25 kg/m2) received placebo (saline), 250 μg Synacthen, or 1 mg dexamethasone with 10-minute sampling to measure total and free cortisol (subcutaneous, intravenous, and saliva) for an hour before and 4 hours after administration.

RESULTS

Following stimulation by Synacthen, total serum cortisol and free cortisol in both compartments rose significantly, achieving and maintaining maximum levels between 2 and 3 hours following the stimulus. A decline in cortisol levels was evident after the administration of dexamethasone or placebo, but there was a clear pulsatile activity around lunchtime in the latter group, which was prominent in the blood compartment (total and free cortisol). There was good correlation between serum total and free cortisol (subcutaneous and intravenous) in the Synacthen and dexamethasone groups with no significant delay (less than 5 minutes) between total and free cortisol.

CONCLUSIONS

This seminal study demonstrated the dynamic responses of total blood cortisol and microdialysis derived free cortisol in blood, subcutaneous tissue, and saliva in men.

Continuous Free Cortisol Profiles-Circadian Rhythms in Healthy Men

CONTEXT

The pituitary-adrenal axis had historically been considered a representative model for circadian rhythms. A recently developed portable collection device has provided the opportunity to evaluate free cortisol profiles using the microdialysis approach in individuals free to conduct their day-to-day activities in their own surroundings.

METHODS

Two separate experiments were conducted in healthy male volunteers. The total and subcutaneous (SC) free cortisol levels were measured at 10-minute intervals for a 24-hour period in one experiment, and the SC free cortisol levels were measured at 20-minute interval for 72 consecutive hours in free-living individuals in the second experiment.

RESULTS

The characteristic circadian rhythm was evident in both serum total and SC free cortisol, with the lowest levels achieved and maintained in the hours surrounding sleep onset and the peak levels occurring in every individual around waking. In all free-living individuals, the circadian rhythm was consistent across the 72-hour period, despite a wide range of activities. All the participants also showed increased cortisol after the consumption of lunch. The lowest levels during all 24-hour periods were observed during the hours after lights off, at the onset of sleep.

CONCLUSIONS

To the best of our knowledge, the present study is the first to report up to three consecutive 24-hour measurements of SC free cortisol in healthy individuals. We believe our study is a landmark study that paves the way for ambulatory monitoring of free cortisol profiles continuously for a period of 72 hours in free-living individuals performing their day-to-day activities whether healthy or with diseases involving the hypothalamic-pituitary-adrenal axis.

Regulation of Circadian Clock Genes on Sleep Disorders in Traumatic Brain Injury Patients

BACKGROUND

In patients with traumatic brain injury (TBI), whether sleep disorder is associated with disturbances in molecular rhythmicity is unclear. This study aimed to investigate the relationship between abnormal sleep and regulation by circadian rhythms in patients with TBI.

METHODS

We sampled buccal cells and human blood samples from patients with TBI diagnosed with sleep disorders and those with normal sleep and investigated differences in the expression levels of Clock, Per2, and Bmal1 between the 2 groups.

RESULTS

The expression peaks of Clock, Per2, and Bmal1 were at 12:00. There was a statistically significant difference between the sleep disorder group and the normal sleep group in the level of Clock mRNA expression (P = 0.0003 in oral mucosa and P < 0.0001 in mononuclear cells). There was no significant between-group difference in Bmal1 mRNA expression level (P = 0.1187 in oral mucosa and P = 0.2094 in mononuclear cells). There were significant between-group differences in Per2 mRNA expression levels at 12:00 (P = 0.0102 in oral mucosa and P = 0.0006 in mononuclear cells) and 18:00 (P = 0.0004 in oral mucosa and P = 0.0015 in mononuclear cells) but no significant difference at 24:00 (P = 0.7838 in oral mucosa and P = 0.2808 in mononuclear cells).

CONCLUSIONS

Abnormal expression levels of Per2, Clock, and Bmal1 were detected in patients with TBI-related sleep disorders. These novel findings demonstrate disturbances in the molecular clock in TBI patients and have important implications for our understanding of the aberrant rhythms reported in this disease.

Redefining the perioperative stress response: a narrative review

The systemic stress response triggered by surgical trauma is characterised by sterile inflammation preceding metabolic and neuroendocrine dysregulation. However, the relevance of the classically described 'stress response' is now highly questionable in an era where profound physiological deconditioning is common in older, frail surgical patients. Commonly used assessment techniques do not accurately reflect hypothalamic-pituitary-adrenal axis integrity after major surgery. Clinical interpretation of plasma concentrations of cortisol, the prototypical stress hormone, is rarely accurate, because of study heterogeneity, the inherently dynamic characteristics of cortisol production, and assay variability. Before surgery, chronic psychosocial stress and common cardiorespiratory co-morbidities are clinically relevant modifiers of neuroendocrine activation to acute stress/inflammation. The frequent development of multi-morbidity after major surgery further clouds the compartmentalised, discrete model of neuroendocrine activation after initial tissue injury. Starvation, impaired mobility, and sepsis after surgery generate distinct neuroendocrine profiles that challenge the conventional model of neuroendocrine activation. Basic science studies suggest that high circulating levels of cortisol may directly cause organ injury. Conversely, randomised controlled clinical trials investigating glucocorticoid supplementation have delivered contrasting results, with some suggesting a protective effect in the perioperative period. Here, we consider many of the confounding factors that have emerged to challenge the conventional model of the surgical stress response, and suggest that a more nuanced understanding of changes in hypothalamic-pituitary-adrenal axis physiology is warranted to advance perioperative medicine. Re-examining the perioperative stress response presents opportunities for improving outcomes through enhancing the understanding of the neuroendocrine aspects of preparation for and recovery from surgery.

Low-Field Magnetic Stimulation Restores Cognitive and Motor Functions in the Mouse Model of Repeated Traumatic Brain Injury: Role of Cellular Prion Protein

Traumatic brain injury (TBI)/concussion is a growing epidemic throughout the world. Memory and neurobehavioral dysfunctions are among the sequelae of TBI. Dislodgement of cellular prion protein (PrPc) and disruption of circadian rhythm have been linked to TBI. Low-field magnetic stimulation (LFMS) is a new noninvasive repetitive transcranial magnetic stimulation (rTMS) technique that generates diffused and low-intensity magnetic stimulation to deep cortical and subcortical areas. The role of LFMS on PrPc, proteins related to the circadian rhythm, and behavior alterations in a repeated TBI mouse model were studied in the present study. TBI was induced to the mice (right hemisphere) using weight-drop method, once daily for 3 days. LFMS treatment was given for 20 min once daily for 4 days (immediately after each TBI induction). The results showed that LFMS-treated TBI mice significantly improved cognitive and motor function as evidenced by open field exploration, rotarod, and novel location recognition tasks. In addition, a significant increase in PrPc and decreased glial fibrillary acidic protein levels were observed in cortical and hippocampal regions of LFMS-treated TBI mice brain compared with sham-treated TBI mice, while neuronal nuclei level was significantly increased in cortical region. In LFMS-treated mice, a decrease in proteins related to circadian rhythm were observed, compared with sham-treated TBI mice. The results obtained from the study demonstrated the neuroprotective effect of LFMS, which may be through regulating PrPc and/or proteins related to circadian rhythm. Thus, the present study suggests that LFMS may improve the subject's neurological condition following TBI.

Sleep Disorders Following Mild and Moderate Traumatic Brain Injury

(1) Background: Sleeping disorders are frequently reported following traumatic brain injury (TBI). Different forms of sleeping disorders have been reported, such as sleepiness, insomnia, changes in sleeping latency, and others. (2) Methods: A case-control study with 62 patients who were victims of mild or moderate TBI with previous admissions to Iraqi tertiary neurosurgical centers were enrolled as the first group, and 158 patients with no history of trauma were considered as the control. All were 18 years of age or older, and the severity of the trauma and sleep disorders was assessed. The Pittsburgh sleep quality index was used to assess sleep disorders with average need for sleep per day and average sleep latency were assessed in both groups. Chi-square and t-test calculations were used to compare different variables. (3) Results: 39 patients (24.7%) of the controlled group experienced sleeping disorders compared to TBI group with 45 patients (72.6%), P-value < 0.00001. A total of 42 patients were diagnosed on admission as having a mild degree of TBI (mean GCS 13.22 ± 1.76) and 20 patients were diagnosed with moderate TBI (mean GCS11.05 ± 1.14. 27). A total of 27 (46.28%) patients with mild severity TBI and 18 patients (90%) of moderate severity were considered to experience sleeping disorders, P-value 0.0339. Each of the mild and moderate TBI subgroups show a P-value < 0.00001 compared to the control group. Average sleep hours needed per day for TBI and the control were 8.02 ± 1.04 h and 7.26 ± 0.58 h, respectively, P-value < 0.00001. Average sleep latency for the TBI and the control groups were 13.32 ± 3.16 min and 13.93 ± 3.07 min respectively, P-value 0.065. (4) Conclusion: Sleep disturbances are more common following mild and moderate TBI three months after the injury with more hours needed for sleep per day and no significant difference in sleep latency. Sleep disturbances increase in frequency with the increase in the severity of TBI.

Traumatic brain injury-induced sleep disorders

Sleep disturbances are frequently identified following traumatic brain injury, affecting 30%-70% of persons, and often occur after mild head injury. Insomnia, fatigue, and sleepiness are the most frequent sleep complaints after traumatic brain injury. Sleep apnea, narcolepsy, periodic limb movement disorder, and parasomnias may also occur after a head injury. In addition, depression, anxiety, and pain are common brain injury comorbidities with significant influence on sleep quality. Two types of traumatic brain injury that may negatively impact sleep are acceleration/deceleration injuries causing generalized brain damage and contact injuries causing focal brain damage. Polysomnography, multiple sleep latency testing, and/or actigraphy may be utilized to diagnose sleep disorders after a head injury. Depending on the disorder, treatment may include the use of medications, positive airway pressure, and/or behavioral modifications. Unfortunately, the treatment of sleep disorders associated with traumatic brain injury may not improve neuropsychological function or sleepiness.

Heart rate variability and serum level of insulin-like growth factor-1 are correlated with symptoms of emotional disorders in patients suffering a mild traumatic brain injury

OBJECTIVE

Patients who have experienced a mild traumatic brain injury (mTBI) are susceptible to symptoms of anxiety or depression. To explore the potential biomarkers for emotional disorders in mTBI patients, we analyzed the frequency domain of heart rate variability (HRV) and serum concentrations of four neurohormones.

METHODS

We assessed mTBI patients on their first visit and follow-up. Symptoms were evaluated by the Beck Anxiety Inventory and the Beck Depression Inventory, respectively. Serum levels of adrenocorticotropic hormone (ACTH), melatonin, cortisol, and insulin-like growth factor (IGF)-1 and HRV follow-ups were measured and compared.

RESULTS

mTBI patients were more vulnerable to symptoms of anxiety or depression than healthy controls. Reduced HRV was noted in mTBI patients compared to healthy controls. The mTBI patients demonstrated higher serum levels of ACTH, lower IGF-1 compared to healthy controls. In correlation analysis, only IGF-1 was positively correlated with HRV in mTBI patients. Both HRV and IGF-1 were correlated with symptom of depression while only HRV was correlated with symptom of anxiety in mTBI patients.

CONCLUSIONS

We infer that HRV may be more significantly correlated with emotional disorders than is IGF-1 in mTBI patients.

SIGNIFICANCE

The study is relevant for specific diagnostic markers in mTBI patients.

Hypopituitarism in Traumatic Brain Injury-A Critical Note

While hypopituitarism after traumatic brain injury (TBI) was previously considered rare, it is now thought to be a major cause of treatable morbidity among TBI survivors. Consequently, recommendations for assessment of pituitary function and replacement in TBI were recently introduced. Given the high incidence of TBI with more than 100 pr. 100,000 inhabitants, TBI would be by far the most common cause of hypopituitarism if the recently reported prevalence rates hold true. The disproportion between this proposed incidence and the occasional cases of post-TBI hypopituitarism in clinical practice justifies reflection as to whether hypopituitarism has been unrecognized in TBI patients or whether diagnostic testing designed for high risk populations such as patients with obvious pituitary pathology has overestimated the true risk and thereby the disease burden of hypopituitarism in TBI. The findings on mainly isolated deficiencies in TBI patients, and particularly isolated growth hormone (GH) deficiency, raise the question of the potential impact of methodological confounding, determined by variable test-retest reproducibility, appropriateness of cut-off values, importance of BMI stratified cut-offs, assay heterogeneity, pre-test probability of hypopituitarism and lack of proper individual laboratory controls as reference population. In this review, current recommendations are discussed in light of recent available evidence.

Diurnal salivary cortisol measurement in the neurosurgical-surgical intensive care unit in critically ill acute trauma patients

Acute trauma patients represent a specific subgroup of the critically ill population due to sudden and dramatic changes in homeostasis and consequently extreme demands on the activity of the hypothalamic-pituitary-adrenocortical (HPA) axis. Salivary cortisol is an accepted surrogate for serum free cortisol in the assessment of HPA axis function. The purpose of this study was (1) to establish the feasibility of salivary cortisol measurement in acute trauma patients in the neurosurgical-surgical intensive care unit (NSICU), and (2) to determine the diurnal pattern of salivary cortisol in the acute phase after injury. Saliva from 50 acute trauma patients was prospectively collected twice a day at 6AM and 4PM during the first week after injury in the NSICU. Mean PM cortisol concentrations were significantly higher in subjects versus controls (p<0.001). Subjects failed to develop the expected PM versus AM decrease in cortisol concentration seen in controls (p=0.005). Salivary cortisol did not vary significantly with baseline Glasgow Coma Scale (GCS), Injury Severity Score, sex, injury type, ethnicity, or age. When comparing mean AM and PM salivary cortisol by GCS severity category (GCS ⩽8 and GCS >8) the AM salivary cortisol was significantly higher in patients with GCS ⩽8 (p=0.002). The results show a loss of diurnal cortisol variation in acute trauma patient in the NSICU during the first week of hospitalization. Patients with severe brain injury had higher morning cortisol levels than those with mild/moderate brain injury.

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.

Does the neuroprotective role of anandamide display diurnal variations?

The endocannabinoid system is a component of the neuroprotective mechanisms that an organism displays after traumatic brain injury (TBI). A diurnal variation in several components of this system has been reported. This variation may influence the recovery and survival rate after TBI. We have previously reported that the recovery and survival rate of rats is higher if TBI occurs at 1:00 than at 13:00. This could be explained by a diurnal variation of the endocannabinoid system. Here, we describe the effects of anandamide administration in rats prior to the induction of TBI at two different times of the day: 1:00 and 13:00. We found that anandamide reduced the neurological damage at both times. Nevertheless, its effects on bleeding, survival, food intake, and body weight were dependent on the time of TBI. In addition, we analyzed the diurnal variation of the expression of the cannabinoid receptors CB1R and CB2R in the cerebral cortex of both control rats and rats subjected to TBI. We found that CB1R protein was expressed more during the day, whereas its mRNA level was higher during the night. We did not find a diurnal variation for the CB2R. In addition, we also found that TBI increased CB1R and CB2R in the contralateral hemisphere and disrupted the CB1R diurnal cycle.

Neuroendocrine changes in patients with spontaneous supratentorial intracerebral hemorrhage

BACKGROUND

Neuroendocrine changes have been reported after ischemic stroke, subarachnoid hemorrhage, and brain trauma. As there are no corresponding data in patients with intracerebral hemorrhage (ICH) we analyzed various neuroendocrine parameters to investigate possible alterations in hormone profiles of patients with ICH.

METHODS

Twenty patients with ICH were prospectively enrolled in the study. Patients were a priori parted into two groups: Ten non-ventilated patients treated on the stroke-unit (hemorrhage volumes <20 ml, "small ICH"), and 10 ventilated patients treated on the neurocritical care unit (hematoma volumes >20 ml with possible additional ventricular involvement ("large ICH"). Neuroendocrine parameters were compared between both groups referring to reference values. The following parameters were obtained over a period of 9 days in 20 patients with spontaneous supratentorial ICH: thyrotropin, free thiiodothyronine and thyroxine, human growth hormone, insulin-like growth factor 1, luteinizing hormone, follicle-stimulating hormone, testosterone, prolactin, adrenocorticotropic hormone, and cortisol.

RESULTS

Small ICH patients were in a median 71 (54-88) years old and had a mean ICH volume of 9.5 ± 6.5 ml, whereas large ICH patients were 65 (47-80) years old and showed a mean volume of 56 ± 30.2 ml. None of the patients revealed pathological alterations for thyrotropin, free thiiodothyronine, thyroxine, human growth hormone, insulin-like growth factor 1, and testosterone. There was only a mild decrease of adrenocorticotropic hormone and cortisol on day 3 in large ICH patients. Small ICH patients showed pathologically elevated levels of luteinizing and follicle-stimulating hormone throughout the observation period. Large ICH patients showed a marked increase of prolactin that developed during the course.

CONCLUSIONS

Overall, neuroendocrine changes in ICH patients are not as profound as reported for ischemic stroke or subarachnoid hemorrhage. The clinical significance of increased LH and FSH levels in small ICH is unclear, whereas elevation of prolactin in large ICH was anticipated. Future randomized controlled trials should also focus on neuroendocrine parameters to clarify the impact of possible hormonal alterations on functional outcome.

Traumatic brain injury and sleep disorders

Sleep disturbance is common after traumatic brain injury (TBI). Insomnia, fatigue, and sleepiness are the most frequent post-TBI sleep complaints with narcolepsy (with or without cataplexy), sleep apnea (obstructive or central), periodic limb movement disorder, and parasomnias occurring less commonly. In addition, depression, anxiety, and pain are common TBI comorbidities with substantial influence on sleep quality. Diagnosis of sleep disorders after TBI may involve polysomnography, multiple sleep latency testing, or actigraphy. Treatment is disorder-specific and includes the use of medications, continuous positive airway pressure, or behavioral modifications. Unfortunately, treatment of sleep disorders associated with TBI often does not improve sleepiness or neuropsychologic function.

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.

Traumatic brain injury-induced dysregulation of the circadian clock

Circadian rhythm disturbances are frequently reported in patients recovering from traumatic brain injury (TBI). Since circadian clock output is mediated by some of the same molecular signaling cascades that regulate memory formation (cAMP/MAPK/CREB), cognitive problems reported by TBI survivors may be related to injury-induced dysregulation of the circadian clock. In laboratory animals, aberrant circadian rhythms in the hippocampus have been linked to cognitive and memory dysfunction. Here, we addressed the hypothesis that circadian rhythm disruption after TBI is mediated by changes in expression of clock genes in the suprachiasmatic nuclei (SCN) and hippocampus. After fluid-percussion TBI or sham surgery, male Sprague-Dawley rats were euthanized at 4 h intervals, over a 48 h period for tissue collection. Expression of circadian clock genes was measured using quantitative real-time PCR in the SCN and hippocampus obtained by laser capture and manual microdissection respectively. Immunofluorescence and Western blot analysis were used to correlate TBI-induced changes in circadian gene expression with changes in protein expression. In separate groups of rats, locomotor activity was monitored for 48 h. TBI altered circadian gene expression patterns in both the SCN and the hippocampus. Dysregulated expression of key circadian clock genes, such as Bmal1 and Cry1, was detected, suggesting perturbation of transcriptional-translational feedback loops that are central to circadian timing. In fact, disruption of circadian locomotor activity rhythms in injured animals occurred concurrently. These results provide an explanation for how TBI causes disruption of circadian rhythms as well as a rationale for the consideration of drugs with chronobiotic properties as part of a treatment strategy for TBI.

Acute serum hormone levels: characterization and prognosis after severe traumatic brain injury

Experimental traumatic brain injury (TBI) studies report the neuroprotective effects of female sex steroids on multiple mechanisms of injury, with the clinical assumption that women have hormonally mediated neuroprotection because of the endogenous presence of these hormones. Other literature indicates that testosterone may exacerbate injury. Further, stress hormone abnormalities that accompany critical illness may both amplify or blunt sex steroid levels. To better understand the role of sex steroid exposure in mediating TBI, we 1) characterized temporal profiles of serum gonadal and stress hormones in a population with severe TBI during the acute phases of their injury; and 2) used a biological systems approach to evaluate these hormones as biomarkers predicting global outcome. The study population was 117 adults (28 women; 89 men) with severe TBI. Serum samples (n=536) were collected for 7 days post-TBI for cortisol, progesterone, testosterone, estradiol, luteinizing hormone (LH), and follicle-stimulating hormone (FSH). Hormone data were linked with clinical data, including acute care mortality and Glasgow Outcome Scale (GOS) scores at 6 months. Hormone levels after TBI were compared to those in healthy controls (n=14). Group based trajectory analysis (TRAJ) was used to develop temporal hormone profiles that delineate distinct subpopulations in the cohort. Structural equations models were used to determine inter-relationships between hormones and outcomes within a multivariate model. Compared to controls, acute serum hormone levels were significantly altered after severe TBI. Changes in the post-TBI adrenal response and peripheral aromatization influenced hormone TRAJ profiles and contributed to the abnormalities, including increased estradiol in men and increased testosterone in women. In addition to older age and greater injury severity, increased estradiol and testosterone levels over time were associated with increased mortality and worse global outcome for both men and women. These findings represent a paradigm shift when thinking about the role of sex steroids in neuroprotection clinically after TBI.