Increased temperature is common after brain trauma and stroke, considered to be detrimental to outcome and usually treated with systemic cooling interventions. However, targeting cooling interventions at the head may be more logical. In addition to arterial blood, the human brain is cooled by heat loss through the skull and heat loss from the upper airways. It is these two mechanisms of heat loss which are the subject of this thesis. The initial research aim was to find out if restoring ‘normal’ airflow through the upper respiratory tracts of intubated, brain-injured patients could reduce brain temperature. Air at room temperature and humidity replicating normal resting minute volume was continuously administered nasally to 15 such patients. After a 30 minute baseline, they were randomised to receive airflow or no airflow for 6 hours and then crossed over for a further 6 hours. The airflow did not produce significant reductions in intracranial temperature (Mean -0.13 °C, SD 0.55 °C, 95% CI -0.43 to 0.17 °C). However, some evidence of heat loss through the skull was serendipitously observed. This was investigated formally in a randomised factorial trial, together with nasal airflow with enhancements (unhumidified air at twice minute volume with 20 ppm nitric oxide gas) intended to overcome some of the possible reasons for the neutral results with ‘normal’ airflow. After a 30 minute baseline, 12 intubated, brain-injured patients received enhanced nasal airflow, bilateral head fanning (8 m/s), both together and no intervention in randomised order. Each intervention was delivered for 30 minutes followed by 30 minutes washout. Mean brain temperature was reduced by 0.15 °C with nasal airflow (p=0.001, 95% CI 0.06 to 0.23 °C) and 0.26 °C with head fanning (p<0.001, 95% CI 0.17 to 0.34 °C). The estimate of the combined effect of airflow and fanning on brain temperature was 0.41 °C. Physiologically, this study demonstrated that heat loss through the upper airways and through the skull can reduce parenchymal brain temperature in brain-injured humans, that the effects are additive and the onset of temperature reduction is rapid. The most promising mechanism appeared to be heat loss through the skull and the final piece of research involved developing and initial (phase I) assessment of a convective head cooling device in healthy volunteers, with intracranial temperature measured non-invasively by magnetic resonance spectroscopy. After a 10 minute baseline, five healthy volunteers received 30 minutes head cooling followed by 30 minutes head and neck cooling via a hood and neck collar delivering 14.5 °C air at 42.5 L/s. The net brain temperature reduction with head cooling was 0.45 °C (SD 0.23 °C, p=0.01, 95% CI 0.17 to 0.74 °C) and with head and neck cooling 0.37 °C (SD 0.30 °C, p=0.049, 95% CI 0.00 to 0.74 °C). There was no significant reduction in cooling with progressive depth into the brain i.e. core brain was cooled. The main relevance of this research is physiological because it adds to knowledge and understanding of mechanisms of heat loss from the upper airways and through the skull in humans. Clinically, factors which enhance or inhibit these mechanisms may have an effect on brain temperature but the therapeutic relevance of head cooling by these methods requires further research.

The majority of the estimated three million traumatic brain injuries that occur each year are classified as “mild” and do not require surgical intervention. However, debilitating symptoms such as difficulties focusing on tasks, anxiety, depression, and visual deficits can persist chronically after a mild traumatic brain injury (TBI) even if an individual appears “fine”. These symptoms have been observed to worsen or be prolonged when an individual has suffered multiple mild TBIs. To test the hypothesis that increasing the amount of time between head injuries can reduce the histopathological and behavioral consequences of repeated mild TBI, a mouse model of closed head injury (CHI) was developed. A pneumatically controlled device with a silicone tip was used to deliver a diffuse, midline impact directly onto the mouse skull. A 2.0mm intended depth of injury caused a brief period of apnea and increased righting reflex response with minimal astrogliosis and axonal injury bilaterally in the entorhinal cortex, optic tract, and cerebellum. When five CHIs were repeated at 24h inter-injury intervals, astrogliosis was exacerbated acutely in the hippocampus and entorhinal cortex compared to a single mild TBI. Additionally, in the entorhinal cortex, hemorrhagic lesions developed along with increased neurodegeneration and microgliosis. Axonal injury was observed bilaterally in the white matter tracts of the cerebellum and brainstem. When the inter-injury interval was extended to 48h, the extent of inflammation and cell death was similar to that caused by a single CHI suggesting that, in our mouse model, extending the inter-injury interval from 24h to 48h reduced the acute effects of repeated head injuries. The behavioral consequences of repeated CHI at 24h or 48h inter-injury intervals were evaluated in a ten week longitudinal study followed by histological analyses. Five CHI repeated at 24h inter-injury intervals produced motor and cognitive deficits that persisted throughout the ten week study period. Based upon histological analyses, the acute inflammation, axonal injury, and cell death observed acutely in the entorhinal cortex had resolved by ten weeks after injury. However, axonal degeneration and gliosis were present in the optic tract, optic nerve, and corticospinal tract. Extending the inter-injury interval to 48h did not significantly reduce motor and cognitive deficits, nor did it protect against chronic microgliosis and neurodegeneration in the visual pathway. Together these data suggested that some white matter areas may be more susceptible to our model of repeated mild TBI causing persistent neuropathology and behavioral deficits which were not substantially reduced with a 48h inter-injury interval. In many forms of TBI, microgliosis persists chronically and is believed to contribute to the cascade of neurodegeneration. To test the hypothesis that post-traumatic microgliosis contributes to mild TBI-related neuropathology, mice deficient in the growth factor progranulin (Grn-/-) received repeated CHI and were compared to wildtype, C57BL/6 mice. Penetrating head injury was previously reported to amplify the acute microglial response in Grn-/- mice. In our studies, repeated CHI induced an increased microglial response in Grn-/- mice compared to C57BL/6 mice at 48h, 7d, and 7mo after injury. However, no differences were observed between Grn-/- and WT mice with respect to their behavioral responses or amount of axonal injury or ongoing neurodegeneration at 7 months despite the robust differences in microgliosis. Dietary administration of ibuprofen initiated after the first injury reduced microglial activation within the optic tract of WT mice 7d after repeated mild TBI. However, a two week ibuprofen treatment regimen failed to affect the extent of behavioral dysfunction over 7mo or decrease chronic neurodegeneration, axon loss, or microgliosis in brain-injured Grn-.- mice when compared to standard diet. Together these studies underscore that mild TBIs, when repeated, can result in long lasting behavioral deficits accompanied by neurodegeneration within vulnerable brain regions. Our studies on the time interval between repeated head injuries suggest that a 48h inter-injury interval is within the window of mouse brain vulnerability to chronic motor and cognitive dysfunction and white matter injury. Data from our microglia modulation studies suggest that a chronically heightened microglial response following repeated mild TBI in progranulin deficient mice does not worsen chronic behavioral dysfunction or neurodegeneration. In addition, a two week ibuprofen treatment is not effective in reducing the microglial response, chronic behavioral dysfunction, or chronic neurodegeneration in progranulin deficient mice. Our data suggests that microglia are not a favorable target for the treatment of TBI.

Glucocorticoid activation of two types of adrenocorticosteroid receptors (ACRs), themineralocorticoid receptor (MR) and the glucocorticoid receptor (GR), influences hippocampalneuron vulnerability to injury. Excessive activation of GR may compromise hippocampalneuron survival after several types of challenge including ischemic, metabolic, and excitotoxicinsults. In contrast, MR prevents adrenalectomy-induced loss of granule neurons in the dentategyrus. The present thesis addresses the respective roles of MR and GR in modulating neuronalsurvival following two forms of neuronal injury, excitotoxicity and traumatic brain injury. MaleSprague-Dawley rats were pretreated with MR antagonist spironolactone or GR antagonistmifepristone (RU486) and subsequently injected with kainic acid, an excitotoxic glutamateanalog, or injured with a controlled cortical impact. Twenty-four hours following injury,hippocampal neuron survival was measured to test the hypotheses that MR blockade wouldendanger and GR blockade would protect hippocampal neurons following injury. MessengerRNA levels of viability-related genes including bcl-2, bax, p53, BDNF, and NT-3 were alsomeasured to test the hypothesis that ACR regulation of these genes wouldcorrelate with neuronal survival. In addition, ACR mRNA levels were measured followingreceptor blockade and injury to test the hypothesis that glucocorticoid signaling is alteredfollowing neuronal injury via regulation of ACR expression.Mineralocorticoid receptor blockade with spironolactone increased neuronal vulnerability toexcitotoxic insult in hippocampal field CA3, and GR blockade with RU486 prevented neuronalloss after traumatic brain injury in field CA1. These results are consistent with the hypothesesthat MR protects and GR endangers hippocampal neurons. Adrenocorticosteroid receptorblockade decreased mRNA levels of the anti-apoptotic gene bcl-2 in select regions of uninjuredhippocampus, yet ACR regulation of bcl-2 did not consistently correspond with measures ofneuronal survival after injury. Kainic acid decreased MR mRNA levels in CA1 and CA3, whileboth kainic acid and controlled cortical impact dramatically decreased GR mRNA levels indentate gyrus. These data suggest that injury modulation of glucocorticoid signaling throughregulation of ACR expression may influence hippocampal neuron viability following injury.

In the hours and days following acute CNS injury, a secondary wave of events is initiated that exacerbate spinal tissue damage and neuronal cell death. A potential mechanism driving these secondary events is opening of the mitochondrial permeability transition pore (mPTP) and subsequent release of several cell death proteins. Previous studies have shown that inhibition of cyclophilin D(CypD), the key regulating component in mPTP opening, was protective against insults that induce necrotic cell death. We therefore hypothesized that CypD-null mice would show improved functional and pathological outcomes following spinal cord injury (SCI) and traumatic brain injury (TBI). Moderate and severe spinal contusion was produced in wild-type (WT) and CypD-null mice at the T-10 level using the Infinite Horizon impactor. Changes in locomotor function were evaluated using the Basso Mouse Scale (BMS) at 3 days post-injury followed by weekly testing for 4 weeks. Histological assessment of tissue sparing and lesion volume was performed 4 weeks post SCI. Calpain activity, measured by calpain-mediated spectrin degradation, was assessed in moderate injury only by western blot 24 hours post SCI. Results showed that following moderate SCI, CypD-null mice had no significant improvement in locomotor recovery or tissue sparing compared to wild-type mice. Following severe SCI, CypD-null mice showed significantly lower locomotor recovery and decreased tissue sparing compared to WT mice. Calpain-mediated spectrin degradation was not significantly reduced in CypD-null mice compared to WT mice 24h post moderate SCI. The lack of protective effects in CypD-null mice suggests that more dominant mechanisms are involved in the pathology of SCI. In addition, CypD may have a pro survival role that is dependent on the severity of the spinal cord injury.

Older individuals sustaining traumatic brain injury (TBI) experience a much higher incidence of morbidity and mortality. This age-related exacerbated response to neurological insult has been demonstrated experimentally in aged animals, which can serve as a model to combat this devastating clinical problem. The reasons for this worse initial response are unknown but may be related to age-related changes in mitochondrial respiration. Evidence is shown that mitochondrial dysfunction occurs early following traumatic brain injury (TBI), persists long after the initial insult, and is severitydependent. Synaptic and extrasynaptic mitochondrial fractions display distinct respiration capacities, stressing the importance to analyze these fractions separately. Sprague- Dawley and Fischer 344 rats, two commonly used strains used in TBI and aging research, were found to show very similar respiration profiles, indicating respiration data are not strain dependent. Neither synaptic nor extrasynaptic mitochondrial respiration significantly declined with age in naïve animals. Only the synaptic fraction displayed significant age-related increases in oxidative damage, measured by 3-nitrotyrosine (3- NT), 4-hydroxynonenal (4-HNE), and protein carbonyls (PC). Alterations in respiration with age appear to be more subtle than previously thought. Subtle declines in respiration and elevated levels of oxidative damage may not to be sufficient to produce detectable deficits until the system is challenged. Following TBI, synaptic mitochondria exhibit dysfunction that increased significantly with age at injury, evident in lower respiratory control ratio (RCR) values and declines in ATP production rates. Furthermore, synaptic mitochondria displayed increased levels of oxidative damage with age and injury, while extrasynaptic mitochondria only displayed significant elevations following the insult. Age-related synaptic mitochondrial dysfunction following TBI may contribute to an exacerbated response in the elderly population.

Brain trauma occurs frequently in children and its consequences cause significant health and financial burden to the patients, their carers and society. This thesis assessed the modulating effects of physiological, genetic, and biochemical factors on the sequelae of childhood brain trauma. Primary brain injury from the mechanical forces of trauma and secondary brain insults consequent on the primary injury are determinants of brain trauma outcome. The most important secondary insults recognised are reduced cerebral perfusion pressure (CPP) and raised intracranial pressure (ICP). CPP is governed by the mean arterial blood pressure and the ICP. During childhood these physiological measures change with age. With continuous physiological recordings, ‘critical’ age-related minimum CPP thresholds for children aged 2-6, 7-10 and 11-15 years were defined as 48, 54 and 58mmHg respectively. Utilising these thresholds and a novel cumulative pressure-time index (PTIc), we have demonstrated that CPP insult still remains a feature in 80% of the severe brain trauma patients and significantly relates to global outcome. Brain trauma and cerebral ischaemia are stimuli to the inflammatory cascade leading to further brain damage. Serum adhesion molecule levels after brain trauma indicate injury severity and predict outcome better than brain specific proteins. Predictability is improved using more than one serum biomarker level. Neuro-inflammatory pathways involving adhesion molecules may have a strong modulating effect on brain trauma outcome but warrants further investigations in relation to CPP insult. Genetic factors such as Apolipoprotein E (APO E) genetic polymorphisms may additionally influence outcome, but it was not known whether genetic factors lessen the quantity of CPP insult or the cellular response to it. We demonstrated that the e4 carriers who had unfavourable outcome had 22 times less CPP insult than the non-e4 carriers, while the e3 homozygous who had good recovery had 26 times more CPP insult than the non-e3 homozygous. This suggests that APO E polymorphisms may affect the patient’s cerebral ischaemic tolerance differently, indicating especially the need to prevent CPP insult among e4 carriers. Cerebral ischaemia may, therefore, be a common pathway through which physiological and genetic factors modulate outcome after brain trauma.

The aims of the thesis were to examine i) whether the endogenous opioid system (EOS) is lateralized in human brain areas involved in processing of emotions and pain; ii) whether EOS responses to unilateral brain injury depend on side of lesion, and iii) whether in human alcoholics, this system is involved in molecular adaptations in brain areas relevant for cognitive control of addictive behavior and habit formation. The main findings were that (1) opioid peptides but not opioid receptors and classic neurotransmitters are markedly lateralized in the anterior cingulate cortex involved in processing of  positive and negative emotions and affective component of pain. The region-specific lateralization of neuronal networks expressing opioid peptides may underlie in part lateralization of higher functions in the human brain including emotions and pain. (2) Analysis of the effects of traumatic brain injury (TBI) demonstrated predominant alteration of dynorphin levels in the hippocampus ipsilateral to the injury, while injury to the right hemisphere affected dynorphin levels in the striatum and frontal cortex to a greater extent than that to the left hemisphere. Thus, trauma reveals a lateralization in the mechanisms mediating the response of dynorphin expressing neuronal networks in the brain. These networks may differentially mediate effects of left or right brain injury on lateralized brain functions. (3) In human alcoholics, the enkephalin and dynorphin systems were found to be downregulated in the caudate nucleus and / or putamen that may underlie in part changes in goal directed behavior and formation of a compulsive habit in alcoholics. In contrast to downregulation in these areas, PDYN mRNA and dynorphins in dorsolateral prefrontal cortex, k-opioid receptor mRNA in orbitofrontal cortex, and dynorphins in hippocampus were upregulated in alcoholics. Activation of the k-opioid receptor by upregulated dynorphins may underlie in part neurocognitive dysfunctions relevant for addiction and disrupted inhibitory control. We conclude that the EOS exhibits region-specific lateralization in human brain and brain-area specific lateralized response after unilateral TBI in mice; and that the EOS is involved in adaptive processes associated with specific aspects of alcohol dependence.

Intact white matter is critical for normal cognitive function. In traumatic brain injury (TBI), chronic cerebral hypoperfusion and Alzheimer’s disease (AD) damage to white matter is associated with cognitive impairment. However, these conditions are associated with grey matter damage or with other pathological states and the contribution of white matter damage in isolation to their pathogenesis is not known. Furthermore, TBI is a risk factor for AD and cerebral hypoperfusion is an early feature of AD. It is hypothesised that white matter damage following TBI or chronic cerebral hypoperfusion will be associated with cognitive deficits and that white matter changes after injury contribute to AD pathogenesis. To investigate this, this thesis examined the contribution of white matter damage to cognitive deficits after TBI and chronic cerebral hypoperfusion and furthermore, investigated the role of white matter damage in the relationship between TBI and AD. Three studies addressed these aims. In the first, mild TBI was induced in wild-type mice and the effects on axons, myelin and neuronal cell bodies examined at time points from 4 hours to 6 weeks after injury. Spatial reference learning and memory was tested at 3 and 6 weeks after injury. Injured mice showed axonal damage in the cingulum, close to the injury site in the hours after injury and at 6 weeks, damage in the thalamus and external capsule were apparent. Injured and sham animals had comparable levels of neuronal damage and no change was observed in myelin. Injured animals showed impaired spatial reference learning at 3 weeks after injury, demonstrating that selective axonal damage is sufficient to impair cognition. In the second study mild TBI was induced in a transgenic mouse model of AD and the effects on white matter pathology and AD-related proteins examined 24 hours after injury. There was a significant increase in axonal damage in the cingulum and external capsule and parallel accumulations of amyloid were observed in these regions. There were no changes in tau or in overall levels of AD-related proteins. This suggests that axonal damage may have a role in mediating the link between TBI and AD. The third study used a model of chronic cerebral hypoperfusion in wild type mice and investigated white matter changes after one and two months of hypoperfusion as well as a comprehensive assessment of learning and memory. Chronic cerebral hypoperfusion resulted in diffuse myelin damage in the absence of ischaemic neuronal damage at both 1 and 2 months after induction of hypoperfusion. Hypoperfused animals also showed minimal axonal damage and microglial activation. Cognitive testing revealed a selective impairment in spatial working memory but not spatial reference or episodic memory in hypoperfused animals, showing that modest reductions in blood flow have effects on white matter sufficient to cause cognitive impairment. These results demonstrate that selective damage to white matter components can have a long-term impact on cognitive function as well as on the development of AD. This suggests that minimisation of axonal damage after TBI is a target for reducing subsequent risk of AD and that repair or prevention of white matter damage is a promising strategy for rescuing cognitive function in individuals who have experienced mild TBI or chronic cerebral hypoperfusion.

Background and aims: The provenance of post-concussion symptoms (PCS) and post-traumatic stress (PTSD) after mild traumatic brain injury (mTBI) is controversial. This thesis investigated factors influencing these two conditions separately, as well as the interplay between PCS and PTSD, in individuals with mTBI and a control sample without mTBI (orthopaedic injuries). Method: Consecutive adult attendees of an Emergency Department with mTBI or orthopaedic injury were prospectively recruited and completed the Rivermead Post-concussion Questionnaire (RPQ) and Trauma Screening Questionnaire (TSQ) for PTSD at two weeks (T1) and three months (T2) post-injury. The sample at T1 consisted of 34 with complicated mTBI, 76 with uncomplicated mTBI and 47 with orthopaedic injury, and 18 with complicated mTBI, 43 with uncomplicated mTBI and 33 orthopaedic controls at T2. Results: Although there were no differences in overall PCS symptomology between groups, a subset of PCS symptoms (headaches, dizziness and nausea) was found to be specific to mTBI at both time points. These symptoms are proposed to have a neurological basis, as opposed to a psychological basis. PTSD interacted with PCS, particularly in mTBI, such that PTSD was associated with greater “neurogenic” and “psychogenic” symptomology in this group, but only a moderate increase in psychogenic symptoms for controls. A model of the influence of PTSD on PCS is presented. PTSD was influenced by poor memory quality for the traumatic event and attribution of blame to others, but not by mTBI. Discussion and conclusions: Though mTBI may set the scene for at least neurogenic symptoms of PCS to occur, psychological mechanisms, particularly PTSD, have a significant role in the persistence of PCS. Our findings suggest the need for a clear story and sense of meaning for a traumatic event for good recovery from PTSD. Taken together, the results suggest that psychological interventions, particularly aimed at PTSD, may be most effective after mTBI.

Bakgrund: Traumatisk hjärnskada (THS) orsakas av våld mot huvud i samband med fallolyckor eller trafikolyckor. Varje år söker 20 000 personer vård på grund av skallskador. Vården för traumatiskt hjärnskadade patienter i Sverige skiljer sig åt, mycket beroende på avstånden som finns till specialistsjukhus, tiden och rätta åtgärder är avgörande faktorer för denna patientgrupp. Syfte: Att undersöka vikten och intensivvårdssjuksköterskors behov av rutiner i samband med vård av patienter med hjärnskador på allmänintensivvårdsavdelningar och på neurointensivvårdavdelningar. Metod: Kvalitativ studie med fokusgruppsintervjuer av tio intensivvårdsjuksköterskor som arbetar på en allmänintensivvårdsavdelning (IVA) och specialistneurointensivvårdavdelningen (NIVA). Resultat: På NIVA finns väl inarbetade rutiner och tydliga riktlinjer nedskrivna. Sjuksköterskornas upplevelse var att det fanns tillräckligt med rutiner, men några rutiner kunde utvecklas. På IVA fanns det inga nedskrivna riktlinjer och inga tydliga rutiner för att vårda denna patientgrupp. Vården och kontrollerna ordinerades av läkare som är i tjänst. Slutsats: Vården kring hjärnskadade patienter är ytterst viktigt då man ständigt måste förebygga sekundära skador/insulter. Rutiner är väl inarbetade på specialistsjukhuset, men vården börjar först på hemsjukhuset på IVA där tydliga rutiner och riktlinjer saknas. / Introduction: Traumatic brain injury caused by violence against the head during a fall or traffic accident. Each year 20000 people gets medical care because of head injuries. The care for traumatic brain injured patients in Sweden differ greatly depending on the distances available to specialist hospitals, the time and the proper measures are crucial factors in this population. Aim: The study aims to examine the importance and intensive care nurses need routines in connection with care of patients with brain injuries in general intensive care units and in neurological intensive care units. The study consists of three group interviews in a general ICU unit in Falun and specialist unit (NIVA). Method: A qualitative study with focus group interviews. Results: The results showed that the level have clear procedures and written guidelines regarding the "avoidable factors" which are well established, their experience was that there were enough procedures, but that some could continue to develop. IVA there were no written guidelines and no clear procedures to care for this population without the care and controls prescribed by the doctor who is on duty. Conclusion: The conclusion is that care about the brain-damaged patients is extremely important when you constantly have to prevent secondary injury / insults and check the "avoidable factors". Routines are well established on specialist hospital care but starts first at home hospital where the importance of working towards the same goal and have clear procedures and guidelines from the start.