Pharmacologic Treatment of Neurobehavioral Sequelae Following Traumatic Brain Injury

Repetitive mild traumatic brain injury impairs norepinephrine system function and psychostimulant responsivity

Traumatic brain injury (TBI) is a complex pathophysiological process that results in a variety of neurotransmitter, behavioral, and cognitive deficits. The locus coeruleus-norepinephrine (LC-NE) system is a critical regulator of arousal levels and higher executive processes affected by TBI including attention, working memory, and decision making. LC-NE axon injury and impaired signaling within the prefrontal cortex (PFC) is a potential contributor to the neuropsychiatric symptoms after single, moderate to severe TBI. The majority of TBIs are mild, yet long-term cognitive deficits and increased susceptibility for further injury can accumulate after each repetitive mild TBI. As a potential treatment for restoring cognitive function and daytime sleepiness after injury psychostimulants, including methylphenidate (MPH) that increase levels of NE within the PFC, are being prescribed "off-label". The impact of mild and repetitive mild TBI on the LC-NE system remains limited. Therefore, we determined the extent of LC-NE and arousal dysfunction and response to therapeutic doses of MPH in rats following experimentally induced single and repetitive mild TBI. Microdialysis measures of basal NE efflux from the medial PFC and arousal measures were significantly lower after repetitive mild TBI. Females showed higher baseline PFC-NE efflux than males following single and repetitive mild TBI. In response to MPH challenge, males exhibited a blunted PFC-NE response and persistent arousal levels following repetitive mild TBI. These results provide critical insight into the role of catecholamine system dysfunction associated with cognitive deficits following repeated injury, outcome differences between sex/gender, and lack of success of MPH as an adjunctive therapy to improve cognitive function following injury.

Dysregulation of the dopaminergic system secondary to traumatic brain injury: implications for mood and anxiety disorders

Traumatic brain injury (TBI) represents a public health issue with a high mortality rate and severe neurological and psychiatric consequences. Mood and anxiety disorders are some of the most frequently reported. Primary and secondary damage can cause a loss of neurons and glial cells, leading to dysfunction of neuronal circuits, which can induce imbalances in many neurotransmitter systems. Monoaminergic systems, especially the dopaminergic system, are some of the most involved in the pathogenesis of neuropsychiatric and cognitive symptoms after TBI. In this work, we summarize the studies carried out in patients who have suffered TBI and describe alterations in the dopaminergic system, highlighting (1) dysfunction of the dopaminergic neuronal circuits caused by TBI, where modifications are shown in the dopamine transporter (DAT) and alterations in the expression of dopamine receptor 2 (D2R) in brain areas with dopaminergic innervation, thus establishing a hypodopaminergic state and (2) variations in the concentration of dopamine and its metabolites in biological fluids of post-TBI patients, such as elevated dopamine (DA) and alterations in homovanillic acid (HVA). On the other hand, we show a large number of reports of alterations in the dopaminergic system after a TBI in animal models, in which modifications in the levels of DA, DAT, and HVA have been reported, as well as alterations in the expression of tyrosine hydroxylase (TH). We also describe the biological pathways, neuronal circuits, and molecular mechanisms potentially involved in mood and anxiety disorders that occur after TBI and are associated with alterations of the dopaminergic system in clinical studies and animal models. We describe the changes that occur in the clinical picture of post-TBI patients, such as alterations in mood and anxiety associated with DAT activity in the striatum, the relationship between post-TBI major depressive disorders (MDD) with lower availability of the DA receptors D2R and D3R in the caudate and thalamus, as well as a decrease in the volume of the substantia nigra (SN) associated with anxiety symptoms. With these findings, we discuss the possible relationship between the disorders caused by alterations in the dopaminergic system in patients with TBI.

Amantadine for Traumatic Brain Injury-Supporting Evidence and Mode of Action

Traumatic brain injury (TBI) is an important global clinical issue, requiring not only prevention but also effective treatment. Following TBI, diverse parallel and intertwined pathological mechanisms affecting biochemical, neurochemical, and inflammatory pathways can have a severe impact on the patient's quality of life. The current review summarizes the evidence for the utility of amantadine in TBI in connection to its mechanism of action. Amantadine, the drug combining multiple mechanisms of action, may offer both neuroprotective and neuroactivating effects in TBI patients. Indeed, the use of amantadine in TBI has been encouraged by several clinical practice guidelines/recommendations. Amantadine is also available as an infusion, which may be of particular benefit in unconscious patients with TBI due to immediate delivery to the central nervous system and the possibility of precise dosing. In other situations, orally administered amantadine may be used. There are several questions that remain to be addressed: can amantadine be effective in disorders of consciousness requiring long-term treatment and in combination with drugs approved for the treatment of TBI? Do the observed beneficial effects of amantadine extend to disorders of consciousness due to factors other than TBI? Well-controlled clinical studies are warranted to ultimately confirm its utility in the TBI and provide answers to these questions.

Paradoxical cognitive and language function recovery by zolpidem in a patient with traumatic brain injury: A case report

BACKGROUND

Traumatic brain injury (TBI) is a significant public health issue, often resulting from traffic accidents and falls, leading to a wide spectrum of outcomes from mild concussions to severe brain damage. The neurorehabilitation of TBI focuses on enhancing recovery and improving quality of life. Zolpidem, traditionally used for short-term management of insomnia, has shown potential in improving cognitive functions and language in TBI patients. Advances in neuroimaging techniques, such as functional near-infrared spectroscopy (fNIRS), have facilitated the exploration of the effects of therapeutic interventions on brain activity and functional connectivity in TBI patients.

CASE SUMMARY

We present the case of a 34-year-old male who sustained a TBI from a traffic collision. Despite severe impairments in cognitive and language functions, administration of 10 mg of zolpidem resulted in temporary but significant improvements in these areas, as evidenced by increased Mini-Mental State Examination scores and observed behavioral changes. fNIRS assessments before and after zolpidem administration revealed notable changes in cerebral cortex activity, including increased left hemisphere activation and a shift in functional connectivity to the bilateral frontal lobes, corresponding with the patient's improvement.

CONCLUSION

This case study highlights the potential of zolpidem, a medication traditionally used for insomnia, in enhancing cognitive and verbal functions in a patient with TBI, suggesting a potential therapeutic role for zolpidem in neurorehabilitation, supported by changes in brain activity and connectivity observed through fNIRS. However, further investigation is warranted to validate these findings and elucidate zolpidem's long-term effects on cognitive and functional outcomes in TBI patients.

Impact of PTSD treatment on postconcussive symptoms in veterans: A comparison of sertraline, prolonged exposure, and their combination

Many Veterans who served in Iraq and Afghanistan struggle with posttraumatic stress disorder (PTSD) and the effects of traumatic brain injuries (TBI). Some people with a history of TBI report a constellation of somatic, cognitive, and emotional complaints that are often referred to as postconcussive symptoms (PCS). Research suggests these symptoms may not be specific to TBI. This study examined the impact of PTSD treatment on PCS in combat Veterans seeking treatment for PTSD. As part of a larger randomized control trial, 198 Operation Iraqi Freedom, Operation Enduring Freedom, Operation New Dawn (OIF/OEF/OND) Veterans with PTSD received Prolonged Exposure Therapy, sertraline, or the combination. Potential deployment related TBI, PCS, PTSD and depression symptoms were assessed throughout treatment. Linear mixed models were used to predict PCS change over time across the full sample and treatment arms, and the association of change in PTSD and depression symptoms on PCS was also examined. Patterns of change for the full sample and the subsample of those who reported a head injury were examined. Results showed that PCS decreased with treatment. There were no significant differences across treatments. No significant differences were found in the pattern of symptom change based on TBI screening status. Shifts in PCS were predicted by change PTSD and depression. Results suggest that PCS reduced with PTSD treatment in this population and are related to shift in depression and PTSD severity, further supporting that reported PCS symptoms may be better understood as non-specific symptoms.

Antioxidant Combo Therapy Protects White Matter After Traumatic Brain Injury

Following traumatic brain injury (TBI), increased production of reactive oxygen species (ROS) and the ensuing oxidative stress promotes the secondary brain damage that encompasses both grey matter and white matter. As this contributes to the long-term neurological deficits, decreasing oxidative stress during the acute period of TBI is beneficial. While NADPH oxidase (NOX2) is the major producer of ROS, transcription factor Nrf2 that induces antioxidant enzymes promotes efficient ROS disposal. We recently showed that treatment with an antioxidant drug combo of apocynin (NOX2 inhibitor) and TBHQ (Nrf2 activator) protects the grey matter in adult mice subjected to TBI. We currently show that this antioxidant combo therapy given at 2 h and 24 h after TBI also protects white matter in mouse brain. Thus, the better functional outcomes after TBI in the combo therapy treated mice might be due to a combination of sparing both grey matter and white matter. Hence, the antioxidant combo we tested is a potent therapeutic option for translation in future.

Role of the Dopaminergic System in the Striatum and Its Association With Functional Recovery or Rehabilitation After Brain Injury

Disabilities are estimated to occur in approximately 2% of survivors of traumatic brain injury (TBI) worldwide, and disability may persist even decades after brain injury. Facilitation or modulation of functional recovery is an important goal of rehabilitation in all patients who survive severe TBI. However, this recovery tends to vary among patients because it is affected by the biological and physical characteristics of the patients; the types, doses, and application regimens of the drugs used; and clinical indications. In clinical practice, diverse dopaminergic drugs with various dosing and application procedures are used for TBI. Previous studies have shown that dopamine (DA) neurotransmission is disrupted following moderate to severe TBI and have reported beneficial effects of drugs that affect the dopaminergic system. However, the mechanisms of action of dopaminergic drugs have not been completely clarified, partly because dopaminergic receptor activation can lead to restoration of the pathway of the corticobasal ganglia after injury in brain structures with high densities of these receptors. This review aims to provide an overview of the functionality of the dopaminergic system in the striatum and its roles in functional recovery or rehabilitation after TBI.

Rivastigmine Transdermal Patch Treatment for Moderate to Severe Cognitive Impairment in Veterans with Traumatic Brain Injury (RiVET Study): A Randomized Clinical Trial

Cognitive impairment is common in veterans with histories of traumatic brain injury (TBI). Cholinergic deficits have been hypothesized as contributors to this impairment. We report the effects of cholinesterase inhibitor rivastigmine transdermal patch treatment in veterans with TBI and post-traumatic memory impairment. Our objective was to evaluate the efficacy and safety of a 9.5 mg/24 h (10 cm²) rivastigmine patch in veterans of military conflicts with persistent moderate to severe memory impairment at least 12 weeks after TBI. This randomized, outpatient, double-blind, placebo-controlled 12-week trial with an exploratory double-blind phase of an additional 14 weeks was conducted at 5 VA Medical Centers, among veterans with closed, non-penetrating TBI who met or exceeded modified American Congress of Rehabilitation Medicine criteria for mild TBI with verbal memory deficits, as assessed by the Hopkins Verbal Learning Test, Revised (HVLT-R). Patients were randomized 1:1 to rivastigmine or matching placebo patches after a 1-week single-blind, placebo run-in phase. At randomization, patients received 4.6 mg/24 h rivastigmine patches or matching placebo increased to a 9.5 mg/24 h patch after 4 weeks. The primary efficacy outcome measure was the proportion of participants who had at least a five-word improvement on the HVLT-R Total Recall Index (Trials 1-3). A total of 3671 participants were pre-screened, of whom 257 (7.0%) were screened; 96 (37%) randomized, and 94 included in study analyses. Responder rates were 40.8% (20 of 49) and 51.1% (23 of 45) in the rivastigmine and placebo groups, respectively (p = 0.41). A mixed-effect model including treatment, time, and treatment-by-time interaction indicated no significant difference in treatment effect over time between the groups (p = 0.24). Overall, there were no significant differences in changes for all secondary outcomes between the rivastigmine and placebo groups. The most commonly observed adverse events were application site reactions. This trial provides the largest sample to date of veterans with TBI and post-traumatic memory deficits enrolled in a pharmacological trial. Trial Registration: clinicaltrials.gov Identifier: NCT01670526.

An Overview and Therapeutic Promise of Nutraceuticals against Sports-Related Brain Injury

Sports-related traumatic brain injury (TBI) is one of the common neurological maladies experienced by athletes. Earlier the term 'punch drunk syndrome' was used in the case TBI of boxers and now this term is replaced by chronic traumatic encephalopathy (CTE). Sports-related brain injury can either be short term or long term. A common instance of brain injury encompasses subdural hematoma, concussion, cognitive dysfunction, amnesia, headache, vision issue, axonopathy, or even death if remain undiagnosed or untreated. Further, chronic TBI may lead to pathogenesis of neuroinflammation and neurodegeneration via tauopathy, formation of neurofibrillary tangles, and damage to the blood-brain barrier, microglial, and astrocyte activation. Thus, altered pathological, neurochemical, and neurometabolic attributes lead to the modulation of multiple signaling pathways and cause neurological dysfunction. Available pharmaceutical interventions are based on one drug one target hypothesis and thereby unable to cover altered multiple signaling pathways. However, in recent time's pharmacological intervention of nutrients and nutraceuticals have been explored as they exert a multifactorial mode of action and maintain over homeostasis of the body. There are various reports available showing the positive therapeutic effect of nutraceuticals in sport-related brain injury. Therefore, in the current article we have discussed the pathology, neurological consequence, sequelae, and perpetuation of sports-related brain injury. Further, we have discussed various nutraceutical supplements as well as available animal models to explore the neuroprotective effect/ upshots of these nutraceuticals in sports-related brain injury.