Age, symptoms, and functional outcome after mild traumatic brain injury

Sensory sensitivity after acquired brain injury: A systematic review

Patients with acquired brain injury frequently report experiencing sensory stimuli as abnormally under- (sensory hyposensitivity) or overwhelming (sensory hypersensitivity). Although they can negatively impact daily functioning, these symptoms are poorly understood. To provide an overview of the current evidence on atypical sensory sensitivity after acquired brain injury, we conducted a systematic literature review. The primary aim of the review was to investigate the behavioural and neural mechanisms that are associated with self-reported sensory sensitivity. Studies were included when they studied sensory sensitivity in acquired brain injury populations, and excluded when they were not written in English, consisted of non-empirical research, did not study human subjects, studied pain, related sensory sensitivity to peripheral injury or studied patients with a neurodegenerative disorder, meningitis, encephalitis or a brain tumour. The Web of Science, PubMed and Scopus databases were searched for appropriate studies. A qualitative synthesis of the results of the 81 studies that were included suggests that abnormal sensory thresholds and a reduced information processing speed are candidate behavioural mechanisms of atypical subjective sensory sensitivity after acquired brain injury. Furthermore, there was evidence for an association between subjective sensory sensitivity and structural grey or white matter abnormalities, and to functional abnormalities in sensory cortices. However, further research is needed to explore the causation of atypical sensory sensitivity. In addition, there is a need for the development of adequate diagnostic tools. This can significantly advance the quantity and quality of research on the prevalence, aetiology, prognosis and treatment of these symptoms.

Aging-Associated Thyroid Dysfunction Contributes to Oxidative Stress and Worsened Functional Outcomes Following Traumatic Brain Injury

The incidence of traumatic brain injury (TBI) increases dramatically with advanced age and accumulating evidence indicates that age is one of the important predictors of an unfavorable prognosis after brain trauma. Unfortunately, thus far, evidence-based effective therapeutics for geriatric TBI is limited. By using middle-aged animals, we first confirm that there is an age-related change in TBI susceptibility manifested by increased inflammatory events, neuronal death and impaired functional outcomes in motor and cognitive behaviors. Since thyroid hormones function as endogenous regulators of oxidative stress, we postulate that age-related thyroid dysfunction could be a crucial pathology in the increased TBI severity. By surgically removing the thyroid glands, which recapitulates the age-related increase in TBI-susceptible phenotypes, we provide direct evidence showing that endogenous thyroid hormone-dependent compensatory regulation of antioxidant events modulates individual TBI susceptibility, which is abolished in aged or thyroidectomized individuals. The antioxidant capacity of melatonin is well-known, and we found acute melatonin treatment but not liothyronine (T3) supplementation improved the TBI-susceptible phenotypes of oxidative stress, excitotoxic neuronal loss and promotes functional recovery in the aged individuals with thyroid dysfunction. Our study suggests that monitoring thyroid function and acute administration of melatonin could be feasible therapeutics in the management of geriatric-TBI in clinic.

Systematic Review and Meta-analysis of Outcome after Mild Traumatic Brain Injury in Older People

OBJECTIVE

Older age is often identified as a risk factor for poor outcome from traumatic brain injury (TBI). However, this relates predominantly to mortality following moderate-severe TBI. It remains unclear whether increasing age exerts risk on the expected recovery from mild TBI (mTBI). In this systematic review of mTBI in older age (60+ years), a focus was to identify outcome through several domains - cognition, psychological health, and life participation.

METHODS

Fourteen studies were identified for review, using PRISMA guidelines. Narrative synthesis is provided for all outcomes, from acute to long-term time points, and a meta-analysis was conducted for data investigating life participation.

RESULTS

By 3-month follow-up, preliminary findings indicate that older adults continue to experience selective cognitive difficulties, but given the data it is possible these difficulties are due to generalised trauma or preexisting cognitive impairment. In contrast, there is stronger evidence across time points that older adults do not experience elevated levels of psychological distress following injury and endorse fewer psychological symptoms than younger adults. Meta-analysis, based on the Glasgow Outcome Scale at 6 months+ post-injury, indicates that a large proportion (67%; 95% CI 0.569, 0.761) of older adults can achieve good functional recovery, similar to younger adults. Nevertheless, individual studies using alternative life participation measures suggest more mixed rates of recovery.

CONCLUSIONS

Although our initial review suggests some optimism in recovery from mTBI in older age, there is an urgent need for more investigations in this under-researched but growing demographic. This is critical for ensuring adequate health service provision, if needed.

Age-at-Injury Determines the Extent of Long-Term Neuropathology and Microgliosis After a Diffuse Brain Injury in Male Rats

Traumatic brain injury (TBI) can occur at any age, from youth to the elderly, and its contribution to age-related neuropathology remains unknown. Few studies have investigated the relationship between age-at-injury and pathophysiology at a discrete biological age. In this study, we report the immunohistochemical analysis of naïve rat brains compared to those subjected to diffuse TBI by midline fluid percussion injury (mFPI) at post-natal day (PND) 17, PND35, 2-, 4-, or 6-months of age. All brains were collected when rats were 10-months of age (n = 6–7/group). Generalized linear mixed models were fitted to analyze binomial proportion and count data with R Studio. Amyloid precursor protein (APP) and neurofilament (SMI34, SMI32) neuronal pathology were counted in the corpus callosum (CC) and primary sensory barrel field (S1BF). Phosphorylated TAR DNA-binding protein 43 (pTDP-43) neuropathology was counted in the S1BF and hippocampus. There was a significantly greater extent of APP and SMI34 axonal pathology and pTDP-43 neuropathology following a TBI compared with naïves regardless of brain region or age-at-injury. However, age-at-injury did determine the extent of dendritic neurofilament (SMI32) pathology in the CC and S1BF where all brain-injured rats exhibited a greater extent of pathology compared with naïve. No significant differences were detected in the extent of astrocyte activation between brain-injured and naïve rats. Microglia counts were conducted in the S1BF, hippocampus, ventral posteromedial (VPM) nucleus, zona incerta, and posterior hypothalamic nucleus. There was a significantly greater proportion of deramified microglia, regardless of whether the TBI was recent or remote, but this only occurred in the S1BF and hippocampus. The proportion of microglia with colocalized CD68 and TREM2 in the S1BF was greater in all brain-injured rats compared with naïve, regardless of whether the TBI was recent or remote. Only rats with recent TBI exhibited a greater proportion of CD68-positive microglia compared with naive in the hippocampus and posterior hypothalamic nucleus. Whilst, only rats with a remote brain-injury displayed a greater proportion of microglia colocalized with TREM2 in the hippocampus. Thus, chronic alterations in neuronal and microglial characteristics are evident in the injured brain despite the recency of a diffuse brain injury.

Sensitivity to Noise Following a Mild Traumatic Brain Injury: A Longitudinal Study

OBJECTIVE

To describe changes in the prevalence and clinical correlates of noise sensitivity (NS) in mild traumatic brain injury (mTBI) across a 12-month period and to determine whether NS at an early stage of recovery has predictive value for later postconcussive symptoms.

SETTING

A mixed urban and rural region of New Zealand.

PARTICIPANTS

Data for 341 adults (201 males, 140 females; age range from 16 to 91 years) were extracted from a 1-year TBI incidence, and outcomes study was conducted in New Zealand.

DESIGN

Secondary analysis of data from a community-based, longitudinal population study of an mTBI incidence cohort collected within 1 week of injury (baseline) and at 1, 6, and 12 months postinjury.

MAIN MEASURES

Measures at baseline (within 2 weeks of the injury) and 1, 6, and 12 months included the Rivermead Post-concussion Symptoms Questionnaire and its NS item, the Hospital Depression and Anxiety Scale, and the computerized CNS-Vital Signs neurocognitive test.

RESULTS

NS progressively declined postinjury, from 45% at baseline to 28% at 12 months. In turn, NS showed itself as a significant predictor of future postconcussive symptoms.

CONCLUSION

Taken together with previous research, the findings of the current study indicate that NS may have clinical utility in flagging vulnerability to persistent postconcussive symptoms.

Cognitive performance in older adults at three months following mild traumatic brain injury

Introduction: In the context of limited research assessing outcomes following mild traumatic brain injury (mTBI) in older adults, this study evaluated cognitive outcomes through prospective memory, and expected that performance of an older mTBI group (≥65 years) would be lower compared to orthopedic and community controls. The study also explored whether cognitive resources (retrospective memory, executive function) moderated any association between presenting Glasgow Coma Scale (GCS) and prospective memory.Method: At three-months post-injury, a mTBI group (n = 39), an orthopedic control group (n = 63), and a community control group (n = 46) completed a neuropsychological assessment, including (i) prospective memory, using a standardized paper-and-pencil task (Cambridge Prospective Memory Test), an augmented reality task and a naturalistic task, and (ii) standardized measures of retrospective memory (Hopkins Verbal Learning Test) and executive function (Trail Making Test). Group performances were compared, and bootstrapped moderation analyses evaluated the role of cognitive resources in the relationship between GCS and prospective memory outcome.Results: The mTBI group, as compared to community controls, performed significantly lower on the augmented reality task (d = -0.64 to d = -0.79), and there was a small-moderate but non-significant effect (d = -0.45) on the naturalistic task. There were no differences between the mTBI group and orthopedic controls. Retrospective memory was a unique predictor of the augmented reality task (B = 1.83) and moderated the relationship between presenting GCS and the naturalistic task (B = -5.60). Executive function moderated the association between presenting GCS and augmented reality (B = -1.13) and naturalistic task (B = -1.57).Conclusions: At three-months post-mTBI, older adults are at risk of poor cognitive performance; and the relationship between GCS and prospective memory can be moderated by cognitive resources. Further follow-up is indicated to determine whether impairments resolve or persist over time.