Repetitive, but Not Single, Mild Blast TBI Causes Persistent Neurological Impairments and Selective Cortical Neuronal Loss in Rats

Exposure to repeated mild blast traumatic brain injury (mbTBI) is common in combat soldiers and the training of Special Forces. Evidence suggests that repeated exposure to a mild or subthreshold blast can cause serious and long-lasting impairments, but the mechanisms causing these symptoms are unclear. In this study, we characterise the effects of single and tightly coupled repeated mbTBI in Sprague-Dawley rats exposed to shockwaves generated using a shock tube. The primary outcomes are functional neurologic function (unconsciousness, neuroscore, weight loss, and RotaRod performance) and neuronal density in brain regions associated with sensorimotor function. Exposure to a single shockwave does not result in functional impairments or histologic injury, which is consistent with a mild or subthreshold injury. In contrast, exposure to three tightly coupled shockwaves results in unconsciousness, along with persistent neurologic impairments. Significant neuronal loss following repeated blast was observed in the motor cortex, somatosensory cortex, auditory cortex, and amygdala. Neuronal loss was not accompanied by changes in astrocyte reactivity. Our study identifies specific brain regions particularly sensitive to repeated mbTBI. The reasons for this sensitivity may include exposure to less attenuated shockwaves or proximity to tissue density transitions, and this merits further investigation. Our novel model will be useful in elucidating the mechanisms of sensitisation to injury, the temporal window of sensitivity and the evaluation of new treatments.

Quantifying Donor Deficits Following Nerve Transfer Surgery in Tetraplegia

PURPOSE

Nerve transfer (NT) surgery can improve function in people with cervical spinal cord injury (SCI). However, the impact of donor nerve deficits remains unclear. The purpose of this study was to quantify donor deficits experienced by individuals with cervical SCI following NT.

METHODS

This prospective single-arm, comparative study included people with SCI undergoing upper extremity NTs. Myometry was used to assess muscle strength at baseline and follow-up. The Spinal Cord Independence Measure was used to measure the ability to perform activities of daily living.

RESULTS

Ten individuals underwent 20 NTs to restore elbow extension (donor, posterior deltoid; n = 2), hand opening (donor, supinator; n = 7), and hand closing (donor, brachialis; n = 11). Shoulder abduction strength decreased (-5.6% at early and -4.5% late follow-up) in the elbow extension NT. Wrist extension strength decreased at early (-46.9% ± 30.3) and increased by late (76.4% ± 154.0) follow-up in the hand opening NT. No statistically significant change in elbow flexion strength was noted in the hand closing NT. Spinal Cord Independence Measure scores did not change significantly between baseline and early postoperative follow-up; they improved at late follow-up.

CONCLUSIONS

Use of expendable donor nerves with redundant function to perform NT surgery has relatively little impact on strength or capacity to perform activities of daily living, even in the unique and highly vulnerable SCI population. Early, temporary loss in wrist extension strength can be seen after the supinator to posterior interosseous nerve transfer. This study offers quantitative data about possible diminution of donor function after NT, enabling hand surgeons to better counsel individuals contemplating upper extremity reconstruction.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic I.

Detecting functional deficits following sub-concussive head impacts: the relationship between head impact kinematics and visual-vestibular balance performance

Introduction: Mild traumatic brain injury (mTBI) continues to be a significant issue facing the US military. While TBI cases in deployed environments are of significant concern, an estimated 80% of diagnoses occur in garrison settings (e.g., military training).Objective: With the aim of improving the detection of potentially concussive exposures, the objective of this study was to evaluate the relationships between head impact kinematics and performance on a visual-vestibular balance task.Methods: Participants (n = 51) were enrolled in the Basic Airborne Training Course. Two sensors to measure head impacts sustained were worn. Performance was measured at four time points: baseline and at the end of each week of the course.Results: Visual-vestibular balance task performance tended to decrease over the course of airborne training for our participants, however, limited to the most challenging levels of the task. Also, head impact kinematic measures correlated with performance outcomes to suggest that worse performance was associated with greater number of impacts and greater linear and rotational acceleration and rotational velocity.Discussion: Our findings suggest that visual-vestibular balance task performance may be a useful measure for detection of sub-concussive impacts and that wearable sensors may provide useful data on head impact kinematics that relates directly to functionally relevant performance.

Brain Susceptibility to Methyl Donor Deficiency: From Fetal Programming to Aging Outcome in Rats

Deficiencies in methyl donors, folate, and vitamin B12 are known to lead to brain function defects. Fetal development is the most studied but data are also available for such an impact in elderly rats. To compare the functional consequences of nutritional deficiency in young versus adult rats, we monitored behavioral outcomes of cerebellum and hippocampus circuits in the offspring of deficient mother rats and in adult rats fed a deficient diet from 2 to 8 months-of-age. We present data showing that the main deleterious consequences are found in young ages compared to adult ones, in terms of movement coordination and learning abilities. Moreover, we obtained sex and age differences in the deleterious effects on these functions and on neuronal layer integrity in growing young rats, while deficient adults presented only slight functional alterations without tissue damage. Actually, the cerebellum and the hippocampus develop and maturate according to different time lap windows and we demonstrate that a switch to a normal diet can only rescue circuits that present a long permissive window of time, such as the cerebellum, whereas the hippocampus does not. Thus, we argue, as others have, for supplements or fortifications given over a longer time than the developmental period.

Functional Deficits in the Less-Impaired Arm of Stroke Survivors Depend on Hemisphere of Damage and Extent of Paretic Arm Impairment

Background. Previous research has detailed the hemisphere dependence and specific kinematic deficits observed for the less-affected arm of patients with unilateral stroke. Objective. We now examine whether functional motor deficits in the less-affected arm, measured by standardized clinical measures of motor function, also depend on the hemisphere that was damaged and on the severity of contralesional impairment. Methods. We recruited 48 left-hemisphere-damaged (LHD) participants, 62 right-hemisphere-damaged participants, and 54 age-matched control participants. Measures of motor function included the following: (1) Jebsen-Taylor Hand Function Test (JHFT), (2) Grooved Pegboard Test (GPT), and (3) grip strength. We measured the extent of contralesional arm impairment with the upper-extremity component of the Fugl-Meyer (UEFM) assessment of motor impairment. Results. Ipsilesional limb functional performance deficits (JHFT) varied with both the damaged hemisphere and severity of contralesional arm impairment, with the most severe deficits expressed in LHD participants with severe contralesional impairment (UEFM). GPT and grip strength varied with severity of contralesional impairment but not with hemisphere. Conclusions. Stroke survivors with the most severe paretic arm impairment, who must rely on their ipsilesional arm for performing daily activities, have the greatest motor deficit in the less-affected arm. We recommend remediation of this arm to improve functional independence in this group of stroke patients.

Differential responses to increasing numbers of mild traumatic brain injury in a rodent closed-head injury model

Following mild traumatic brain injury (mTBI), further mild impacts can exacerbate negative outcomes. To compare chronic damage and deficits following increasing numbers of repeated mTBIs, a closed-head weight-drop model of repeated mTBI was used to deliver 1, 2 or 3 mTBIs to adult female rats at 24 h intervals. Outcomes were assessed at 3 months following the first mTBI. No gross motor, sensory or reflex deficits were identified (p > 0.05), consistent with current literature. Cognitive function assessed using a Morris water maze revealed chronic memory deficits following 1 and 2, but not 3 mTBI compared to shams (p ≤ 0.05). Oxidative damage to DNA was assessed immunohistochemically in the dentate hilus of the hippocampus and splenium of the corpus callosum; no changes were observed. IBA1-positive microglia were increased in size in the cortex following 1 mTBI and in the corpus callosum following 2 mTBI compared to shams (p ≤ 0.05); no changes were observed in the dentate hilus. Glial fibrillary acidic protein (GFAP)-positive astrocyte immunoreactivity was assessed in all three brain regions and no chronic changes were observed. Integrity of myelin ultrastructure in the corpus callosum was assessed using transmission electron microscopy. G ratio was decreased following 2 mTBIs compared to shams (p ≤ 0.05) at post hoc level only. The changing patterns of damage and deficits following increasing numbers of mTBI may reflect dynamic responses to small numbers of mTBIs or a conditioning effect such that increasing numbers of mTBIs do not necessarily result in worsening pathology. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Cover Image for this issue: doi: 10.1111/jnc.14508.

Repeated Mild Traumatic Brain Injury: Potential Mechanisms of Damage

Mild traumatic brain injury (mTBI) represents a significant public healthcare concern, accounting for the majority of all head injuries. While symptoms are generally transient, some patients go on to experience long-term cognitive impairments and additional mild impacts can result in exacerbated and persisting negative outcomes. To date, studies using a range of experimental models have reported chronic behavioral deficits in the presence of axonal injury and inflammation following repeated mTBI; assessments of oxidative stress and myelin pathology have thus far been limited. However, some models employed induced acute focal damage more suggestive of moderate–severe brain injury and are therefore not relevant to repeated mTBI. Given that the nature of mechanical loading in TBI is implicated in downstream pathophysiological changes, the mechanisms of damage and chronic consequences of single and repeated closed-head mTBI remain to be fully elucidated. This review covers literature on potential mechanisms of damage following repeated mTBI, integrating known mechanisms of pathology underlying moderate–severe TBIs, with recent studies on adult rodent models relevant to direct impact injuries rather than blast-induced damage. Pathology associated with excitotoxicity and cerebral blood flow-metabolism uncoupling, oxidative stress, cell death, blood-brain barrier dysfunction, astrocyte reactivity, microglial activation, diffuse axonal injury, and dysmyelination is discussed, followed by a summary of functional deficits and preclinical assessments of therapeutic strategies. Comprehensive characterization of the pathology underlying delayed and persisting deficits following repeated mTBI is likely to facilitate further development of therapeutic strategies to limit long-term sequelae.

Integrating cognitive rehabilitation: A preliminary program description and theoretical review of an interdisciplinary cognitive rehabilitation program

BACKGROUND

Interdisciplinary cognitive rehabilitation is emerging as the expected standard of care for individuals with mild to moderate degrees of cognitive impairment for a variety of etiologies. There is a growing body of evidence in cognitive rehabilitation literature supporting the involvement of multiple disciplines, with the use of cognitive support technologies (CSTs), in delivering cognitive therapy to individuals who require cognitive rehabilitative therapies. This article provides an overview of the guiding theories related to traditional approaches of cognitive rehabilitation and the positive impact of current theoretical models of an interdisciplinary approach in clinical service delivery of this rehabilitation.

OBJECTIVE

A theoretical model of the Integrative Cognitive Rehabilitation Program (ICRP) will be described in detail along with the practical substrates of delivering specific interventions to individuals and caregivers who are living with mild to moderate cognitive impairment. The ultimate goal of this article is to provide a clinically useful resource for direct service providers. It will serve to further clinical knowledge and understanding of the evolution from traditional silo based treatment paradigms to the current implementation of multiple perspectives and disciplines in the pursuit of patient centered care.

METHODS

The article will discuss the theories that contributed to the development of the interdisciplinary team and the ICRP model, implemented with individuals with mild to moderate cognitive deficits, regardless of etiology. The development and implementation of specific assessment and intervention strategies in this cognitive rehabilitation program will also be discussed.

RESULTS

The assessment and intervention strategies utilized as part of ICRP are applicable to multiple clinical settings in which individuals with cognitive impairment are served.

CONCLUSIONS

This article has specific implications for rehabilitation which include: (a) An Interdisciplinary Approach is an effective method for cognitive rehabilitation; and (b) Recent theories offer beneficial evaluation and intervention techniques for cognitive rehabilitation.

Values in First-Episode Schizophrenia

OBJECTIVE

Functional impairment continues to represent a major challenge in schizophrenia. Surprisingly, patients with schizophrenia report a level of happiness comparable with control subjects, even in the face of the prominent functional deficits, a finding at odds with evidence indicating a positive relation between happiness and level of functioning. In attempting to reconcile these findings, we chose to examine the issue of values, defined as affectively infused criteria or motivational goals used to select and justify actions, people, and the self, as values are related to both happiness and functioning.

METHODS

Fifty-six first-episode patients in remission and 56 healthy control subjects completed happiness and values measures. Statistical analyses included correlations, analysis of variance, structural equation modelling, and smallest space analysis.

RESULTS

Results indicated that patients with schizophrenia placed significantly greater priority on the value dimensions of Tradition (P = 0.02) and Power (P = 0.03), and significantly less priority on Self-direction (P = 0.007) and Stimulation, (P = 0.008).

CONCLUSIONS

Essentially, people with schizophrenia place more emphasis on the customs and ideas that traditional culture or religion provide in conjunction with a decreased interest in change, which is at odds with the expectations of early adulthood. This value difference could be related to functional deficits. To this point, we have assumed that people hold to the same values that guided them before the illness' onset, but this may not be the case. Our study indicates that values differ in people with schizophrenia, compared with control subjects, even early in the illness and in the face of symptomatic remission.

Multiplanar Knee Laxity and Perceived Function During Activities of Daily Living and Sport

CONTEXT

Greater knee-joint laxity may lead to a higher risk of knee injury, yet it is unknown whether results of self-reported outcome measures are associated with distinct knee-laxity profiles.

OBJECTIVE

To identify the extent to which multiplanar knee laxity is associated with patient-reported outcomes of knee function in healthy individuals during activities of daily living and sport.

DESIGN

Descriptive laboratory study.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Forty healthy individuals (20 men, 20 women; age = 18-31 years).

MAIN OUTCOME MEASURE(S)

All participants were given the Knee Outcome Survey Activities of Daily Living Scale (KOS-ADL) and Sports Activities Scale (KOS-SAS) and subsequently measured for knee laxity in the sagittal, frontal, and transverse planes. Separate backward stepwise regression analyses were performed to determine the extent to which multiplanar knee-laxity values predicted KOS-ADL and KOS-SAS scores within each sex.

RESULTS

Women had higher magnitudes of anterior, posterior (POST(LAX)), varus (VAR(LAX)), valgus (VAL(LAX)), and internal-rotation laxity than men and trended toward greater external rotation (ER(LAX)) laxity. Greater POST(LAX), less VAL(LAX), and greater VAR(LAX) was associated with lower KOS-ADL scores (KOS-ADL = -4.8 [POST(LAX)], + 3.3 [VAL(LAX)] - 2.2 [VAR(LAX)] + 100.4, R2 = 0.74, P < .001) and greater POST(LAX) and less VAL(LAX) was associated with lower KOS-SAS scores (KOS-SAS = -8.2 [POST(LAX)], + 3.6 [VAL(LAX)] + 96.4, R2 = 0.67, P < .001) in women. In men, greater POST(LAX) and less ER(LAX) was associated with lower KOS-SAS scores (KOS-ADL = -4.7 [POST(LAX)], + 0.9 [ER(LAX)] + 96.4, R2 = 0.49, P < .001).

CONCLUSIONS

The combination of POST(LAX) with less relative VAL(LAX) (women) or less relative ER(LAX) (men) was a strong predictor of KOS scores, suggesting that a self-reported outcome measure may be beneficial as part of a preparticipation screening battery to identify those with perceived functional deficits associated with their knee laxity.

Risk factors for psychosis: impaired social and role functioning

OBJECTIVES

Risk for psychosis is currently defined primarily on the basis of attenuated positive symptoms (APS), with no inclusion of the functional deficits characteristic of schizophrenia. Impaired social and role functioning have been of interest for reflecting poor outcome but far less is known about the developmental impact of these deficits as vulnerability or risk factors.

METHODS

Age-appropriate social and role functioning were prospectively assessed in 100 individuals at clinical high risk (CHR) for psychosis included in the 8-site North American Prodromal Longitudinal Study database. A nested case-control design was used to compare changes in social and role functioning in 26 individuals converting to psychosis shortly after baseline assessment and 24 converting over a year later. Individuals in each converter subgroup were directly matched to a non-converter at the same site, controlling for time to conversion, age, gender, and severity of baseline symptoms.

RESULTS

At baseline, CHR subjects who later became psychotic were significantly more likely to be impaired socially than matched non-converters. Onset of psychosis did not further disrupt social difficulties. Role functioning showed some of the same trends, but the overall pattern was not as consistent as for the social domain. Controlling for neurocognition did not change the pattern of group differences.

CONCLUSIONS

Early impaired social functioning appears to be a risk factor for psychosis and, added to APS, could potentially contribute to accurate identification of CHR individuals and provide a new direction for early intervention to reduce long-term disability.

Elevated blood pressure aggravates intracerebral hemorrhage-induced brain injury

Elevated blood pressure (BP) is commonly seen in patients with intracerebral hemorrhage (ICH), and is independently associated with poor functional outcomes. Little is known about how elevated BP influences ICH-related brain injury. In the present study, we investigated the physiological and brain histological changes, as well as functional recovery following ICH in renovascular hypertensive rats. Renovascular hypertension (RVHT) was achieved by applying a silver clip onto the left renal artery of adult Sprague-Dawley rats. ICH was induced by an intrastriatal injection of bacterial collagenase IV about 5-6 weeks after left renal artery clipping or the sham operation. Following induction of ICH, both the normotensive and RVHT rats demonstrated an ultra-acute elevation in BP. Elevated BP increased hematoma volume, brain swelling, and apoptosis in the perihematomal areas. Brain degeneration, including local atrophy and lateral ventricle enlargement, was greater in the RVHT rats. In addition, many proliferating cells were seen over the ipsilateral striatum in the RVHT rats after ICH. The modified limb placing tests were done weekly for 3 weeks. In line with the histological damage, elevated BP worsened neurological deficits. These results suggest that ICH in the hypertensive rats mimics the clinical scenario of hypertensive ICH and may provide a platform to study the mechanisms of ICH-induced brain injury and potential therapies for ICH.

Predicting longitudinal patterns of functional deficits in children with traumatic brain injury

Longitudinal patterns of functional deficits were investigated in 37 children with severe traumatic brain injury (TBI), 40 children with moderate TBI, and 44 children with orthopedic injuries. They were from 6 to 12 years of age when injured. Their neuropsychological, behavioral, adaptive, and academic functioning were assessed at 6 months, 12 months, and 3-5 years postinjury. Functional deficits (<10th percentile for age) were identified within each outcome domain at each occasion. Children were classified into 4 a priori longitudinal patterns of outcomes within domains (i.e., no deficits, improvement, deterioration, persistent deficits). In multinomial logistic regression analyses, severe TBI predicted an increased likelihood of persistent deficits in all outcome domains, as well as deterioration in behavioral functioning and improvement in neuropsychological, adaptive, and academic functioning. Severe TBI also predicted a greater total number of functional deficits across domains at each occasion. However, many children with severe TBI showed no deficits from 6 months to 4 years postinjury in 1 or more outcome domains. The findings help clarify the course of recovery for individual children following TBI.

Infant mortality: The role of the macaque as a model for human disease

Factors which have been identified as the leading causes of infant mortality include birth defects, hemoglobinopathies, prematurity, and Sudden Infant Death Syndrome (SIDS). In order to further our understanding of the specific causes of infant mortality and the mechanisms by which they occur, suitable animal models will be required. Studies with nonhuman primates (specifically the macaque) have addressed malformation/functional deficit syndromes such as those associated with Fetal Alcohol Syndrome (FAS), nutritional deficiencies, and retinoid teratogenicity. These studies have provided critical information for further basic and preventive research. In addition, efforts to evaluate the safety of diagnostic ultrasound continue to aid in identifying safe methods for exposure. From a prenatal perspective, cellular transplantation has been shown to be a feasible method for treating individuals with inherited defects in utero, thereby avoiding postnatal transplantation and the associated risks. Longterm complications of prematurity have also been pursued with growth factors (i.e., epidermal growth factor) noted to play an important role in both pre- and postnatal development of the gastrointestinal tract and lung. As one of the most distressing causes of death in infancy, SIDS will require a concentrated effort to understand the basic mechanism(s) responsible for the characteristic respiratory complications. The nonhuman primate will continue to provide critical information as the model of choice for the human in determining the causes, mechanisms, and treatments for these significant causes of infant death. © 1994 Wiley-Liss, Inc.