Traumatic brain injury history and baseline symptoms outweigh sex differences for risk of concussion in a sample of collegiate athletes.

OBJECTIVE: To test the hypothesis that a history of traumatic brain injury (TBI) prior to the collegiate pre-season is associated with risk for re-injury. We also investigate sex differences, cognitive functioning, and self-reported concussion symptoms and their associations with concussion risk. METHODS: A longitudinal cohort study consisting of collegiate athletes (n = 212) who completed consecutive preseason evaluations (P1 and P2) between 2012 and 2015, averaging 12.9 (SD = 4.2) months apart. RESULTS: There were 40 new concussions recorded between P1 and P2, 21 (53%) of which were among athletes who reported a lifetime history of mild TBI/concussion at P1. New P1-P2 concussions occurred in 24% of female athletes (n = 23) and 15% of male athletes (n = 17). History of TBI and female sex were significant predictors of new concussion between P1 and P2; however, in adjusted models, the inclusion of Impulse Control and PCSS Total symptom scores attenuated the effect of sex on the risk for new injury. CONCLUSION: Collegiate athletes with a lifetime history of TBI had a significantly higher risk of sustaining a subsequent concussion. Pre-season emotional and somatic symptomology may contribute to incident concussion risk. The findings highlight the importance of considering lifetime head injury exposure and baseline symptomatology when interpreting sex differences and evaluating concussion risk.

Age and sex effects on corpus callosum morphology across the lifespan.

The corpus callosum (CC) is the largest interhemispheric white matter tract in the human brain, and is characterized by pronounced differences in morphology among individuals. There are limited data, however, regarding typical development, sex differences, and the neuropsychological correlates of individual differences within CC subregions. Magnetic resonance (MR) imaging exams were collected in a large cohort (N = 305) of healthy individuals (ages 8-68). We used a highly reliable program to automatically identify the midsagittal plane and obtain CC subregion measures according to approaches described by Witelson [1989]: Brain 112:799-835 and Hampel et al. [1998]: Arch Neurol 55:193-198 and a measure of whole CC shape (i.e., circularity). CC measurement parameters, including area, perimeter, length, circularity, and CC subregion area values were generally characterized by inverted U-shaped curves across the observed age range. Peak values for CC subregions were observed between ages 32 and 45, and descriptive linear correlations were consistent with sharper area changes in development. We also observed differing age-associated changes across the lifespan between males and females in the CC subregion corresponding to the genu (Witelson's subregion 2), as well as CC circularity. Mediation analysis using path modeling indicated that genu area mediated the relationship between age and processing speed for females, and the relationship between age and visual learning and executive functioning for males. Taken together, our findings implicate sex differences in CC morphology across the lifespan that are localized to the genu, which appear to mediate neuropsychological functions.

Effects of age on prefrontal subregions and hippocampal volumes in young and middle-aged healthy humans.

There are limited data available regarding the effects of age and sex on discrete prefrontal gray and white matter volumes or posterior and anterior hippocampal volumes in healthy humans. Volumes of the superior frontal gyrus, anterior cingulate gyrus, and orbital frontal lobe were computed manually from contiguous magnetic resonance (MR) images in 83 (39M/44F) healthy humans (age range = 16-40) and segmented into gray and white matter. Volumes of the posterior and anterior hippocampal formation were also computed with reliable separation of the anterior hippocampal formation from the amygdala. There were significant age-by-tissue type interactions for the superior frontal gyrus and orbital frontal lobe such that gray matter within these regions correlated significantly and inversely with age. In contrast, no significant age effects were evident within regional white matter volumes. Analysis of hippocampal volumes indicated that men had larger volumes of the anterior, but not posterior hippocampal formation compared to women even following correction for total brain size. These data highlight age effects within discrete prefrontal cortical gray matter regions in young and middle aged healthy humans and suggest that the white matter comprising these regions may be more resistant to age effects. Furthermore, understanding the potential role of sex and age in mediating prefrontal cortical and hippocampal volumes may have strong relevance for psychiatric disorders such as schizophrenia that have implicated neurodevelopmental abnormalities within frontotemporal circuits in their pathogenesis.

Identifying dyslexia risk for sport-related concussion management: Sensitivity and specificity of self-report and rapid naming.

BACKGROUND: Dyslexia is the most common type of learning disability and studies have shown that student-athletes with learning disabilities sustain more concussions than their non-affected peers. However, current methods of dyslexia identification in college students are potentially invalid because they rely on students to self-report formal dyslexia diagnoses. METHODS: To test the accuracy of self-report against two alternative methods of dyslexia screening, 94 college students completed three dyslexia symptom inventories, two rapid naming (RAN) tasks, and a standard word reading measure. RESULTS: Reliability was acceptable for screening purposes on the inventories (α =.70, -.72), and excellent for RAN (α = .91, -.94). Specificity was acceptable (82.5%), but sensitivity was low (14.3%) when students self-reported suspected diagnoses of reading impairment. Sensitivity and specificity were higher for the digit RAN task (71 and 98%, respectively) compared to the letter RAN task (57 and 90%). Sensitivity (92.7%) and specificity (92.5%) were optimal when a cut-score of ≥27 seconds was used. A binary logistic regression showed digit RAN alone significantly predicted whether students were classified as typical or inefficient readers, p< .001, whereas the most reliable dyslexia inventory alone did not, p=.284. Including inventories along with RAN provided no additional predictive value. CONCLUSION: Self-report inventories missed many cases of inefficient word reading. The digit RAN task classified 93.6% of the cases correctly compared to 72.3% for self-report inventory. Thus, we recommend that neuropsychologists working with college concussion management programs add to their baseline screening protocols the digit RAN task, which can be completed in less than one minute.

Identifying Dyslexia Risk in Student-Athletes: A Preliminary Protocol for Concussion Management.

Learning disability (LD) has been identified as a potential risk factor for a sport-related concussion, yet students with LD are rarely included in concussion research. Here, we draw special attention to dyslexia, a common but often underdiagnosed LD. Reading and learning problems commonly associated with dyslexia are often masked by protective factors, such as high verbal ability or general intelligence. Hence, high-achieving individuals with dyslexia may not be identified as being in a high-risk category. To ensure that students with dyslexia are included in LD concussion research and identified as LD in baseline testing, we provide athletic trainers with an overview of dyslexia and a preliminary screening protocol that is sensitive to dyslexia, even among academically high-achieving students in secondary school and college.

Delineation of hippocampal subregions using T1-weighted magnetic resonance images at 3 Tesla.

Although several novel approaches for hippocampal subregion delineation have been developed, they need to be applied prospectively and may be limited by long scan times, the use of high field (>3T) imaging systems, and limited reliability metrics. Moreover, the majority of MR imaging data collected to date has employed a T1-weighted acquisition, creating a critical need for an approach that provides reliable hippocampal subregion segmentation using such a contrast. We present a highly reliable approach for the identification of six subregions comprising the hippocampal formation from MR images including the subiculum, dentate gyrus/cornu Ammonis 4 (DG/CA4), entorhinal cortex, fimbria, and anterior and posterior segments of cornu Ammonis 1-3 (CA1-3). MR images were obtained in the coronal plane using a standard 3D spoiled gradient sequence acquired on a GE 3T scanner through the whole head in approximately 10 min. The average ICC for inter-rater reliability across right and left volumetric regions-of-interest was 0.85 (range 0.71-0.98, median 0.86) and the average ICC for intra-rater reliability was 0.92 (range 0.66-0.99, median 0.97). The mean Dice index for inter-rater reliability across right and left hemisphere subregions was 0.75 (range 0.70-0.81, median 0.75) and the mean Dice index for intra-rater reliability was 0.85 (range 0.82-0.90, median 0.85). An investigation of hippocampal asymmetry revealed significantly greater right compared to left hemisphere volumes in the anterior segment of CA1-3 and in the subiculum.

Microendoscopic lumbar discectomy: technical note.

OBJECTIVE: The microendoscopic discectomy (MED) technique was initially developed in 1997 to treat herniated lumbar disc disease. Since then, thousands of cases have been successfully performed at more than 500 institutions. This article discusses the technical aspects of this procedure and presents a consecutive case series. METHODS: A total of 150 consecutive patients underwent MED. MED is performed by a muscle-splitting approach using a series of tubular dilators with consecutively increasing diameters. A tubular retractor is then inserted over the final dilator, and a specially designed endoscope is placed inside the tubular retractor. The microdiscectomy is performed endoscopically while the surgeon views the procedure on a video monitor. RESULTS: Clinical outcomes were determined using a modified MacNab criteria, which revealed that 77% of patients had excellent, 17% had good, 3% had fair, and 3% had poor outcomes. The average hospital stay was 7.7 hours. The average return to work period was 17 days. Complications primarily included dural tears, which occurred in 8 patients (5%) and were seen early on in the patient series. Complication rates diminished as the surgeon's experience with this technique increased. CONCLUSION: MED for lumbar herniated disc disease can be performed safely and effectively, resulting in a shortened hospital stay and faster return to work; however, there is a learning curve to this procedure.

A meta-analysis of diffusion tensor imaging studies of the corpus callosum in schizophrenia.

BACKGROUND: The corpus callosum has been hypothesized to play an important role in neurobiological models of schizophrenia. Diffusion tensor imaging studies have provided evidence for a disruption in corpus callosum morphology in schizophrenia, but the regional distribution of abnormalities is not well known. METHODS: We conducted 2 meta-analyses investigating the genu and splenium of the corpus callosum in schizophrenia, respectively, based on published diffusion tensor imaging studies that employed a region-of-interest approach. Seven studies investigating the genu and splenium involving a total of 202 patients with schizophrenia and 213 healthy volunteers were included. RESULTS: The meta-analysis of the genu yielded an effect size of 0.223 and was not statistically significant. The second meta-analysis investigating the splenium yielded a modest effect size of 0.527 (p=0.001), indicating that patients had lower fractional anisotropy in this region compared to healthy volunteers. Studies that included fewer men had a larger effect size for the splenium. DISCUSSION: These findings implicate an abnormality involving the splenium of the corpus callosum in the neurobiology of schizophrenia as inferred by diffusion tensor imaging. A defect in the splenium could contribute to abnormalities in posterior interhemispheric connectivity in patients, including regions of the heteromodal association cortex.

Mechanism and strategies for preventing post-traumatic stress disorder in forensic workers responding to mass fatality incidents.

Mass fatality incidents (MFIs) expose medical examiners/coroners and associated staff to circumstances that may increase their risk for developing post-traumatic stress disorder (PTSD). The aim of this paper is to provide guidance for efforts to prevent the development of PTSD in forensic teams who respond to mass disasters. We present a model of the paths through which exposure to mass fatality incidents may lead to PTSD symptoms in forensic and recovery workers. The model is based on current research in stress and coping and the psychophysiology of PTSD and is used to generate worksite intervention strategies to reduce the risk for PTSD.