Bertrand R. Huber

Clinicopathological evaluation of chronic traumatic encephalopathy in players of American football

Importance Players of American football may be at increased risk of long-term neurological conditions, particularly chronic traumatic encephalopathy (CTE). Objective To determine the neuropathological and clinical features of deceased football players with CTE. Design, Setting, and Participants Case series of 202 football players whose brains were donated for research. Neuropathological evaluations and retrospective telephone clinical assessments (including head trauma history) with informants were performed blinded. Online questionnaires ascertained athletic and military history. Exposures Participation in American football at any level of play. Main Outcomes and Measures Neuropathological diagnoses of neurodegenerative diseases, including CTE, based on defined diagnostic criteria; CTE neuropathological severity (stages I to IV or dichotomized into mild [stages I and II] and severe [stages III and IV]); informant-reported athletic history and, for players who died in 2014 or later, clinical presentation, including behavior, mood, and cognitive symptoms and dementia. Results Among 202 deceased former football players (median age at death, 66 years [interquartile range, 47-76 years]), CTE was neuropathologically diagnosed in 177 players (87%; median age at death, 67 years [interquartile range, 52-77 years]; mean years of football participation, 15.1 [SD, 5.2]), including 0 of 2 pre–high school, 3 of 14 high school (21%), 48 of 53 college (91%), 9 of 14 semiprofessional (64%), 7 of 8 Canadian Football League (88%), and 110 of 111 National Football League (99%) players. Neuropathological severity of CTE was distributed across the highest level of play, with all 3 former high school players having mild pathology and the majority of former college (27 [56%]), semiprofessional (5 [56%]), and professional (101 [86%]) players having severe pathology. Among 27 participants with mild CTE pathology, 26 (96%) had behavioral or mood symptoms or both, 23 (85%) had cognitive symptoms, and 9 (33%) had signs of dementia. Among 84 participants with severe CTE pathology, 75 (89%) had behavioral or mood symptoms or both, 80 (95%) had cognitive symptoms, and 71 (85%) had signs of dementia. Conclusions and Relevance In a convenience sample of deceased football players who donated their brains for research, a high proportion had neuropathological evidence of CTE, suggesting that CTE may be related to prior participation in football.

Inflammatory Enteric Neuropathy With Severe Constipation After Ipilimumab Treatment for Melanoma : A Case Report

Ipilimumab (MDX-010), a human anti-cytotoxic T-lymphocyte antigen (CTLA)-4 monoclonal antibody, is currently being investigated for the treatment of patients with melanoma. The most frequent toxicities observed with ipilimumab involve the gastrointestinal tract and are attributed to activation of the immune system. Constipation has been reported as a symptom in the clinical trials of anti-CTLA-4 antibody and is mostly low grade. However, it is not traditionally perceived as an immune-mediated toxicity. We report the case of a patient who developed severe refractory constipation during treatment with ipilimumab for metastatic melanoma. Biopsies of the colonic wall revealed prominent inflammatory infiltrates of mononuclear lymphocytes associated with the myenteric nervous system. There was a pathologic complete remission of melanoma. To our knowledge, this is the first clinical report of either inflammatory enteric neuropathy or constipation as an immune-related adverse event from anti-CTLA-4 antibody treatment. We discuss the pathophysiology and suggest careful monitoring of patients for development of this complication from ipilimumab therapy.

Traumatic brain injury, neuroinflammation, and post-traumatic headaches.

Concussions following head and/or neck injury are common, and although most people with mild injuries recover uneventfully, a subset of individuals develop persistent post‐concussive symptoms that often include headaches. Post‐traumatic headaches vary in presentation and may progress to become chronic and in some cases debilitating. Little is known about the pathogenesis of post‐traumatic headaches, although shared pathophysiology with that of the brain injury is suspected. Following primary injury to brain tissues, inflammation rapidly ensues; while this inflammatory response initially provides a defensive/reparative function, it can persist beyond its beneficial effect, potentially leading to secondary injuries because of alterations in neuronal excitability, axonal integrity, central processing, and other changes. These changes may account for the neurological symptoms often observed after traumatic brain injury, including headaches. This review considers selected aspects of the inflammatory response following traumatic brain injury, with an emphasis on the role of glial cells as mediators of maladaptive post‐traumatic inflammation.

Microglial neuroinflammation contributes to tau accumulation in chronic traumatic encephalopathy

The chronic effects of repetitive head impacts (RHI) on the development of neuroinflammation and its relationship to chronic traumatic encephalopathy (CTE) are unknown. Here we set out to determine the relationship between RHI exposure, neuroinflammation, and the development of hyperphosphorylated tau (ptau) pathology and dementia risk in CTE. We studied a cohort of 66 deceased American football athletes from the Boston University-Veteran’s Affairs-Concussion Legacy Foundation Brain Bank as well as 16 non-athlete controls. Subjects with a neurodegenerative disease other than CTE were excluded. Counts of total and activated microglia, astrocytes, and ptau pathology were performed in the dorsolateral frontal cortex (DLF). Binary logistic and simultaneous equation regression models were used to test associations between RHI exposure, microglia, ptau pathology, and dementia. Duration of RHI exposure and the development and severity of CTE were associated with reactive microglial morphology and increased numbers of CD68 immunoreactive microglia in the DLF. A simultaneous equation regression model demonstrated that RHI exposure had a significant direct effect on CD68 cell density (p < 0.0001) and ptau pathology (p < 0.0001) independent of age at death. The effect of RHI on ptau pathology was partially mediated through increased CD68 positive cell density. A binary logistic regression demonstrated that a diagnosis of dementia was significantly predicted by CD68 cell density (OR = 1.010, p = 0.011) independent of age (OR = 1.055, p = 0.007), but this effect disappeared when ptau pathology was included in the model. In conclusion, RHI is associated with chronic activation of microglia, which may partially mediate the effect of RHI on the development of ptau pathology and dementia in CTE. Inflammatory molecules may be important diagnostic or predictive biomarkers as well as promising therapeutic targets in CTE.

Repetitive blast exposure in mice and combat veterans causes persistent cerebellar dysfunction.

Ventral regions of the cerebellum in combat veterans and mice are vulnerable to long-term traumatic brain injury caused by repetitive blast exposure. The cerebellum is vulnerable to blast injury in mice and combat veterans Mild traumatic brain injury (TBI) is often referred to as the “signature injury” of the wars in Iraq and Afghanistan. Most of these TBIs are blast-related. Currently, there is limited understanding of how mild blast causes persistent brain injuries. There is also limited insight into how blast-induced brain injuries in animal models correspond to humans with mild TBI. Meabon et al. report that the cerebellum, a brain structure important for integrating sensory information and movement, is injured by blast exposure in mice in specific areas that correspond to abnormal brain imaging findings obtained in similar cerebellar regions in blast-exposed combat veterans. Blast exposure can cause mild traumatic brain injury (TBI) in mice and other mammals. However, there are important gaps in our understanding of the neuropathology underlying repetitive blast exposure in animal models compared to the neuroimaging abnormalities observed in blast-exposed veterans. Moreover, how an increase in the number of blast exposures affects neuroimaging endpoints in blast-exposed humans is not well understood. We asked whether there is a dose-response relationship between the number of blast-related mild TBIs and uptake of 18F-fluorodeoxyglucose (FDG), a commonly used indicator of neuronal activity, in the brains of blast-exposed veterans with mild TBI. We found that the number of blast exposures correlated with FDG uptake in the cerebellum of veterans. In mice, blast exposure produced microlesions in the blood-brain barrier (BBB) predominantly in the ventral cerebellum. Purkinje cells associated with these BBB microlesions displayed plasma membrane disruptions and aberrant expression of phosphorylated tau protein. Purkinje cell loss was most pronounced in the ventral cerebellar lobules, suggesting that early-stage breakdown of BBB integrity may be an important factor driving long-term brain changes. Blast exposure caused reactive gliosis in mouse cerebellum, particularly in the deep cerebellar nuclei. Diffusion tensor imaging tractography of the cerebellum of blast-exposed veterans revealed that mean diffusivity correlated negatively with the number of blast-related mild TBIs. Together, these results argue that the cerebellum is vulnerable to repetitive mild TBI in both mice and humans.

Concussion, microvascular injury, and early tauopathy in young athletes after impact head injury and an impact concussion mouse model

The mechanisms underpinning concussion, traumatic brain injury (TBI) and chronic traumatic encephalopathy (CTE) are poorly understood. Using neuropathological analyses of brains from teenage athletes, a new mouse model of concussive impact injury, and computational simulations, Tagge et al. show that head injuries can induce TBI and early CTE pathologies independent of concussion.

Biomarkers for Cognitive Impairment in Parkinson Disease

Cognitive impairment, including dementia, is commonly seen in those afflicted with Parkinson disease (PD), particularly at advanced disease stages. Pathologically, PD with dementia (PD‐D) is most often associated with the presence of cortical Lewy bodies, as is the closely related dementia with Lewy bodies (DLB). Both PD‐D and DLB are also frequently complicated by the presence of neurofibrillary tangles and amyloid plaques, features most often attributed to Alzheimer disease. Biomarkers are urgently needed to differentiate among these disease processes and predict dementia in PD as well as monitor responses of patients to new therapies. A few clinical assessments, along with structural and functional neuroimaging, have been utilized in the last few years with some success in this area. Additionally, a number of other strategies have been employed to identify biochemical/molecular biomarkers associated with cognitive impairment and dementia in PD, e.g. targeted analysis of candidate proteins known to be important to PD pathogenesis and progression in cerebrospinal fluid or blood. Finally, interesting results are emerging from preliminary studies with unbiased and high throughput genomic, proteomic and metabolomic techniques. The current findings and perspectives of applying these strategies and techniques are reviewed in this article, together with potential areas of advancement.

Repetitive Head Impacts and Chronic Traumatic Encephalopathy

Chronic traumatic encephalopathy (CTE) is a distinctive neurodegenerative disease that occurs as a result of repetitive head impacts. CTE can only be diagnosed by postmortem neuropathologic examination of brain tissue. CTE is a unique disorder with a pathognomonic lesion that can be reliably distinguished from other neurodegenerative diseases. CTE is associated with violent behaviors, explosivity, loss of control, depression, suicide, memory loss and cognitive changes. There is increasing evidence that CTE affects amateur athletes as well as professional athletes and military veterans. CTE has become a major public health concern.

Potential Long-Term Consequences of Concussive and Subconcussive Injury.

Repeated concussive and subconcussive trauma is associated with the later development of chronic traumatic encephalopathy (CTE), a neurodegenerative disease associated with clinical symptoms in multiple domains and a unique pattern of pathologic changes. CTE has been linked to boxing and American football; CTE has also been identified in soccer, ice hockey, baseball, rugby, and military service. To date, most large studies of CTE have come from enriched cohorts associated with brain bank donations for traumatic brain injury, although several recent studies re-examining neurodegenerative disease brain banks suggest that CTE is more common than is currently appreciated.

Blast exposure causes dynamic microglial/macrophage responses and microdomains of brain microvessel dysfunction

Exposure to blast overpressure (BOP) is associated with behavioral, cognitive, and neuroimaging abnormalities. We investigated the dynamic responses of cortical vasculature and its relation to microglia/macrophage activation in mice using intravital two-photon microscopy following mild blast exposure. We found that blast caused vascular dysfunction evidenced by microdomains of aberrant vascular permeability. Microglial/macrophage activation was specifically associated with these restricted microdomains, as evidenced by rapid microglial process retraction, increased ameboid morphology, and escape of blood-borne Q-dot tracers that were internalized in microglial/macrophage cell bodies and phagosome-like compartments. Microdomains of cortical vascular disruption and microglial/macrophage activation were also associated with aberrant tight junction morphology that was more prominent after repetitive (3×) blast exposure. Repetitive, but not single, BOPs also caused TNFα elevation two weeks post-blast. In addition, following a single BOP we found that aberrantly phosphorylated tau rapidly accumulated in perivascular domains, but cleared within four hours, suggesting it was removed from the perivascular area, degraded, and/or dephosphorylated. Taken together these findings argue that mild blast exposure causes an evolving CNS insult that is initiated by discrete disturbances of vascular function, thereby setting the stage for more protracted and more widespread neuroinflammatory responses.