Katz, Douglas I.

AbstractBackgroundTraumatic encephalopathy syndrome (TES) is the proposed clinical syndrome of chronic traumatic encephalopathy (CTE), a neurodegenerative disease associated with repetitive head impacts in contact/collision sports. A core clinical feature of TES is cognitive impairment, particularly in memory and executive functions. Cognitive intraindividual variability (IIV) is the extent of variability in neuropsychological test performance (i.e., dispersion of test scores) and is believed to be an indicator of disruption in executive control, linked to altered fronto‐subcortical circuits. Here, we examined cognitive IIV as a method to detect subtle executive dysfunction in TES that may not be captured by traditional neuropsychological measures.MethodThe sample included former American football players (120 professional, 60 college); participants were males, aged 45‐74. Participants completed a baseline neuropsychological test battery (n = 8 excluded for suboptimal performance validity). A multidisciplinary diagnostic consensus conference classified participants using the 2021 NINDS Consensus Diagnostic Criteria for TES (see Table‐1): (1) No‐TES (n = 62); (2) TES‐CTE Suggestive (n = 35); (3) TES‐CTE Possible (n = 21); (4) TES‐CTE Probable (n = 54). TES‐CTE Possible and Probable were combined. The coefficient of variation (CoV) was used to measure cognitive IIV (CoV = iSD/iOTBM, iOTBM = average T‐score across neuropsychological tests; iSD = standard deviation of iOTBM). A higher CoV indicates greater score dispersion. To avoid circularity, memory and executive tests used for classifying TES groups were intentionally excluded from the CoV calculation. Analysis of covariance compared the TES groups on CoV, controlling for age, education, and race.ResultResults showed a significant difference in CoV between TES groups, F(2, 165) = 8.20 p<.001, partial η2 = .09. The TES‐CTE Possible/Probable group had the highest CoV (M = .226, SE = .007), compared with the TES‐no (M = .192, SE = .008, p<.001) and TES‐CTE Suggestive groups (M = .178, SE = .011, p<.001). CoV did not significantly differ between the TES‐no and TES‐CTE suggestive groups (Mdiff = 0.014, SE = .013, p = .293).ConclusionThe TES‐CTE possible/probable group had the highest cognitive IIV with ∼23% dispersion (vs. ∼18‐19% in TES‐no and TES‐CTE suggestive groups), suggesting greater cognitive variability in those with the greatest likelihood for having underlying CTE (based on TES criteria). This finding emphasizes the potential utility of exploring cognitive IIV as a method for detecting nuanced executive dysfunction in TES.

Abstract Former American football players are at risk for developing traumatic encephalopathy syndrome (TES), the clinical disorder associated with neuropathologically diagnosed chronic traumatic encephalopathy (CTE). The objective of this study was to determine whether hyposmia is present in traumatic encephalopathy syndrome. The study included 119 former professional American football players, 60 former college football players, and 58 same-age asymptomatic unexposed men from the DIAGNOSE CTE Research Project. All subjects included in the analysis had completed the Brief Smell Identification Test (B-SIT). Traumatic encephalopathy syndrome and the level of CTE certainty were diagnosed using the 2021 NINDS consensus diagnostic criteria. TES is categorized antemortem by provisional levels of increasing CTE certainty: Suggestive, Possible, and Probable. Former players who had traumatic encephalopathy syndrome and Probable CTE had lower B-SIT scores than those with TES and Suggestive CTE. Hyposmia was more likely in the former players with TES who were either CTE Possible or Probable than in those who did not have TES or had TES but were less likely to have CTE, or CTE Suggestive. There was no difference in B-SIT scores between all former players versus unexposed men nor overall between the football players with and without TES. We conclude that lower B-SIT scores may be a clinical biomarker for underlying CTE in former American football players.

AbstractINTRODUCTIONBlood‐based biomarkers offer a promising approach for the detection of neuropathologies from repetitive head impacts (RHI). We evaluated plasma biomarkers of amyloid, tau, neurodegeneration, and inflammation in former football players.METHODSThe sample included 180 former football players and 60 asymptomatic, unexposed male participants (aged 45–74). Plasma assays were conducted for beta‐amyloid (Aβ) 40, Aβ42, hyper‐phosphorylated tau (p‐tau) 181+231, total tau (t‐tau), neurofilament light (NfL), glial fibrillary acidic protein (GFAP), interleukin‐6 (IL‐6), Aβ42/p‐tau181 and Aβ42/Aβ40 ratios. We evaluated their ability to differentiate the groups and associations with RHI proxies and traumatic encephalopathy syndrome (TES).RESULTSP‐tau181 and p‐tau231(padj = 0.016) were higher and Aβ42/p‐tau181 was lower(padj = 0.004) in football players compared to controls. Discrimination accuracy for p‐tau was modest (area under the curve [AUC] = 0.742). Effects were not attributable to AD‐related pathology. Younger age of first exposure (AFE) correlated with higher NfL (padj = 0.03) and GFAP (padj = 0.033). Plasma GFAP was higher in TES‐chronic traumatic encephalopathy (TES‐CTE) Possible/Probable (padj = 0.008).DISCUSSIONPlasma p‐tau181 and p‐tau231, GFAP, and NfL may offer some usefulness for the characterization of RHI‐related neuropathologies.Highlights Former football players had higher plasma p‐tau181 and p‐tau231 and lower Aβ42/ptau‐181 compared to asymptomatic, unexposed men. Younger age of first exposure was associated with increased plasma NfL and GFAP in older but not younger participants. Plasma GFAP was higher in participants with TES‐CTE possible/probable compared to TES‐CTE no/suggestive.

AbstractBackgroundThe NINDS criteria define Traumatic Encephalopathy Syndrome (TES) as the clinical manifestation of the neuropathologically diagnosed chronic traumatic encephalopathy (CTE). The core clinical features of TES include both cognitive and neuropsychiatric symptoms, the latter termed neurobehavioral dysregulation (NBD). We explored potential biological correlates of NBD by investigating fluid biomarkers of neuronal damage, astrogliosis, phosphorylated tau (pTau), neuroinflammation, and catecholamines in former American football players.MethodOur cohort consisted of former professional (PRO) and college (COL) American football players from the DIAGNOSE CTE Research Project. NBD was measured by four subscales (i.e., explosivity, emotional dyscontrol, impulsivity, affective lability) and a total NBD score, derived by factor analysis of multiple self‐report neuropsychiatric measures. Plasma neurofilament light (NfL) and glial fibrillary acidic protein (GFAP), CSF total tau and pTau181/231/217, as well as CSF biomarkers related to neuroinflammation (IL‐6, CRP, TNF‐α, VEGF‐A), were measured with various well‐validated immunoassay methods. Catecholamines in CSF (dopamine, 3,4‐dihydroxyphenylacetic acid, 3,4‐dihydroxyphenylalanine, noradrenaline, 3,4‐dihydroxyphenylglycol) were measured with HPLC. Multivariate linear regression models assessed the relationships between biomarkers and NBD scales, adjusted for age, BMI, race, and APOE e4, including stratification by exposure group, i.e., PRO, COL.ResultDemographics and biomarker levels are displayed in Table 1. High levels of IL‐6 were significantly associated with higher scores of all NBD subscales, independent of exposure group. Other significant relationships included plasma NfL with emotional dyscontrol and impulsivity. Within the college group, CSF pTau181 was significantly associated with emotional dyscontrol and CSF noradrenaline with explosivity, emotional dyscontrol, impulsivity, and total NBD score. (Table 2 & Figure 1). IL‐6 models were repeated with measures of cognitive dysfunction (another core feature of TES) added as covariates; these analyses again found significant relationships between IL‐6 and NBD, irrespective of cognitive functioning.ConclusionWe observed specific fluid biomarkers related to NBD in former American football players. Of note were the associations between IL‐6 and all NBD subscales (and not with cognitive functioning), suggesting that neuroinflammation may be a specific component in the expression of NBD symptoms. Future studies will investigate how these neuroinflammatory processes are related to other biomarkers, level of RHI exposure, and neuropathology.

AbstractBackgroundChronic traumatic encephalopathy (CTE) is a neurodegenerative disease thought to be caused, in part, by repetitive head impact (RHI) exposure and characterized by phosphorylated tau deposition with varying patterns in the cerebral cortex. Flortaucipir tau PET data from the DIAGNOSE CTE Research Project was examined to investigate tau PET patterns and its relation to RHI exposure in former professional and college American football players.MethodIn this study, 218 DIAGNOSE CTE participants, ages 45‐74, with flortaucipir PET were included; 104 were former National Football League players (PRO), 58 were former college football players (COL), and 56 had no history of contact sports, other exposure to RHI, or traumatic brain injury (UE). Regional flortaucipir uptake was quantified using established procedures for three previously defined statistical regions (superior frontal, left parietal, and medial temporal) and compared across the three groups. Association analyses were also performed to examine the relationship between flortaucipir uptake and exposure to RHI using the cumulative head impact index for linear acceleration g‐force (CHII‐G). The potential clinical utility of flortaucipir PET for CTE was also investigated by examining its ability to differentiate participants meeting criteria for traumatic encephalopathy syndrome (TES) and probable or possible level of certainty for CTE pathology from those who do not meet those criteria.ResultSignificantly higher flortaucipir uptake was observed in former football players than in participants without RHI exposure, controlling for age and race for the superior frontal region (Fig. 1A), left parietal, and medial temporal regions. Association between regional flortaucipir uptake and CHII‐G was only observed in the superior frontal region in former players (PRO+COL) 60 years and older (Fig. 1B) and no association was observed in the full PRO+COL group. Flortaucipir PET was not able to differentiate TES groups in former football players (Fig. 1C).ConclusionElevated flortaucipir uptake was observed in former American football players to a group of unexposed men. The association between flortaucipir uptake and exposure to RHI may require a long latent period to manifest. Further investigation of more sensitive tau PET tracers and quantification techniques is warranted to better characterize CTE related tau pathology.

AbstractINTRODUCTIONTau is a key pathology in chronic traumatic encephalopathy (CTE). Here, we report our findings in tau positron emission tomography (PET) measurements from the DIAGNOSE CTE Research Project.METHODWe compare flortaucipir PET measures from 104 former professional players (PRO), 58 former college football players (COL), and 56 same‐age men without exposure to repetitive head impacts (RHI) or traumatic brain injury (unexposed [UE]); characterize their associations with RHI exposure; and compare players who did or did not meet diagnostic criteria for traumatic encephalopathy syndrome (TES).RESULTSSignificantly elevated flortaucipir uptake was observed in former football players (PRO+COL) in prespecified regions (p < 0.05). Association between regional flortaucipir uptake and estimated cumulative head impact exposure was only observed in the superior frontal region in former players over 60 years old. Flortaucipir PET was not able to differentiate TES groups.DISCUSSIONAdditional studies are needed to further understand tau pathology in CTE and other individuals with a history of RHI.

AbstractBackgroundChronic traumatic encephalopathy (CTE) is a neurodegenerative disease that is characterized by perivascular foci of phosphorylated tau (p‐tau) notably in the depths of sulci, with varying patterns in the cerebral cortex. Prior studies show elevated flortaucipir (FTP) PET binding in former American professional football players(PRO). However, the association of p‐tau with clinical measures remains unclear using regional FTP SUVR as early signs of CTE related tau pathology. Graph theory (GT) takes advantages of the spatial variability in p‐tau load and allows the integration of regional measures to define GT based measures. Here we examine the GT based measures in two CTE cohorts to evaluate their utility in assessing p‐tau related pathology in CTE.MethodThe graph procedure was optimized in FTP PET images in a group of 26 PRO with reported cognitive and/or behavorial symptoms and 30 asymptomatic controls without a history of traumatic brain injury (the DETECT Study) and identified the GT measure, entorhinal tau strength, as the target metric with the best group separation between PRO and controls. The optimized graph procedures were then applied to the DIAGNOSE CTE Research Project dataset (99 former PRO, 51 former college football players [COL], and 52 controls without exposure to repetitive head impacts [CTL]) and we examined entorhinal tau strength’s ability to differentiate the exposure groups and relationship to consensus based diagnoses of Traumatic Encephalopathy Syndrome (TES), the clinical syndrome associated with CTE.ResultEntorhinal tau strength was significantly different among the three exposure groups (p=0.0001) similar to regional SUVR measures (Figure 1). Regional SUVR did not differentiate players (PRO+COL) with and without TES, while entorhinal tau strength approached although did not reach significance (Figure 2). Entorhinal tau strength is the only FTP measure that showed significant differences (p=0.006) between those players with cognitive impairment and players without (Figure 3).ConclusionWhile there is still considerable overlap in between‐group measurements, GT based entorhinal tau strength, is potentially more sensitive in detecting tau changes in players with and without TES. Additional studies are necessary to clarify the value of this new measure in detecting underlying CTE pathology.