Faculty Bibliography

OBJECTIVES/OBJECTIVE:In mild traumatic brain injury, imaging biomarkers are needed to support clinical management. In four antecedent publications, we used two new (sodium and fingerprinting) and two established (spectroscopy and diffusion) MR techniques in a longitudinally followed patient cohort. Here we report final results and combine all data to determine which marker(s) from the four modalities offer the greatest utility for detecting injury and predicting outcomes. We also leverage the independent specificities offered by each modality to explore injury mechanisms. MATERIALS AND METHODS/METHODS:The longitudinal spectroscopy data were analysed to complete a full data set of proton (spectroscopy, fingerprinting, diffusion) and sodium MRI, acquired alongside symptomatic, cognitive, and functional assessments in 27 patients at 1, 3, and 12 months following injury. Twenty-three matched controls were scanned once. Testing for associations between nine MR markers and three outcome measures was standardized across the entire data set, and performed using Spearman correlations and logistic regression. RESULTS:from fingerprinting (marker of the cellular microenvironment). CONCLUSIONS:We identified independent, dynamic, metabolic and ionic changes, with choline and creatine from spectroscopy fulfilling the most criteria for a clinical biomarker.

Repetitive head impacts are associated with structural brain changes and an increased risk for chronic traumatic encephalopathy, a progressive neurodegenerative disease that can only be diagnosed after death. Chronic traumatic encephalopathy is defined by the abnormal accumulation of phosphorylated tau protein, particularly at the depths of the superior frontal sulci, suggesting that sulcal morphology may serve as a relevant structural biomarker. Contact sport athletes, such as former football players, are at elevated risk due to their prolonged exposure to repetitive head impacts. Cortical atrophy linked to underlying tau accumulation may result in shallower and wider sulci, potentially making sulcal morphology an imaging marker for identifying individuals at risk for this disease. This study investigated sulcal morphological differences in former football players and examined associations with age, football-related exposure, clinical diagnosis of traumatic encephalopathy syndrome, levels of certainty for chronic traumatic encephalopathy pathology, neuropsychological performance, and positron emission tomography imaging using flortaucipir. We analysed structural magnetic resonance imaging data from 169 male former football players (mean age 57.2 (8.2) years, range 45-74) and 54 age-matched, unexposed asymptomatic male controls (mean age 59.4 (8.5) years, range 45-74). Sulcal depth and width were quantified using the CalcSulc, focusing on two regions in each hemisphere commonly affected by chronic traumatic encephalopathy pathology: the superior frontal and occipitotemporal sulci. Generalized least squares models were used to assess group differences and interactions with age and football exposure variables, including age of first exposure, total years played, and cumulative head impact exposure. An analysis of covariance evaluated relationships between sulcal morphology, clinical measures, and flortaucipir uptake, adjusting for age, race, body mass index, education, imaging site, apolipoprotein E4 status, and total intracranial volume. Former football players demonstrated significantly shallower sulcal depth in the left superior frontal sulcus compared to unexposed controls. Earlier age of first exposure and longer football careers were associated with greater widening of the left occipitotemporal sulcus. Higher cumulative head impact exposure was linked to reduced sulcal depth in the left superior frontal region. However, sulcal morphology was not associated with clinical diagnosis, levels of certainty, neuropsychological test performance, or flortaucipir imaging. These findings suggest that sulcal morphology may reflect cumulative exposure to repetitive head impacts, particularly in brain regions vulnerable to chronic traumatic encephalopathy pathology. Future ante- and post-mortem validation studies are needed to determine whether sulcal morphology can serve as a reliable in vivo biomarker of risk.

Ionic imbalances and sodium channel dysfunction, well-known sequelae of traumatic brain injury (TBI), promote functional impairment in affected subjects. Therefore, non-invasive measurement of sodium concentrations using ²³Na MRI has the potential to detect clinically relevant injury and predict persistent symptoms. Recently, we reported diffusely lower apparent total sodium concentrations (aTSC) in mild TBI patients compared to controls, as well as correlations between lower aTSC and worse clinical outcomes. The main goal of this study was to determine whether these aTSC findings, and their changes over time, predict outcomes at 3- and 12-month from injury. Twenty-seven patients previously studied with ²³Na MRI and outcome measures at 22 ± 10 days (average ± standard deviation) after injury (visit-1, v1) were contacted at 3- (visit-2, v2) and 12-month after injury (visit-3, v3) to complete the Rivermead post-concussion symptoms questionnaire (RPQ), the extended Glasgow outcome scale (GOSE), and the brief test of adult cognition by telephone (BTACT). Follow-up ¹H and ²³Na MRI were additionally scheduled at v2. Linear regression was used to calculate aTSC in global grey and white matters. Six hypotheses were tested in relation to the serial changes in outcome measures and in aTSC, and in relation to the cross-sectional and serial relationships between aTSC and outcome. Twenty patients contributed data at v2 and fifteen at v3. Total RPQ and composite BTACT z-scores differed significantly for v2 and v3 in comparison to v1 (each P < 0.01), reflecting longitudinally reduced symptomatology and improved performance on cognitive testing. No associations between aTSC and outcome were observed at v2. Previously lower grey and white matter aTSC normalized at v2 in comparison to controls, in line with a statistically detectable longitudinal increase in grey matter aTSC between v1 and v2 (P = 0.0004). aTSC values at v1 predicted a subset of future BTACT subtest scores, but not future RPQ scores nor GOSE-defined recovery status. Similarly, aTSC rates of change correlated with BTACT rates of change, but not with those of RPQ. Tissue aTSC, previously shown to be diffusely decreased compared to controls at v1, was no longer reduced by v2, suggesting normalization of the sodium ionic equilibrium. These changes were accompanied by marked improvement in outcome. The results support the notion that early aTSC from ²³Na MRI predicts future BTACT, but not RPQ scores, nor future GOSE status.

PURPOSE/OBJECTIVE:H MRS) offers biomarkers of metabolic damage after mild traumatic brain injury (mTBI), but a lack of replicability studies hampers clinical translation. In a conceptual replication study design, the results reported in four previous publications were used as the hypotheses (H1-H7), specifically: abnormalities in patients are diffuse (H1), confined to white matter (WM) (H2), comprise low N-acetyl-aspartate (NAA) levels and normal choline (Cho), creatine (Cr) and myo-inositol (mI) (H3), and correlate with clinical outcome (H4); additionally, a lack of findings in regional subcortical WM (H5) and deep gray matter (GM) structures (H6), except for higher mI in patients' putamen (H7). METHODS:26 mTBI patients (20 female, age 36.5 ± 12.5 [mean ± standard deviation] years), within two months from injury and 21 age-, sex-, and education-matched healthy controls were scanned at 3 Tesla with 3D echo-planar spectroscopic imaging. To test H1-H3, global analysis using linear regression was used to obtain metabolite levels of GM and WM in each brain lobe. For H4, patients were stratified into non-recovered and recovered subgroups using the Glasgow Outcome Scale Extended. To test H5-H7, regional analysis using spectral averaging estimated metabolite levels in four GM and six WM structures segmented from T1-weighted MRI. The Mann-Whitney U test and weighted least squares analysis of covariance were used to examine mean group differences in metabolite levels between all patients and all controls (H1-H3, H5-H7), and between recovered and non-recovered patients and their respectively matched controls (H4). Replicability was defined as the support or failure to support the null hypotheses in accordance with the content of H1-H7, and was further evaluated using percent differences, coefficients of variation, and effect size (Cohen's d). RESULTS:Patients' occipital lobe WM Cho and Cr levels were 6.0% and 4.6% higher than controls', respectively (Cho, d = 0.37, p = 0.04; Cr, d = 0.63, p = 0.03). The same findings, i.e., higher patients' occipital lobe WM Cho and Cr (both p = 0.01), but with larger percent differences (Cho, 8.6%; Cr, 6.3%) and effect sizes (Cho, d = 0.52; Cr, d = 0.88) were found in the comparison of non-recovered patients to their matched controls. For the lobar WM Cho and Cr comparisons without statistical significance (frontal, parietal, temporal), unidirectional effect sizes were observed (Cho, d = 0.07 - 0.37; Cr, d = 0.27 - 0.63). No differences were found in any metabolite in any lobe in the comparison between recovered patients and their matched controls. In the regional analyses, no differences in metabolite levels were found in any GM or WM region, but all WM regions (posterior, frontal, corona radiata, and the genu, body, and splenium of the corpus callosum) exhibited unidirectional effect sizes for Cho and Cr (Cho, d = 0.03 - 0.34; Cr, d = 0.16 - 0.51). CONCLUSIONS:H MRS biomarkers for mTBI may best be achieved by using high signal-to-noise-ratio single-voxels placed anywhere within WM. The biochemical signature of the injury, however, may differ and therefore absolute levels, rather than ratios may be preferred. Future replication efforts should further test the generalizability of these findings.

OBJECTIVE:To determine the incidence of cognitive dependence in adults who are physically independent at discharge from acute traumatic brain injury (TBI) rehabilitation. DESIGN/METHODS:Analysis of historical clinical and demographic data obtained from inpatient stay. SETTING/METHODS:Inpatient rehabilitation unit in a large, metropolitan university hospital. PARTICIPANTS/METHODS:Adult inpatients with moderate-to-severe TBI (N = 226) who were physically independent at discharge from acute rehabilitation. INTERVENTIONS/METHODS:Not applicable MAIN OUTCOME MEASURES: FIM Motor and Cognitive subscales, discharge destination, and care plan. RESULTS:Approximately 69% (n = 155) of the physically independent inpatients were cognitively dependent at discharge from acute rehabilitation, with the highest proportions of dependence found in the domains of problem solving and memory. Most (82.6%; n =128) of these physically independent, yet cognitively dependent, patients were discharged home. Of those discharged to home, 82% (n = 105) were discharged to the care of family members, and 11% (n = 15) were discharged home alone. Patients from racial-ethnic minority backgrounds were significantly more likely than White patients to be discharged while cognitively dependent. CONCLUSIONS:The majority of physically independent TBI patients were cognitively dependent at the time of discharge from acute inpatient rehabilitation. Further research is needed to understand the impact of cognitive dependence on caregiver stress and strain and the disproportionate burden on racial-ethnic minority patients and families. Given the potential functional and safety limitations imposed by cognitive deficits, healthcare policy and practice should facilitate delivery of cognitive rehabilitation services in acute TBI rehabilitation.

BACKGROUND:Early neurorehabilitation improves outcomes in patients with disorders of consciousness (DoC) after brain injury, but its applicability in COVID-19 is unknown. We describe our experience implementing an early neurorehabilitation protocol for patients with COVID-19-associated DoC in the intensive care unit (ICU) and evaluate factors associated with recovery. METHODS:During the initial COVID-19 surge in New York City between March 10 and May 20, 2020, faced with a disproportionately high number of ICU patients with prolonged unresponsiveness, we developed and implemented an early neurorehabilitation protocol, applying standard practices from brain injury rehabilitation care to the ICU setting. Twenty-one patients with delayed recovery of consciousness after severe COVID-19 participated in a pilot early neurorehabilitation program that included serial Coma Recovery Scale-Revised (CRS-R) assessments, multimodal treatment, and access to clinicians specializing in brain injury medicine. We retrospectively compared clinical features of patients who did and did not recover to the minimally conscious state (MCS) or better, defined as a CRS-R total score (TS) ≥ 8, before discharge. We additionally examined factors associated with best CRS-R TS, last CRS-R TS, hospital length of stay, and time on mechanical ventilation. RESULTS:Patients underwent CRS-R assessments a median of six (interquartile range [IQR] 3-10) times before discharge, beginning a median of 48 days (IQR 40-55) from admission. Twelve (57%) patients recovered to MCS after a median of 8 days (IQR 2-14) off continuous sedation; they had lower body mass index (p = 0.009), lower peak serum C-reactive protein levels (p = 0.023), higher minimum arterial partial pressure of oxygen (p = 0.028), and earlier fentanyl discontinuation (p = 0.018). CRS-R scores fluctuated over time, and the best CRS-R TS was significantly higher than the last CRS-R TS (median 8 [IQR 5-23] vs. 5 [IQR 3-18], p = 0.002). Earlier fentanyl (p = 0.001) and neuromuscular blockade (p = 0.015) discontinuation correlated with a higher last CRS-R TS. CONCLUSIONS:More than half of our cohort of patients with prolonged unresponsiveness following severe COVID-19 recovered to MCS or better before hospital discharge, achieving a clinical benchmark known to have relatively favorable long-term prognostic implications in DoC of other etiologies. Hypoxia, systemic inflammation, sedation, and neuromuscular blockade may impact diagnostic assessment and prognosis, and fluctuations in level of consciousness make serial assessments essential. Early neurorehabilitation of these patients in the ICU can be accomplished but is associated with unique challenges. Further research should evaluate factors associated with longer-term neurologic recovery and benefits of early rehabilitation in patients with severe COVID-19.

OBJECTIVES/OBJECTIVE:To assess whether MR fingerprinting (MRF)-based relaxation properties exhibit cross-sectional and prospective correlations with patient outcome and compare the results with those from DTI. METHODS:from MRF were compared in 12 gray and white matter regions with Mann-Whitney tests. Bivariate associations between MR measures and outcome were assessed using the Spearman correlation and logistic regression. RESULTS:, accounted for five of the six MR measures with the highest utility for identification of non-recovered patients at timepoint 2 (AUC > 0.80). CONCLUSION/CONCLUSIONS:, FA, and ADC for predicting 3-month outcome after mTBI. KEY POINTS/CONCLUSIONS:, and FA.

The pathological cascade of tissue damage in mild traumatic brain injury is set forth by a perturbation in ionic homeostasis. However, whether this class of injury can be detected in vivo and serve as a surrogate marker of clinical outcome is unknown. We employ sodium MRI to test the hypotheses that regional and global total sodium concentrations: (i) are higher in patients than in controls and (ii) correlate with clinical presentation and neuropsychological function. Given the novelty of sodium imaging in traumatic brain injury, effect sizes from (i), and correlation types and strength from (ii), were compared to those obtained using standard diffusion imaging metrics. Twenty-seven patients (20 female, age 35.9 ± 12.2 years) within 2 months after injury and 19 controls were scanned with proton and sodium MRI at 3 Tesla. Total sodium concentration, fractional anisotropy and apparent diffusion coefficient were obtained with voxel averaging across 12 grey and white matter regions. Linear regression was used to obtain global grey and white matter total sodium concentrations. Patient outcome was assessed with global functioning, symptom profiles and neuropsychological function assessments. In the regional analysis, there were no statistically significant differences between patients and controls in apparent diffusion coefficient, while differences in sodium concentration and fractional anisotropy were found only in single regions. However, for each of the 12 regions, sodium concentration effect sizes were uni-directional, due to lower mean sodium concentration in patients compared to controls. Consequently, linear regression analysis found statistically significant lower global grey and white matter sodium concentrations in patients compared to controls. The strongest correlation with outcome was between global grey matter sodium concentration and the composite z-score from the neuropsychological testing. In conclusion, both sodium concentration and diffusion showed poor utility in differentiating patients from controls, and weak correlations with clinical presentation, when using a region-based approach. In contrast, sodium linear regression, capitalizing on partial volume correction and high sensitivity to global changes, revealed high effect sizes and associations with patient outcome. This suggests that well-recognized sodium imbalances in traumatic brain injury are (i) detectable non-invasively; (ii) non-focal; (iii) occur even when the antecedent injury is clinically mild. Finally, in contrast to our principle hypothesis, patients' sodium concentrations were lower than controls, indicating that the biological effect of traumatic brain injury on the sodium homeostasis may differ from that in other neurological disorders. Note: This figure has been annotated.