Neurofilament light as a biomarker in traumatic brain injury.

OBJECTIVE: To determine whether serum neurofilament light (NfL) correlates with CSF NfL, traumatic brain injury (TBI) diagnosis, injury severity, brain volume, and diffusion tensor imaging (DTI) estimates of traumatic axonal injury (TAI). METHODS: Participants were prospectively enrolled in Sweden and the United States between 2011 and 2019. The Swedish cohort included 45 hockey players with acute concussion sampled at 6 days, 31 with repetitive concussion with persistent postconcussive symptoms (PCS) assessed with paired CSF and serum (median 1.3 years after concussion), 28 preseason controls, and 14 nonathletic controls. Our second cohort included 230 clinic-based participants (162 with TBI and 68 controls). Patients with TBI also underwent serum, functional outcome, and imaging assessments at 30 (n = 30), 90 (n = 48), and 180 (n = 59) days and 1 (n = 84), 2 (n = 57), 3 (n = 46), 4 (n = 38), and 5 (n = 29) years after injury. RESULTS: In athletes with paired specimens, CSF NfL and serum NfL were correlated (r = 0.71, p < 0.0001). CSF and serum NfL distinguished players with PCS >1 year from PCS ≤1 year (area under the receiver operating characteristic curve [AUROC] 0.81 and 0.80). The AUROC for PCS >1 year vs preseason controls was 0.97. In the clinic-based cohort, NfL at enrollment distinguished patients with mild from those with moderate and severe TBI (p < 0.001 and p = 0.048). Serum NfL decreased over the course of 5 years (ß = -0.09 log pg/mL, p < 0.0001) but remained significantly elevated compared to controls. Serum NfL correlated with measures of functional outcome, MRI brain atrophy, and DTI estimates of TAI. CONCLUSIONS: Serum NfL shows promise as a biomarker for acute and repetitive sports-related concussion and patients with subacute and chronic TBI. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that increased concentrations of NfL distinguish patients with TBI from controls.

Elevated cerebrospinal fluid total tau in former professional athletes with multiple concussions.

OBJECTIVE: To identify CSF biomarkers that are related to decreased white matter (WM) integrity and poor cognitive performance in former professional athletes with a history of multiple concussions. METHODS: Concentrations of phosphorylated tau181, total tau (t-tau), and ß-amyloid in the CSF were measured in 3 groups: 22 former professional athletes with multiple concussions (mean ± SD age 55.9 ± 12.2 years), 5 healthy controls (age 57.4 ± 5.2 years), and 12 participants (age 60.0 ± 6.6 years) diagnosed with Alzheimer disease (AD). All participants in the former athletes group underwent diffusion tensor imaging to determine WM tract integrity and completed neuropsychological testing. We divided the former athletes group into those with normal (<300 pg/mL) and high (>300 pg/mL) CSF t-tau. RESULTS: CSF t-tau in the former athletes group was significantly higher than in the healthy control group (349.3 ± 182.6 vs 188.8 ± 39.9 pg/mL, p = 0.003) and significantly lower than in the patients with AD (349.3 ± 182.6 vs 857.0 ± 449.3 pg/mL, p = 0.007). Fractional anisotropy values across all the tracts were significantly lower in the high CSF t-tau group compared to the normal CSF t-tau group (p = 0.036). Participants in the high CSF t-tau group scored significantly lower on the Trail Making Test (TMT) Part B compared to the normal CSF t-tau group (t scores 45.6 ± 18.8 vs 62.3 ± 10.1, p = 0.017). CONCLUSION: Our findings indicate that former athletes with multiple concussions are at increased risk of elevated levels of CSF t-tau and that high CSF t-tau is associated with reduced WM integrity and worse scores on the TMT Part B.

The current state of biomarkers of mild traumatic brain injury.

Mild traumatic brain injury (mTBI) is a common occurrence, with over 3 million cases reported every year in the United States. While research into the underlying pathophysiology is ongoing, there is an urgent need for better clinical guidelines that allow more consistent diagnosis of mTBI and ensure safe return-to-play timelines for athletes, nonathletes, and military personnel. The development of a suite of biomarkers that indicate the pathogenicity of mTBI could lead to clinically useful tools for establishing both diagnosis and prognosis. Here, we review the current evidence for mTBI biomarkers derived from investigations of the multifactorial pathology of mTBI. While the current literature lacks the scope and size for clarification of these biomarkers' clinical utility, early studies have identified some promising candidates.

Neurochemical Aftermath of Repetitive Mild Traumatic Brain Injury.

IMPORTANCE: Evidence is accumulating that repeated mild traumatic brain injury (mTBI) incidents can lead to persistent, long-term debilitating symptoms and in some cases a progressive neurodegenerative condition referred to as chronic traumatic encephalopathy. However, to our knowledge, there are no objective tools to examine to which degree persistent symptoms after mTBI are caused by neuronal injury. OBJECTIVE: To determine whether persistent symptoms after mTBI are associated with brain injury as evaluated by cerebrospinal fluid biochemical markers for axonal damage and other aspects of central nervous system injury. DESIGN, SETTINGS, AND PARTICIPANTS: A multicenter cross-sectional study involving professional Swedish ice hockey players who have had repeated mTBI, had postconcussion symptoms for more than 3 months, and fulfilled the criteria for postconcussion syndrome (PCS) according to the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) matched with neurologically healthy control individuals. The participants were enrolled between January 2014 and February 2016. The players were also assessed with Rivermead Post Concussion Symptoms Questionnaire and magnetic resonance imaging. MAIN OUTCOMES AND MEASURES: Neurofilament light protein, total tau, glial fibrillary acidic protein, amyloid ß, phosphorylated tau, and neurogranin concentrations in cerebrospinal fluid. RESULTS: A total of 31 participants (16 men with PCS; median age, 31 years; range, 22-53 years; and 15 control individuals [11 men and 4 women]; median age, 25 years; range, 21-35 years) were assessed. Of 16 players with PCS, 9 had PCS symptoms for more than 1 year, while the remaining 7 returned to play within a year. Neurofilament light proteins were significantly increased in players with PCS for more than 1 year (median, 410 pg/mL; range, 230-1440 pg/mL) compared with players whose PCS resolved within 1 year (median, 210 pg/mL; range, 140-460 pg/mL) as well as control individuals (median 238 pg/mL, range 128-526 pg/mL; P = .04 and P = .02, respectively). Furthermore, neurofilament light protein concentrations correlated with Rivermead Post Concussion Symptoms Questionnaire scores and lifetime concussion events (ρ = 0.58, P = .02 and ρ = 0.52, P = .04, respectively). Overall, players with PCS had significantly lower cerebrospinal fluid amyloid-ß levels compared with control individuals (median, 1094 pg/mL; range, 845-1305 pg/mL; P = .05). CONCLUSIONS AND RELEVANCE: Increased cerebrospinal fluid neurofilament light proteins and reduced amyloid ß were observed in patients with PCS, suggestive of axonal white matter injury and amyloid deposition. Measurement of these biomarkers may be an objective tool to assess the degree of central nervous system injury in individuals with PCS and to distinguish individuals who are at risk of developing chronic traumatic encephalopathy.

Serum visinin-like protein-1 in concussed professional ice hockey players.

PRIMARY OBJECTIVE: Visinin-like protein-1 (VILIP-1) has shown potential utility as a biomarker for neuronal injury in cerebrospinal fluid. This study investigated serum VILIP-1 as a diagnostic and prognostic marker in sports-related concussion. METHODS: This multi-centre prospective cohort study involved the 12 teams of the professional ice hockey league in Sweden. A total of 288 players consented to participate in the study. Thirty-five players sustained concussions, of whom 28 underwent repeated blood samplings at 1, 12, 36 and 144 hours after the trauma or when the player returned to play (7-90+ days). MAIN OUTCOMES AND RESULTS: The highest levels of VILIP-1 were measured 1 hour after concussion and the levels decreased during rehabilitation, reaching a minimum level at the 36-hour sampling. However, the levels of serum VILIP-1 at 1 hour after concussion were not significantly higher than pre-season baseline values. Serum levels of VILIP-1 1 hour post-concussion did not correlate with the number of days for the concussion symptoms to resolve. Further, serum levels of VILIP-1 increased after a friendly game in players who were not concussed. CONCLUSIONS: These results provide evidence that serum VILIP-1 may not be a useful biomarker for diagnosis and prognosis of sports-related concussion.

Fluid markers of traumatic brain injury.

Traumatic brain injury (TBI) occurs when an external force traumatically injures the brain. Whereas severe TBI can be diagnosed using a combination of clinical signs and standard neuroimaging techniques, mild TBI (also called concussion) is more difficult to detect. This is where fluid markers of injury to different cell types and subcellular compartments in the central nervous system come into play. These markers are often proteins, peptides or other molecules with selective or high expression in the brain, which can be measured in the cerebrospinal fluid or blood as they leak out or get secreted in response to the injury. Here, we review the literature on fluid markers of neuronal, axonal and astroglial injury to diagnose mild TBI and to predict clinical outcome in patients with head trauma. We also discuss chronic traumatic encephalopathy, a progressive neurodegenerative disease in individuals with a history of multiple mild TBIs in a biomarker context. This article is part of a Special Issue entitled 'Traumatic Brain Injury'.

Systematic review of clinical studies examining biomarkers of brain injury in athletes after sports-related concussion.

The aim of this study was to systematically review clinical studies examining biofluid biomarkers of brain injury for concussion in athletes. Data sources included PubMed, MEDLINE, and the Cochrane Database from 1966 to October 2013. Studies were included if they recruited athletes participating in organized sports who experienced concussion or head injury during a sports-related activity and had brain injury biomarkers measured. Acceptable research designs included experimental, observational, and case-control studies. Review articles, opinion papers, and editorials were excluded. After title and abstract screening of potential articles, full texts were independently reviewed to identify articles that met inclusion criteria. A composite evidentiary table was then constructed and documented the study title, design, population, methods, sample size, outcome measures, and results. The search identified 52 publications, of which 13 were selected and critically reviewed. All of the included studies were prospective and were published either in or after the year 2000. Sports included boxing (six studies), soccer (five studies), running/jogging (two studies), hockey (one study), basketball (one study), cycling (one study), and swimming (one study). The majority of studies (92%) had fewer than 100 patients. Three studies (23%) evaluated biomarkers in cerebrospinal fluid (CSF), one in both serum and CSF, and 10 (77%) in serum exclusively. There were 11 different biomarkers assessed, including S100ß, glial fibrillary acidic protein, neuron-specific enolase, tau, neurofilament light protein, amyloid beta, brain-derived neurotrophic factor, creatine kinase and heart-type fatty acid binding protein, prolactin, cortisol, and albumin. A handful of biomarkers showed a correlation with number of hits to the head (soccer), acceleration/deceleration forces (jumps, collisions, and falls), postconcussive symptoms, trauma to the body versus the head, and dynamics of different sports. Although there are no validated biomarkers for concussion as yet, there is potential for biomarkers to provide diagnostic, prognostic, and monitoring information postinjury. They could also be combined with neuroimaging to assess injury evolution and recovery.

Monitoring concussion in a knocked-out boxer by CSF biomarker analysis.

Concussion is common in many sports, and the incidence is increasing. The medical consequences after a sport-related concussion have received increased attention in recent years since it is known that concussions cause axonal and glial damage, which disturbs the cerebral physiology and makes the brain more vulnerable for additional concussions. This study reports on a knocked-out amateur boxer in whom cerebrospinal fluid (CSF) neurofilament light (NFL) protein, reflecting axonal damage, was used to identify and monitor brain damage. CSF NFL was markedly increased during 36 weeks, suggesting that neuronal injury persists longer than expected after a concussion. CSF biomarker analysis may be valuable in the medical counselling of concussed athletes and in return-to-play considerations.

[The value of immune enzyme testing of qualitative content of blood serotonin and liquor, in differentiate diagnostic of craniocerebral injury].

The sample of 72 patients with craniocerebral injury of light and medium degree in acute period was used to study the content of serotonin in blood serum and spinal liquor. The increase of the level of serotonin in blood serum depending on degree of severity of trauma was established. This occurrence can be used as a technique of differential diagnostic of concussion and contusion of brain.

Increased adrenomedullin in cerebrospinal fluid after traumatic brain injury in children: a preliminary report.

Adrenomedullin is a recently discovered 52-amino-acid peptide that is a potent vasodilator. Infusion of adrenomedullin increases regional cerebral blood flow and reduces infarct volume after vascular occlusion in rats. Adrenomedullin may represent an endogenous neuroprotectant since it is increased after focal brain ischemia. Cerebral hypoperfusion is present after traumatic brain injury (TBI) in children. We hypothesized that adrenomedullin levels would be increased in children with severe TBI. Total adrenomedullin concentrations were measured using a radioimmunometric assay. Thirty-six samples of ventricular cerebrospinal fluid (CSF) from 10 pediatric patients were collected during the first 10 days after severe TBI (GCS < 8). Control CSF was obtained from 5 children undergoing lumbar puncture, who had normal CSF parameters and no evidence of central nervous system infection. Patients underwent standard neuro-intensive care, including cerebrospinal fluid drainage. Data were analyzed using a univariate regression model. Adrenomedullin concentration was markedly elevated in CSF of children following TBI versus control (mean level 10.65 vs 1.51 fmol/ml, p = 0.006). All 36 case samples had an adrenomedullin concentration above the median value for the controls (1.52 fmol/ml). We conclude adrenomedullin is elevated in the CSF of children following severe TBI. We speculate that it participates in the endogenous response to cerebral hypoperfusion after TBI.

Glutamate and taurine are increased in ventricular cerebrospinal fluid of severely brain-injured patients.

Glutamate contributes to secondary brain damage, resulting in cell swelling and brain edema. Under in vitro conditions, increased extracellular levels of the amino acid taurine reflect glutamate-induced osmotic cell swelling. In vivo, increases in cerebrospinal fluid (CSF) taurine could, therefore, unmask glutamate-mediated cytotoxic edema formation and possibly differentiate it from vasogenic edema. To test this hypothesis, ventricular CSF glutamate and taurine levels were measured in 28 severely brain-injured patients on days 1, 5, and 14 after trauma. Posttraumatic changes in CSF amino acids were investigated in regard to extent of tissue damage and alterations in brain edema as estimated by computerized tomography. On day 1, CSF glutamate and taurine levels were significantly increased in patients with subdural or epidural hematomas (8+/-0.8/71+/-12 microM), contusions (21+/-4.1/122+/-18 microM), and generalized brain edema (13+/-3.2/80+/-15 microM) compared to lumbar control CSF (1.3+/-0.1/12+/-1 microM; p < 0.001). CSF amino acids, however, did not reflect edema formation and resolution as estimated by computerized tomography. CSF taurine correlated positively with glutamate, eventually depicting glutamate-induced cell swelling. However, parallel neuronal release of taurine with its inhibitory function cannot be excluded. Thus, the sensitivity of taurine in unmasking cytotoxic edema formation is weakened by the inability in defining its origin and function under the conditions chosen in the present study. Overall, persisting pathologic ventricular CSF glutamate and taurine levels are highly suggestive of ongoing glial and neuronal impairment in humans following severe traumatic brain injury.

Concentration of enkephalins in cerebrospinal fluid of patients after severe head injury.

We studied head-injured patients treated at the Department of Neurosurgery, Silesian University School of Medicine, Katowice. The patients underwent lumbar puncture on days 1, 4 and 7 for diagnostic reasons. The levels of leu-enkephalin (LENK) and met-enkephalin (MENK) were examined in 4.5 ml of cerebrospinal fluid (CSF). The control group included patients with lumbar discopathy from whom CSF fluid was collected during myelography. Enkephalins were extracted by column chromatography and their levels were assayed radioimmunologically. The results indicate that enkephalins may play a certain role in the pathophysiological response of nervous tissue to traumatic injury. Constantly elevated MENK levels together with decreasing LENK levels in patients with a Glasgow coma scale score < or = 8 may be useful as a poor prognostic factor. It is also suggested that LENK and MENK play different pathophysiological roles.

[The characteristics of the biochemical reactions of the cerebrospinal fluid in victims with gunshot wounds of the skull and brain in relation to treatment outcome]. / Osobennosti biokhimicheskikh reaktsii tserebrospinal'noi zhidkosti u postradavshikh s ognestrel'nymi raneniiami cherepa i golovnogo mozga v zavisimosti ot iskhoda lecheniia.

Biochemical reactions of the liquor were investigated in 68 patients with gunshot wounds of the skull and brain and in closed treatment of the brain wound. The reactivity of biochemical system plays a certain role in the development of infectious complications. In dead people the developing pathogenetical biochemical syndromes having a sanogenic role of clearance from antigens of the injured tissues turn pathogenesis into thanatogenesis.

[The immunochemical indices of the structural damage to brain tissue at different periods of traumatic brain disease]. / Immunokhimicheskie pokazateli strukturnogo povrezhdeniia mozgovoi tkani v razlichnye periody travmaticheskoi bolezni golovnogo mozga.

Interorganic and neurospecific liquor proteins were measured in brain injury patients using enzyme immunoassay and radioimmunoassay (maximum sensitivity 2.0 and 0.05-1 ng/ml, respectively). The protein concentrations were found to vary with the time which elapsed since the injury.

[Repeated closed craniocerebral trauma]. / Povtornaia zakrytaia cherepno-mozgovaia trama.

As many as 446 patients with repeated craniocerebral injury and 386 patients with primary injury, analogous in respect of severity, were subjected to clinical and physiological examinations. On comparison of the results of examining the above two patients' groups it has been revealed that repeated brain injury may be characterized by its own features and runs a graver course as compared to primary injury. This manifests by more pronounced and persistent general cerebral and focal symptoms, disorders of the dynamics of the CSF toward hypotension, vegetative disorders in the form of lability and asymmetry of arterial pressure, thermal asymmetry, prolongation of the time of the thermoregulation vascular reflex and resolution of the blister according to the McClure-Aldrich test, and so forth. According to the therapeutic indications, 204 patients with repeated injury underwent pneumoencephalography. Manifest alterations in CSF-containing spaces, the intensity of which depended on the number of injuries, were revealed in 90.2% of them early after the injury. A special complex of pathogenetic therapy provided to 212 patients with repeated injury allowed attaining more favourable results as compared to 234 analogous patients who received routine treatment.

[Cerebrospinal fluid lactate and peroxide compounds in young children with craniocerebral trauma]. / Issledovanie laktata i perekisnykh soedinenii likvora u detei rannego vozrasta pri cherepno-mozgovoi travme.

The content of lactate and products of lipid peroxidation in the c. s. f. of infants with craniocerebral trauma was studied. The content of lactate and malonic dialdehyde in the c. s. f. was significantly increased, which correlated with the severity of the trauma. The results of the study make it possible to followup the course of the cerebral traumatic disease and the efficacy of the applied therapy and also may severe as prognostic criteria in evaluating the possible sequelae of the craniocerebral trauma.

[Dissociated symptoms of the progressive course of brain injury]. / Dissotsiirovannye simptomy progredientnogo techeniia travmaticheskoi bolezni golovnogo mozga.

Hypotension of the cerebrospinal fluid (CSF) was detected in 18% of 856 patients with brain trauma examined in the study. Three syndromes of dissociated hypotension of the CSF were described: (1) at the level of the Magendie-Luschka openings; (2) at the level of the aqueduct of Sylvius; (3) at the level of the third ventricle. Each level of hypotension of the CSF was attended by a specific clinical syndrome. The parameters of the progressive course of the disease made it possible upon their identification to begin the rehabilitation of patients at the earliest stage which led to a faster compensation. Special attention was given to apitherapy, phytococtails and instillations of special coctails for controlling the dissociation between CSF hypotension and hydrocephaly. The conducted rehabilitation made it possible to significantly reduce the incidence of crises indicative of the decompensation of brain injury.