Capillary blood protein markers of posttraumatic headache in children after concussion.

OBJECTIVE: Posttraumatic headache (PTH) represents the most common acute and persistent symptom in children after concussion, yet there is no blood protein signature to stratify the risk of PTH after concussion to facilitate early intervention. This discovery study aimed to identify capillary blood protein markers, at emergency department (ED) presentation within 48 hours of concussion, to predict children at risk of persisting PTH at 2 weeks postinjury. METHODS: Capillary blood was collected using the Mitra Clamshell device from children aged 8-17 years who presented to the ED of the Royal Children's Hospital, Melbourne, Australia, within 48 hours of sustaining a concussion. Participants were followed up at 2 weeks postinjury to determine PTH status. PTH was defined per clinical guidelines as a new or worsened headache compared with preinjury. An untargeted proteomics analysis using data-independent acquisition (DIA) was performed. Principal component analysis and hierarchical clustering were used to reduce the dimensionality of the protein dataset. RESULTS: A total of 907 proteins were reproducibly identified from 82 children within 48 hours of concussion. The mean participant age was 12.78 years (SD 2.54 years, range 8-17 years); 70% of patients were male. Eighty percent met criteria for acute PTH in the ED, while one-third of participants with follow-up experienced PTH at 2 weeks postinjury (range 8-16 days). Hemoglobin subunit zeta (HBZ), cystatin B (CSTB), beta-ala-his dipeptidase (CNDP1), hemoglobin subunit gamma-1 (HBG1), and zyxin (ZYX) were weakly associated with PTH at 2 weeks postinjury based on up to a 7% increase in the PTH group despite nonsignificant Benjamini-Hochberg adjusted p values. CONCLUSIONS: This discovery study determined that no capillary blood protein markers, measured at ED presentation within 48 hours of concussion, can predict children at risk of persisting PTH at 2 weeks postinjury. While HBZ, CSTB, CNDP1, HBG1, and ZYX were weakly associated with PTH at 2 weeks postinjury, there was no specific blood protein signature predictor of PTH in children after concussion. There is an urgent need to discover new blood biomarkers associated with PTH to facilitate risk stratification and improve clinical management of pediatric concussion.

Post-traumatic headache pathophysiology in paediatric concussion: A systematic review.

Post-traumatic headache (PTH) represents the most common acute and persistent symptom following concussion in children, yet the underlying pathophysiology remains unclear. This systematic review sought to: (i) rigorously examine the current evidence of PTH pathophysiology in paediatric concussion (0-18 years), (ii) assess the quality of evidence, and (iii) provide directions for future research in accordance with PRISMA guidelines. Eligible studies (n = 19) totalling 1214 concussion participants investigated cerebrovascular function (n = 6), white matter integrity (n = 3), functional connectivity (n = 3), electrophysiology (n = 1), neurometabolics (n = 2), biological fluid markers (n = 4), vestibular and oculomotor function (n = 4); two studies used a multi-modal approach. Majority of studies were rated as fair quality (90%) and Level 3 evidence (84%). The true underlying mechanisms of PTH following paediatric concussion remain unclear. Overall quality of the available evidence is generally weak with a fair risk of bias and characterised by relative scarcity and lack of specificity of PTH pathophysiology. Future research is required to rigorously isolate pathophysiology specific to PTH with strict adherence to clinical definitions and standardised measurement tools of PTH.

Cerebral blood flow in children with persisting postconcussive symptoms and posttraumatic headache at 2 weeks postconcussion.

OBJECTIVE: Persisting postconcussive symptoms (pPCS), particularly headache, can significantly disrupt children's recovery and functioning. However, the underlying pathophysiology of these symptoms remains unclear. The goal in this study was to determine whether pPCS are related to cerebral blood flow (CBF) at 2 weeks postconcussion. The authors also investigated whether variations in CBF can explain the increased risk of acute posttraumatic headache (PTH) in female children following concussion. METHODS: As part of a prospective, longitudinal study, the authors recruited children 5-18 years old who were admitted to the emergency department of a tertiary pediatric hospital with a concussion sustained within 48 hours of admission. Participants underwent pseudocontinuous arterial spin labeling MRI at 2 weeks postconcussion to quantify global mean gray and white matter perfusion (in ml/100 g/min). Conventional frequentist analysis and Bayesian analysis were performed. RESULTS: Comparison of recovered (n = 26) and symptomatic (n = 12) groups (mean age 13.15 years, SD 2.69 years; 28 male) found no differences in mean global gray and white matter perfusion at 2 weeks postconcussion (Bayes factors > 3). Although female sex was identified as a risk factor for PTH with migraine features (p = 0.003), there was no difference in CBF between female children with and without PTH. CONCLUSIONS: Global CBF was not associated with pPCS and female PTH at 2 weeks after pediatric concussion. These findings provide evidence against the use of CBF measured by arterial spin labeling as an acute biomarker for pediatric concussion recovery.

The influence of alcohol on genioglossus single motor units in men and women during wakefulness.

NEW FINDINGS: What is the central question of this study? How does alcohol intake, which worsens obstructive sleep apnoea, alter motor control of the genioglossus muscle, an upper airway dilator, in healthy awake human volunteers, and does alcohol alter genioglossus muscle afterdischarge? What is the main finding and its importance? Alcohol consumption had a very minor effect on the activity of the genioglossus in healthy young individuals studied during wakefulness and did not alter afterdischarge, leaving open the possibility that alcohol worsens obstructive sleep apnoea via other mechanisms. ABSTRACT: Alcohol worsens obstructive sleep apnoea (OSA). This effect is thought to be due to alcohol's depressant effect on upper airway dilator muscles such as the genioglossus, but how alcohol reduces genioglossal activity is unknown. The aim of this study was to investigate the effect of alcohol consumption on genioglossus muscle single motor units (MUs). Sixteen healthy individuals were studied on two occasions (alcohol: breath alcohol concentration ∼0.07% and placebo). They were instrumented with a nasal mask, four intramuscular genioglossal EMG electrodes, and an ear oximeter. They were exposed to 8-12 hypoxia trials (45-60 s of 10% O2 followed by one breath of 100% O2 ) while awake. MUs were sorted according to their firing patterns and quantified during baseline, hypoxia and recovery. For the alcohol and placebo conditions, global muscle activity (mean ± SD peak inspiratory EMG = 119.3 ± 44.1 and 126.5 ± 51.9 µV, respectively, P = 0.53) and total number of MUs recorded at baseline (68 and 67, respectively) were similar. Likewise, the peak discharge frequency did not differ between conditions (21.2 ± 4.28 vs. 22.4 ± 4.08 Hz, P = 0.09). There was no difference between conditions in the number (101 vs. 88, respectively) and distribution of MU classes during hypoxia, and afterdischarge duration was also similar. In this study, alcohol had a very minor effect on genioglossal activity and afterdischarge in these otherwise healthy young individuals studied while awake. If similar effects are observed during sleep, it would suggest that the worsening of OSA following alcohol may be related to increased upper airway resistance/nasal congestion or arousal threshold changes.

Accuracy of Components of the SCAT5 and ChildSCAT5 to Identify Children with Concussion.

The Sport Concussion Assessment Tool 5th Edition (SCAT5) is a standardized measure of concussion. In this prospective observational study, the ability of the SCAT5 and ChildSCAT5 to differentiate between children with and without a concussion was examined. Concussed children (n=91) and controls (n=106) were recruited from an emergency department in three equal-sized age bands (5-8/9-12/13-16 years). Analysis of covariance models (adjusting for participant age) were used to analyze group differences on components of the SCAT5. On the SCAT5 and ChildSCAT5, respectively, youth with concussion reported a greater number (d=1.47; d=0.52) and severity (d=1.27; d=0.72) of symptoms than controls (all p<0.001). ChildSCAT5 parent-rated number (d=0.98) and severity (d=1.04) of symptoms were greater for the concussion group (all p<0.001). Acceptable levels of between-group discrimination were identified for SCAT5 symptom number (AUC=0.86) and severity (AUC=0.84) and ChildSCAT5 parent-rated symptom number (AUC=0.76) and severity (AUC=0.78). Our findings support the utility of the SCAT5 and ChildSCAT5 to accurately distinguish between children with and without a concussion.

Validation of the SCAT5 and Child SCAT5 Word-List Memory Task.

The Sports Concussion Assessment Tool-5th Edition (SCAT5) and the child version (Child SCAT5) are the current editions of the SCAT and have updated the memory testing component from previous editions. This study aimed to validate this new memory component against the Rey Auditory Verbal Learning Test (RAVLT) as the validated standard. This prospective, observational study, carried out within The Royal Children's Hospital Emergency Department, Melbourne, Australia, recruited 198 participants: 91 with concussion and 107 upper limb injury or healthy sibling controls. Partial Pearson correlations showed that memory acquisition and recall on delay aspects of the SCAT5 were significantly correlated with the RAVLT equivalents when controlling for age (p < 0.001, r = 0.565 and p < 0.001, r = 0.341, respectively). Factor analysis showed that all RAVLT and SCAT5 memory components load on to the same factor, accounting for 59.13% of variance. Logistic regression models for both the RAVLT and SCAT5, however, did not predict group membership (p > 0.05). Receiver operating curve analysis found that the area under the curve for all variables and models was below the recommended 0.7 threshold. This study demonstrated that the SCAT5 and Child SCAT5 memory paradigm is a valid measure of memory in concussed children.

After-discharge in the upper airway muscle genioglossus following brief hypoxia.

STUDY OBJECTIVES: Genioglossus (GG) after-discharge is thought to protect against pharyngeal collapse by minimizing periods of low upper airway muscle activity. How GG after-discharge occurs and which single motor units (SMUs) are responsible for the phenomenon are unknown. The aim of this study was to investigate genioglossal after-discharge. METHODS: During wakefulness, after-discharge was elicited 8-12 times in healthy individuals with brief isocapnic hypoxia (45-60 s of 10% O2 in N2) terminated by a single breath of 100% O2. GG SMUs were designated as firing solely, or at increased rate, during inspiration (Inspiratory phasic [IP] and inspiratory tonic [IT], respectively); solely, or at increased rate, during expiration (Expiratory phasic [EP] or expiratory tonic [ET], respectively) or firing constantly without respiratory modulation (Tonic). SMUs were quantified at baseline, the end of hypoxia, the hyperoxic breath, and the following eight normoxic breaths. RESULTS: A total of 210 SMUs were identified in 17 participants. GG muscle activity was elevated above baseline for seven breaths after hyperoxia (p < 0.001), indicating a strong after-discharge effect. After-discharge occurred due to persistent firing of IP and IT units that were recruited during hypoxia, with minimal changes in ET, EP, or Tonic SMUs. The firing frequency of units that were already active changed minimally during hypoxia or the afterdischarge period (p > 0.05). CONCLUSION: That genioglossal after-discharge is almost entirely due to persistent firing of previously silent inspiratory SMUs provides insight into the mechanisms responsible for the phenomenon and supports the hypothesis that the inspiratory and expiratory/tonic motor units within the muscle have idiosyncratic functions.