Ultrasound, photoacoustic, and magnetic resonance imaging to study hyperacute pathophysiology of traumatic and vascular brain injury

Early GFAP and UCH-L1 point-of-care biomarker measurements for the prediction of traumatic brain injury and progression in patients with polytrauma and hemorrhagic shock

OBJECTIVE

Traumatic brain injury (TBI) and hemorrhage are responsible for the largest proportion of all trauma-related deaths. In polytrauma patients at risk of hemorrhage and TBI, the diagnosis, prognosis, and management of TBI remain poorly characterized. The authors sought to characterize the predictive capabilities of glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase L1 (UCH-L1) measurements in patients with hemorrhagic shock with and without concomitant TBI.

METHODS

The authors performed a secondary analysis on serial blood samples derived from a prospective observational cohort study that focused on comparing early whole-blood and component resuscitation. A convenience sample of patients was used in which samples were collected at three time points and the presence of TBI or no TBI via CT imaging was documented. GFAP and UCH-L1 measurements were performed on plasma samples using the i-STAT Alinity point-of-care platform. Using classification tree recursive partitioning, the authors determined the measurement cut points for each biomarker to maximize the abilities for predicting the diagnosis of TBI, Rotterdam CT imaging scores, and 6-month Glasgow Outcome Scale-Extended (GOSE) scores.

RESULTS

Biomarker comparisons demonstrated that GFAP and UCH-L1 measurements were associated with the presence of TBI at all time points. Classification tree analyses demonstrated that a GFAP level > 286 pg/ml for the sample taken upon the patient's arrival had an area under the receiver operating characteristic curve of 0.77 for predicting the presence of TBI. The classification tree results demonstrated that a cut point of 3094 pg/ml for the arrival GFAP measurement was the most predictive for an elevated Rotterdam score on the initial and second CT scans and for TBI progression between scans. No significant associations between any of the most predictive cut points for UCH-L1 and Rotterdam CT scores or TBI progression were found. The predictive capabilities of UCH-L1 were limited by the range allowed by the point-of-care platform. Arrival GFAP cut points remained strong independent predictors after controlling for all potential polytrauma confounders, including injury characteristics, shock severity, and resuscitation.

CONCLUSIONS

Early measurements of GFAP and UCH-L1 on a point-of-care device are significantly associated with CT-diagnosed TBI in patients with polytrauma and shock. Early elevated GFAP measurements are associated with worse head CT scan Rotterdam scores, TBI progression, and worse GOSE scores, and these associations are independent of other injury attributes, shock severity, and early resuscitation characteristics.

Neuroimaging, wearable sensors, and blood-based biomarkers reveal hyperacute changes in the brain after sub-concussive impacts

Impacts in mixed martial arts (MMA) have been studied mainly in regard to the long-term effects of concussions. However, repetitive sub-concussive head impacts at the hyperacute phase (minutes after impact), are not understood. The head experiences rapid acceleration similar to a concussion, but without clinical symptoms. We utilize portable neuroimaging technology - transcranial Doppler (TCD) ultrasound and functional near infrared spectroscopy (fNIRS) - to estimate the extent of pre- and post-differences following contact and non-contact sparring sessions in nine MMA athletes. In addition, the extent of changes in neurofilament light (NfL) protein biomarker concentrations, and neurocognitive/balance parameters were determined following impacts. Athletes were instrumented with sensor-based mouth guards to record head kinematics. TCD and fNIRS results demonstrated significantly increased blood flow velocity (p = 0.01) as well as prefrontal (p = 0.01) and motor cortex (p = 0.04) oxygenation, only following the contact sparring sessions. This increase after contact was correlated with the cumulative angular acceleration experienced during impacts (p = 0.01). In addition, the NfL biomarker demonstrated positive correlations with angular acceleration (p = 0.03), and maximum principal and fiber strain (p = 0.01). On average athletes experienced 23.9 ± 2.9 g peak linear acceleration, 10.29 ± 1.1 rad/s peak angular velocity, and 1,502.3 ± 532.3 rad/s2 angular acceleration. Balance parameters were significantly increased following contact sparring for medial-lateral (ML) center of mass (COM) sway, and ML ankle angle (p = 0.01), illustrating worsened balance. These combined results reveal significant changes in brain hemodynamics and neurophysiological parameters that occur immediately after sub-concussive impacts and suggest that the physical impact to the head plays an important role in these changes.