Citation

Purkayastha S, Sorond FA, Lyng S, Frantz J, Murphy MN, Hynan LS, Sabo T, Bell K. J. Neurotrauma 2019; 36(16): 2385-2390.

Affiliation

University of Texas Southwestern Medical School, Physical Medicine and Rehabilitation , 5323 Harry Hines , CS2.122 , Dallas, Texas, United States , 75390-9055 ; Kathleen.Bell@UTSouthwestern.edu.

Copyright

(Copyright © 2019, Mary Ann Liebert Publishers)

DOI

10.1089/neu.2018.5861

PMID

30693827

Abstract

Traumatic brain injury (TBI) is associated with increased risk of later-life neurodegeneration and dementia. However, the underpinning mechanisms are poorly understood and secondary injury resulting from perturbed physiological processes play a significant role. Cerebral vasoreactivity (CVR), a measure of hemodynamic reserve, is known to be impaired in TBI. However, the temporal course of this physiological perturbation is not established. We examined CVR and clinical symptoms on day-3 (T1), day-21 (T2), and day-90 (T3) following concussion in collegiate athletes and cross-sectionally in non-injured controls. Changes in middle cerebral artery blood flow velocity (MCAV) (transcranial Doppler ultrasonography) were measured during changes in end-tidal CO₂ (PetCO₂) at normocapnia, hypercapnia (inspiring 8% CO₂), and hypocapnia (hyperventilation). CVR was determined as the slope of the linear relationship and expressed as percent change in MCAV per mmHg change in PetCO₂. CVR was attenuated during the acute phase T1 (1.8±0.4U P=0.0001), sub-acute phases T2 (2.0±0.4U P=0.0017) and T3 (1.9±0.6U P=0.023) post-concussion compared to the controls (2.3±0.3U). Concussed athletes exhibited higher symptom number (2.5±3 vs.12.1±7; P<0.0001) and severity (4.2±6 vs. 29.5±23; P<0.0001), higher Patient Health Questionnaire-9 score (2.2±2 vs. 9.1±6; P=0.0003) at T1. However, by T2 symptoms had resolved. We show that CVR is impaired as early as 4 days and remains impaired up to three months post-injury despite symptom resolution. Persistent perturbations in CVR may therefore be involved in secondary injury. Future studies with a larger sample size and longer follow-up period are needed to validate this finding and delineate the duration of this vulnerable period.

Language: en

Keywords

BLOOD FLOW; HUMAN STUDIES; TRAUMATIC BRAIN INJURY; VASCULAR REACTIVITY