The reticular activating system: a narrative review of discovery, evolving understanding, and relevance to current formulations of brain death

A series of landmark experiments conducted throughout the 20 th century progressively localized the regions involved in consciousness to the reticular activating system (RAS) and its ascending projections. The first description of the RAS emerged in 1949 through seminal experiments performed by Moru...

Full description

Saved in:
Bibliographic Details
Published in:Canadian journal of anesthesia 2023-04, Vol.70 (4), p.788-795
Main Authors: Taran, Shaurya, Gros, Priti, Gofton, Teneille, Boyd, Gordon, Briard, Joel Neves, Chassé, Michaël, Singh, Jeffrey M.
Format: Article
Language:English
Subjects:
Anesthesiology
Animals
Brain
Brain death
Brain Death - diagnosis
Canada
Cardiology
Cats
Consciousness
Critical Care Medicine
Humans
Injuries
Intensive
Medicine
Medicine & Public Health
Pain Medicine
Pediatrics
Pneumology/Respiratory System
Review /Brief Review
Review Article/Brief Review
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:A series of landmark experiments conducted throughout the 20 th century progressively localized the regions involved in consciousness to the reticular activating system (RAS) and its ascending projections. The first description of the RAS emerged in 1949 through seminal experiments performed by Moruzzi and Magoun in feline brainstems; additional experiments in the 1950s revealed connections between the RAS and the thalamus and neocortical structures. This knowledge has allowed for the explanation of disorders of consciousness with exquisite anatomic precision. The clinical relevance of the RAS is further apparent in modern definitions of brain death/death by neurologic criteria (BD/DNC), which require demonstration of the complete and permanent loss of capacity for consciousness as one of their core criteria. BD/DNC is currently understood across jurisdictions in terms of “whole brain” and “brainstem” formulations. Although their clinical examination between formulations is indistinguishable, policies for BD/DNC declaration may differ in the rare scenario of patients with isolated infratentorial brain injuries, in which ancillary testing is advised in the whole brain formulation but not the brainstem formulation. Canadian guidelines acknowledge that the distinction between whole brain and brainstem formulations is unclear with respect to clinical implications for patients with isolated infratentorial injuries. This has led to variability in Canadian clinicians’ use of ancillary testing when the mechanism of BD/DNC is suspected to be an isolated infratentorial injury. The present narrative review highlights these concepts and explores implications for determination of BD/DNC in Canada, with specific emphasis on the RAS and its relevance to both formulations.
ISSN:0832-610X
1496-8975
DOI:10.1007/s12630-023-02421-6