Coma and impaired consciousness are common presentations in neurocritical care. This chapter reviews the definitions of different levels of awareness and discusses the diagnosis and management of comatose patients. DEFINITIONS • ▪ Coma is a state of unresponsiveness to external or internal stimuli in which a patient lies with eyes closed unaware of the environment. Although this definition seems quite straightforward, coma actually lies on a continuum of disorders of consciousness. • Consciousness, defined as a state of awareness of both the self and the environment, is composed of two key elements: arousal and content. ▸ Arousal is mediated by the ascending reticular activating system that localizes to the rostral pons, midbrain, thalamus, and hypothalamus, and is characterized by wakefulness or alertness. ▸ Content, on the other hand, requires the higher-level structures of the cerebral cortex and its connections to subcortical white matter, and is composed of affective and cognitive functions such as attention, memory, motivation, and executive function. • RATING IMPAIRED CONSCIOUSNESS • Disruptions to either the reticular activating system or bilateral cortices can therefore result in impaired consciousness, and the extent of the damage determines where on the spectrum of consciousness a patient may lie. Several scales have been created to rate the severity of impaired consciousness.
ASJC Scopus subject areas
- Clinical Neurology
- Critical Care and Intensive Care Medicine