The natural history of chronic disorders of consciousness

Chronic disorders of consciousness comprise a tragic group of conditions for which determining prognosis is a prerequisite for clinical decision-making.¹ The vegetative state (VS) of wakefulness without awareness was first described in 1972 by Jennett and Plum but achieved national attention through highly publicized judicial rulings on discontinuing the medical treatment of young women named Karen Quinlan, Nancy Cruzan, and Theresa Schiavo. The minimally conscious state (MCS), formerly and more accurately called the minimally responsive state, was defined diagnostically in 2002 as profound unresponsiveness despite nominal and intermittent evidence for awareness.²

The VS and MCS are syndromes, encompassing a spectrum of severity with various etiologies, most commonly traumatic brain injury or hypoxic-ischemic or hemorrhagic neuronal injury; they can be a transient stage during recovery from an acute brain insult or can be chronic and stable.¹ Although functional neuroimaging studies are changing our understanding and bedside assessment of conscious awareness,³ the VS and MCS remain clinically defined syndromes.

Published analyses of the prognosis of these syndromes, such as the 1994 Multi-Society Task Force on PVS,⁴ have been limited by several factors. First, there was no agreed-upon definition of, or …