When the general public is asked to describe the consequences of brain injury, the most frequent responses will involve some concept of the victim’s loss of consciousness. This is unfortunate since, as those of us that deal with the long-term consequences are all too aware, the real “battle” doesn’t begin until after consciousness returns. For the purpose of this general overview, we may define any change from a state of full self-awareness to a state of decreased (or absent) self-awareness as a disorder of consciousness.

In the medical literature, recovery from a disorder of consciousness is defined as occurring along a continuum; which is to say that such recovery progresses in a direct, linear, and predictable fashion. The rapidity and completeness of recovery, of course, varies between individuals and with the underlying disease process that is the cause of such disorders. None the less, it will be helpful to review the general stages that may or may not be encountered.

The first, and by far the most serious, stage in the disorders of consciousness is that of coma; a state of profound (deep) unconsciousness in which the victim is unable to move, open his/her eyes, or respond appropriately in any way to external stimulation. Those in a coma are unable to breathe on their own and depend on mechanical support of respiratory activity, as well as intensive medical and nursing care, in order to survive.

Coma as a distinct clinical condition is very rarely a persistent condition, meaning that those surviving the initial event which induced coma will either progress to a less severe level of neurological compromise or will die. Despite the occasional “sensational” or “anecdotal” reports in the news media, there has never been a documented case of spontaneous recovery from coma directly to “consciousness. Such “miracle” recoveries have always been from a less severe level of impaired consciousness and have further been complicated by marked loss of motor skills such as speaking, use of table utensils, or the ability to perform simple self-care functions.

The next stage in the continuum is the vegetative state (VS), which is defined as a state in which the patient may be able to breathe without assistance yet remains dependent on skilled medical and nursing care in order to survive. Those in the vegetative state may open their eyes and may even make occasional non-purposeful sounds such as grunting or laughter but they are incapable of making intentional responses to external events. In the vegetative state, the patient has an established sleep/wake cycle, which can give the illusion of conscious activity.

The vegetative state, unlike coma, may persist for years upon years without obvious improvement in the victim’s clinical condition

The final stage, and the stage that is currently the focus of intense clinical research (Owen, 2006; Schiff, 2007), is the minimally conscious state (MCS). In this state the victim demonstrates

“…limited and intermittent capacity for conscious behavior. These patients occasionally demonstrate clear-cut signs of self- or environmental awareness… the diagnosis of MCS is based on the presence of specific behavioral manifestations of conscious awareness. These behaviors occur inconsistently, must be differentiated reliably from reflexive, random, and spontaneous behavior, and include functions such as simple command following, production of yes/no responses, intelligible verbalization, and contingent behavioral responses… (Hirsch, 2005).”

As with the vegetative state, the minimally conscious state may also persist for years. But, in contrast to the vegetative state, the victim may continue to demonstrate a slow overall improvement. Once again, changes are impossible to predict.

Notes

Hirsch, Joy (2005): Raising Consciousness, Journal of Clinical Investigation, 115:1102.

Owen, Adrian et al (2006): Detecting awareness in the vegetative state, Science 313 (5792), 1402.

Schiff, Nicholas et al (2007): Behavioural improvements with thalamic stimulation after severe traumatic brain injury, Nature 448, 600-603 (2 August 2007).