March 22, 2005
Persistent Vegetative State, Coma, and Minimal Consciousness
Dr. Amy Movius, MD
There's probably not a person among us who hasn't heard at least something about the Terri Schiavo case. Different terms have been used to describe this case in media outlets all over the country, often in confusing or even inaccurate ways. Though opinions surely vary regarding living wills, death with dignity, and the right to life movements, the medical terms actually have specific definitions and characteristics. Below is a summary of some definitions given in the hope that it may help folks navigate the sea of information/misinformation surrounding this unfortunate case.
Coma is a state of profound unconsciousness from which one cannot be roused. There are no sleep-wake cycles during coma and no movement beyond reflexes or "posturing". All patients who survive coma begin to awaken within 2 to 4 weeks no matter how severe the brain damage. Once "awake" they are no longer in a coma even though they may never again show any conscious intelligence.
A Persistent Vegetative State or PVS denotes a state in which a personal is incapable of voluntary or "on-purpose" acts and only has a reflex to pain. It is a form of "eyes-open permanent unconsciousness" with no awareness of themselves or the environment. Patients return to a state of wakefulness and have sleep-wake cycles. They may have occasional nonpurposeful movements and will posture or withdraw to pain, though they cannot localize the area of pain, such as pull away the arm that is pinched. They might have reflexive crying or smiling and might briefly fix their eyes on something or turn toward a sound. When present, these findings are not consistent. Their eyes may move side to side but they do not follow objects with their eyes The most common cause of PVS is lack of oxygen to the brain.
The Minimally Conscious State (MCS) describes very abnormal brain function that does not meet the criteria for PVS. These patients have minimal but definite behavioral evidence of self or environmental awareness. They can localize pain, reach for objects and display "automatic" movements such as scratching. They might follow some verbal commands, though not consistently. They do consistently orient to sound and will look at something and follow it with their eyes. They may vocalize (not intelligible) or gesture in a consistent way in response to a situation. They may show a similar consistency in emotional display, such as smiling or crying.
1. Stedman's Medical Dictionary, 25th Edition
2. Diagnosis of Stupor and Coma, Plum and Posner,Edition 2
3. The Minimally Conscious State, Definition and diagnostic criteria. Giacino et al, Neurology 2002;58:349-353.
4. Medical Aspects of the Persistent Vegetative State. The Multi-Society Task Force on PVS, N Engl J Med 1994;330:1499-508.