Monday, March 28, 2005

When does the brain go blank?

Time Magazine

When does the brain go blank?


Much of the ammunition in the battle over Terri Schiavo's fate has been medical language that's fairly new in the public realm. The terms can mean one thing to experts and another thing entirely when wielded by passionate partisans in the debate. On the basis of interviews with specialists in the fields of neurology and palliative care, we offer answers to some of the most perplexing questions:

WHAT IS A PERSISTENT VEGETATIVE STATE? People who suffer enough brain damage that they are unaware of themselves or their surroundings, but still demonstrate certain reflexes and are able to breathe and pump blood on their own, are in what doctors call a vegetative state. If that condition lasts for at least a month without any sign of improvement, the diagnosis may be changed to persistent vegetative state (PVS).

IS THAT THE SAME AS BEING BRAIN DEAD? No. Brain death occurs when there is no activity anywhere in the brain. In PVS, certain primitive regions of the brain, including the brain stem, which controls autonomic functions such as breathing and the beating of the heart, are still alive. However, the cortex, which is the thinking part of the cerebrum, and/or the thalamus, which connects the brain stem to the cortex, are so badly damaged that they no longer function.

HOW IS A DIAGNOSIS OF PVS MADE? A neurologist examines the patient on several occasions, looking for signs of awareness. Are there consistent responses to simple requests—to move a finger, for example? Do the eyes follow the doctor across the room? The specialist often observes the patient in the presence of family to see if there is any response. Brain scans may show the extent of any damage, particularly after some time has passed and dead neural tissue is replaced by cerebrospinal fluid.

WHY DOES TERRI SCHIAVO OPEN HER EYES, BLINK AND APPEAR TO SMILE IN THE VIDEO HER PARENTS MADE? The most difficult thing to understand about a vegetative state is that it allows one to be awake but not aware. (In a coma, you are unresponsive and your eyes are closed.) Because the sleep-wake cycle and certain eye movements are not controlled by the cortex or the thalamus, they can continue without conscious awareness. Even acts of crying and smiling may be reflexive events that do not occur in response to specific stimuli.

HOW LONG CAN A PERSON IN A PERSISTENT VEGETATIVE STATE LIVE THAT WAY? With sufficient medical care, including the use of feeding tubes, patients can survive for decades. They are, however, particularly susceptible to infections, including pneumonia and bed sores.

WHAT ARE THE CHANCES OF RECOVERY FROM PVS? The prognosis is better when the condition results from a head injury, which is why in those cases, doctors usually wait at least a year before concluding that the patient is permanently vegetative. When the condition is triggered by a prolonged lack of oxygen to the brain, as was true for Schiavo, the chances of any kind of recovery diminish rapidly after three months.

HOW IS A VEGETATIVE STATE DIFFERENT FROM A MINIMALLY CONSCIOUS STATE? A comparatively new designation, minimally conscious state describes people who are not in a vegetative state but who don't show consistent evidence of awareness. For example, they may indicate yes-or-no responses even if they aren't accurate. (Schiavo's parents have argued that their daughter is minimally conscious.) A recent study using specialized brain scans found near normal activity levels in the cortical language centers of some such patients when their loved ones spoke to them, indicating they may retain the potential for cognitive function. Patients in a minimally conscious state are also more likely to improve and benefit from therapy than those in a vegetative state.

DOES A PERSON IN A VEGETATIVE STATE SUFFER AFTER NUTRITION AND HYDRATION HAVE BEEN WITHDRAWN? No one knows for certain, of course, what it feels like to be unaware—hence the awful anxiety that is at the heart of the Schiavo debate. But it's quite possible for death under those conditions to be peaceful, at least as far as outside observers can tell. (Indeed, taking to one's bed and refusing to eat while drinking little or nothing was until recently a common way to die.) Moistening the lips and mouth will keep the skin in this area from cracking. The lack of fluid leads to a buildup of ketones that induces a coma, along with kidney failure or cardiac arrest—a deceptively dramatic-sounding breakdown that nonetheless can release a patient from life quite gently.

originally posted March 27, 2005