A Bit of Basic Brain Science

Revolutionary Worker #1274, April 10, 2005, posted at rwor.org

"It is impossible to separate thought from matter that thinks."

— Karl Marx, The Holy Family, 1844

Q: What happened to Terri Schiavo's brain after her heart attack?

A: The human brain has several different parts that play their role in creating consciousness and maintaining life functions.

In Terri Schiavo's case, one part of the brain survived the lack of oxygen resulting from her heart attack: the brain stem , which sits at the base of the human brain, right above the spinal column. This brain stem is the part of the brain that regulates and controls basic life functions of the body —breathing, heartbeat, blood pressure.

But the lack of oxygen had killed virtually all the nerve tissues that once made up Terri Schiavo's cerebral cortex . This cortex is the upper part of the brain. It is the part of the brain that controls consciousness, processes ideas, responds to other humans, and stores memories. This cortex is the part of the brain that allows humans to know things—the part of the brain that distinguishes human brains as matter conscious of itself. Without this cortex, a human being cannot know anything or think any thoughts.

It was also believed that her thalamus was irreparably damaged. The thalamus is the part deep within the brain that is a center for sensation, including pain and pleasure. The thalamus helps human beings be aware of themselves and their surroundings, and plays a role in certain emotions.

Q: How did doctors determine that Terri could not regain any conscious mental function?

A : Doctors have several ways of telling how much of a human brain is damaged, whether there is any conscious activity, and whether any consciousness may return.

In one important test, they searched for electrical brain waves in Terri Schiavo's brain, using an electroencephalogram (EEC). Brain cells communicate by small electrical pulses, and these can be detected by placing sensitive electrodes on the scalp over areas of the brain. In Terri Schiavo's case, EECs were performed by independent medical examiners assigned by state courts. And they showed that her brain waves were essentially flat— with an extremely low level of electrical activity from the brain stem, but otherwise showing no brain activity and no thoughts .

A second important test is the close observation of the behavior and change of the patient over time to determine whether there is a chance of a return to consciousness. This was the principle diagnostic tool in Terri Schiavo's case. Such examinations of Terri Schiavo over many years determined (and then confirmed) that she was in a " permanent vegetative state " (PVS), meaning that over a long period of time, the patient had not made any meaningful response.

A third brain test, done by CAT scans , gave a detailed picture of what had actually gone on inside Terri Schiavo's skull. CAT scans are a series of X-rays that show the inside of the human body in slices. CAT scans of Terri Schiavo's brain showed that her brain tissue had not just died, but many parts of her brain had actually disappeared —being reabsorbed into the body or dissolved into the brain's surrounding fluid. The brain itself had shrunken, and large spaces had opened up inside of her skull. The brain's cerebrospinal fluid had filled up those physical spaces where Terri Schiavo's thinking tissues had once been.

Q: What is a persistent vegetative state? Some of Terri's relatives have claimed that she was following them with her eyes—is that possible given the damage to her brain?

A:The RW spoke with Dr. David A. Goldstein about this diagnosis. He is a physician and educator with the Keck School of Medicine of the University of Southern California and Co-director of the USC Pacific Center for Health Policy and Ethics.

Dr. Goldstein said: "The main difference is that patients in a persistent vegetative state usually have their eyes open. In truth, that's the main difference. There are lots of different levels of coma, but all of those are associated with someone's eyes being closed. But to the non-medical-professional, the stark difference is that patients in the persistent vegetative state can have their eyes open. They have a lot of rudimentary reflexes, but no evidence of any relationship with the outside world. Even though they sometimes blink, they sometimes seem to 'eye follow,' a good neurologist will examine these patients and be able to determine relatively quickly if they've been in that state six weeks or so, that's PVS, persistent vegetative state. It's not a difficult diagnosis to make at that juncture."

Dr. Goldstein added that this condition is permanent: "No one wakes up from persistent vegetative state."