Right-to-die case highlights brain mysteries
Researchers still far from full understanding of vegetative states.
The bitter wrangle over the fate of an American brain-damaged woman has thrown up both legal and ethical conundrums. But it has also highlighted neurologists' dearth of knowledge about the brain's workings after injury.
Terri Schiavo was severely brain-damaged in 1990, after her heart temporarily stopped and starved her body of oxygen. Her husband has fought to allow her to die; her parents have opposed this on the grounds that she shows some signs of awareness and might recover.
The debate escalated dramatically after a Florida judge permitted Schiavo's feeding tube to be removed last week, prompting President George W. Bush to sign emergency legislation ordering a review of her case. But on Tuesday 22 March, a federal judge turned down a request to have the tube reinserted.
Brain specialists say that those hoping for Schiavo's recovery are ignoring medical consensus: that the widespread damage caused to her oxygen-deprived brain, and the length of time she has been sick, make the probability of any recuperation close to zero. "There is no evidence that there is anything we can do," says neurologist Nicholas Schiff at the Weill Medical College of Cornell University, New York.
Columbia University, New York
Some such patients may spontaneously move, cry or smile, but are unable to respond to commands. They are said to be in a persistent vegetative state (PVS). Their chances of recovery are very slim and decline with time. As in Schiavo, this type of profound damage often occurs after a heart attack robs the entire brain of oxygen.
Within the past 15 years, however, doctors have recognized a second category of patients, who occasionally respond to commands by, say, moving their eyes or reaching for a glass of water. These people are said to be in a minimally conscious state (MCS). They have generally suffered traumatic injuries that have left parts of their brain intact, and are thought to stand a slightly better chance of some recovery.
The common perception that irreparably brain-damaged patients can undergo miraculous recoveries, doctors say, is based on confusion between the two different conditions. "The frustrating thing is the conflation of these brain states," says medical ethicist Joseph Fins, also at Weill Medical College.
Hazy in mind
Although doctors have formal criteria for diagnosing PVS and MCS, they know very little about how the brains of such patients work. It is only in the past few years, for example, that researchers have begun to scan the brains of those suffering these conditions.
One study, published in Neurology this year, suggests that some brain circuits in minimally conscious patients process information normally1. The researchers used functional magnetic resonance imaging to scan two minimally conscious men while they listened to relatives read personal accounts of situations they had experienced, such as a wedding.
The patients' brain areas for processing language lit up, the researchers showed, in a very similar way to those in healthy volunteers. By contrast, studies looking at PVS patients suggest that only isolated fragments of brain networks survive.
The researchers nevertheless have no idea whether the brain activity translates into any kind of feeling or experience for MCS patients. "We can watch this circuitry go but we don't know what it means," says the study's lead author, Joy Hirsch of Columbia University in New York.
Even so, her team is now examining a further 20 patients to test whether brain scans could be used to diagnose a patient more accurately. If such a test existed, it would help to resolve the debate about whether Schiavo might recover, Hirsch suggests.
Such investigations might also reveal the best ways to stimulate intact brain areas in brain-damaged patients and speed up their recovery. "We'd love to be at that point," Hirsch says.
- Schiff N. D., et al. Neurology, 64. 514 - 523 (2005).