For close patients in a vegetative state, a light has appeared in the tunnel: scientists probably already know how to accurately predict the future of patients. At least for some families, this means a positive boost of hope.
In the unexplored space between full consciousness and death, the time of many seriously ill people, heavily injured in accidents who have found themselves in a vegetative state, passes. Some of them will manage to get out of the shadow zone over time and regain health. If it were possible to accurately predict which of the patients has a chance to regain consciousness, their relatives would gain a source of comfort and hope. The benefits would also apply to the sick themselves, especially those wishing to tell those around them that they are “still here” and that they sometimes suffer pain that no one notices.
In the United States alone, 9-37 thousand people are treated in hospitals. patients with minimal awareness or in a vegetative state. The large spread of the figures is related to the imprecise determination of who belongs to these categories.
Work on a test that can reliably predict the fate of a patient in a vegetative state has so far not yielded any results. However, a new study found that scanning the person’s brain for areas of increased metabolic activity increases the likelihood of an accurate prediction.
The authors of a recent research paper in the Lancet journal followed 102 patients in a vegetative state for at least a year, assessing their condition with brain imaging, medical checks, and sophisticated tests to determine the severity of their impairment. All of these patients were classified as either minimally conscious or as confined and in a vegetative state.
Brain imaging with the PET positron emission tomography method allowed scientists to accurately predict the progress of these patients in the annual perspective: in 74 percent. of these, the chances of regaining consciousness were correctly assessed. More often it was possible to state that in a year the patient’s condition would not change (he would still show no signs of consciousness) – a prolonged vegetative state or minimal awareness in an annual perspective was accurately assessed in 92% of patients. subjects. However, also in 67 percent. cases, it was possible to establish, using PET, that the patient would regain some consciousness – and it did. The authors of the study reported that people with loss of consciousness resulting from traumatic brain injury were more accurate predictions than in patients whose condition resulted from hypoxia, a prolonged lack of oxygen in the blood that nourishes the brain.
PET imaging in a control group of 39 healthy volunteers made it possible to compare a well-functioning central nervous system with the brain of people with disabilities. Even if the levels of consciousness observed were identical in two patients, the metabolic functions of the brain in a vegetative state were fundamentally different from that of the brain experiencing occasional flashes of consciousness. If PET imaging detected even a slight trace of fleeting consciousness in a person in a vegetative state, there was reason to believe that their condition would improve over time.
In the group of 41 patients in a vegetative state, PET imaging allowed to distinguish 13 people with a very limited, but noticeable level of consciousness. After one year, nine patients in this group made progress, moving to at least the minimally conscious category (the remaining three died of complications or after treatment discontinuation, and one patient remained in a vegetative state). None of the remaining 28 people in whom PET gave grounds for hope showed improvement.
Hence the conclusion that PET imaging, which detects signs of metabolic activity in various regions of the brain, allows to more accurately determine the patient’s further fate than functional magnetic resonance imaging, fMRI, focusing on those parts of the brain that are better oxygenated at a given moment. It was with fMRI that it was previously established that some people in a vegetative state are able to hear, understand and even respond appropriately to doctors’ orders. In the current study, as well as in many other experiments previously performed, patients who were found to be in a vegetative state were asked to recall a familiar landscape or to imagine a game of tennis: in some cases, fMRI then showed obvious stimulation of the parts of the brain responsible for spatial sensations or planning motor activity. However, the same study found that functional MRI was unable to pick up subtle signs of fleeting awareness.
For people in a vegetative state, surprisingly skilled at performing imaginary tasks that are then recorded by MRI, fMRI is a convenient tool as it enables them to assess the intellectual abilities of these patients and potentially allows them to communicate their needs or desires to their surroundings, note the authors of the Lancet article. On the other hand, however, even a sick person in a vegetative state, who is unable to play imaginary tennis or wander in his family home, may show hopeful flashes of consciousness, and these will only be registered by PET. This is why emission computed tomography seems to be a better tool for assessing a patient’s chances of future recovery.
Melissa Healy