Predicting Recovery with a PET


The inspiration for this post was an article written by Sarah Boseley for the Guardian. Text under the heading titled “Article” was written by Boseley. I have not read the journal article nor crunched the numbers in the study. I chose to write this post because the issue described in the article pertains to recovery and it is worthy of discussion.


PET scans are used for cancer patients but have not been employed to detect consciousness in brain-injured patients due to the cost. Photograph: Noemi Bruzak/EPA
PET scans have not been employed to detect consciousness in brain-injured patients. Photograph by Noemi Bruzak/EPA

Doctors believe they may have found a reliable way to assess whether patients in a vegetative state after a severe brain injury are likely to wake up, raising ethical questions about the best treatment for those in an unresponsive state.

In a hospital trial, brain scans using PET technology – positron emission tomography – identified hidden levels of consciousness in a third of patients who had been unresponsive and diagnosed as in a vegetative state for more than a year. Most of these “woke up” or moved to a more responsive state within 12 months.

The results of the four-year trial – which took place in a specialist hospital in Belgium, with patients from all over Europe including the UK – raise ethical questions and could change clinical practice.

If the testing proves to be as accurate as it appears, there may be an argument for such patients to be treated differently – doctors might want to reconsider their need for painkillers, for instance. But there could also be a strengthened case for switching off life support for those in whom no consciousness is detected.

Doctors at the University of Liège carried out the trial to establish whether PET scans or another form of brain scan using functional magnetic resonance imaging (fMRI) were more reliable predictors of recovery than the assessments by doctors using standardized bedside tests. Those result in up to 40% of patients being misdiagnosed.

In the latest trial, involving 126 patients, the results of which have been published in the Lancet medical journal, 41 were in a persistent vegetative state, 81 were in a minimally conscious state and four had locked-in syndrome. PET correctly predicted the extent of recovery in the following year in 74% of patients and fMRI in 56%.

Professor Steven Laureys from the University of Liège, who led the study, said a third of the patients referred to them by doctors elsewhere had been misdiagnosed. Of 41 patients whose doctors had diagnosed a vegetative state, 13 were found by a PET scan to have some level of consciousness. Of the 13, nine regained consciousness within the year, three died of other causes such as pneumonia and just one was still in a vegetative state.

Other scientists were enthusiastic about the results. “This really exciting study suggests for the first time that a brain scanning technique called PET could be used in the future to predict the likelihood that a patient may wake-up a long time after a severe brain injury,” said Dr. Michael Bloomfield, clinical research fellow at the Medical Research Council Clinical Sciences Centre in London.

“If the results of this study are confirmed in future research, this could have far-reaching clinical, ethical and legal implications, including whether to offer an apparently unconscious patient pain relief and, ultimately, whether treatments that may be keeping someone alive should be continued or not.”

Professor Martin Monti from the departments of psychology and neurosurgery at the University of California, Los Angeles, said: “This new report marks a long-awaited first step towards translating cutting-edge science into clinical practice.”

Shadow of Doubt

Since I have not read the journal article, I don’t know the amount of overlap between PET results and fMRI results. We are told the “PET correctly predicted the extent of recovery in the following year in 74% of patients and fMRI in 56%.” What we are not told is whether or not all 56% of the fMRI results are included in the 74% PET results. In other words, we do not know if one or both scans provide useful information, nor do we know what brain activity is responsible for the diagnosis. In addition, we are told some people emerge from their vegetative state, but we are not informed whether or not the people who emerge live on life support, if they have a quality life, or if they are happy after emerging from their vegetative state. Furthermore, we do not know if the additional information from a scan would alter the decision of family members.


Thanks to Google for helping me find the picture and text I used in this post; Sarah Boseley for writing the article; the Guardian for committing its resources to publishing the article; Lancet for publishing the study upon which the article is based; Awesomely Cute for providing the picture I used on social media; and all the people who, directly or indirectly, made it possible for me to include the picture and text I used in this post.

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