PET Better than Standard Tests in Predicting Recovery from Severe Brain Damage

Researchers have found that a brain imaging technique called positron emission tomography (PET) is better than standard tests in predicting recovery of brain injury patients in vegetative state. 

The study, conducted by researchers at the University of Liége and colleagues, found that the traditional clinical examinations are only 40 percent accurate in assessing the condition of a patient in vegetative state.

The study was based on data from 126 patients in a minimally conscious state (MCS) or in a vegetative state due to severe brain damage. Patients in MCS have minimal awareness while those in vegetative state can neither move, nor respond to stimuli. In the present study, 41 patients had unresponsive wakefulness syndrome (vegetative state).  

Patients underwent two types of brain imaging techniques; PET and function magnetic resonance imaging, which show brain activity in real time, according to HealthDay.

PET scans use a radioactive substance called a tracer to look for injury in the brain. Other tests such as magnetic resonance imaging (MRI) and computed tomography (CT) show the blood flow to the affected organ, according to Medline Plus.

The team then compared test results with Coma Recovery Scale-Revised (CSR-R) behavioural test scores, which is used as a standard to determine awareness.

"Our findings suggest that PET imaging can reveal cognitive processes that aren't visible through traditional bedside tests, and could substantially complement standard behavioural assessments to identify unresponsive or "vegetative" patients who have the potential for long-term recovery," said Professor Steven Laureys from the University of Liége in Belgium, lead author of the study.

Researchers found that PET with the imaging agent fluorodeoxyglucose (FDG-PET) was better than fMRI and standard tests in distinguishing between patients with MCS and  those with VS.

fMRi was 56 percent accurate in predicting whether a person would recover from the brain condition while PET was 74 percent accurate in predicting patient recovery.

What's more is that a third of the 36 patients who were classified as unresponsive under the standard tests, showed some brain activity during PET scanning. Also, nine of them recovered consciousness,

"We confirm that a small but substantial proportion of behaviourally unresponsive patients retain brain activity compatible with awareness. Repeated testing with the CRS-R complemented with a cerebral FDG-PET examination provides a simple and reliable diagnostic tool with high sensitivity towards unresponsive but aware patients," Laureys said in a news release.

The study is published in the journal The Lancet.