Using brain imaging to predict which vegetative patients have potential to recover
According to new research, positron emission tomography (PET), a functional brain imaging technique, is a promising tool for determining which brain damaged individuals in vegetative states have the potential to recover consciousness. This is the first time researchers have tested the accuracy of functional brain imaging for diagnosis in clinical practice.
The researchers from the University of Liége in Belgium suggest that PET imaging can reveal cognitive processes that would otherwise be hidden to traditional testing. Using imaging in addition to standard behavioral assessments could improve patients with the potential for long-term recovery.
Up to 40% of severely brain-damaged patients are misdiagnosed when judging their level of consciousness. Clinical examinations have been used to decide whether patients are in a minimally conscious state (MCS), in which there is some awareness and response to stimuli, or are in a vegetative state (VS), where there is neither, and the chance of recovery is much lower. Improving the methods of diagnosis would give those with some cognitive function the chance to recover.
The researchers conducted the study to decide between two functional brain imaging techniques for distinguishing between vegetative and MCS patients, PET and functional MRI (fMRI) during mental imagery tasks. The researchers compared their results with the standardized Coma Recovery Scale–Revised (CSR-R) behavioral test.
They found that PET was better than fMRI in distinguishing conscious from unconscious patients. Furthermore, a third of the 36 patients diagnosed as unresponsive on the CSR-R test who were scanned with PET showed brain activity with the presence of some consciousness. Nine patients in this group later recovered a reasonable level of consciousness.
Testing with the CRS–R along with a PET scan provides what the researchers claim is a “simple and reliable diagnostic tool with high sensitivity towards unresponsive but aware patients.” The study was done in a lab for diagnostic neuroimaging of disorders of consciousness, so getting it used in less specialized locations, like a hospital, might be more challenging. Hopefully, as functional brain imaging becomes cheaper and more widely used, diagnosis of a vegetative state will not be based solely on behavioral testing.