Although there are means of assessing whether a comatose patient has the potential to recover, these methods aren't always reliable. Bedside tests, for instance, which are currently used as standard for evaluating the chances of comatose patients to recover, are associated with high rates of misdiagnosis. A new study, however, suggests that brain scans could be helpful in identifying comatose patients who have the chance to wake up.

For the study "Diagnostic precision of PET imaging and functional MRI in disorders of consciousness: a clinical validation study" published in The Lancet April 16, researchers looked at 122 patients with brain injuries. Forty-one of these subjects were considered to be in vegetative state which means that they are awake but do not show evidence of awareness. Patients in vegetative state for a year are believed to have no chance of recovering at all and this could be used as grounds for terminating medical treatment.

The other 81 patients in the study were considered as minimally conscious which means that there are times that they show signs of responsiveness and awareness. These patients are generally considered to have better chances of recovering than patients who are in vegetative state.

The researchers gave the patients two types of imaging tests: PET, which measured the activities in the regions of the brain that are associated with consciousness and MRI which monitors brain activity. The researchers observed minimal conscious in 13 of the patients who were in vegetative state. Of these, nine progressed into minimally conscious state a year later which means that they exhibit consciousness albeit it isn't the same as those in fully conscious individuals.

The researchers noted that PET scans are better at identifying conscious and unconscious patients. A third of the subjects who were diagnosed as behaviorally unresponsive using bedside tests were found to have some level of consciousness when assessed using PET scans.

Study researcher Steven Laureys, of the University of Liege, said that PET scans can detect processes in the brain that are not detected by bedside tests. Laureys and his colleagues said that brain scans can provide valuable help to standard behavioral tests in identifying vegetative state patients who have the potential to recover.

"Cerebral 18F-FDG PET could be used to complement bedside examinations and predict long-term recovery of patients with unresponsive wakefulness syndrome," the researchers wrote. "Active fMRI might also be useful for differential diagnosis, but seems to be less accurate."