Some brain injury patients may appear to be in a coma, but they are not. They are processing at least some of what is happening around them but cannot physically respond.
Without a physical response, a physician might assume that a patient hasn’t understood, said Sudhin Shah, a neuroscientist at Weill Cornell Medicine in New York City. And, she said, referring to the patient, “Unfortunately, it could be that you were processing, you were understanding, you were wanting to talk to me. You just can’t.”
This break between understanding and responding is called cognitive motor dissociation (CMD), a disorder of consciousness following brain injury.
About 15 percent of patients believed to be unresponsive are predicted to be experiencing CMD, but most do not get a diagnosis because that requires both advanced equipment and training.