Coma Patients With ‘Hidden Consciousness’ Are Likely To Recover From Brain Injury [Study]

Some coma patients are unresponsive for weeks, months, or even years. However, a new study suggested that there's a way to gauge their chances of recovery.

Coma Patients With Hidden Consciousness or Cognitive Motor Dissociation (CMD)

In a new study published on Monday, researchers identified a determining factor of a coma patient's chances of survival. According to them, a curious phenomenon known as "hidden consciousness" or cognitive motor dissociation (CMD) was observed among patients with acute brain injury who were in a coma or an unresponsive state.

Study author Jan Claassen, a critical care neurologist at New York-Presbyterian/Columbia University Irving Medical Center and a researcher at Columbia University, said patients with CMD appear to hear and understand verbal commands even though they are unable to follow them because their bodies do not respond.

Only recently has the CMD phenomena been recognized, and it is still not fully understood. But there are ways to identify CMD in patients who are not responding.

Analyzing alterations in cerebral blood flow or electrical activity, as shown on an electroencephalogram (EEG) or functional magnetic resonance imaging (fMRI), respectively, is one of them. However, there are currently drawbacks to both of these approaches.

Claassen said that when assessed using such techniques, it is believed that 15 to 20 percent of people who appear to be in a coma or similar unresponsive state exhibit evidence of CMD. Their knowledge of patients in comatose or other unresponsive states is changing due to the discovery of CMD.

Patients With CMD Can Hear, Understand Verbal Commands

The most recent study examined 107 individuals with acute brain injuries who were not responding using EEG. One-quarter of the patients appeared to be in a vegetative state, and over half of them appeared to be comatose. Despite having open eyes, they were unable to obey directions.

The remaining patients were minimally conscious, allowing them to gaze at or track an examiner with their eyes but not respond to commands.

The EEG can detect whether patients are attempting but failing to comply with instructions like "keep opening and closing your right hand."

In 21 of the patients, they identified CMD. The researchers next examined the structural MRI brain scans of each patient.

Using a unique analysis technique, the researchers compared the brain injury patterns shared by patients with CMD to those who did not exhibit symptoms of concealed consciousness.

The scientists discovered that the brain regions connected to arousal and command comprehension were all intact in the CMD patients. This lends credence to the notion that they could hear and comprehend verbal orders.

They also discovered that the CMD patients' inability to act was due to impairment in brain areas in charge of integrating and executing motor commands.

According to Claassen's research, people with hidden consciousness can hear and understand verbal commands, but they cannot follow them because of damage to the brain circuits that transmit those signals to the muscles.

In earlier studies, Claassen and colleagues were able to link CMD to patients' long-term recovery of independence and their return to consciousness in brain-damaged patients.

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