Stephen Kintz
Nov 13, 2011

New diagnostic test for coma patients

Consciousness is tricky. There is little understanding of consciousness, and there is no universally agreed upon definition of consciousness. So how can we tell if a person is conscious?


In healthy individuals, it is generally safe to assume they have some level of brain function that can be considered conscious. However, what happens when an individual has suffered a traumatic brain injury? How are doctors able to determine if a patient retains any level of consciousness? More importantly, how can doctors be sure of their diagnosis?  


Typically, when faced with an individual with traumatic brain injury, doctors are forced to determine if the individual is in a minimally conscious state (retains some consciousness) or persistent vegetative state (retains no consciousness). To make this diagnosis, doctors perform a simple verbal test where they ask patients to wiggle a toe, move a finger or blink an eye. Unfortunately, if a patient has suffered traumatic brain injury, the patient might be able to comprehend the doctor’s commands but not execute them.


This inability to execute commands can lead to a misdiagnosis, thus doctors cannot be sure of their diagnosis. In fact, the Coma Science Group estimated that nearly 40% of the patients labeled as in a vegetative state retain some level of consciousness.   So, the question becomes, can modern brain measuring techniques be used on coma patients?


In 2006, Owen and colleagues answered this question by putting a patient diagnosis as being in a vegetative state in an fMRI. In the study, the researchers used simple verbal commands. They asked the patient to imagine playing tennis or imagine her house. The brain scans looked remarkably similar to the scans of healthy individuals [1].


This was an amazing result. It demonstrated that modern brain measuring techniques could be used on coma patients. More importantly, these techniques could be used to determine the consciousness of a patient.   The downside is that fMRI scans are expensive. Really expensive. Also, doctors have to book the fMRI and wait for the results.


This led researchers at the Coma Science Group to look for a cheaper alternative, Electroencephalography (EEG). EEG is the recording of electrical impulses on the surface of the scalp from the firing of neurons. The researchers at the Coma Science Group placed the EEG electrodes on the scalp in the area of the motor cortex and performed the same verbal test used by doctors to determine if a patient was minimally conscious or in a vegetative state. The researchers discovered that EEG was able to pick up activation within the motor cortex even if patients were unable to move [2].  


This is a remarkable test. EEG is one of the cheapest forms of brain recording devices. It is portable, can be used in the homes of patients, and almost every single hospital in the developed world has access to EEG devices. In fact, most hospitals have many EEG devices. EEG also has the added benefit of having a quick turnaround, so families with not have to wait long for the test to be administered or for the results.


In a world with rising health care cost, this is one of those medical tests that have the perfect balance of affordability and reliability.   Of course, the EEG or fMRI tests are not perfect. If the brain sustained damage to areas that comprehend verbal cues, the patient would not show responses to either the EEG or the fMRI. This means that these patients could still be labeled as being in a persistent vegetative state even if they retain some level of consciousness.