In this post I thought I would talk a little about persistent vegetative state (PVS) and minimally conscious state (MCS). Though this topic may not concern many of you, I feel it should be discussed as the question of PVS is raised frequently by family members of patients who are in coma.
Doctor is he brain dead? Would he wake up? If yes when? Is he going to be a “vegetable” for the rest of his life?
So what is PVS and how does it differ from brain death. I shall try to make this simple and explain with the aid of a crude example. Let us assume a person suffers major head trauma in a motor vehicle accident. He is brought to the hospital and CT scan shows extensive bleeding in the brain. He is in the intensive care unit on a mechanical ventilator while his blood pressure is been supported with the help of medications (we call such medications vasopressors). Now a neurologist is called to see him regarding prognosis. On examining him the neurologist notices that his pupils are dilated and fixed (do not react to light) and the rest of his brain stem reflexes are also not elicitable (please see my previous post on brain death). An EEG is ordered to confirm the diagnosis of brain death. The EEG shows no cortical (brain) activity above 2 microvolts (meaning it is essentially a flat line) and is thus consistent with electrocerebral inactivity (ECI). SUCH A PERSON IS BRAIN DEAD AND CAN THUS BE REMOVED FROM THE VENTILATOR (OF COURSE WE TAKE THE FAMILY’S WISHES INTO CONSIDERATION). BUT FOR TECHNICAL PURPOSES HE IS DEAD. Remember what I said earlier one cannot die twice, once when the brain stops and once when the heart stops.
Now lets take the second scenario. The neurologist examines the patient and notices that he does not respond to verbal commands, does not respond to a painful stimuli such as a pinch but the brain stem reflexes are intact. His pupils react to light, he gags when the back of his throat is touched, he takes a gasp on his own when he is temporarily disconnected from the ventilator. THE NEUROLOGIST RIGHLY SAYS” PATIENT IS NOT BRAIN DEAD BUT HIS PROGNOSIS FOR RECOVERY IS GUARDED“. Time goes by say about a week. The patient is now still in the intensive care unit but at times responds when he is stimulated, does not open his eyes or talk but moves his arm if he is pinched. More time goes by say about 2 weeks. The patient is now opening his eyes. He now has a tracheostomy and slowly is been weaned off the ventilator. He is still not able to talk and does not interact with any of his nursing staff or his family. More time goes by, the patient has been weaned off the ventilator. He is now out of the intensive care unit and is transferred to the hospital floor. A neurologist’s opinion is asked for as “the patient does not respond”. The neurologist examines the same patient whom he had seen in the aftermath of the trauma. 10 weeks have gone by since the injury. The neurologist finds that the patient open his eyes spontaneously, at times even yawns, he is told by the family at bedside that the patient has sleep wake cycles (meaning he sleeps at night and then wakes up after some time just like any other “normal” person). As the patient’s mother walks into the patient’s room, the neurologist notices that the patient tracks her with his eyes for a short time when she enters. But there is no meaningful interaction of the patient with his environment. It is as if the patient is there but not there. He does not make purposeful eye-contact with anyone. There is nothing in his actions to suggest that he is truly responding to those around him or interacting with them. The tracking movements of the eyes are semipurposeful and so is the yawning behavior–more like a reflex if not anything else.
A person like the one above may be labelled as one who is heading into the persistent vegetative state (PVS) category. You can imagine the delimma for the family members if you tell them that though the patient may remain “alive” for years, he shall never have any meaningful neurological interaction and hence it is better to let him go. “BUT DOCTOR HE IS ALIVE, HE YAWNED TODAY, HE LOOKED AT ME WHEN I WALKED INTO HIS ROOM”: they will say.
Patients who are truly in the PVS shall never recover any meaningful neurological interaction with the environment–this is by defination. But as is true in medicine, everything is not black and white. there are shades of grey. Patients who meet the criteria for PVS but then who later on start showing “some” recovery. Some purposeful goal directed behavior starts emerging. So a new category of minimally conscious state has not come into the literature. There have been some studies done to show that the brains of these patients do actually respond and they are far from a PVS. A lot of research is now been carried out to determine how we can benefit these patients.
If the right procedure is followed and the neurological examination and relevant investigations are carried out and repeated if required after an interval of time, most of these patients can be rightly categorised into the brain dead, PVS or MCS category thus avoiding confusion and anguish to the family members.
Nitin Sethi, MD