Girlfriend in a coma, I know
I know - it's serious
My, my, my, my, my, my baby, goodbye
The Smiths - 'Girlfriend in a Coma'
Comas are a fantastic plot device, oft abused by many an ailing soap opera. Will they die? Will they recover? Will we find out who it was that attacked them from behind with a lead pipe? Will we ever find out who's the real father of the baby? Do I even care? I tend to take the moral high ground when it comes to such things as soaps and sitcoms, choosing instead to spend my precious, limited life-seconds on more rewarding experiences than sitting in front of the television each night. Also, I'd rather spend the TV licence fee money on beer. Ignore me; I'm just a poor and bitter student who desperately wants to have started earning a wage about three years ago. Of course, I do occasionally mull during my TV-bereft time over the irony that your brain usage during a television watching session drops to a level that is almost comparable to that seen in someone in a coma, apart from that you're still awake.
Mechanism
We are all familiar with the state that is 'sleep'; a mental and physical unresponsiveness from which a person is (usually) easily roused from. To contrast, a coma is defined as being a state of unrousable unresponsiveness that has lasted in excess of an hour. A person in a coma has no awareness, makes no purposeful movements, and has a loss of their sleep-wake cycles. A coma can be the product of three mechanisms in the brain:
- Diffuse brain dysfunction - caused by either toxins or a divergence of the body's normal levels of metabolites, resulting in an inhibition of overall brain function. e.g., alcohol abuse, sedative abuse, diabetic ketoacidosis, septicaemia, respiratory failure... (the list goes on and on)
- Direct effect within the brainstem - a lesion to the brainstem that damages the reticular activating system portion of the reticular formation. This is the tract of the brain that controls consciousness and sleep/wake cycles. e.g., brainstem stroke, brainstem tumour, trauma
- Pressure effect on the brainstem - the skull is a closed box, so if there is a bleed into the skull, or if brain starts to swell, there's only one way for the skull contents to move; down through the foramen magnum, compressing the brainstem. This, as a consequence, compresses the reticular activating system, leading to a loss of consciousness. Rapidly leads to death if the pressure is not relieved. e.g., traumatic brain injury, haemorrhagic brain stroke, brain tumour
Assessment
The management of coma is reliant on an accurate assessment of the patient, over a period of time from when the unconsciousness was first noticed. There are three common methods of scoring a patient whose consciousness is impaired:
Glasgow Coma Scale (GCS): the most commonly used because it's very quick and easy, and also gives the attending physician / surgeon the particulars of the patient's condition. The score is marked out of 15, with 15 being the maximum score (alert) and 3 being the lowest (coma / death). Points are given for the patient's responsiveness in terms of Eye opening (4 possible points), Verbal response (5 points), and Movement / reaction to pain (6 points). This is actually an incredibly useful scale, though it is fairly rough and ready. While ER tends to have people shouting "GSC of 12!" at each other, in a real life situation the overall score is stated, followed (more importantly) by its breakdown. For instance, for reasons that I shan't go into in this write-up, it's vitally important to know if a patient's movement / pain score is 1, 2 or 3; 1 is actually less worrying than either 2 or 3, which indicate serious brain damage has occurred. Neurosurgeons are notoriously sensitive souls, but even they'll get out of bed for a M2 / M3. The GCS is a great way of assessing the patient's condition and deterioration, but isn't a good method of predicting the eventual outcome of the patient's recovery.
Rancho Los Amigos Level of Cognitive Functioning Scale (LCFS): This scale is not commonly used, at least not in the UK. My personal opinion is that this scale is next to useless; it's neither a good assessment of a patient's condition, nor a predictor of the patient's outcome or prognosis. There have been very few papers published on its efficacy, and most of those were by the hospital that developed it.
Disability Rating Scale (DRS): This is the most fiddly of the scales to mark, which means it's not so good for quick assessment. It does, however, give a brilliant indication of a patient's prognosis and eventual outcome. It has eight different categories to score, with a possible total score of 0 (no disability) to 29 (extreme vegetative state). In an ideal situation, a patient is admitted into hospital using GCS, and is then switched to DRS as soon as their condition has stabilised.
It is probably unnecessary to say that somebody in a coma will score badly in any of the scales that you care to use; consciousness is a digital rather than an analogue state, and coma occupies the space next to 'dead' in the vast majority of cases.
Prognosis
Medicine is not a case of knowing a definitive diagnosis and prognosis; most of the time it's like gambling on the horses. You know that "Mary Hinge" at 2-1 is the most likely contender, but they're facing stiff competition from "Noble Locks" at 5-1, "ForTeeTewDoubleDee" at 9-1, "WearTheFoxHat" at 15-1, and as an outsider, "Joe Blob" at 69-1. Unlike horse racing, medicine has a barrage of diagnostic tests that can be thrown at a patient in an attempt to narrow the odds a little, but it's still sometimes a case of cross your heart and hope for the best. A coma is not a permanent diagnosis; it will eventually progress to something else, the four main options being recovery, persistent vegetative state, locked-in syndrome, or death. A coma will usually last for a few days to a week, but can sometimes remain for up to a month. From there, the patient will either significantly improve and become responsively aware; settle down into a persistent vegetative state; die; or (rarely) emerge as a locked-in syndrome case.
Vegetative state (VS) - a consequence of widespread cortical damage, but with normal brainstem activity. There is a loss of sentient behaviour; the body's there, but the personality's long gone. However, the body continues to breathe of its own volition, and usually exhibits sleep-wake cycles. This state can be maintained until the patient eventually succumbs to death, but will sometimes improve to the minimally conscious state.
Minimally conscious state (MCS) - there is some vague response to things like pain and voices; a person can progress from a VS to MCS.
Locked-in Syndrome - a very interesting syndrome, but bloody awful to be on the receiving end of I'd imagine. There is massive brainstem damage, but below the level that would compromise respiratory function (and result in death). The cerebral cortex (the bit that contains *you*) still functions, but it is unable to communicate with the rest of the body. Thus, the patient is fully aware of the world and their surroundings, but is unable to move or communicate, except by vertical eye movements.
Brain death - brain death is the result of irredeemable damage to the brainstem, such that vital centres, like the ones that control respiration, are destroyed leading to a state that is incompatible with life.
Reference
- Kumar P, Clark M, 2005, "Clinical Medicine", 6th edition, Elsevier Saunders
All race horse names used in the course of this write-up are genuine. God bless the gee-gees