Disclaimer: This is for the purpose of education only.
What Are Comas?
From the basic principles all the way to the treatment concerns when you are facing someone who is not responsive to any stimuli, coma will fascinate. A Coma means there is no sensation to any stimuli. So painful stimuli are often elicited to provoke a response. But… No response.
So something MUST be going down to mess up one of two areas of your brain (or both!). One of these two areas must be affected for you to be in a coma. Brainstem OR Bilateral hemispheres. So, it’s the whole supratentorial portion of your brain (an anatomical term that refers to everything brain that lives above the tentorium, a horizontal support structure in your brain); OR infratentorial. So either everything above the tentorium is a no go, or everything below the tentorium is out. Or both, of course.
The brainstem lives below the 10 Tory him. Lesions in the brainstem wiping it out can cause a coma. Those lesions can be primary, intrinsic to the brainstem; or secondary, affecting some region outside it to mess it up.
- 1 hemisphere only, but enough to –> E so severe that ICP affects brainstem
- Demyelinating conditions
B. MS variant disorders
And here’s the big pneumonic for causes of coma. This the good clinician must memorize in order to rule out and entertain everyone of these even if they feel they have found one already because some comas might have two things going on.
Causes of Comas
“AEIOU TIPS“ <- LAB points these out
- Alcohol, All get B’S
- Endocrine, Electrolytes
- Insulin, Infections
- Opiates, Oxygen
- Uremia, Uncooperative
- Temperature, Toxicology
- Infection, Increased ICP
- Psychiatric, Post-ictal States, Primary Neuro-disorders
- Space-occupying Lesions, Strokes, Shock, Seizures
Physical Examination for Comas
While doing his ABCs to resuscitate the patient in a coma, the doctor pays close attention to the following physical signs:Breathing abnormalities, patterns can point to areas of the brainstem that may be affected if not causing the coma:
- Cheyenne’s Stokes => diffuse cerebral
- Short panting breaths => mid-brain
- Slow shallow gasping => pontine
- Regular rate & depth => medullary
Doll’s eye exam is something the doctor does – in coma pts only! (& they must make sure there’s no cervical spine injury going on before they try it!)If eyes track, It implies that the cerebellum/cortex are both intact.(Or cold calorics testing that reveals nystagmus implies the same)
Funduscopic exam (Looking at the patients right now with an ophthalmoscope): if the intercranial pressure (ICP) is <20, there will be no papilledema, a blunting of the edge of the optic disc on funduscopic exam. If the ICP is < 15, The doctor will be able to see spontaneous venous pulsations; so, pretty normal.
If there is anisocoria (Unequal pupils), it implies uncal herniation (The brain is starting to drop into it’s under casing, herniating the ventral aspect of the brainstem; vs. Cranial nerve three lesions which are also possibility; either one of these situations are really bad).
Bilateral meiosis (Constricted pupils) implies a pontine CVA (cerebrovascular accident, i.e. stroke) vs. an OD from opiates, clonidine, cholinergics, or phenothiazines.
Motor exam findings reveal the following possibilities. Of course the patient isn’t being very cooperative. So you have to elicit pain to generate your motor response. And the motor response to pain can give clues to where there is damage:
Decorticate: Motor activity points up on pain (“up”, think up pointing to the cortex.
Decerebrate: M points down & out on pain (think pointing down to the cerebellum below is the old med school pneumonic).
Treatment of Comas
Classically, the emergency room physician administers what has come to be called the:“Coma Cocktail“: dextrose, oxygen, naloxone (10+ mg if drug hx), thiamine
LAST: R/O NON-CONVULSIVE STATUS E.
The last thing the good clinician must do once they’ve exhausted all possibilities, both diagnostic and therapeutic, if they’re not having any luck, is rule out the possibility that the “coma” in front of them is actually a seizure without any motor activity – and not a coma at all!