What’s a coma, the definition?
A state of unarousable
Describes the level of
consciousness in terms
of response to the various
levels of stimuli.
And patients with only reflexive responses
may still be described as being in a coma.
So, reflexes could be intact
but still will be in a coma.
May be due to diffuse cerebral
insult or to the focal processes.
Examining the possibility
of comatose patient.
We have to say/yell
Shake/tap, this is tactile stimulation.
Press on patient’s
nail beds, and this is
sensations or stimulation.
Sternal rub or nasal swab, we call
this central painful stimulation.
And if these tests fail
to reveal a response,
your patient is possibly in a coma.
The brainstem exam is done to determine
if the brain death is present.
Remember, you ask yourself
how awake is your patient
if you’re thinking about
level of consciousness.
At this point, obviously, functionality
has been lost, not cognition.
Cognition has been lost.
So, what are some of these brainstem
reflexes that we’re paying attention to?
Remember please, the
pupillary light reflex.
referring to optic nerve, is going to
then take in the stimuli of light.
And the efferent is
going to come way of
oculomotor, parasympathetic, therefore,
causing constriction of your pupil.
Your brainstem functioning,
pupillary light reflex.
We have known as oculocephalic
reflex or doll’s eye.
And with this, the afferent here is
going to be your eighth cranial nerve,
which is your vestibulocochlear.
The efferent would be
through your oculomotor,
and then you have your trochlear and
abducens all in the form of your eye,
in which if you have
oculocephalic or doll’s eye,
then everything should remain
within stable or balanced.
You have a corneal reflex, here
literally, you’re going to touch.
So, the afferent would be through
your trigeminal, ophthalmic branch,
and then with the closure of your
eyelid, that would be from your facial.
Your corneal reflex, you touch your cornea,
and then there should be blinking.
The gag reflex, afferent would be
through your glossopharyngeal.
Take a swab or whatnot, touch
the back of the throat.
And then the efferent would
be through your vagus.
These are all important
at this point, you’re going
to try to figure out as to
whether or not brainstem
functioning is even intact or not.
And the brainstem reflexes
are the cold calorics.
What happens here?
Fifty milliliter ice water injected
into the ear, for example.
Cold is an inhibitory stimulus
to the vestibular nerve.
The vestibular nerve projects
to the contralateral,
cranial nerve or abducens.
Normal response is slow deviation of eye,
eye, towards the side of the cold water,
then a fast return to the midline,
and that portion
is your nystagmus.
So, towards the cold and then
a fast return to the midline.
we’re talking about the cold caloric or
we talk about the doll’s eye reflex.
We have the eighth cranial nerve,
and along with this, the
pathways are intact.
The eyes tonically deviate toward the
cold stimulus with no fast phase.
In coma, there is no fast phase
to come back to the midline.
Remember, primitive brain
looks to stimulus,
higher brain brings eye to the midline,
and that is what is
lost, please, in coma.