ICL 10.9: Evaluation of the Unconscious Patient Flashcards
what is consciousness?
“the state of awareness of self and environment, and normal responsiveness to external stimulation and inner need”
what are the qualifications where you would consider someone as conscious?
consciousness is a state in which both of the following are preserved:
- ability to be aware of oneself and one’s environment
- ability to respond appropriately to environmental stimuli
what are the 5 levels of consciousness?
- awake/alert: fully attentive, aware and responsive
- sleepy: awake but appears sleepy with decreased attention and slow responses
- obtunded: asleep, wakes to verbal or light physical stimulation, falls back to sleep easily if stimulus stops
- stupor: deep sleep requires noxious and persistent stimulation to maintain arousal/participate in exam
- coma: eyes closed, unresponsive to external stimuli, with the exception of brainstem and spinal reflexes
what is the ascending reticular activating system?
ARAS is a complex poorly defined neural network that involves input &/or output with all of the following:
- brainstem reticular formation
- hypothalamus & forebrain
- thalamus
- cortical, cerebellar & spinal feedback
ARAS starts in the brainstem reticular formation and it’s located more in the upper brainstem so the upper 1/2 of the pons to the midbrain
it’s divided into 3 functional 4 neurochemical components
what are the 3 functional components of the ascending reticular activating system?
- efferents –> thalamus
- efferents –> hypothalamus and forebrain
- direct diffusion projections –> cortex
what are the 4 neurochemical divisions of the ascending reticular activating system?
there are key nuclei in the ARAS portion of the reticular formation that produce the main neurotransmitters of consciousness = Ach, serotonin, histamine and norepinephrine
what is the function of the hypothalamus in consciousness?
even though it’s considered that arousal starts in the ascending reticular formation, the arousal system includes initiation in the hypothalamus
so the lateral hypothalamus releases orexin 1 and 2 on the various nuclei in the ARAS pathway in the brainstem to stimulate the release of their respective NTs
what is the function of cortical, cerebellar and spinal feedback in relation to consciousness?
these are super important because think about how you wake up based on when you perceive light or how you don’t want to sleep when you smell smoke so there’s feedback from all the senses into the ARAS activation system
so there’s visual, auditory, smell, tactic feedback etc. to make sure we have the mechanisms to preserve our survival so we don’t sleep through important things
how do we localize impaired consciousness?
- bilateral cortex problems = ARAS pathway has diffuse output to the cortex so anything that diffusely effects the bilateral cortices can cause impaired consciousness –> usually these are toxibolic syndromes, hyper/hypoglycemia, global ischemia, etc.
- bilateral thalamus problems = most pathways go through the thalamus so each thalamus communicates its arousal pathways to the ipsilateral cortex so if you knock out both thalami you can impair consciousness
- contralateral cortex and thalamus = if you were to have a lesion that effects an entire cortex and the contralateral thalamus, you can also impair consciousness that way
so when you’re trying to see what’s causing lost consciousness, you need to try and localize it to the brainstem, thalamus or the cortex?
what are the 6 disorders of consciousness?
- locked-in state
- catatonia
- akinetic Mutism
- minimally conscious State
- unresponsive wakefulness syndrome
- coma
what causes locked-in syndrome?
classically seen in basilar strokes
but can also be seen in:
1. MS
- infection
- tumor
- hemorrhage
- trauma
what is locked-in syndrome?
aka cerebromedullospinal disconnection OR de-efferented state
it’s where the anterior pons and midbrain are effected usually due to a basilar stroke
the reticular formation and dorsal midbrain are spared though!
what are the signs of locked-in syndrome?
because the dorsal motor nuclei are spared that means the oculomotor nerve is spared, they still have vertical eye movements, and can still blink – the reticular activating tracts and sensory tracts are also still in tact!
what’s effected is basically all of their motor outputs
what are the 3 forms of locked-in syndrome?
all of these forms include full consciousness, sensation, emotional and startle responses so they’re cognitively still there
- pure = spares only vertical eye movements & blinking – so this is how a lot of them communicate
- incomplete = wide range of spared motor function depending on how extensive the stroke or infection was
- total = no spared function, not even eye movements and blinking – in this case it’s really hard to differentiate them from someone who is comatose
how do you differentiate between the locked in state and a comatose patient?
many of these patients initially present with impaired or loss of consciousness so that’s why it’s so important to test the occulocephalic reflex when examining an unconscious patient
so most physicians do the dolls eye test where they move the head side to side to make sure the eyes stay on the target but you also need to move the head up and down and make sure it stays on the target as well so you don’t miss any vertical eye movements before they’re awake and able to blink/move their eyes up and down
this might be the only thing that differentiates them from a comatose patient!!! a locked-in syndrome patient will have spared vertical eye movements
some patients actually feel that they have a reasonable quality of life in the locked in state because they have power chairs and lift systems and are able to communicate with their family and recognize them – this is what really differentiates the patients from coma because some feel that the are still in a meaningful state of life
what is catatonia?
a state in which a person appears unresponsive or unconscious
it simulates akinetic mutism, stupor or light coma
it’s often associated with psychiatric disorders, severe depression etc.
what will be seen on a PE of a catatonic patient?
- brainstem reflexes intact
- oculocephalic testing consistent with awake state = eyes move/track with the head
- resistance to eye opening
- waxy flexibility = if you position their limb in a certain way they’ll maintain it for a long time
- catalepsy = hold uncomfortable postures for a long time
- adventitious movements like repetitive motor mannerisms or choreiform jerking (consider EEG to make sure it’s not seizures)
what is akinetic mutism?
silent & inert – profound apathy
it’s a complete lack of spontaneous speech or movement due to a lack of motivation or drive. Patients are fully aware and visual tracking is preserved
patients are conscious, aware of their surroundings and depending on the localization can register and retain what happens during time in that state
what part of the brain is effected with akinetic mutism?
localization can be due to injury to the midbrain, anterior thalamus or uni-/bilateral medial frontal lobe lesions
usually associated with diminished dopamine pathways
we see a lot of this with ACA stroke patients where nurses will say they stopped following commands or they can’t get them to do anything – it’s not that the patient isn’t capable, it’s that they don’t have the motivation to do it
what is a minimally conscious state?
it’s a spectrum of states! these people can be anywhere from being comatose to a akinetic mute state
it can be transitional; like people coming out of a coma can go through this spectrum before being totally awake –> or they can get stuck along this spectrum at various severities of impaired consciousness
this is the most important loss of consciousness condition to be aware of because with every day there’s improvements in the patient so you need to look at the subtle changes to be able to identify progression along the different stages
how can you identify if someone is in a minimally conscious state?
with every day there’s improvements in the patient so you need to look at the subtle changes to be able to identify progression along the different stages
EYES
dysconjugate –> roving –> midline –> fixation –> tracking
MOTOR
flaccid –> posturing –> withdrawal –> localize –> following
what is the unresponsive wakefulness syndrome?
a return of arousal without the return of awareness following a coma –> this is basically what happens if you never make it into a minimally conscious state –> so coma patients will eventually die from medical complications or they’ll transition into an UWS
a person in a vegetative state may open their eyes, wake up and fall asleep at regular intervals and have basic reflexes, such as blinking when they’re startled by a loud noise, or withdrawing their hand when it’s squeezed hard – they’re also able to regulate their heartbeat and breathing without assistance
however, a person in a vegetative state doesn’t show any meaningful responses, such as following an object with their eyes or responding to voices. They also show no signs of experiencing emotions nor of cognitive function.
UWS causes the brain to halt the ability to create thoughts, experience sensation, and remember past events. Patients in a vegetative state are awake, but show no signs of awareness
this is what was previously known as a vegetative state and it’s considered persistent if it goes on for more than 3 months –> with traumatic brain injury it’s considered persist UWS if it persists for more than a year and this is because with traumatic brain injury there’s a lot of axonal damage that could potentially remyelinate over the year so you have to wait before giving them the diagnosis of persistent UWS
what is the clinical presentation of someone in an unresponsive wakefulness syndrome?
from a cognitive standpoint, the patient remains unresponsive and mostly unconscious and does not appear to have awareness of self, environment or needs
eyes might open to pain; may progress to spontaneous opening or a diurnal pattern – there might be intermittent blinking or brief fixation/tracking of faces and objects but it’s never consistent and it doesn’t progress into anything more
from a motor perspective they might swallow spontaneously, grind their teeth, front or moan – they can also assume some primitive postures and reflexes of the limb like cortical thumbing that babies do
what causes an unresponsive wakefulness state?
- diffuse cortical injury like from a cardiac arrest
- diffuse subcortical injury like with diffuse axonal injury from a traumatic brain injury
- thalamic injury like from influenza
