B7.049 Prework: Disorders of Consciousness Flashcards
coma
pathological absence of consciousness
determination of levels of consciousness
stimulus required for eye opening
awake
spontaneous eye opening
lethargic
speech stimulus required for eye opening
stupor
pain stimulus required for eye opening
coma
no stimuli can open eyes
which systems can be affected to cause coma
cortical systems
RAS
lesion categories that can lead to coma
midline (RAS)
-this section more resistant to toxic/metabolic stimuli than cortical neurons
diffuse (cortex)
diencephalic lesion
affects RAS at level of thalamus
possible basilar occlusion
sudden onset
subtentorial lesion
affects RAS at level of brainstem
sudden onset of coma
supratentorial lesion
early: diencephalic
late: brainstem
caused by space occupying lesion that distorts the RAS due to herniation
focal signs can precede coma
metabolic lesion
diffuse throughout the cortex
delirium can precede coma
psychogenic lesion
psychological stressors precede coma
why is a neurologic examination useful in coma
- anatomic proximity of pupillary and oculomotor subsystems to RAS
- selective susceptibility of neurologic subsystems to metabolic insults (cortex susceptible, pupillary system resistant)
components of neuro exam in coma
level of consciousness
pupils
extraocular movements
motor function
parasympathetic pupillary system susceptibility
resistant to toxic-metabolic processes
sympathetic pupillary system susceptibility
sensitive to toxic-metabolic processes
psychogenic pupil
mid range
reactive
metabolic pupils
small (sym knocked out)
reactive (para ok)
diencephalic pupils
small (sym knocked out in anatomic region)
reactive (para region not affected)
supratentorial pupils
early: small, reactive
late: mid range, unreactive
subtentorial pupils
mid range (no para or sym function) unreactive
fast eye movements in coma
if intact: cortex intact
sensitive to toxic-metabolic processes
slow eye movements in coma
if intact: brainstem intact
moderately sensitive to toxic-metabolic processes
how to assess eye movements in coma
oculocephalic reflex (move neck and see if eyes stay centered) cold calorics (show slow deviation to the side that is being irrigated, should not see nystagmus if in a real coma)
psychogenic eye movements
intact fast
intact slow
metabolic eye movements
absent fast
intact or abnormal slow
diencephalic eye movements
absent fast
intact slow
supratentorial eye movements
early: absent fast, intact slow
late: absent fast, abnormal slow
subtentorial eye movements
absent fast
abnormal slow
motor function in coma
bilateral, symmetric motor abnormalities characterize most patients including these with metabolic coma
bilateral corticospinal tract findings
different types of motor responses in coma
decorticate: abnormal flexion (lesion between cortex and red nucleus)
decerebrate: abnormal extension (lesion between red and vestibular nuclei)
usefulness of motor response in localizing source of coma
not very
usefulness of CT in localizing source of coma
used to evaluate for supratentorial mass
helps distinguish between diencephalic, supratentorial, or subtentorial based on findings
brainstem intact lesions
psychogenic metabolic diencephalic early supratentorial have intact slow eye movements and pupillary response
brainstem not intact lesions
late supratentorial
subtentorial
pupils unreactive
abnormal slow eye movements
cortex intact lesions
psychogenic
pupils reactive and fast eye movements can be present
coma algorithm
- check if cortex or brainstem intact (eye movements and pupils)
- check for mass (CT)
psychogenic coma prevalence
5%
metabolic/diencephalic coma prevalence
60%
supratentorial coma prevalence
25%
subtentorial coma prevalence
10%
further workup for toxic metabolic comas
routine labs (kidney failure, liver failure, etc)
stat lumbar puncture
EEG if history or signs of seizures (uncommon)
MRI
