Coma Flashcards
A lesion to the rostral periaqueductal gray (PAG) and area posterior to the 3rd ventricle will cause insomnia or sleepiness?
Sleepiness- the Rostral PAG and post. 3rd ventricle are responsible for arousal and wakefulness
A lesion to the Ventrolateral Perioptic Nucleus (VLPO) will cause insomnia or sleepiness?
Insomnia- the VLPO is the sleep promoting area of the rostral hypothalamus
A lesion to the area between the rostral PAG and VLPO, i.e. the posteriolateral hypothalamus, will cause:
Narcolepsy- loss of orexin secreting neurons
Describe the coma causing lesions, anatomically.
Complete bihemispheric lesions
Thalamus, midbrain PAG lesions
Upper pontine tegmentum
ALL involve reticular gray formation
Pontin hemorrhage = ________
Lesions caudal to the rostral pons = ________ but _______
Use: Quadriplegia, Coma, and Consciousness to complete
Coma
Quadriplegia but Consciousness
Damage to the reticular activating system (RAS) results in:
COMA
Are the reticular nuclei responsible for arousal?
NO, nearby nuclei pass axons through this area. The nearby neurons are actually responsible for arousal.
Cholinergic axons project to the _______ to stimulate wakefulness by inhibiting the ______.
Thalamus
Thalamus
Monoaminergic axons project to the ________ to stimulate wakefulness.
Cortex
Cholinergic failure —-> incr. spontaneous thalamic firing—-> ________
sleep
Monoaminergic failure —–> decr. signal/noise ration from thalamus —> sensory hallucinations/confusion —-> _______
delirium
VLPO is the ______ promoting center!
How does it work?
Sleep
Utilizes GABA and galanin (Neuropeptide) to inhibit the ascending arousal system.
PAG/ posterior 3rd ventricle is the ______ promoting center!
Wakefulness/arousal
EtOH and benzodiazepines stimulate the action of this center by mimicking GABA activity, causing sleepiness.
VLPO
Describe the consequences of a supratentorial mass lesion causing coma.
Supratentorial mass (tumor/epidural hemorrhage):
- -> pushes temporal lobe/uncus past tentorium to compress CNIII (ipsi ptosis, oculoparesis).
- -> midbrain compression –> structural stress on RAS–> lethargy, stupor, COMA
- -> compression of descending motor pathways–> hemiparesis of contralateral side (bc before decussation)
- –> PCA compression –> ipsi occipital infarxn–> contralateral field loss
You will see early loss of pupillary light reactivity! EMERGENCY!
Describe the clinically apparent signs of central brain herniation and why they are occurring.
1) lethargy from ^ pressure on reticular gray in thalami
2) Small reactive pupils from pressure on hypothalamus–> v SNS output to dilator muscle.
3) Loss of pupil tone from ^ pressure on EWN in midbrain
4) Decorticate (flexor) —-> Decerebrate (extensor) posture
5) Cheyne-Stokes respirations: ^ apnea w/ ^ hyperventillations due to pressure on brainstem respiratory center
Watch out for these pathological events in infratentorial lesions (masses):
1) Basilar artery compression —> ischemic stroke of occipital lobe/superior cerebellum
2) Pontine hemorrhage—> COMA EVERY TIME
- findings: abrupt coma, pinpoint pupils, flaccid or decerebrate quadriplegia, horizontal gaze paresis, vertical gaze bobbing.
WATCH OUT FOR LOCKED-IN SYNDROME ON “AWAKENING” : GET PT ON EEG TO ASSESS
What is the MCC of metabolic encephalopathy resulting in coma?
Drugs!
Which prion dz can on rare occasions cause coma?
CJD
Whereas in structurally induced comas (tumor, hemorrhage) the pupillary light reflexes are first to go, in metabolic induced coma, pupillary light reflexes are lost:
Late in dz
Exceptions: Pupils dilate early in botulism, atropine, and glutithimide intoxication.
What is asterixis?
sudden and recurrent lapses in muscle tone.
Hands flap when making “stop” sign.
Common in elderly
A pt just came into your ED in a coma. What are you immediately going to do?
1- Establish airway (A-B-Cs)
2- Put pt in C-collar (assume trauma/neck broken until CT neg)
3- Give thiamine, D50 (hypoglycemia), and naloxone (Narcan - will reverse opiate overdose)
Normal vital signs will suggest a ____ cause of coma.
Psychogenic - verify w/ caloric cold water test- look for nystagmus (no nystagmus = true coma)
What are some diagnostics you are going to collect on your emergent coma pt?
STAT head CT/MRI for trauma/tumor
CXR- for pneumonia, CV failure, lung cancer
STAT tox screen for sedative/opioid overdose
LP (infectious), MRI spine (trauma)
Besides airway, glucose, and narcan, what are some other emergent tx you will give your ED coma pt?
1) v ICP w/ hyperventilation/ hypertonics (mannitol)
2) Dz specific tx: narcan, seizure meds, Abx,
3) Hypothermia- high temp very bad for brain
4) If pt agitated give Haldol/Ativan unless hypoxia is cause, then give O2.
