Coma

Question 1

A lesion to the rostral periaqueductal gray (PAG) and area posterior to the 3rd ventricle will cause insomnia or sleepiness?

Answer 1

Sleepiness- the Rostral PAG and post. 3rd ventricle are responsible for arousal and wakefulness

Question 2

A lesion to the Ventrolateral Perioptic Nucleus (VLPO) will cause insomnia or sleepiness?

Answer 2

Insomnia- the VLPO is the sleep promoting area of the rostral hypothalamus

Question 3

A lesion to the area between the rostral PAG and VLPO, i.e. the posteriolateral hypothalamus, will cause:

Answer 3

Narcolepsy- loss of orexin secreting neurons

Question 4

Describe the coma causing lesions, anatomically.

Answer 4

Complete bihemispheric lesions
Thalamus, midbrain PAG lesions
Upper pontine tegmentum

ALL involve reticular gray formation

Question 5

Pontin hemorrhage = ________
Lesions caudal to the rostral pons = ________ but _______

Use: Quadriplegia, Coma, and Consciousness to complete

Answer 5

Coma

Quadriplegia but Consciousness

Question 6

Damage to the reticular activating system (RAS) results in:

Answer 6

COMA

Question 7

Are the reticular nuclei responsible for arousal?

Answer 7

NO, nearby nuclei pass axons through this area. The nearby neurons are actually responsible for arousal.

Question 8

Cholinergic axons project to the _______ to stimulate wakefulness by inhibiting the ______.

Answer 8

Thalamus

Thalamus

Question 9

Monoaminergic axons project to the ________ to stimulate wakefulness.

Answer 9

Cortex

Question 10

Cholinergic failure —-> incr. spontaneous thalamic firing—-> ________

Answer 10

sleep

Question 11

Monoaminergic failure —–> decr. signal/noise ration from thalamus —> sensory hallucinations/confusion —-> _______

Answer 11

delirium

Question 12

VLPO is the ______ promoting center!

How does it work?

Answer 12

Sleep

Utilizes GABA and galanin (Neuropeptide) to inhibit the ascending arousal system.

Question 13

PAG/ posterior 3rd ventricle is the ______ promoting center!

Answer 13

Wakefulness/arousal

Question 14

EtOH and benzodiazepines stimulate the action of this center by mimicking GABA activity, causing sleepiness.

Answer 14

VLPO

Question 15

Describe the consequences of a supratentorial mass lesion causing coma.

Answer 15

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!

Question 16

Describe the clinically apparent signs of central brain herniation and why they are occurring.

Answer 16

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

Question 17

Watch out for these pathological events in infratentorial lesions (masses):

Answer 17

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

Question 18

What is the MCC of metabolic encephalopathy resulting in coma?

Answer 18

Drugs!

Question 19

Which prion dz can on rare occasions cause coma?

Answer 19

CJD

Question 20

Whereas in structurally induced comas (tumor, hemorrhage) the pupillary light reflexes are first to go, in metabolic induced coma, pupillary light reflexes are lost:

Answer 20

Late in dz

Exceptions: Pupils dilate early in botulism, atropine, and glutithimide intoxication.

Question 21

What is asterixis?

Answer 21

sudden and recurrent lapses in muscle tone.
Hands flap when making “stop” sign.
Common in elderly

Question 22

A pt just came into your ED in a coma. What are you immediately going to do?

Answer 22

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)

Question 23

Normal vital signs will suggest a ____ cause of coma.

Answer 23

Psychogenic - verify w/ caloric cold water test- look for nystagmus (no nystagmus = true coma)

Question 24

What are some diagnostics you are going to collect on your emergent coma pt?

Answer 24

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)

Question 25

Besides airway, glucose, and narcan, what are some other emergent tx you will give your ED coma pt?

Answer 25

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.