Unit 7 - Neuro - Spinal Cord Flashcards
most important radicular artery
artery of adamkiewicz
where does the artery of adamkiewicz most commonly originate
T11-T12
what does the artery of adamkiewicz supply
anterior cord in thoracolumbar region (along with anterior spinal artery)
how do sensory neurons enter the CNS from periphery
via dorsal nerve root
3 neuron pathway common to spinal tracts
- 1st order = periphery to spinal cord or brainstem
- 2nd order = spinal cord/brainstem to a subcortical structure
- 3rd order = subcortical structure to cerebral cortex
function of dorsal column - medial lemniscal system
transmits mechanoreceptive sensations:
* fine touch
* proprioception
* vibration
* pressure
fibers that make up dorsal column
large, myelinated, rapidly conducting
which transmits sensory info faster - dorsal column or anterolateral system
dorsal
which is capable of 2 point discrimination - medial lemniscal system (dorsal) or spinothalamic tract (anterolateral)?
medial lemniscal (dorsal)
type of fibers that make up spinothalamic tract
smaller, myelinated, slower conducting
most important motor pathway
corticospinal tract
aka pyramidal tract
bedside exam that can assess integrity of corticospinal tract
babinski test
responses to babinski test
- normal = downward motion of all toes
- upper motor neuron injury: upward extension of big toe, fanning of other toes
- lower motor neuron injury: no response
where do upper motor neurons begin and end
begin: cerebral cortex
end: ventral horn of spinal cord
where do lower motor neurons begin & end
begin: ventral horn
end: NMJ
how do upper vs lower motor neuron injury present
- upper = hyperreflexia, spastic paralysis
- lower = impaired reflexes, flaccid paralysis
why does neurogenic shock result in bradycardia & reduced inotropy
impaired cardioaccelerator fibers = unopposed cardiac vagal tone
what causes decreased CO and BP in neurogenic shock
decreased SNS tone = vasodilation, venous pooling
what causes hypothermia in neurogenic shock
impaired sympathetic pathways from hypothalamus to blood vessels impairs ability to vasoconstrict or shiver
blood flow redistributes toward periphery & allows more heat to escape
differentiate neurogenic shock vs. hypovolemic shock
- neurogenic = bradycardia, hypotension, hypothermia with pink warm extremities
- hypovolemic = tachycardia, hypotension, cool clammy extremities
use of succs in spinal cord injury
avoid for 24 hours after injury & shouldn’t be used for at least 6 months after (some say a year)
when does a pt with SCI become at risk for autonomic hyperreflexia
after shock phase ends (1-3 weeks)
patho of autonomic hyperreflexia
spinal sympathetic reflexes return below level of injury but without inhibitory influences that would normally come from above level of injury
stimulation below SCI leads to overactive sympathetic reflexes below injury
level of injury assoc with autonomic hyperreflexia
85% of pts with injury above T6 will develop
very unlikely to occur below T10
higher level of injury = more intense response
6 situations that can precipitate autonomic hyperreflexia
- Stimulation of the hollow organs - bladder, bowel, or uterus
- Bladder catheterization
- Surgery - especially cystoscopy or colonoscopy
- Bowel movement
- Cutaneous stimulation
- Childbirth
classic presentation of autonomic hyperreflexia
HTN
bradycardia
other s/s: nasal stuffiness, HTN, malignant HTN
what causes bradycardia in autonomic hyperreflexia
baroreceptor reflex activation in carotid sinus
best anesthesia techniques for SCI pts
general or neuraxial
best treatment for HTN assoc with autonomic hyperreflexia
- remove stimulus
- deepen anesthetic
- rapid acting vasodilator (Nipride)
patho of ALS
progressive degeneration of motor neurons in corticospinal tract
upper & lower motor neurons affected
use of NMBs in ALS
- sensitive to succs
- sensitive to NDNMBs
