Spinal Cord Flashcards
Blood flow to spinal cord
Perfused by:
1 anterior spinal a. (anterior 2/3)
2 posterior spinal a. (posterior 1/3)
6-8 radicular a.
Posterior spinal arteries (2)
Perfuses posterior 1/3 of SC (green)
Aorta –> subclavian a. –> vertebral a. –> posterior spinal a.
Aorta –> segmental a. –> posterior radicular a. –> posterior spinal a.
Anterior spinal artery (1)
Perfuses anterior 2/3 SC (blue)
Aorta –> subclavian a. –> vertebral a. –> anterior spinal a.
Aorta –> segmental a. –> anterior radicular a. –> anterior spinal a.
What is the most important radicular artery?
artery of Adamkiewicz
Which spinal segment does the artery of Adamkiewicz typically enter the spinal cord?
T11-T12
What area does the artery of Adamkiewicz supply?
anterior cord in thoracolumbar region
Great radicular artery
Artery of Adamkiewicz
Anterior spinal artery syndrome
AKA Beck’s syndrome
aortic cross clamp above artery of Adamkiewicz –> ischemia to lower portion of anterior SC
S/S:
- flaccid paralysis of LE (corticospinal tract)
- bowel & bladder dysfunction (autonomic motor fibers)
- loss of temp & pain (spinothalamic tract)
-preserved touch & proprioception (dorsal column is perfused by posterior)
3 spinal pathways supplied by anterior spinal artery
- corticospinal
- autonomic motor fibers
- spinothalamic
List 1 spinal pathway supplied by posterior spinal artery
dorsal column
spinal cord anatomy
Grey matter
- contains neuronal cell bodies
- processing center for afferent signals
- “H” shape
- subdivided into 10 laminae
1-6 in dorsal grey matter (sensory)
7-9 in ventral grey matter (motor)
10 central canal
White matter
- contains axons of ascending & descending tracts
- divided into dorsal, lateral, ventral columns
Sensory tracts
- Dosal column: cutaneous & gracilis
- Tract of Lissauer
- Lateral spinothalamic tract
- Ventral spinothalamic tract
Motor tracts
- Lateral corticospinal tract
- Ventral corticospinal tract
Dosal column: cutaneous & gracilis
fine touch & proprioception
Dosal Column - Medial Leminiscal System
- fine touch, proprioception, vibration, pressure
- 2 point discrimination
- large, myelinated, rapid-conducting fibers
- SSEPs monitor integrity
Meissner’s corpuscles
2 point discriminative touch
vibration
Merkel’s discs
continuous touch
Ruffini’s endings
proprioception
prolonged touch & pressure
Pacinian corpuscles
vibration
Tract of Lissauer
pain & temp
Anterolateral system- spinothalamic tracts
- lateral & ventral
- pain, temp, crude touch, tickle, itch, sexual
- no 2 point discrimination
-smaller, myelinated & nonmyelinated, slower conducting fibers- A-delta: 1st pain, mechanoreceptors
- C fibers: slow pain, polymodal nociceptors
Lateral spinothalamic tract
pain & temp
Ventral spinothalamic tract
crude touch & pressure
Corticospinal tract (pyramidal tract)
- motor
- lateral & ventral
- voluntary fine motor control to limbs & coordination of posture
-MEPs monitor integrity
Upper motor neurons
- cell body: cerebral cortex
- synapse in ventral horn of SC
- pass messages from brain to SC
Upper motor neuron injury
- contralateral spastic paralysis
- hyperreflexia
- positive Babinski
ex: cerebral palsy, ALS
Lower motor neuron
- cell bodies: ventral horn of SC
- synapse in NMJ of muscle
- send message from SC to muscles
lower motor neuron injury
- ipsilateral flaccid paralysis
- impaired reflexes
- absent Babinski
Lateral corticospinal tract
limb motor
Ventral corticospinal tract
posture motor
What bedside exam assesses the integrity of the corticospinal tract?
Babinski test
Babinksi test
Assesses integrity of corticospinal tract
-normal = downward motion of toes
- upper motor neuron injury = upward ext of big toe w/ fanning of other toes
- lower motor neuron injury = no response
Acute SCI
- causes: fall, MVC, assault, sports injury
- C7 injury most common
- flaccid paralysis & loss of sensation below level of injury
- loss of bowel, bladder fx
- spinal reflexes return after acute phase –> spasticity
- neurogenic shock
Neurogenic shock
- sympathectomy below level of injury
- Triad:
- hypotension
- bradycardia
- hypothermia (impaired hypothalamus)
- impaired cardioaccelerator fibers (T1-4)
> unopposed cardiac vagal tone, bradycardia,
reduced inotropy - decreased SNS tone –> vasodilation –>
venous pooling –> decreased CO, BP - impaired cutaneous vasoconstriction –> heat loss
How can you differentiate neurogenic shock from hypovolemic shock?
- Neurogenic shock = bradycardia, hypotension, hypothermia w/ pink warm extremities
- Hypovolemic shock = tachycardia, hypotension, cool clammy extremities
Discuss the use of sux in a patient w/ SCI
-“safe” within 24 hours
- Avoid 24 hours after injury & at least 6 months thereafter
When is a patient w/ SCI at risk for autonomic hyperreflexia?
1-3 weeks after spinal shock phase
Autonomic hyperreflexia (AH)
- involuntary reaction to external stimuli in pt w/ SCI
- increased SNS response below SCI
- injuries above T6
- stimulation below SCI –> vasoconstriction BELOW injury & vasodilation ABOVE injury
- Classic presentation: HTN & bradycardia
AH triggers
- bladder, bowel, uterus stimulation
- catheter
- surgery esp. cysto or colonoscopy
- BM
- cutaneous stimulation
- childbirth
AH MGMT
- stimulation below level of SCI can trigger event
- GA or spinal
- Tx HTN:
~ remove stimuli
~ deepen anesthetic
~ rapid-acting vasodilator (Na+ nitroprusside) - Tx bradycardia w/ atropine or glyco
- Sux contraindicated w/ chronic SCI
- close postop monitoring
Amyotrophic Lateral Sclerosis (ALS)
- progressive degenerative of motor neurons in corticospinal tract
- replaced by astrocytic gliosis
- S/S
- upper motor neurons
~ spasticity, hyperreflexia, loss of
coordination - lower motor neurons
~ muscle wknss, fasciculation, atrophy - begins in hands spreads to rest of body
- ocular muscles not affected
- autonomic dysfunction
~ orthostatic hypotension, resting
tachycardia - sensation intact
- upper motor neurons
- Riluzole (NMDA ant) reduces mortality
- Resp failure most common cause of death
ALS MGMT
- NO SUX –> lethal hyperkalemia
- increased sensitivity to NDNMB
- bulbar muscle dysfx –> aspiration risk
- chest wknss –> reduced VC
- consider postop mechanical ventilation
