Spine Flashcards
Sensory peripheral nerves enter the spinal cord via what?
Dorsal nerve root
Motor and autonomic neurons exit the spinal cord via what?
Ventral nerve root
What is a ganglion?
Collection of cell bodies OUTSIDE of the CNS
What is Grey matter?
Contains neuronal cell bodies
Processing center for afferent signals that arrive from periphery
What is white matter?
Contains the axons of the ascending and descending tracts
(Divided into the dorsal, lateral, and central columns)
What are the 4 sensory tracts?
Dorsal column: ci eat us and gracilis
Tract of Lissauer: pain and temperature
Lateral spinothalamic tract: pain and temp
Ventral spinothalamic tract: crude touch and pressure
What are the two motor tracts?
Lateral corticospinal tract: limb motor
Ventral corticospinal Tract: posture motor
What are some traits about the dorsal column?
Mechanoreceptive sensations (fine touch, vibration, pressure)
Capable of two-point discrimination
Contains LARGE MYELINATED fibers
Transmits faster than anterolateral system
Which mechanoreceptor can discriminate between two points?
Meissner’s corpuscles
Which mechanoreceptor is related to continuous touch?
Merkel’s discs
Which mechanoreceptor relates to proprioception, prolonged touch and pressure?
Ruffini’s endings
Which mechanoreceptor is related to vibration?
Pacinian corpuscles
What is the order of transmission in the dorsal column?
Usually an a-beta neuron
First order: enters spinal cord via dorsal root > ascends in same side > synapses with second order neuron in the medulla (cuneate and gracile nuclei)
Second order: cross side in medulla > thalamus > synapses with 3rd order in the thalamus relay station
Third order: advance towards somatosensory cortex in post central gyrus
What is the pathway via the spinothalamic tract?
Mostly A-delta or C-fibers
1st order neuron: cell body is in dorsal root ganglion > may ascend 1-3 levels before synapsing with second order
Second order: crosses sides in the spinal cord and ascends via two paths > anterior spinothalamic or lateral spinothalamic > synapse with 3rd in the RAS and thalamus
3rd order: pass through thalamus and advance to somatosensory cortex
With the corticospinal tract, if an injury happens above the decussation (crossing) what will result?
Spastic paralysis on the CONTRALATERAL side
With the corticospinal tract, if an injury happens below the decussation (crossing) what will result?
Flaccid paralysis on the IPSILATERAL side
What is the corticospinal tract also called?
Pyramidal tract
What is the path of transmission in the corticospinal tract?
Motor neurons begin in cerebral cortex and synapse with lower motor neurons in the ventral horn
Injury to an upper motor neuron results in what?
Contralateral spastic paralysis and hyperreflexia
(Cerebral palsy and ALS)
What does the babinski sign test?
Corticospinal integrity
What does a negative babinski test say?
Corticospinal tract is INTACT ~ GOOD sign
Produces a downward motion of the toes (toes curl)
What does a positive babinski test determine?
Damage to corticospinal tract ~ BAD sign
Upward extension of the big toe with fanning of the other toes
Where does lower motor neurons begin?
Ventral horn and end at the neuromuscular junction
What will result in a LOWER motor neuron injury?
Ipsilateral flaccid paralysis
(Impaired reflexes and flaccid paralysis)
**babinski sign is absent in a lower motor injury
What does SSEPs monitor?
Dorsal column (posterior blood flow)
What do MEPs monitor?
Monitor the integrity of the corticospinal tract (anterior perfusion)
What is the triad to spinal cord injury? Aka neurogenic shock?
Hypotension
Bradycardia
Hypothermia
(This lasts 1-3 weeks)
What does impairment to the cardioaccelerator fibers cause?
Unopposed vagal tone ~ resulting in bradycardia and reduced inotropy
What is hypothermia the results of in neurogenic shock?
Impairment of the sympathetic pathways ~ inability of cutaneous vasculature to vasoconstrict, cause a redistribution of blood flow towards the periphery and allowing more heat to escape
What is the difference b/t neurogenic shock and hypovolemic shock?
Neurogenic: hypotension, bradycardia, warm, pink extremities
Hypovolemic: hypotension, tachycardia, cool clammy extremities
What is the vasopressors of choice in neurogenic shock?
LEVO
and volume expansion
What is the major cause of morbidity and mortality in patients with cervical and upper thoracic lesions?
Ineffective alveolar ventilation and the inability to clear secretions.
What is autonomic hyperflexia?
Following a spinal cord injury (and spinal shock) the body begins to mend itself in a pathological and disorganized way. reflexes returns but are not inhibited in any way ~ results in an overactive state.
What % of patients (with an injury above T6) will develop autonomic hyperreflexia?
85%
What are some common events that cause autonomic hyperreflexia?
Stimulation of the hollow organs (bladder, bowel, uterus)
Bladder catherization
Surgery (cysto)
Bowel mov.
Childbirth
What is the classic presentation of autonomic hyperreflexia?
Hypertension and bradycardia
Where does vasoconstriction occur in autonomic hyperreflexia?
Below the level of injury
Where does vasodilation occur in autonomic hyperreflexia?
Above the level of injury
What are some other S&S of spinal cord injury?
Nasal stuffiness
Hypertension (headache and blurred vision)
Severe HTN: stroke, seizure, LV failure, pulmonary edema
What is the best management for autonomic hyperreflexia?
Prevention!!!
(Then either a GA or Spinal)
How is hypertension best treated with? In AH following SCI
Removal of the stimulus
Deepening of the anesthetic
Rapid-vasodilator
How is bradycardia best treated in AH following SCI?
Atropine or Glyco
What is amyotrophic lateral sclerosis (ALS)?
Progressive degeneration of motor neurons in the corticospinal tract. Both upper and lower neurons are affected.
S&S of ALS?
Upper neurons involvement: spasticity, hyperreflexia, loss of coordination
Lower neuron involvement: musc weakness, fasciculations, atrophy
Where does ALS typically begin?
Hands
What is the only drug that reduces mortality in ALS?
Riluzole (NMDA antagonist)
What is the most common cause of death in ALS?
Resp failure
How should an anesthetic provider approach paralysis for a patient with ALS?
NO SUX
Increased sensitivity to NMB
