Spinal Shock

Question 1

What is the definition of spinal shock?

Answer 1

A highly variable period after spinal cord injury where there is a shutdown of neural activity below the level of the lesion, with no reflex activity

Question 2

What type of spinal injuries do vs do not cause spinal shock? What is required for spinal shock?

Answer 2

Do cause: quick transections, almost never: tumors.

Required: lesion of corticospinal tract, usually bilaterally

Question 3

What can prolong spinal shock?

Answer 3

Infection and fever, can also cause it to recur

Question 4

What are the characteristics of spinal shock?

Answer 4

Below the level of the lesion:
Flaccid paralysis, loss of reflexes, and disuse muscular atrophy.

Loss of SANS from reticulospinal tract causes loss of sweating, slow heart rate since vagus is unaffected, flushed or pink skin due to vessel dilation, lowered blood pressure since SANS cannot constrict.

PANS lost from sacral outflow: loss of bowel + bladder reflexes

Question 5

What is the first reflex to return after spinal shock, and what joints are involved? What after that?

Answer 5

Flexor withdrawal reflex, includes ankle, knee, and hip joints, slowly moving.

Secondly: Babinski sign

Question 6

What visceral reflexes return from spinal shock? Which one is special?

Answer 6

Bladder, bowel, and sweating (but not for temp regulation, induced by tactile stimulation recircuiting)

Question 7

Does vascular tone return after spinal shock?

Answer 7

Yes -> skin color returns to nomal

Question 8

Why are reflexes hyperactive after spinal shock?

Answer 8

They are no longer inhibited by cortical control

Question 9

What is mass reflex?

Answer 9

After spinal shock, small noxious stimuli will induce flexor spasms, penile erection + ejaculation, sweating, evacuation of bowel and bladder due to recircuitry

Question 10

What are the last reflexes to return?

Answer 10

Extensor reflexes, which would make sitting in a wheelchair much easier.

Question 11

What innervates the detrussor muscle?

Answer 11

Smooth muscle in bladder wall innervated PANS from S2-S4 levels, postganglionics are in bladder wall.

Question 12

What innervates the internal sphincter muscle?

Answer 12

It’s smooth muscle which is innervated by sympathetics at the L1-L2 spinal levels. Tonically excite the muscle to keep the urethra closed

Question 13

What innervates the external sphincter muscle?

Answer 13

Pudendal nerve, tonically contracts the skeletal muscle to keep the urethra closed

Question 14

What is the function of the stretch receptors in the bladder?

Answer 14

They send their signals to S2-S4 levels of the spinal cord, project to cortex to make us aware of bladder distention as well as collaterals

Question 15

What is the function of the pontine micturition center? What neurotransmitters are involved?

Answer 15

coordinates contraction of detrussor muscle and relaxation of internal sphincter (GABA to internal sphincter SANS for relaxation, Glutamate to detrussor for contraction)

Question 16

What normally inhibits the firing of the pontine micturition center?

Answer 16

The frontal cortex, via the anterior cingulate gyrus

Question 17

What disinhibits and hence releases the firing of the pontine micturition center?

Answer 17

Ascending fibers from stretch receptors release GABA on anterior cingulate gyrus fibers in the frontal cortex (which synapse on fibers which project to pontine micturition centers to inhibit it)

Question 18

What causes detrusor hyperreflexia? What is it also called?

Answer 18

A suprapontine lesion, as in MS, Parkinson’s, or a stroke. Caused by a loss of cortical inhibition of the pontine micturition center.

Also called “neurogenic detrusor overactivity”

Question 19

What is detrusor hyperreflexia?

Answer 19

Constant activation of pontine micturition center / it is easily excited. Uninhibited detrusor contraction + coordinated relaxation of sphincters

Question 20

What happens to the bladder reflex in spinal shock due to spinal cord injury just rostral to the sacral levels? How do you treat this?

Answer 20

Areflexic bladder -> urine retention. Could lead to overflow incontinence when the pressure is great enough to physically overcome the sphincter muscle.

Treat via catheterizing

Question 21

What happens to the bladder reflex after spinal shock due to spinal cord injury just rostral to the sacral levels?

Answer 21

Detrusor sphincter dyssynergia (DSD). The pontine micturition center cannot simultaneously cause contraction of and release of PANS/SANS

Question 22

What leads to permanently areflexic bladder?

Answer 22

Spinal cord injury at sacral levels, due to neurons mediating the reflex being lost. I.e. conus medullaris syndrome or cauda equina syndrome.

Question 23

Why would injury at C2 be fatal?

Answer 23

Loss of reticulospinal drive to phrenic motoneurons, leading to complete diaphragm paralysis

Question 24

What is Hangman’s fracture?

Answer 24

Fracture at C2 from dens process, common in hanging

Question 25

What is Brown-Sequard Syndrome? Is it associated with spinal shock? What is one thing doctors easily forget?

Answer 25

Spinal cord hemisection lesion, not associated with spinal shock since it's not bilateral. Ipsilateral: UMN spastic paralysis, loss of tactile sense, varied LMN involvement, loss of conscious proprioception Contralateral: Loss of pain and temperature 2 segments below the level of the lesion all the way down to the lowest segments Bilateral: Anterior white commissure knockout causes loss of pain/temp on both sides 1 segment caudal to injury

Question 26

What causes anterior cord syndrome?

Answer 26

Anterior compression injuries of vertebral bodies or occlusion of anterior spinal artery

Question 27

What happens in anterior cord syndrome?

Answer 27

Variable motor function loss + loss of ability to perceive pain / temp on contralateral side

Question 28

What are the common causes of central cord syndrome?

Answer 28

Traumatic: Severe hyperextension of neck, as in old people falling on the tub Nontraumatic: syringomyelia

Question 29

What are the symptoms of central cord syndrome?

Answer 29

Affects almost totally the cervical cord, produces greater weakness in upper than lower limbs, with some sacral sparing. There will still be some transient bladder dysfunction.

Question 30

In conus medullaris syndrome, when will bulbocavernosus reflexes and bladder reflexes be preserved vs not?

Answer 30

Higher conus medullaris = preservation. Generally, however, this leads to areflexic bladder and bowel.

Question 31

What causes cauda equina syndrome? how does this differ from conus medullaris syndrome?

Answer 31

Cauda equina -> lower, due to injury of lumbosacral nerve roots within the vertebral canal, but still considered peripheral (outside the cord). Leads to areflexic bladder, bowel, and lower limbs, but is much more variable since it is a peripheral root injury

Question 32

How does muscle paralysis differ in conus medullaris vs cauda equina syndrome?

Answer 32

Cauda equina -> peripheral = flaccid paralysis, LMN lesion | Conus -> UMN affected, often spastic paralysis

Question 33

What is defined as the "level" of the spinal cord injury?

Answer 33

Most caudal segment of the spinal cord with NORMAL function (both sensory and motor)

Question 34

What is complete vs incomplete injury?

Answer 34

Complete - no sensory or motor function is preserved at S4-S5 segments Incomplete - partial preservation of sensory / motor function below the "level", and ALWAYS S4-S5

Question 35

What is a "zone of partial preservation" and when is it used?

Answer 35

Only in complete injuries -> dermatomes and myotomes caudal to the most normal level that are partially innervated. These can regain function

Question 36

How many dermatomes are tested on each side, and what is used to test?

Answer 36

Pinprick - safety pin (test ALS) Fine touch - cotton ball (test DC-ML) 28 dermatomes

Question 37

What do the thumb, middle, and little finger correspond to in dermatomes?

Answer 37

Thumb - C6 Middle finger - C7 Little finger - C8

Question 38

What level is the nipple at?

Answer 38

T4

Question 39

What level is the umbilicus at?

Answer 39

T10

Question 40

What level is the lateral heel?

Answer 40

S1