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Neuroscience Unit 1 > Spinal Shock > Flashcards

Spinal Shock Flashcards

1
Q

What is the definition of spinal shock?

A

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

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2
Q

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

A

Do cause: quick transections, almost never: tumors.

Required: lesion of corticospinal tract, usually bilaterally

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3
Q

What can prolong spinal shock?

A

Infection and fever, can also cause it to recur

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4
Q

What are the characteristics of spinal shock?

A

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

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5
Q

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

A

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

Secondly: Babinski sign

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6
Q

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

A

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

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7
Q

Does vascular tone return after spinal shock?

A

Yes -> skin color returns to nomal

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8
Q

Why are reflexes hyperactive after spinal shock?

A

They are no longer inhibited by cortical control

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9
Q

What is mass reflex?

A

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

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10
Q

What are the last reflexes to return?

A

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

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11
Q

What innervates the detrussor muscle?

A

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

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12
Q

What innervates the internal sphincter muscle?

A

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

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13
Q

What innervates the external sphincter muscle?

A

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

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14
Q

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

A

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

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15
Q

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

A

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

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16
Q

What normally inhibits the firing of the pontine micturition center?

A

The frontal cortex, via the anterior cingulate gyrus

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17
Q

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

A

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)

18
Q

What causes detrusor hyperreflexia? What is it also called?

A

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”

19
Q

What is detrusor hyperreflexia?

A

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

20
Q

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?

A

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

Treat via catheterizing

21
Q

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

A

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

22
Q

What leads to permanently areflexic bladder?

A

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

23
Q

Why would injury at C2 be fatal?

A

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

24
Q

What is Hangman’s fracture?

A

Fracture at C2 from dens process, common in hanging

25
Q

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

A

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

26
Q

What causes anterior cord syndrome?

A

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

27
Q

What happens in anterior cord syndrome?

A

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

28
Q

What are the common causes of central cord syndrome?

A

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

29
Q

What are the symptoms of central cord syndrome?

A

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.

30
Q

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

A

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

31
Q

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

A

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

32
Q

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

A

Cauda equina -> peripheral = flaccid paralysis, LMN lesion

Conus -> UMN affected, often spastic paralysis

33
Q

What is defined as the “level” of the spinal cord injury?

A

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

34
Q

What is complete vs incomplete injury?

A

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

35
Q

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

A

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

36
Q

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

A

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

28 dermatomes

37
Q

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

A

Thumb - C6
Middle finger - C7
Little finger - C8

38
Q

What level is the nipple at?

A

T4

39
Q

What level is the umbilicus at?

A

T10

40
Q

What level is the lateral heel?

A

S1

Neuroscience Unit 1 (20 decks)

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