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Phase 2 4. Neurology > PBL 4 > Flashcards

PBL 4 Flashcards

1
Q

What is spinal shock?

A

relates to the loss of all neurological activity below the level of injury, including:

  • motor
  • sensory
  • reflex
  • autonomic
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2
Q

How long does spinal shock usually last?

A

30-60 minutes up to 6 weeks post injury

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3
Q

What are the clinical features of spinal shock?

A
  • loss of pain
  • loss of proprioception
  • sympathetic dysfunction (bowel and bladder)
  • loss of thermoregulation
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4
Q

What are the 4 phases of spinal shock?

A
  • areflexia
  • initial reflex return
  • hyperreflexia
  • hyperreflexia - spasticity
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5
Q

Describe the underlying physiology of arreflexia

A

loss of descending facilitation

  • neurons involved in various reflex arcs lose the basal level of excitatory stimulation they normally receive from the brain
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6
Q

describe the underlying physiology of the return of initial reflexes

A

Denervation supersensitivity

  • reflexes return due to hypersensitivity of reflex muscles following denervation
  • more receptors and neurotransmitters are expressed and muscles are easier to stimulate
  • restoration of reflexes from polysynaptic to monosynaptic
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7
Q

Describe the underlying physiology of the initial hyperreflexia and hyperreflexia and spasticity

A

Axon-supported synapse growth
Soma-supported synapse growth (respectively)

  • interneurons and lower motor neurons below the transection begin sprouting, attempting to re-establish synapses
  • phase 3 = first synapses to form are from shorter axons (usually from interneurons)
  • phase 4 = takes longer since synapse formation is some mediated (takes longer for axonal transport to push growth factors and proteins from soma to the end of the axon)
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8
Q

How can spinal shock be tested?

A
  • checking the bulbocavernosus reflex
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9
Q

What is the bulbocavernosus reflex?

A

monitor internal/external anal sphincter contraction by squeezing the glans penis or clitoris

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10
Q

Which is the first reflex to return after spinal shock subsides?

A

The babinski reflex (plantar reflex)

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11
Q

What marks the end of spinal shock?

A

the return of reflexes

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12
Q

How can spinal injury occur?

A
  • trauma (contusion or penetration/transection of neural tissue)
  • compression (tumour, haematoma or bony encroachment)
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13
Q

What are the major mechanisms of spinal cord injury?

A
  • hyperflexion
  • hyperextension
  • compression
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14
Q

What are the secondary effects of spinal cord injury?

A
  • oedema
  • inflammatory/immune processes
  • ischaemia
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15
Q

What is neurogenic shock?

A

from of disruptive shock caused by the loss of brainstem and higher centre control of the sympatheric nervous sysem

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16
Q

What is the result of neurogenic shock

A
  • loss of sympathetic outflow results in hypotension caused by peripheral vasodilation
  • bradycardia, due to reduced venous return
  • the loss of impulses from the thermoregulatory centre in the brain prevents the ability to sweat below the level of injury
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17
Q

describe the location of pre-ganglionic neurons in the sympathetic region

A

thoracolumbar region (leave via T1-L3)

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18
Q

describe the location of the ganglia in the sympathetic system

A

sympathetic trunk (next to vertebral column from T1 to coccyx)

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19
Q

Describe the relative length of the neurons in the sympathetic system

A

short preganglionic neurons and long postganglionic neurons

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20
Q

What is the function of the sympathetic system

A

fight or flight

  • increased HR
  • decreased gut activity
  • pupils dilate
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21
Q

describe the location of pre-ganglionic neurons in the parasympathetic region

A

brainstem (leave via CNIII, IX and X)

sacral region (leave via S2-S4)

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22
Q

describe the location of the ganglia in the parasympathetic system

A

near target organ (walls of viscera they innervate)

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23
Q

Describe the relative length of the neurons in the sympathetic system

A

long preganglionic neurones and short postganglionic neurons

24
Q

What is the function of the parasympathetic system

A

rest and digest

  • heart rate decreases
  • gut activity increases
  • secretions increase
25
Q

Injury at what level can affect the diaphragm?

A

C3, 4, 5, which makes up the phrenic nerve which innervates the diaphragm

26
Q

Injury at what level can affect the intercostal muscles?

A

C6, 7 which supply the intercostal muscles

27
Q

What is the affect on breathingof an injury at C3-5?

A

diaphragm can be affected

28
Q

What is the affect on breathing of an injury at c6,7?

A

breathing will occur but without the assistance of respiratory/accessory muscles

Difficulty in coughing, may need help clearing secretions

29
Q

What is the affect on breathing of a spinal cord injury above the level of C4?

A

disconnection of all motor neurones innervating the respiratory muscles from the respiratory centres in the hind/midbrain

30
Q

What limb movements will be affected by a spinal cord injury at C1-4?

A

Quadriplegia (paralysis of all 4 limbs)

31
Q

What limb movements will be affected by a spinal cord injury at C5?

A

Control of shoulder & biceps but no wrist/hand control

32
Q

What limb movements will be affected by a spinal cord injury at C6?

A

wrist control but no hand control

33
Q

What limb movements will be affected by a spinal cord injury at C7/T1?

A

most upper limb control, however fine dexterous control of hands/fingers affected

34
Q

What limb movements will be affected by a spinal cord injury at T1-8?

A

Paraplegia (both lower limbs), poor control of trunk/abdominal movements

35
Q

What limb movements will be affected by a spinal cord injury at lumbar/sacral region?

A

decreased control of hip flexors and legs

36
Q

What affect on the bladder does an injury above S2 have?

A

loss of bladder control as the micturition centre is in S2-4

37
Q

What affect on the bladder does an injury below S4/5?

A

Some bladder control will be retained

38
Q

Why might SCI patients struggle to empty their bladder?

A

loss of sympathetic control via hypogastric nerve (T12-L1), which doesnt act on beta3 receptors, therefore keeping the detrusor muscle constricted

39
Q

Describe the return of somatic reflexes following a spinal cord injury

A
  • never regain voluntary control of skeletal musculature
  • reflex activity gradually recovers (together with autonomic activity)
  • flexor reflexes return first, followed by extensor
  • final stage = predominant extensor activity with spasms
40
Q

Which somatic reflexes return first?

A
  • flexor reflexes

- ankle, knee and hip in sequence

41
Q

Which somatic reflexes return later?

A
  • extensor reflexes, about 6 months following transection

- tend to be exaggerated leading to spastic paralysis

42
Q

Describe the return of autonomic reflexes following a spinal cord injury

A

mass reflex (autonomic dyreflexia) occurs, which is the stage of reflex activity that follows the primary flaccidity of the shock due to massive sympathetic discharge

43
Q

What autonomic reflexes return following spinal cord injury

A
  • trivial stimulus to groin or sole of foot = exaggerated reflex response with flexion of legs, defaecation, micturition and erection in males
  • prfound sweating triggered by cutaneous stimulation
44
Q

What is the effect of autonomic reflex return on BP following SCI

A

BP control remains unstable despite return

  • rises with filling of bladder due to stretch receptor bombardment
  • change of posture from lying to standing causes pooling of blood in the legs and leads to reduction of venous return but autonomic compensating mechanisms are inadequate = bp falls and patient may faint (orthostatic hypotension)
45
Q

What are upper motor neurons?

A

neurons in the primary motor cortex that have axons in the spinal cord and excite alpha-motorneurons directly or by spinal interneurons (CNS)

46
Q

what are lower motor neurons?

A

alpha-motorneurons that run from the spinal cord to the periphery (PNS)

47
Q

Which motor neuron lesion causes mucle wasting?

A

lower motor neuron lesion

48
Q

Which motor neuron lesion causes fasciculations

A

lower motor neuron lesion

49
Q

Which motor neuron lesion causes flaccid tone?

A

lower motor neuron lesion

50
Q

Which motor neuron lesion causes spastic tone?

A

upper motor neuron lesion

51
Q

Which motor neuron lesion causes reduced or absent tenson jerk reflex?

A

lower motor neuron lesion

52
Q

Which motor neuron lesion causes exaggerated tendon jerk reflex?

A

upper motor neuron lesion

53
Q

Which motor neuron lesion causes a negative babinski response?

A

lower motor neuron lesion

normal toe flexion

54
Q

Which motor neuron lesion causes positive babinski response?

A

upper motor neuron lesion

55
Q

Why does LMN lesion cause weakness or paralysis?

A

= loss in muscle bulk

56
Q

Why does UMN lesion cause weakness or paralysis?

A

insufficient recruitment of alpha-motorneurons

Phase 2 4. Neurology (29 decks)

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