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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
Injury at what level can affect the diaphragm?
C3, 4, 5, which makes up the phrenic nerve which innervates the diaphragm
26
Injury at what level can affect the intercostal muscles?
C6, 7 which supply the intercostal muscles
27
What is the affect on breathingof an injury at C3-5?
diaphragm can be affected
28
What is the affect on breathing of an injury at c6,7?
breathing will occur but without the assistance of respiratory/accessory muscles Difficulty in coughing, may need help clearing secretions
29
What is the affect on breathing of a spinal cord injury above the level of C4?
disconnection of all motor neurones innervating the respiratory muscles from the respiratory centres in the hind/midbrain
30
What limb movements will be affected by a spinal cord injury at C1-4?
Quadriplegia (paralysis of all 4 limbs)
31
What limb movements will be affected by a spinal cord injury at C5?
Control of shoulder & biceps but no wrist/hand control
32
What limb movements will be affected by a spinal cord injury at C6?
wrist control but no hand control
33
What limb movements will be affected by a spinal cord injury at C7/T1?
most upper limb control, however fine dexterous control of hands/fingers affected
34
What limb movements will be affected by a spinal cord injury at T1-8?
Paraplegia (both lower limbs), poor control of trunk/abdominal movements
35
What limb movements will be affected by a spinal cord injury at lumbar/sacral region?
decreased control of hip flexors and legs
36
What affect on the bladder does an injury above S2 have?
loss of bladder control as the micturition centre is in S2-4
37
What affect on the bladder does an injury below S4/5?
Some bladder control will be retained
38
Why might SCI patients struggle to empty their bladder?
loss of sympathetic control via hypogastric nerve (T12-L1), which doesnt act on beta3 receptors, therefore keeping the detrusor muscle constricted
39
Describe the return of somatic reflexes following a spinal cord injury
- 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
Which somatic reflexes return first?
- flexor reflexes | - ankle, knee and hip in sequence
41
Which somatic reflexes return later?
- extensor reflexes, about 6 months following transection | - tend to be exaggerated leading to spastic paralysis
42
Describe the return of autonomic reflexes following a spinal cord injury
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
What autonomic reflexes return following spinal cord injury
- 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
What is the effect of autonomic reflex return on BP following SCI
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
What are upper motor neurons?
neurons in the primary motor cortex that have axons in the spinal cord and excite alpha-motorneurons directly or by spinal interneurons (CNS)
46
what are lower motor neurons?
alpha-motorneurons that run from the spinal cord to the periphery (PNS)
47
Which motor neuron lesion causes mucle wasting?
lower motor neuron lesion
48
Which motor neuron lesion causes fasciculations
lower motor neuron lesion
49
Which motor neuron lesion causes flaccid tone?
lower motor neuron lesion
50
Which motor neuron lesion causes spastic tone?
upper motor neuron lesion
51
Which motor neuron lesion causes reduced or absent tenson jerk reflex?
lower motor neuron lesion
52
Which motor neuron lesion causes exaggerated tendon jerk reflex?
upper motor neuron lesion
53
Which motor neuron lesion causes a negative babinski response?
lower motor neuron lesion | normal toe flexion
54
Which motor neuron lesion causes positive babinski response?
upper motor neuron lesion
55
Why does LMN lesion cause weakness or paralysis?
= loss in muscle bulk
56
Why does UMN lesion cause weakness or paralysis?
insufficient recruitment of alpha-motorneurons

Phase 2 4. Neurology (29 decks)

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