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PL6009 Neurology > Nerve conduction studies/ EMG > Flashcards

Nerve conduction studies/ EMG Flashcards

1
Q

List the components of the peripheral nervous system

A
  • nerve root
  • brachial/lumbar/sacral plexus
  • peripheral nerves (motor/sensory/mixed)
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2
Q

List the components of motor nerves

A
  • anterior horn cell
  • nerve root/plexus
  • peripheral nerve
  • neuromuscular junction
  • muscle
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3
Q

what is a motor unit

A

anterior horn cell, motor nerve fiber and all muscles supplier by that fiber

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4
Q

What do you stimulate in a sensory nerve conduction study

A

the sensory nerve

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5
Q

What is it called when you record the response distal to the site of stimulation

A

antidromic

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6
Q

what is it called when you record proximal to the site of the site of stimulation

A

orthodromic

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7
Q

How do you calculate the velocity in a sensory nerve conduction study

A

velocity = distance (between site of stimulation and recording)/latency of the response

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8
Q

what are the types of latencies

A

peak or onset

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9
Q

what do you record in a motor nerve conduction study

A

the muscle

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10
Q

what method of measurement is used in motor nerve conduction study

A

belly tendon method

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11
Q

You need …. and … sites to stimulation

A

proximal and distal

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12
Q

how do you calculate velocity in motor nerve conduction studies

A

Velocity = distance (between proximal and distal site)/(proximal latency - distal latency)

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13
Q

what does SNAP stand for

A

sensory nerve action potential

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14
Q

what does CMAP stand for

A

compound motor action potential

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15
Q

what does DML stand for

A

distal motor latency

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16
Q

What does SNCV stand for

A

sensory nerve conduction velocity

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17
Q

What is a conduction block

A

a drop in amplitude proximal to distal

18
Q

What is amplitude of response determined by

A

axons

19
Q

What does the slow loss of motor axons lead to

A

increase in motor unit size

20
Q

What happens to CMAP if denervation is slow

A

despite losing axons the CMAP can be preserved due to increase in motor unit size

21
Q

what does axonal loss result in

A

loss of amplitude
normal latencies
normal conduction velocity

22
Q

what does demyelination result in

A

slowing of conduction velocity > conduction block
dispersion if acquired

23
Q

List some nerve compression syndromes

A

carpal tunnel syndrome
ulnar nerve compression at the elbow
common peroneal compression

24
Q

Describe the pathology of carpal tunnel syndrome

A

compression of the median nerve at the wrist
local demyelination at the site of compression followed by axonal loss

25
Q

What happens in mild carpal tunnel syndrome

A

slowing of sensory conduction

26
Q

What happens in moderate carpal tunnel syndrome

A

slowing of motor conduction

27
Q

What happens in severe carpal tunnel syndrome

A

loss of sensory response

28
Q

What happens in very severe carpal tunnel syndrome

A

loss of motor amplitude

29
Q

What is an F wave

A

stimulate motor nerve
get antidromic conduction
backfiring of some anterior horn cells
late response
give information of the proximal nerve

30
Q

What is a H response

A

analogous to tendon reflex
stimulate mixed nerve
get activation of tendon afferents
reflex response
lower threshold than CMAP/motor response

31
Q

what is electromyography

A

extracellular electrical activity of skeletal muscle

32
Q

What types of activity do we see in EMGs

A

spontaneous
weak voluntary contraction
full activation

33
Q

List examples of spontaneous activity

A
  1. fibrillations
  2. fasiculations
  3. myotonia
  4. myokymia
  5. complex repetitive discharges
  6. neuromyotonia
34
Q

What are fibrillations

A

generated by muscle - are a cardinal sign of denervation

35
Q

what generate fasiculations and what are they a sign of

A

generated by nerves - sign of denervation

36
Q

what is the caveat to fibrillations/fasiculations

A

can take 1-2 weeks to appear in acute denervation

37
Q

How do we measure weak voluntary contraction

A

measure motor unit action potentials
amplitude, duration and number of phases

38
Q

Describe weak voluntary contractions in chronic denervation

A

large and prolonged, increased number of phases

39
Q

Describe weak voluntary contractions in muscle disease

A

small, short duration, increased phases

40
Q

What do we look for in maximum contraction

A

an’interference pattern’
(this is reduced in denervation
and early in muscle disease)

41
Q

What happens to interference pattern in denervation

A

reduced

42
Q

what happens to interference pattern in muscle disease

A

early

PL6009 Neurology (4 decks)

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