Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuro > Nerve conduction studies > Flashcards

Nerve conduction studies Flashcards

1
Q

What do nerve conduction studies check?

A

Diseases of peripheral nerves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

TRUE or FALSE? NCSs study all the nerves

A

FALSE

They measure the fastest nerves only

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the types of NCS stimulations?

A

Supramaximal stimulation

Submaximal stimulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is supramaximal stimulation?

A

Completely non-physiological: use a supramaximal stimulus (enough to make all the axons in the bundle make an action potential) - never happens in real life

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are F waves?

A

A late CMAP evoked from a muscle by a supramaximal electrical stimulus to the nerve, and it is due to antidromic activation (backfiring) of alpha motor neurons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are supramaxial stiumulations used to check?

A

compound motor action potentials

sensory action potentials

mixed sensory and motor responses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are H waves?

A

Hoffman reflex:(stimulate muscle spindle fibres –> sensory fibres –> come back)

electical correlate of tendon reflex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the NCS amplitude determined by?

A

the number of axons
impedance
distance from nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

TRUE or FALSE? NCS amplitudes vary a lot between people.

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does reduced NCS velocity suggest?

A

demyelination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does a reduced NCS amplitude suggest?

A

axonal loss/degeneration/lesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are examples of when NCS amplitudes are decreased

A

Axonotmesis: injury to the peripheral nerve axons

Neurotmesis: cut of axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do median sensory studies work (SAP)?

A
  1. Use ring electrodes around finger to electrocute fingers
  2. Find out how long it takes AP to get to wrist
  3. Distance/time = velocity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Define orthodromic

A

normal direction of AP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Define antidromic

A

reverse direction of AP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In a median motor study which wave is bigger? Muscle or nerve?

A

Muscle

17
Q

Why do we not study velocity in motor studies?

A

bc of NMJ being involved (distorts)

18
Q

What is temporal dispersion?

A

when there is myelin damage due to inflammation then certain areas are more affected than others thus velocities are spread out in a random way

19
Q

What are the conduction velocities in distal and proximal parts of upper and lower limbs?

A

Upper limb:
Distal >50m/s
Proximal >60m/s

Lower limbs:
Proximal >50m/s
Distal >40m/s

20
Q

Why are leg velocities slower than arms?

A

Because the axon diameter is smaller in the legs

21
Q

What are the types of neuropathy defined by neurophysiological findings + examples?

A

Length dependent (e.g. CMT)

Non-length dependent (e.g. CIDP) -patchy

Mono-neuropathy (carpal tunnel syndrome)

22
Q

What are the patterns of NCS abnormalities?

A

Gereneralised: length dependent

Patchy: acquired inflammatory conditions

Anatomically defined abnormalities - carpal tunnel

23
Q

What do we see in preganglionic lesions?

A

Sensory conduction looks normal bc has cell body but connection to NS is damage

SAP: normal
CMAP : abnormal

24
Q

What do we see in postganglonic lesions?

A

SAP: abnormal
CMAP: abnormal

25
Q

Give an example of preganglionic damage

A

Radiculopathies

Motor neuron disease (e.g. anterior horn cell disease)

26
Q

Give examples of post ganglionic damage

A

Plexopathy
Mononeuropathy
peripheral neuropathy

27
Q

What does repetitive nerve stimulation do in myasthenia gravis?

A

If you stimulate a motor response repetitively you get a drop in amplitude due to failure of transmission across NMJ

28
Q

Which part of the synapse does MG affect?

A

post synaptic disorder

29
Q

What happens if you repetitively stimulate lambert-eaton myasthenic syndrome nerves?

A

it improves after repeated stimulation

30
Q

Which part of the synapse does lambert-eaton myasthenic syndrome affect?

A

pre-synaptic disorder

31
Q

What happens if you repetitively stimulate botulism nerves?

A

And you can force the Ach across the NJM so you get an increase in amplitude

32
Q

How does botulinum toxin work?

A

Prevents Ach Release

33
Q

How do you do an EMG??

A

Put needle in the muscle and look at the pattern of electical activity

uncomfortable

34
Q

What happens if you denervate a muscle?

A

the muscle will start to fire off on its own - useful to see axon damage

35
Q

What are the limitation of NCSs?

A

Supra maximal stimulation is non physiological (Can show abnormalities which are not useful)

Normal ranges are very wide

Only accessible nerves can be examined

The method only examines large demyelination (Most fibres are small)
We can look at fibres that supply skeletal fibres and those for proprioception

Some people can’t tolerate the stimulus

Neuro (23 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions