9: Intoduction to Electrodiagnostic Studies & Lab - Lewis

Question 1

What are EMG & NCS studies?

Answer 1

EMG - electromyography
NCS- Nerve conduction studies

EXTENSIONS of the neurological and musculoskeletal examination

Question 2

Who performs electrodiagnositc studies?

Answer 2

• physiatrists
• neurologists
• PTs

Question 3

Why are electrodiagnostic studies done?

Answer 3

• represent a physiologic piece of the diagnostic puzzle by giving real time information about what is happening physiologically with respect to n. and m.
• **criteria for ordering ***
• establish a correct diagnosis
• localize the lesion
• determine treatment if the diagnosis is already known
• provide info about prognosis

Question 4

When should electrodiagnostic studies be performed?

Answer 4

EMG/NCS should NOT be performed prior to 21 days after injury or onset of symptoms

Question 5

What is the Seddon classification of nerve injury?

Answer 5

• NEURAPRAXIA ( no wallerian degeneration/ failure of n. conduction across the affected n. segment combined with normal n. conduction above and below the segment)
• AXONOTMESIS ( disruption of axon continuity with wallerian degeneration but perineurium/endoneurium are still intact)
• NEUROTMESIS (severance of n. carries poor prognosis and surgical repair is needed for functional recovery)

Question 6

What are some criteria for ordering studies?

Answer 6

• is the test necessary
• will it help you determine the diagnosis, treatment, or prognosis of a pt?
• is there a test that is less intrusive and may be more cost-effective that can provide the same info?

Question 7

How do you interpret ‘normal’ studies?

Answer 7

• “the n. may be compressed and cause signs and symptoms but not enough to damage the wiring or coating around the wiring of the nerves)

Question 8

purpose of electrodiagnositc studies?

Answer 8

• determine if there is a problem in the peripheral nervous system and if so where the problem is occuring

Question 9

If you suspect an L5 radiculopathy in your pt, which test would you order to view the pathology? to objectively demonstrate physiologic changes in n. or m.?

Answer 9

CT scan/ MRI/ US

EMG/NCS

Question 10

injury to axon causes…

Answer 10

Wallerian degeneration 
(degenerative changes which occur in the distal axonal segments and their myelin sheath secondary to proximal axonal injury or death of the cell body )

Question 11

what type of n. injury has wallerian degeneration but still has perineurium and/or endoneurium intact?

Answer 11

axonotmesis

Question 12

strict contraindications to electrodiagnostic studies

Answer 12

• severe bleeding disorder/anticoagulation out of control
• NCs contraindicated in pts with automated implanted cardiac defibrillator
• active skin/soft tissue infection (cellulitis)

Question 13

Describe Nerve Conduction Studies

Answer 13

• determine if there is a pathology of the n. and at what level the pathology originates

Question 14

CMAP motor nerve conduction

Answer 14

stimulation of a peripheral n. while recording from a m. unnervated by that n.

Question 15

SNAP sensory nerve conduction

Answer 15

stimulation of a sensory or mixed n. while recording from a mixed or cutaneous n.

Question 16

interval between the stimulus and the onset of a response

Answer 16

Latency

Question 17

maximum voltage difference between two points

Answer 17

amplitude

• proportional to the number and size of nerve fibers that are depolarized
• provides an estimate of the amount of n. tissue that is electrically active

Question 18

Comparison of conduction between two segments of the same n. can localize a lesion

Answer 18

conduction velocity

age and temperature can affect conduction

latency is prolonged, amplitude is greater and conduction velocity is decreased with cooling

Question 19

F wave and H reflex

Answer 19

• late response

- useful for detecting proximal n. pathologies

Question 20

what is useful in detecting guillain barre syndrome

Answer 20

F wave

Question 21

primary value is in distinguishin gS1 from L5 radiculopathies **

Answer 21

H reflex

in an S1 radiculopathy, the H reflex will be abnormally slow when compared to non-involved limb

Question 22

describe electromyography

Answer 22

electric activity is recorded by a needle electrde in m. fibers during firing singly or iin groups near the electrode

• displays real time picture of the electrical activity of muscle membrane

Question 23

pathologic spontaneous activity

Answer 23

• fibrillation potentials

- positive sharp waves

Question 24

NCS v. EMG

Answer 24

NCS - n. will be stimulated or shocked and recorded with surface electrodes

EMG - m. membrane activity will be evaluated at rest and with contraction with a needle inserted into the m.

Question 25

screening needs to be ________ on everybody

Answer 25

same and done

Question 26

strength testing

Answer 26

0-5

2- full ROM with gravity eliminated
3- full ROM with gravity only (overcome with pinky)
4- full ROM that can be overcome with force
5- normal

Question 27

normal reflex

Answer 27

2/4 reproduced at least 2 times

Question 28

normal Babinski in adults

Answer 28

downgoing toes

Question 29

where does the spinal cord end?

Answer 29

L1

Question 30

motor dance

L2
L3
L4
L5
S1

Answer 30

hip flexors
knee extensors
ankle dosiflexors
extensor hallicus longus 
plantar flexors

Question 31

4 muscle groups you should never be able to overcome

Answer 31

shoulder shrug
elbow extensors
knee extensors
ankle dorsiflexors