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Semester 5 FSNM Exam 8 > Diagnostic EMG > Flashcards

Diagnostic EMG Flashcards

1
Q

Electrodiagnosis (EDX) studies includes

A

NC - nerve conduction studies
EMG - elecromyography
Often both are referred to as an EMG

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2
Q

Entire purpose of EDX is to determine

A

Is there a problem in the peripheral nervous system

AND if so, where it the problem occurring

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3
Q

EMG and NCS are extensions of

A

the neuro and musculoskeletal exam

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4
Q

EDX needs to be interpreted in accordance with

A

the entire clinical picture
It is a complete exam, not simply a test
The more you know about basic anatomy of the nerves and mm, the easier it will be to learn about and interpret EDX

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5
Q

EDX - history

A

Originated 19th century
Only consistently used in past 30-40 yrs
First machine had no screens, only speakers

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6
Q

People who perform EDX

A

Physiatrists
Neurologists
PT/Technicians `

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7
Q

Why do EDX studies

A

To distinguish between many peripheral and mm disorders
Represents a physiologic piece of the diagnostic puzzle - real time info about what is happening physiologically with respect to the nerve and mm

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8
Q

EDX vs. MRI

A

EMG will tell you where the problem is, but not exactly what is causing it
MRI will help you determine what is causing it

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9
Q

EDX studies are used to

A

1 Establish correct dx
2 Localize the lesion
3 Determine tx if dx is already known
4 Provide info about prognosis

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10
Q

If you suspect an L5 radiculopathy in your pt, which test will you order to view the possible pathology

A

MRI

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11
Q

If you suspect an L5 radiculopathy in your pt, which test will you order to objectively demonstrate physiological changes in the nerve or muscle

A

EMG

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12
Q

Wallerian Degeneration - define

A

Degenerative changes that occur in the distal axonal segments and their myelin sheath secondary to proximal axonal injury or death of the cell body

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13
Q

Neurapraxia

A

Failure of nerve conduction across the affected nerve segment combined with normal nerve conduction above and below the segment
NO WALLERIAN DEGENERATION INVOLVED

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14
Q

Axonotmesis

A

Disruption of axon continuity with Wallerian degeneration, but perineurium and/or endoneurium are still intact
Destroy the axon but there is still stuff around it that is intact

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15
Q

Neurotmesis

A

Severance of nerve; carries poor prognosis and surgical repair is needed for functional recovery

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16
Q

What type of nerve injury has Wallerian degeneration but still has perineurium and/or endoneurium intact

A

axonotmesis

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17
Q

Common reasons for NCS/EMG - Symptoms

A

N/T
Extremity or radicular pain
Weakness

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18
Q

Common reasons for NCS/EMG - Physical findings

A 
Reflex loss or asymmetry
Weakness
Sensory loss 
Limp 
MM atrophy
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19
Q

Timing - when to do EDX studies - Main rule of thumb -

A

EMG or NCS should not be performed prior to 21 days after the injury or onset of symptoms
Very few exceptions to this rule

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20
Q

Contraindications - Strict

A

1 Sever bleeding disorder/Anticoagulation out of control
2 NCS contraindicated with automated implanted cardiac defibrillator
3 Active skin/soft tissue infection

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21
Q

Relative contraindications

A

In extremity of someone who has undergone axillary lymph node dissection
Pt needed mm biopsy

22
Q

Complications

A

Infection
Bleeding
Accidental penetration of the needle into something other than intended muscle

23
Q

Good criteria for ordering or performing

A

Is the test necessary
Will it help you determine dx, tx, or prognosis
Is there a test less intrusive and may be more cost effective that can provide the same info

24
Q

You have a 66 y/o patient reporting stocking and glove distribution of numbness and tingling in the limbs and history of diabetes, now on treatment with insulin
- do you order EDX

A

Based on hx alone seems like diabetic peripheral neuropathy

But you don’t know for sure until go through exam

25
Q

Interpretation - How do you explain a normal EDX exam

A

Normal EDX does not necessarily mean normal function or that the patient’s symptoms have no physiologic basis
May mean that the sensitivity and specificty of the exam can’t define a specific problem by available techniques

26
Q

Interpretation of EDX - normalized values

A

Different labs have different normalized values

27
Q

How we would explain a normal (or negative) EDX study to a patient who has positive signs and symptoms (i.e. Tinel’s, paresthesias, etc.) in layman’s terms

A

“The nerve may be compressed and cause signs and symptoms but not enough to damage the ‘wiring’ or ‘coating’ around the wiring of the nerves.”

28
Q

EDX Results are dependent on what

A

Examiner dependent!
Vary with technique, ability, and thoroughness of the examiner
Technical error is the most important factor leading to incorrect conclusions about the data obtained

29
Q

Types of nerve conduction studies

A

Motor nerve conduction
Sensory nerve conduction
Both study waveforms generated in the peripheral nervous system

30
Q

Types of nerve conduction studies - motor nerve conduction

A
  • Compound Motor Action Potential (CMAP)

- Stimulation of a peripheral nerve while recording from a muscle innervated by that nerve

31
Q

Nerve conduction studies - sensory nerve conduction

A
  • Sensory Nerve Action Potential (SNAP)

- Stimulation of a sensory (cutaneous) or mixed nerve while recording from a mixed or cutaneous nerve

32
Q

NCS Latency

A

Interval between the onset of a stimulus and the onset of a response

33
Q

NCS Amplitude

A

Maximum voltage difference between two points

Proportional to number and size of nerve fibers that are depolarized

34
Q

NCS amplitude provides an estimate of the

A

amount of nerve tissue that is electrically active (estimate of axons conducting electricity)

35
Q

NCS - Conduction velocity

A

The “speed” at which the nerve fibers are carrying the electrical stimulus between two sites
V = distance/time

36
Q

NCS - Conduction velocity - comparison of conduction between two segments of the same nerve can

A

localize a lesion

37
Q

NCS - Late responses

A

(F wave & H reflex)
Most useful for detecting proximal nerve pathologies
Especially early in disease (like GB)

38
Q

NCS - H Reflex

A

Due to a monosynaptic spinal reflex
Primary value of the H reflex is in distinguishing S1 from L5 radiculopathies
H reflex will be abnormal in an S1 radiculopathy `

39
Q

Elecromyography

A

The electric activity recorded by a needle electrode in muscle fibers during firing singly or in groups near the electrode

40
Q

EMG - Insertional activity

A

The sound you hear when you insert the needle in - there is a normal sound and an abnormal one

41
Q

EMG - Spontaneous activity

A

Activity that happens without the patient moving their muscle

42
Q

EMG - Voluntary Activity

A

Ask the patient to contract/move their muscle and look at the Motor Unit Action Potentials
Amplitude, Duration, Recruitment

43
Q

EMG - Spontaneous Activity can include

A 
Fibrillation potentials
Positive sharp waves
Fasciculation potentials (common with ALS) 
Myotonic discharges
Complex repetitive discharges
Myokymic discharges
Cramps
Neuromyotonic discharge
44
Q

Radiculopathy - NCS

A

Main reason for NCS in this case is to rule out other pathologies

45
Q

Radiculopathy - NCS - Sensory NCS in a radiculopathy study

A

Majority are normal
Damage is proximal to the DRG therefore the axon is still intact with its cell body and no Wallerian deg. takes place
If sensory NCS is abnormal, we look for other pathology

46
Q

Radiculopathy - NCS - Motor NCS

A

May be normal

In a severe radicular lesion the axon loss can lead to Wallerian degeneration and th CAMP amplitude may be reduced

47
Q

Radiculopathy - EMG

A

Most useful procedure in localizing radiculopathy and predicting prognosis

48
Q

Radiculopathy - EMG - most objective evidence of acute denervation

A

Presence of spontaneous activity (fibrillations, PSW)
Begins in the proximal paraspinal mm within 5-7 days of compression
Limb mm show spont activity within 3 weeks

49
Q

Radiculopathy - EMG - choice of mm

A

Is critical!

Typical screen will be modified based on abnormal findings on the physical exam

50
Q

Radiculopathy - NCS findings

A

Normal SNAP amp

Normal CMAP amp

51
Q

Radiculopathy - EMG findings

A

Spontaneous potentials (fibs and PSWs) in the paraspinal mm and two mm from different peripheral nerves innervated by the same affected root level

52
Q

NCS and needle EMG are great studies because

A

they provide information about the injured or diseased nerves’ pathophysiology (demyelination and/or axonal loss, or complete severing of nerve)

Semester 5 FSNM Exam 8 (5 decks)

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