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IMA > EMG and NCV Testing > Flashcards

EMG and NCV Testing Flashcards

1
Q

Do you need board certification?

A

No, only for Medicare reimbursement

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2
Q

Signs & symptoms that warrant electrophysiological testing? (8)

A
  • Paresthesias
  • Weakness
  • Muscle pain that doesn’t fit pattern of ache/strain
  • Neurogenic pain
  • h/o trauma or repetitive stress
  • Delayed recovery of orthopedic injury (ankle sprain grade 2 & 3) >> Neurogenic inflammation
  • Unexpected weakness post surgery

>> Anterior THR Tourniquet, traction

>> Radial artery graft Isolated blood supply to median/ulnar nerves

• Patients with mid-cervical SCI

>> Determine distal nerve integrity prior to undergoing tendon transfers

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3
Q

Electrophysiological testing purposes? (6)

A
  • Identify presence of nerve injury or muscle disease
  • Identify which nerve(s) or muscle(s) are damaged
  • Characterize injury

>> Fiber types, severity

• Identify where damage is

>> Focus treatment plan

• Determine stage of tissue healing

>> Does not always match time of injury

• Determine prognosis

>> Estimate recovery time

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4
Q

Electrophysiological testing precautions/contraindications? (6)

A
  • Bleeding risk: Pts. on coagulotherapy, platelets < 50,000/mm3
  • Infection risk: Lymphedema, immune compromise (HIV or other)
  • Specific sites: Pneumothorax, peritoneal insertion, biopsy site
  • Avoid stimulation on pts with implanted electrical devices,
  • pregnant pts - PATIENT DISCOMFORT!!!!!
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5
Q

Nerve conduction studies (NCS) measure? How?

A
  • Measure how well a peripheral nerve can conduct an induced stimulus = evoked potential
  • Electrically stimulate/activate nerve at various points along the superficial path of the nerve & record output at target organ
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6
Q

NCS areas for testing and their corresponding study type? (3)

A
  • Muscle = motor nerve conduction study
  • Skin = sensory nerve conduction study
  • Proximal nerve components = late responses (H-reflex & f-wave)
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7
Q

NCS measurable characteristics - what is distal latency? Useful for?

A

• Distal latency – time it takes for electrical signal to reach target tissue from the most distal point of stimulation

  • Useful for distal entrapment neuropathies (carpal/tarsal tunnel syndrome)
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8
Q

NCS measurable characteristics - what is conduction velocity? Useful for?

A

• Conduction velocity – time it takes for electrical impulse to travel between two given points along course of nerve

  • Useful for proximal entrapment neuropathies (cubital tunnel syndrome)
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9
Q

NCS measurable characteristics - what is amplitude? Useful for?

A

• Amplitude – measure of how many working axons are activated when nerve is electrically stimulated

  • Useful for systemic conditions (diabetes)
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10
Q

NCS tells us? Helps to?

A

• Tell us specifically what component of the nerve is injured

  • Helps determine prognosis & guide treatment
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11
Q

Latency & velocity are measures of? Speed of a nerve is determined by? What indicates a myelin problem? Slowing identifies what?

A
  • time
  • myelin integrity
  • Prolonged latency or slow velocity indicates myelin problem
  • Slowing identifies where the compression injury is
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12
Q

Amplitude is measure of? Output of nerve is determined by? Low amplitude indicates?

A
  • signal strength
  • axonal integrity
  • axon problem (most of the time)
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13
Q

Onset/Peak Distal latency = ? Amplitude = ? Velocity = ?

A
  • how fast nerve travels in distal segment
  • how many axons are firing when nerve stimulated
  • how fast nerve travels btwn limb segments
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14
Q

F/H Latency = ? L-R F/H latency = ?

A
  • how fast nerve travels in entire segment
  • how fast nerve travels compared to opposite limb
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15
Q

NCS good for detection of? (4)

A
  • Compression neuropathies (CTS)
  • Plexopathies
  • Demyelinating polyneuropathies (GBS)
  • Neuromuscular junction disorders (Mysethenia Gravis)
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16
Q

NCS poor for detection of? (3)

A
  • Radiculopathies (except H-reflex for S1)
  • Myopathies (muscular dystrophy)
  • Lower motor neuron disorders (ALS)
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17
Q

EMG determines? It is? Needle acts as? Detecting? Displaying? Examines what? (3)

A
  • Determines the integrity of all components of a motor unit: alpha motor neuron, axon, all muscle fibers innervated by that motor neuron
  • Invasive: needled recording electrode inserted through skin and fascia into various depths of the muscle
  • Needle acts as antenna, detecting electrical impulses of motor units & displaying as waveforms
  • Examines 3 states of the muscle: at rest, with minimal voluntary contraction, increasing effort of voluntary contraction
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18
Q

EMG Resting assessment steps? (3)

A
  • Insert needle into muscle
  • Move needle into different depths & quadrants
  • Observe electrical activity generated
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19
Q

Normal Resting Assessment - what kind of insertional activity? (2)

A
  • Brief discharge of electrical activity cause by mechanical stimulus of muscle fiber
  • Electrical silence after needle stops moving
20
Q

Abnormal Resting Assessment - decreased insertional activity indicates? Increased?

A
  • Indicates muscle fiber fibrosis/necrosis
  • Precursor to spontaneous potentials
21
Q

Another abnormal resting response? How do they appear?

A
  • Spontaneous potentials
  • Sustained waveforms that appear @ rest
22
Q

Types of spontaneous potentials? (5)

A
  • Fibrilation potentials (Fibs)
  • Positive sharp waves (PSW)
  • Fasiculation potentials
  • Complex repetitive discharges (CRD)
  • Myotonic discharges
23
Q

Fibs and PSW caused by?

A

Caused by muscle fiber denervation – electrical discharge of muscle fiber w/o input from nerve

24
Q

Fasiculation Potentials are? Often accompanied by? Only considered abnormal if?

A
  • Spontaneous irregular discharge of motor unit w/o voluntary control
  • Often accompanied by visible or palpable muscle twitch
  • consistently present and in diffuse muscles of the limbs and/or face
25
Q

CRD caused by? How do they appear?

A
  • Caused by severe/chronic muscle fiber denervation
  • Abruptly start & stop
26
Q

Myotonic Discharges caused by? How do they appear?

A
  • Caused by muscle fiber’s delayed relaxation
  • Wax & wane in amplitude and firing rate
27
Q

What is an EMG Minimal Contraction Assessment? How do you perform it? Use? (2) They examine? Each one has?

A
  • Gentle, sustained, resisted isometric contraction allows for Motor Unit Action Potential (MUAP) analysis
  • Gently move needle close to muscle fiber of active motor unit
  • Use auditory & visual feedback
  • Examine 12 – 20 different motor units in each muscle • Each MUAP has different shape
28
Q

Normal MUAP parameters - size = ? Width? Shape? What is it? How many usually?

A
  • Size = Amplitude = 300-8000 microvolts
  • Width = Duration = 3-15 ms
  • Shape = Phases
  • # times waveform crosses baseline
  • 2-4 phases
29
Q

Abnormal MUAP is indicated when?

A

Size of MUAP does not match muscle effort

30
Q

EMG moderate to maximal assessment measures? Steps? (2)

A
  • Measures recruitment of motor units
  • Without moving needle, ask patient to gradually increase level of effort to maximum
  • Observe size and number of motor units
31
Q

EMG Normal Recruitment presents how? (2)

A
  • As patient contracts stronger, additional MUAP are recruited that are larger than initial one(s)
  • All recruited MUAP keep firing to “fill up the screen”
32
Q

Abnormal Recruitment - Reduced recruitment - presents how? (3)

A
  • Initial MUAP are large
  • As effort increases few/no other MUAP activated, existing ones fire faster
33
Q

Abnormal Recruitment - Rapid recruitment - presents how? (2) Abnormal resting tone = ? Abnormal MUA? Abnormal Recruitment analysis?

A
  • With initial minimal effort, many small MUAP are recruited
  • Size or number of MUAP does not increase with increasing effort
  • acute axonal damage/denervation
  • chronic MU destruction/reorganization
  • altered muscle activation
34
Q

Clinical correlation of abnormal EMG - Decreased insertional activity = ?Fibs/PSW? Fasiculation potentials? CRD?

A
  • neurogenic muscle atrophy

– acute entrapment or systemic axonal neuropathy (abnormal)

– lower motor neuron disorder

– chronic or severe entrapment or systemic axonal neuropathy

35
Q

Clinical correlation of abnormal EMG - Myotonic discharges? Abnormal MUAP? Reduced recruitment? Rapid recruitment?

A

– myotonic or muscular dystrophies

– chronic condition with re-innervation

– chronic entrapment or systemic axonal neuropathy

– myopathy

36
Q

EMG Good for detection of? (3)

A
  • Radiculopathies
  • Myopathies (muscular dystrophy)
  • Lower motor neuron disorders (ALS)
37
Q

EMG Poor detection of? (4)

A
  • Compression neuropathies (CTS)
  • Plexopathies
  • Demyelinating polyneuropathies (GBS)
  • Neuromuscular junction disorders (Mysethenia Gravis)
38
Q

Purpose of EMG/NCS Exam? Basic principles? (3)

A
  • Aid in differential diagnosis of possible neuromuscular disorders
  • Maximize true positives and true negatives
  • Minimize false positives
  • Minimize false negatives
39
Q

Planning the EMG/NCS Exam principles? (6)

A
  • Take history
  • Perform clinical exam •

Establish differential diagnosis/working hypothesis

  • Base NCS/EMG on history/exam
  • Rule-out with “sensitive” tests
  • Rule-in with “specific” tests
40
Q

EMG/NCV Studies Should be interpreted just like any other? What kind? (3) Referring provider must?

A
  • ancillary tests
  • Films
  • Labs
  • Clinical exam - correlate with other studies and clinical exam
41
Q

MRI/X-Ray tell us about? NCS/EMG tell us about?

A
  • the structure of the neuromuscular system

• the functional integrity of the neuromuscular system

42
Q

Testing & Analysis Procedure - select? Compare? (3) Look for?

A
  • Select nerves/muscles to test based on history, clinical exam, & ancillary test findings
  • Compare NCS results to published norms and to non-involved limb
  • Compare EMG results of suspected muscles to published norms and to non-involved muscles
  • Compare values to norms to determine extent and type of injury
  • Look for patterns of abnormality to classify injury
43
Q

What is this?

A

EMG - normal resting assessment

44
Q

What is this?

A

Fibs/PSW

45
Q

What is this?

A

CRD

46
Q

What is this?

A

Myotonic Discharges

IMA (7 decks)

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