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Electrophysiology > Unit III > Flashcards

Unit III Flashcards

1
Q

What section supports EMG/NCS in the KY state practice act?

A

KRS 327.10

“…evaluations performed to determine…nerve and muscle function including subcutaneous bioelectrical potentials…”

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2
Q

T/F: Medicare recognizes and reimburses EMG services performed by ABPTS certified and non-certified clinicians

A

False; only certified PTs are reimbursed for EMG testing

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3
Q

What is the primary goal of rehabilitation?

A

optimization of motor control

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4
Q

What is a motor unit?

A

anterior horn cell > nerve root > plexus > nerve (proper) > NMJ > muscle fibers innervated by nerve

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5
Q

What is the relationship between lateral ankle sprains and the tibialis posterior?

A

86% of patients with grade III demonstrated denervation of the gastrocnemius/soleus complex; patients have difficulty eccentrically lowering their foot to the ground

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6
Q

What is the relationship between proximal shoulder dislocations and proximal humeral neck fractures and EMG changes?

A

54% of patients demonstrated EMG changes following proximal humeral neck fractures

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7
Q

What is the effect of NMES on denervated muscles?

A

delays reinnervation if applied too soon

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8
Q

How does EMG testing assist clinical decision-making?

A
  • diagnosis
  • prognosis
  • motor unit recruitment
  • aggressiveness
  • timeframes
  • refer/triage
  • when the patient is safe to return to sport, work, etc.
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9
Q

What are the three important physiology principles?

A
  • separation of charge
  • “all-or-none” depolarization
  • volume conduction
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10
Q

Resting membrane potential is maintained by:

A
  1. semi-permeable membrane = passive flow of ions

2. sodium-potassium pump (active transport)

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11
Q

What are the three functions of myelin?

A
  1. speeds up conduction
  2. conserves energy
  3. conserves space
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12
Q

What are the three categories of nerve injury described by Seddon in 1945?

A
  1. neuropraxia
  2. axonotmesis
  3. neurotmesis
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13
Q

Neuropraxia

A

transient loss of myelin

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14
Q

Axonotmesis

A

degeneration/injury to the axon; Wallerian degeneration occurs

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15
Q

Neurotmesis

A

injury to the epineurium nerve sheath

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16
Q

Signs of denervation

A
  • positive sharp waves

- fibrillations

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17
Q

What changes occur in the cell body following denervation?

A
  • central chromatolysis

- nissl substance gets darker

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18
Q

Signs of nerve regeneration are indicated by:

A

polyphasic voluntary motor units

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19
Q

Re-innervation

A
  • nodal sprouts
  • terminal sprouts
  • Early (nascent polyphasic potentials and RFR)
  • Late (RFR and giant complex polyphasics)
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20
Q

Sources of error associated with EMG instrumentation

A
  • dirty electrodes
  • broken lead wires
  • poor ground
  • too much electrode gel
  • fluorescent lights
  • cell phone signal
  • incorrect connection of electrodes at pre-amp box
  • power line load
  • the motor of high-low tables
21
Q

Segmental demyelination

A
  • nerve conduction study
  • abnormal almost immediately after onset
  • mild to moderate compression, auto-immune disorders, etc.
22
Q

Axonal degeneration

A
  • needle EMG
  • 21 days post-onset (7-14 days for paraspinals)
  • severe compression, ischemia, inflammation
23
Q

EMG testing principles

A
  • examine motor and sensory when possible
  • test several segments of nerve suspected
  • may need to test upper and lower limb nerves
  • test when likely to obtain the optimal diagnostic yield (≥21 days)
24
Q

Influencing factors

A
  • upper vs. lower extremity
  • age = decreased 10% per decade after 60 YOA
  • temperature
  • anatomical anomalies
25
Q

NCS abnormalities

A
  • slowed latency = myelin issue
  • reduced amplitude = axonal issue
  • attenuated duration = sawtooth appearance
  • slowed conduction velocity
  • absent response
26
Q

Repetitive stimulation will demonstrate a ___ abnormality

A

neuromuscular junction

27
Q

Normal NCS

A

≤ 4.0 milliseconds

28
Q

Treatment for mild CTS

A
  • prolonged DML = 4.0-5.4

- observation, conservative Rx

29
Q

Treatment for moderate CTS

A
  • prolonged DML = 5.4-7.2

- conservative modalities first; surgery later if needed

30
Q

Treatment for severe CTS

A
  • prolonged DML = >7.2
  • surgery strongly recommended
  • increased fibrillations, polyphasic VMUs, or electrical silence
31
Q

Treatment for severe CTS

A
  • prolonged DML = >7.2
  • surgery strongly recommended
  • increased fibrillations, polyphasic VMUs, or electrical silence
32
Q

Steps of EMG testing

A
  • insertion (300 milliseconds)
  • Rest
  • Minimal contraction
  • Maximal contraction
33
Q

Abnormal EMG findings at rest

A
  • 1+ = induced by electrode movement
  • 1-2+ = spontantoue appearance
  • 3+ = many spontaneuous potentials
  • 4+ = screen filled with abnormal potentials
34
Q

Reduced insertional activity

A
  • resistance to needle movement in tissue
  • associated with chronic denervation - fibrotic degeneration, fat infiltration
  • “woody” feel
35
Q

Increased insertional activity

A
  • after cessation of needle movement

- associated with myotonic disorders, myogenic disorders, and denervation

36
Q

Smaller than normal amplitudes may be the result of:

A

axonal degeneration or myopathy

37
Q

What is the most sensitive imaging study for spinal stenosis?

A

CT myelography

38
Q

Typical nEMG findings in lumbar spinal stenosis

A
  • early = little if any abnormality
  • over time = conduction block, axonal loss, demyelination or re-myelination
  • first change may be absent H-reflexes
  • Bilateral findings in up to 50-87%
39
Q

Non-invasive quantitative EMG

A
  • patient follow-up
  • children
  • measure response to Rx
40
Q

Rationale for EMG biofeedback

A
  • adjunct to a total rehab program
  • control of motor unit activity with EMG ( recruitment, relaxation)
  • contraindications (gel, tape skin irritations, and metabolic confusion)
41
Q

Recruitment EMG Biofeedback

A
  • peripheral nerve injury
  • muscle weakness (post-immobilization, joint surgery, deconditioning)
  • muscle transfers
  • postural control
42
Q

Relaxation EMG Biofeedback

A
  • stress-related ANS arousal
  • pain (migraine, tension headaches)
  • spasticity
  • rigidity (i.e. adult onset torticollis)
43
Q

EMG Biofeedback Goals

A
  • increase amplitude
  • increase the total number of MUs firing
  • increase frequency of MU firing
  • restore joint movement
  • return motor unit recruitment to normal to protect and move joint properly
44
Q

Appropriate patient selection for EMG biofeedback

A
  • Does patient have motor impairment?
  • Does motor impairment seem likely to benefit from biofeedback information?
  • Does patient demonstrate the ability for voluntary control?
  • Is patient sufficiently motivated and cognitively aware to use feedback info?
45
Q

Appropriate patient selection for EMG biofeedback

A
  • Does patient have motor impairment?
  • Does motor impairment seem likely to benefit from biofeedback information?
  • Does patient demonstrate the ability for voluntary control?
  • Is patient sufficiently motivated and cognitively aware to use feedback info?
46
Q

Myopathy will demonstrate what on EMG?

A

smaller than normal amplitudes, highly polyphasic, short duration MUPs

47
Q

Normal MUP Duration

A

3 to 12 msec

48
Q

According to Haig et al, what is the most significant predictors of LSS?

A

paraspinal mapping and absent tibialis H-reflex

Electrophysiology (2 decks)

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