Transcript EMG Testing - Ramsey Rehabilitation Inc.

EMG Testing
Edison H.Wong, M.D., M.S.
Center for Pain & Medical Rehab, P.C.
Ramsey Rehab Lecture Series
September 29, 2009
EMG testing
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What is it?
Who does it?
Why is it needed?
What does it measure?
What are results like?
What is actually done?
How can testing be done more easily?
What is it?
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EMG is a type of Electrodiagnostic testing
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Use of electrical testing to diagnose disorders of
muscles and nerves
EMG stands for
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Electromyelogram = graph of electrical activity in
muscles
Electromyography = study of…
Electromyograph = instrument used in…
Let’s be more specific
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Nerves – peripheral nervous system
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Sensory nerves – light touch, proprioception
Motor nerves – nerves control skeletal muscles
Muscles – skeletal muscles
Who does it?
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Electromyopraphers or specialists in
electrodiagnostic medicine
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Physiatrists or specialists in physical medicine and
rehabilitation
Neurologists
May or may not be board certified: 2 boards
Technicians/Physical Therapists may perform
limited portions
No Chiropractors, other practitioners
Why is it needed?
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Medical gold standard test for nerve function
(physiological)
Better assessment of nerve damage than
current imaging measures
Does not replace imaging studies (anatomical)
One of many diagnostic tools used for
neuromusuclar disorders
Why is testing needed?
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Symptoms of nerve damage
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Numbness and tingling
Funny sensations
Weakness, fatigue, clumsiness
Pain
Signs of nerve damage
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Loss of or change in reflexes
Falls, gait difficulty
What does it measure?
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Nerve function is not a simple measure
Two parts of test
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NCS/NCVS – nerve conduction study
Needle EMG
NCS uses external electricity to measure the
body’s electrical pathways
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Amplitudes
Conduction velocities
Sensory and motor nerves
Importance of NCS
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Nerves are comprised of axons and myelin
sheaths
Conduction velocity affected by myelin
sheath; slowing = damage
Amplitudes matter also
NCS tells only part of the story
Needle EMG
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Measures body’s intrinsic electrical activity
generated by muscles
Spontaneous activity
Voluntary activity
Amplitudes
Frequencies
Patterns of electrical activity
Audio and visual information
What are results like?
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Dependent on the question asked by ordering
physician
Dependent on skill of examiner
Specific diagnoses: i.e., Carpal Tunnel
entrapment of Median Nerve
Non-specific diagnoses: peripheral
polyneuropathy
Nerve Damage
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Amount of damage - relative
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Mild, moderate, severe
Temporary (myelin) or permanent (axon)
Location of damage
Chronicity
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Acute or ongoing
Chronic/long term
Can results vary?
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By skill of examiner
Limitations of testing imposed by
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Patient – voluntary or involuntary
Conditions – room, equipment, etc.
Do not depend on patient symptoms!
Lack of signal does not always mean
abnormality
Interpretation matters
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diagnoses don’t read; “greedy” patients
What is actually done?
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NCS
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Superficial electrodes
Stimulus probe – “zapper”
Electrical stimuli applied by individual shocks
Electricity doesn’t care where it goes
Level of stimuli safe, regulated by machine
Other limbs may be done for comparison
What is actually done?
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Needle EMG – Monopolar vs. Concentric
Individual muscles studied
Sampling: different nerves, proximal vs distal
Technique matters for discomfort
Relaxation matters
Paraspinal needle study important
How can things be done more easily?
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Expectations given to patient – like they do for
MRIs
Preparation: none!
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Don’t starve
Don’t be a martyr
Avoid lotions/creams – skin moisturizers!
Anxiety – premedicate
Pain – premedicate or bring with you
Temperature – cold makes a difference
How can things be done more easily?
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Relax – radio or listening device
Special considerations:
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Lymphedema
Anticoagulation
AV fistulas
Implanted devices: AICD/pacers, stimulators
Don’t be afraid to ask questions
Get the test done but do it right!