electrodiagnosis for medical student 2017
TRANSCRIPT
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Pariya Wimonwattrawatee, MD.
Electrodiagnosis
• Electro + Diagnosis
• Nerve conduction studies
• Needle electromyography (EMG) studies
• Evoked potentials (EPs)
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
Nerve Conduction Studies (NCS)
• Stimulate the nerves
How fast & how well
the nerve responded
• Motor & sensory
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
Axonal Neuropathy
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Pariya Wimonwattrawatee, MD.
Demyelination
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Pariya Wimonwattrawatee, MD.
Conduction Block
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
Physiological Factors Affecting Nerve Conduction
• Age: <5, >50 yo
• Temperature
– UE: 32oC
– LE: 30oC
• Location: proximal / distal
• Nerve size
• Height
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
Electromyography (EMG)
EMG vs NCS
• Use a needle
• Not use any electrical shocks
• Direct information about the muscles & indirect information about the nerves
– Inflammatory myopathy
– Axonopathy
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
• Insertional activities
• Spontaneous activities
• Motor unit action potentials
• Recruitment pattern
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
Spontaneous activities
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
Motor Unit
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
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Pariya Wimonwattrawatee, MD.
Nerve Injury
• Wallerian degeneration
– Sensory and motor electrical responses similarly remain normal
– Several days – weeks
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Pariya Wimonwattrawatee, MD.
Day 1 after a Lesion
• NCS:
– Distal to the lesion: not changed
– Proximal to the lesion: small-amplitude or absent response
• EMG:
– Severe: reduced or discrete recruitment
– Mild: normal
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Pariya Wimonwattrawatee, MD.
Days 7 to 10
• Wallerian degeneration
• Complete lesion: SNAPs will be absent
• Incomplete lesions: less marked changes
• Distinguish a neurapraxicinjury from an axon loss lesion
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Pariya Wimonwattrawatee, MD.
Days 14 to 21
• Needle EMG:
– Increased insertional activities
– Fibrillation potentials & positive sharp waves in proximal muscles
• Persistent for several months to several years
– Not forever
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Pariya Wimonwattrawatee, MD.
Reinnervation
• Axonal regrowth
• Axonal sprouting
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Pariya Wimonwattrawatee, MD.
Axonal Regrowth
• 1 mm/day or 1 inch/month
• Short-duration, small-amplitude potentials (nascent potentials)
• Become larger, more polyphasic & longer in duration
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Pariya Wimonwattrawatee, MD.
Axonal Sprouting
• Polyphasicity & increased duration
• large-amplitude, long-duration MUAPs
• Usually persist indefinitely
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Pariya Wimonwattrawatee, MD.
Advantage of EDx
• Diagnosis– Structure / function
• Pathology– Axon / myelin
– AHC / nerve (motor, sensory) / NMJ
• Degree– Mild / moderate / severe
– Neurapraxia / axonotmesis
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Pariya Wimonwattrawatee, MD.
• Localize the lesion
• Determine treatment
• Disease progression
• Provide information about the prognosis
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Pariya Wimonwattrawatee, MD.
• WHEN?
• WHY?
• Further physical examination
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Pariya Wimonwattrawatee, MD.