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neuro ex 1 > electrodiagnostic studies > Flashcards

electrodiagnostic studies Flashcards

1
Q

what are EMG used to determine? what tests does it include?

A

used to determine if theres a prob IN PERIPHERAL nervous system. if so where? can it be dx? **

EMG: electromyography

NCS: nerve conduction studies

EMG= can be used to describe both

they are extension of neurological and musculoskeletal examination

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2
Q

who performs electrodiagnostic studies

A

physiatrist, neurologist, physical therapists

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3
Q

why is important to do EDX? **

What are some reasons to use EDX

A

represents the PHYSIOLOGICAL CHANGES to the puzzle

****
 Establish correct dx
localize lesion
determine tx
provide info for prognosis
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4
Q

when should electrodiagnostic studies be performed

A

EMG/NCS should NOT be performed prior to 21 days–it takes about 21 days for the full injury to occur after injury or onset of symptoms; if you do it earlier may miss the pathology

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5
Q

failure of nerve conduction across the affected nerve segment combined w/ normal nerve conduction above and below the segment.

NO wallerian degeneration involved

Good prognosis

A

Neurapraxia

similar to “bruise” to nerve

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6
Q

Disruption of axon continuity with Wallerian degeneration but perineurium and/or endoneurium are still intact

A

axonotmesis

some disruption to axon

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7
Q

Neurotmesis

A

require nerve surgery

complete transection/severence through the nerve; carries poor prognosis and surgical repair is needed for functional recovery

endoneurium and perineurium disrupted

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8
Q

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

A

Wallerian degeneration

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9
Q

what are the contraindication for electrodiagnostic studies

A

severe bleeding disorder(high INR)

NCS is contraindicated in patient with automated cardiac defibrillator

Cellulitis (skin/soft tissue infection)–due to infection

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10
Q

stimulation of peripheral nerve while recording from a muscle innervated by that nerve

A

motor nerve conduction (CMAP)

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11
Q

stimulation of cutaneous or mixed nerve while recording from a mixed or cutaneous nerve

A

sensory nerve conduction (SNAP)

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12
Q

latency:NCS

A

interval between onset of a stimulus and onset of response

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13
Q

Amplitude:NCS

A

max voltage difference between two points, it is proportional to the number and size of nerve fibers that are depolarized providing an estimate of the amt of nerve tissue that is electrically active

Tells how much info nerve is transmitting*

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14
Q

NCS: Conduction velocity

factors that affect conduction

what can decreased temp could affect?

A

Speed at which nerve fibers carry electrical stimulus between two sites

cV determines how many axons are conducting.
More useful for distal peripheral nerves

factors:
Age: infant=1/2 adult, 5 yrs=adult, 60=10% decline per decade

Temp: ideal of upper extremity is 32 deg C, and lower extremity of 30 deg C

Decrease temp:
prolong latency
INCREASED amp
decreased CV

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15
Q

what is most useful for detecting proximal nerve pathologies

A

late responses: F waves and H reflex

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16
Q

what response is usefult for detecting gullian barre syndrome

A

Late response: F wave

17
Q

which reflex is Very good at distinguishing between S1 from L5 radiculopathies and often difficult with physical exam/EMG due to overlapping myotomes

how does it distinguish the two?

A

H reflex:monosynaptic spinal reflex

H reflex will be ABNORMAL in S1 radiculopathy

18
Q

insertional response for EMG studies

A
  1. Insertional activity :
    - increased: denervated muscle/myopathy

-normal/decreased: replacement of fat/connective tissue

=

19
Q

spontaneous activity of EMG

when is it pathologic?

A

pathologic if abnormal electrical activity occurs at rest:
Fibrillation potential**
positive sharp waves,**

fasciculations potentials , myotonic dischrages, complex reptetitive discharges, myokymic dischrages, neuromyotonic discharges

20
Q

voluntary activity in EMG

A

appearance of motor unit AP–one axon and all its muscle fibers

observe amplitude, duration, recruitment

21
Q

Interpreting Normal EDX

A

does not necesssary mean normal function. just means that sensitivity and specificity of exam cannot define a specific problem by available technique

22
Q

what is one of the most important physical findings that will continue onto NCS/EMG

A

Reflex loss or asymmetry: involuntary response should be reflexive regardless–with the loss would indicate neuro prob

23
Q

If you suspect an L5 radiculopathy in your patient, what test would you order:

  1. for the best view of pathology?
  2. objectively demonstrate physiologic changes in nerve or muscle?
A
  1. pinched nerve: best test is MRI

2. EMG/NCS

24
Q

which nerve root does H reflex travel on?

A

S1

25
Q

How do you know if its L5 radiculopathy

A

H reflex is normal on both sides

26
Q

what are the 2 main parts of EDX? and what are their functions?

A

NCS: nerve will be stimulated/shocked and recorded with surface electrodes (NO NEEDLE)!

EMG: NEEDLE electromyography: muscle membrane activity will be evaluated at rest with contraction with a needle inserted in muscle

Electrical activity recorded by needle electrode in muscle fibers firing

displays ‘real time’ picture and sounsd of electrical activity of the muscle membrane

NCS/EMG provide info about injusred or diseased nerve pathophysiology (demyelination vs axonal lsos, or complete severing of nerve)

this is just a PHYSIOLOGIC piece to puzzle, does not DX the cause!

27
Q

Hypereflexia vs hyporeflexia damage where?

A

Central: HYPERreflexia

Peripheral: HYPO reflexia

28
Q

atrophy is Central or peripheral nerve damage?

A

peripheral nerve damage

29
Q

positive babinski indicates central or peripheral nerve damage:

A

CENTRAL

30
Q

what are the symptoms and physical findings for NCS/EMG

A

Symptoms: numbness, tingling, pain, weakness

Physical findings: reflex loss or asymmetry, weakness, sensory loss, limp, muscle atrophy

31
Q

purpose for NCS?

where are the waveforms generated from?

A

determine if theres a pathology of nerve or nerves, if so what level the pathology originates

studies generated in peripheral nervous system

32
Q

whats a way to localize lesion

A

comparison of conduction between two segments of same nerve

33
Q

what are good criterias for ordering or performing EDX

A

is it necessary?

will it help determine dx, tx, or prognosis?

is there a test that is less intrusive or more cost effective with the same info?

neuro ex 1 (14 decks)

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