Electrodiagnostic Studies Flashcards
What 3 abnormal spontaneous activities seen on EMG arise from motor unit pathology
- Fasciculations
- Myokymic discharges
- Neuromyotonic discharge
What happens to SNAP in ALS
Normal
Amplitude of fibs and PSWs
Fibs = ~300 microvolts PSWs = ~1000 microvolts
What is the initial deflection of myotonic discharge
Varies - can be positive deflection or biphasic or triphasic
What 2 muscles can you use for H-reflex
FCR and gastroc-soleus
what type of neuropathy is seen in diabetic neuropathy
axonal and demyelinating sensory motor neuropathy
Normal amplitude of a MUAP
1 mV
what is the correlation between firing frequency and recruitment pattern
increased firing frequency = decreased recruitment
Are large amplitude long duration MUAPs seen in myopathic or neuropathic processes
Neuropathic
Normal duration of a MUAP
5-15 ms
Are short duration small amplitude MUAPs seen in myopathic or neuropathic processes
Myopathic
in the newborn, nerve CV are what percentage of adult values
50%. 1 yo = 75% of adult values
What denervation potential sounds like dive bomber
Myotonic discharge
what type of neuropathy is seen in alcohol neuropathy
axonal sensory motor neuropathy
SSEPs only evaluates nerve fibers that sense _________ and __________
Vibration and proprioception
In a neuropathic process, what happens to recruitment pattern
Reduced recruitment
What 4 abnormal spontaneous activities seen on EMG arise from muscle or nerve pathology
- Fibs
- PSWs
- Myotonic discharge
- Complex repetitive discharge
What happens to MUAP amplitude, duration, and recruitment in myopathy?
Small amplitude, short duration, early recruitment
What nerves are commonly used for testing in somatosensory evoked potentials
Median nerve for upper limb and tibial nerve for lower limb
What denervation potential sounds like motor boat
CRDs
What do somatosensory evoked potentials test?
Ascending sensory pathways to the somatosensory cortex
In normal recruitment, what is the frequency of firing rate
Every 5 Hz another motor unit fires
Which denervating potential sounds like marching soldiers
Myokymic discharge
Miniature end plate potentials is also known as
Endplate noise
side to side latency of H-reflex is significant if it is greater than what?
1.5 ms
Are SSEPs done with submaximal or supramaximal stimulation?
Submaximal
normal gain for sensory nerve study
20 microvolts/division
What happens to conduction velocity if measured distance is falsely low
Conduction velocity will be falsely decreased. (Measured distance is 10cm, when it is actually 15cm will give you a slow conduction velocity when it is actually faster)
Amplitude of miniature endplate potentials
10 to 50 microvolts
Which denervating potential resembles a MUAP
Fasciculations
What causes miniature end plate potentials
Release of individual quanta of ACh
what happens to latency, CV and amplitude in a cold limb
latency increases
CV decreases
amplitude increases
what type of neuropathy is seen in paraneoplastic syndrome
axonal sensory neuropathy
What 3 main problems do SSEPs monitor for
- Peripheral nerve injuries
- Central nervous system lesions
- Intraoperative spinal surgery monitoring
