Sachen: Introduction to Electrodiagnostic Medicine Flashcards
Indications for an EDX consultation
-suspected nm or msk disease involving the motor neuron, nerve root, plexus, peripheral nerve, nm junction, or muscle
complaints suggestive of nm or msk pathology
- numbness or tingling
- decreased sensation
- pain
- cramping or spasms
- weakness
- gait difficulty
- fatigue
Utility of an EDX medicine consultation
- clarify etiology of symptoms
- localize a pns lesion
- assist in therapeutic decision making
- predict neurological prognosis
- exclude other disorders
What is EDX used for?
- to assess the function and integrity of the PNS
- considered an extension of a comprehensive clinical evaluation that includes a detailed history and specialized physical examination
what are the components of EMG?
- nerve conduction studies (NCS)
- electromyography (EMG)
- special tests like repetitive nerve stimulation
What happens with nerve conduction studies?
- peripheral nerves are stimulated with a controlled electrical stimulus
- responses are recorded: compound motor action potential, sensory nerve action potential, F wave, H reflex
What are the nerve conduction studies basic elements?
- motor nerve conductions
- sensory nerve conductions
- late responses: F wave latency measures, H reflexes
What are the measured parameters in nerve conductino studies?
- motor latency
- motor amplitude
- sensory latency
- sensory amplitude
- conduction velocity
Motor latency
-measure of conduction time from stimulation across a nerve segment through the nm junction to initial activation of muscle fibers
Motor amplitude
-measure of the number of activated muscle fibers
Sensory latency
-measure of conduction time of AP from stimulation across a nerve segment
Sensory amplitude
-meausure of the number of activated sensory axons
Conduction velocity
-measure of the velocity of the fastest conducting axons (motor and sensory)
What is needle electromyography?
- needle electrode is inserted into the muscle
- disposable, single use
- multiple muscle are accessible for examination
- combo of muscles tested
- level of discomfort is mild which is nice
- muscle is studid at rest and at different levels of sustained, voluntary contraction
- at rest, the muscle should be silent, any spontaneous activity may signal a nerve or muscle abnormality
During activity, what can distinguishe between nerve and muscle disease?
-the shape and pattern of the response
What parameters are evaluated in needle electromyography?
- insertional activity
- spontaneous activity
- motor unit configuration
- motor unit recruitment
- interference pattern
What is insertional activity
- burst of electrical activity as needle is inserted into muscle
- due to disruption of muscle fiber membranes
- prolonged with denervation, some muscle diseases
What is spontaneous activity?
- fibrillations, positive sharp waves, fasciculations
- hallmark of denervation, muscle membrane irritation
How do you grad the spontaneous activity of needle electromyography?
- 0: no fibs/psw’s
- +/-: fibs/PSWs that are NOT PERSISTENT
- 1+: persistent fibs/PSWs in AT LEAST 2 AREAS
- 2+ persistent fibs/PSWs of moderate #’s in 3 or more areas
- 3+: persistent fibs/PSWs of large #’s but NOT OBSCURING BASELINE
- 4+:BASELINE OBLITERATED in all areas examined
What do we look at when talking about motor unit configuration?
- muscle is volitionally activated at different force levels
- single motor units are assessed
- single motor unit: a motor axon and all its muscle fibers
- Motor unit configuration: amplitude, duration, morphology
Motor unit recruitment
-pattern of motor unit activation with increasing volitional activation
Interference patterns
-motor unit pattern with full voluntary activation
Are EDX a replacement for H and P?
-no, just a supplement!
Are EDX results time-dependent?
-yes
Are EDX studies standardized?
- no
- may be modified by the practioner to answer the diagnostic question
What does EMG study?
-the integrity of the peripheral nervous system
what direction is a positive sharp wave going in on the screen?
-down
What does a fibrillation look like?
-kinda like an ECG reading
what do we mean when something is poly phasic?
-it has a lot of turns on it
what did he point out when he said that EMG is time dependent?
-if a nerve get’s severed for example at the elbow, function tests will still be ok for a little bit because nerve atrophy hasn’t happened yet
