Lecture 3:Edx medicine in Podiatry – Flashcards
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How the EDX medicine consultation goes?
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1. similar format to other medical subspecialty consultations 2. focused neuromuscular and musculoskel history and physical examination 3. synthesis of a differential diagnosis based on history and physical examination 4. electrodiagnostic examination of nerves using nerve conduction studies and muscles using needle electromyography 5. formulation of a final diagnosis
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who is a qualified to be an electrodiagnostic practitioner?
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-MDs -Generally: Neurologists or Physical Medicine and Rehabilitation (PM&R) physicians -others-PT's, chiropractors
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what are the indications for an EDX medicine consultation?
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1. suspected neuromuscular or musculoskeletal disease involving the a. motor neuron b. nerve root c. plexus d. peripheral n e. neuromuscular junction f. muscle
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complaints suggestive of neuromuscular or musculoskeletal pathology
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1. numbness or tingling 2. decreased sensation 3. pain 4. cramping or spasms 5. weakness 6. gait difficulty 7. fatigue
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utility of an EDX medicine consultation
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1. clarify etiology of symptoms -radiculopathy vs. plexopathy vs neuropathy -clarify the type of neuropathy -identify a potential source of pain 2. localize a PNS lesion 3. assist in therapeutic decision making 4. predict neurological prognosis 5. exclude other disorders
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EDX testing is used to assess the function and integrity of the __.
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peripheral nervous system
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3 components of an EMG
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1. nerve conduction studies 2. electromyography 3. special tests (repetitive nerve stimulation, single fiber evaluations)
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parts of the nerve conduction study
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1. motor nerves 2. sensory nerves 3. repetitive stimulation
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parts of the electromyography
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1. qualitative 2. quantitative 3. single fiber
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responses of the nerve conduction study
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1. compound motor action potential (CMAP) 2. sensory nerve action potential (SNAP) 3. F wave 4. H reflex
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nerve conduction studies: basic elements
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1. motor nerve conductions 2. sensory nerve conductions 3. late responses -F wave latency measures -H reflexes
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measure of conduction time from stimulation across a nerve segment through the neuromuscular junction to initial activation of muscle fibers
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motor latency
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measure of conduction time of action potential from stimulation across a nerve segment
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sensory latency
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measure of the number of activated muscle fibers
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motor amplitude
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measure of the number of activated sensory axons
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sensory amplitude
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measure of the velocity of the fastest conducting axons
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conduction velocity
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2 nerve conduction late responses
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1. f wave latency 2. h reflex
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F wave latency has a retrograde "rebound" motor impulse. It travels the full length of motor axon and back. Tells info about __ segments. Limited sensitivity/specificity.
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proximal
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H reflex has an afferent(sensory axons(group 1a fibers) and efferent pathway (alpha motor neurons). It follows _____. ____ latency most valuable.
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muscle stretch reflex arc. side to side
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how do you test neuromuscular junction?
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repetitive nerve stimulation
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In Repetitive Nerve Stimulation, (3 Hz stimulation) 1. stimulate nerve with train of supramaximal stimuli before and after ___ 2. record from muscle 3. attention to technical factors impt 4. more sensitive recording from ___ muscles.
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exercise proximal
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In needle electromyography is the needle disposable?
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yes, single use
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how many muscles are examined in needle electromyography?
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multiple muscles -combination of muscles tested, dependent upon clinical question -level of discomfort is MILD
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in needle electromyography, how should the muscle sound at rest?
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silent
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if the muscle is not silent at rest, what does this mean?
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spontaneous activity may signal a nerve or MUSCLE abnormality
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during activity how can you distinguish between diseases by NEEDLE ELECTROMYOGRAPHY
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the electrical shape and pattern of the response can distinguish bw nerve and muscle disease
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what are the parameters evaluated in needle electromyography?
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1. insertional activity 2. spontaneous activity 3. motor unit configuration 4. motor unit recruitment 5. interference pattern
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insertional activity -burst of electrical activity as needle is inserted into muscle - due to disruption of muscle fiber membranes - prolonged with ____, some muscle diseases
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denervation
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spontaneous activity -fibrillations, positive sharp waves, fasciculations -hallmark of _____
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denervation, muscle membrane irritation
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types of spontaneous activity
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1. fibrillation potentials 2. positive sharp waves 3. fasciculations 4. complex repetitive discharges 5. myokymia 6. myotonia
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scale for grading spontaneous activity
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0-4+
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+/-
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fibs/PSWs that are not persistent
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1+
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persistent fibs PSWS in atleast 2 areas
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2+
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persistent fibs/PSWs of moderate #'s in 3 or more areas
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3+
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persistent fibs/PSWs of large #'s but NOT obscuring baseleine
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4+
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baseline obliterated in all areas examined
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Motor unit configuration 1. muscle is volitionally activated at diff force levels 2. single motor units are assessed 3. ____: a motor axon and all its muscle fibers 4. motor unit configuration: amplitude, duration, morphology
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single motor unit
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Motor unit recruitment: -a pattern of motor unit activation with increasing ____ ___
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volitional activation
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interference patterns: motor unit pattern with ____ ___ _____
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full voluntary activation
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specialized EDX testing does what?
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1. interference pattern analysis 2. quantitative motor unit analysis 3. single fiber analysis 4. segmentation analysis 5. cranial nerve testing 6. brainstem and somatosensory evoked potentials 7. pelvic floor and respiratory muscles
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things an EMG can diagnose
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1. normal 2. radiculopathy 3. plexopathy 4. neuropathy 5. myopathy 6. widepread denervation (MND)-amyotrophic lateral sclerosis leugerigs disease 7. Disorders of neuromuscular transmission (myostanis gravis, eaton lambert disease)
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EDX findings
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1. acute vs chronic vs. acute & chronic 2. mild vs. moderate vs. severe 3. anatomic location -root, plexus, nerve, neuromuscular junction, muscle 4. distribution -polyradiculopathy -trunk, cord -mono vs multiplex vs distal symmetric
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1. mildest, transient disruption of nerve function 2. ischemic, metabolic, or microstructural abnormalities 3. axonal integrity maintained 4. reversible failure of nerve conduction 5. most often compressive/ischemic 6. normalizes in hours to weeks
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neuropraxia
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1. disruption of the axon and myelin sheath 2. supporting and ct tissue spared 3. recovery -may be minimal, incomplete, or full -dependent upon severity and length of nerve injured - via axonal sprouting and regeneration -growth rate: 1-3 mm/day -crush, stretch most common causes -slower, usually months
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Axonotmesis
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1. nerve transection -wallarian degeneration: when transect the nerve, nerves cant be reconnected, occurs weeks after injury 2. disruption of axons, myelin sheaths, and supporting ct tissue 3. most commonly due to transection, severe crush , avulsion 4. recovery: -requires juxtaposition of transected ends and axonal growth - early surgical intervention and juxtaposition often needed
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neurotmesis
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neuronal degeneration DISTAL to injury site: 1. follows axonal transection 2. due to isolation of distal nerve segment from the cell body 3. __ ___ of the AXON and SHEATH
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WALLARIAN DEGENERATION
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Neuronal Degeneration: Proximal to Injury site 1. degeneration back to the ____ 2. if very proximal , ____ in the cell body of the transected axon may occur
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1. nearest node of Ranvier 2. chromatolysis
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3 common causes of nerve trauma
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1. penetrating trauma 2. anatomic and extrinsic compression 3. iatrogenic injury
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meralgiaparesthetica involves what nerve?
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Lateral Femoral Cutaneous Nerve
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meralgiaparesthetica is caused by what?
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1. gynecologic / obstetrical procedures 2. anterolateral thigh intramuscular injections 3. obesity 4. pregnancy 5. tight clothing & work belts
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tibial nerve injury is caused by what?
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1. knee dislocation 2. ankle fractures 3. posterior tarsal tunnel syndrome at ankle
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peroneal nerve injury is caused by what?
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1. knee dislocation 2. knee arthroplasty/arthroscopic knee surgery 3. fibular neck fractures 4. retrograde popliteal artery puncture 5. total knee replacement 6. acupuncture 7. prolonged squatting 8. leg crossing 9. bungee jumping 10. braces/plaster casts
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neuropraxia vs. more severe injury cannot be distinguished for first __ days
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7 to 10 days
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initial studies 1. nerve conduction studies -motor CMAP amplitudes decline first (__ days)
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usually in 5 days
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what else declines in the nerve conduction studies?
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precede sensory SNAP decline by 2-3 days
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initial studies. 2. EMG what change confirms axonal injury? when does it appear?
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1. acute denervation change -spontaneous activity- fibrillations and positive sharp waves 2. within 14 to 21 days after axonal disruption
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what studies are needed to distinguish neuropraxia from axonotmesis?
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serial studies can help determine indications for surgical repair/release
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Progressive _______ declines on the NCS in the days following injury support axonal loss.
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amplitude
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Reinnervation can be gauged by EMG studies. reinnervation change begins to appear after how long?
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2 months
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serial increases in motor __ accompany recovery
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amplitude
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failure of reinnervation=
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poor prognosis assessed by EMG
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sensory nerve conductions -may take longer to reappear if absent. -__ improvement also correlates with axonal repair
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amplitude
