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Neurophysiology Book 1, Section 8

CME Financial Disclosure Statement

I, or an immediate family member including spouse/partner, have at present and/or have Clinical Neurophysiolgy: had within the last 12 months, or anticipate Electromyography & Nerve Conductions NONO financial interest/arrangement or Matthew McCoyd, MD affiliation with one or more organizations that could be perceived as a real or apparent Assistant Professor of Neurology conflict of interest in context to the design, [email protected] implementation, presentation, evaluation, etc of CME activities ––MatthewMatthew McCoyd

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Question 1 Question 2

A 78 year old female with history of breast cancer A 34 year old male presents with two weeks of right presents with left arm weakness. Exam reveal foot weakness. Examination is notable for weakness of right ankle dorsiflexion and inversion. weakness of left shoulder abduction and forearm Plantarflexion and eversion are normal. What are flexion. EMG is notable for myokymic discharges. the most likely findings on the nerve conduction What is the most likely mechanism of injury? study? 1. C5/C6 radiculopathy due to herniated disc 1.1. Absent right superficial peroneal SNAP response 2. PostPost--radiationradiation plexopathy 2.2. Absent right sural SNAP response 3. Metastatic invasion of the brachial plexus 3.3. Conduction block across the fibular head 4.4. Spontaneous activity in the lumbar paraspinal 4. Left axillary neuropathy muscles

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Question 3 Question 4

A 67 year old male present A 38 year old female with complaint of slowly presents for progressive progressive weakness. difficulty walking and distal Repetive stimulation reveals numbness. Proximal the following. What is the stimulation of the right tibial most likely cause of his nerve results in the following weakness? CMAP. What is the most 1.1. Presynaptic blockade of likely diagnosis? ACh release 1. HSMN I (CMT) 2.2. Presynaptic blockade of 2. HSMN II calcium channels 3. Vitamin B12 3.3. Postsynaptic blockade of polyneuropathy ACh receptors 4. CIDP 4.4. Failure of AChRs to congregate at the NMJ

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Clinical Neurophysiolgy Clinical Neurophysiology

Basic Tenets: Goals of the EDX 1. EMG/NCS is an extension of the history of physical examination….it confirms your suspicions Localization Severity 2. You should never be “surprised” by the findings Muscle Nerve NMJ 3. If the study does not match your clinical index of suspicion, something is wrong with your EMG (likely technical) Fiber Type Pathology Temporal Course 4. Your “answer” should be clinically relevant

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Goals of EDX: Localization Goals of EDX: Fiber Type

EMG/NCS is a test of Myelinated Diameter C.V. m/s the Peripheral Nervous Cutaneousafferents 6-12 µm 35-75 System Muscle afferents 12-21 µm 80-120 Neuron (DRG, AHC) Muscleefferents 6-12 µm 35-75 Nerve Root Unmyelinated Plexus Afferents to the DRG 0.2-1.5 µm 1-2 Nerve Motor, Sensory, Mixed 1. The large myelinated fibers are the fibers measured in nerve Large/Small Fiber conduction studies NMJ 2. Neuropathies that preferentially affect small fibers may Muscle have NORMAL nerve conduction studies

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Goals of EDX: Pathology Nerve Conductions: CMAP

Area: measured Pathologic Responses to Injury: between the baseline & negative peak Amplitude: reflects the number of muscle fibers 1. Neuronopathy(Motor or Sensory) that depolarize Distal Latency: time 2. Axonal Transectionwith Wallerian from stimulus to initial Degeneration deflection 3. Axonal Loss Conduction Velocity: 4. Demyelinating taken from two points (to account for NMJ)

Duration: measure of synchrony—the extent to which fiber fire at the same time (increases in conditions that slow fibers) 11 American Physician Institute for Advanced Professional Studies 12 American Physician Institute for Advanced Professional Studies

Nerve Conductions: Late Responses Nerve Conductions: SNAP F (Foot) Response Peak Latency: midpoint Conduction Velocity: of the negative peak Antidromic response taken from two points (to account for NMJ) towards the spinal cord Travels to the anterior horn cell and backfires a small Duration: should be shorter (1.5 ms vs 5- population of AHCs 6ms) compared to motor Represents 11--5%5% of all muscle fibers Onset Latency: stimulus to Amplitude: sum of all Pure motor ….it is not a reflex deflection; represents the sensory fibers that arcarc largest fibers depolarize

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Nerve Conductions: Basic Patterns Nerve Conductions: Basic Patterns

Neuropathic Patterns Neuropathic Lesions Axonal Loss Demyelination Conduction Block Reduced amplitude is the Associated with marked Occurs in acquired primary abnormality slowing of CV demyelination (and is not seen associated with axonal loss Slower than 75% of the in hereditary demyelinating Conduction velocity & distal lower limit of normal conditions) latency are normal (*) Arms: <35 m/s Drop in CMAP amplitude or CV should never be less than Legs: <30 m/s area of at least ≥≥20% and/or 75% of normal Distal latencies markedly increase in duration of ≥≥15% DL do not exceed 130% of prolonged (>130%) normal

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Nerve Conductions: Basic Patterns Demyelinating Neuropathies

Neuropathic Lesions Hereditary Acquired Temporal Dispersion Charcot Marie Tooth I AIDP/GuillianAIDP/Guillian--BarreBarre Implies demyelination DejerineDejerine--SottasSottas(HSMN III) CIDP Slower fibers lag behind the Refsum Disease (HSMN IV) HIV faster ones HNPP MGUS (IgM) More prominent with sensory fibers than motor normally Metachromatic AntiAnti--MAGMAG Leukodystrophy More prominent with proximal Osteosclerotic myeloma stimulation Krabbe Disease Waldenstrom Can cause the amplitude to drop Adrenoleukodystrophy macroglobulinemia by >50% without true Cockayne Syndrome MMN with CB (GM Ab) conduction block 11 NiemannNiemann--PickPick Disease Diptheria Drop in area of >50% always signifies conduction block Cerebrotendinous Toxic (amiodarone, arsenic) xanthomatosis

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Demyelinating Neuropathies Common Sources of Error AIDP CIDP First changes are delayed, absent or >8 weeks Temperature impersistent FF--waveswaves (reflecting proximal demyelination) Prolonged DL, slowing of CV, conduction block/temporal The most important/common source of error Prolonged DL, conduction block/temporal dispersion are dispersion Cooler temperatures slow conduction velocity common Nerve conductions are often Present in 50% by 2 weeks and 85% asymmetric and increase amplitude by 3 weeks Secondary axonal changes are Motor abnormalties (90%) are more CV slows by 1.51.5--2.52.5 m/s for every 1 °C drop common than sensory (often the rule normal) Needle examination with in temperature and DL prolongs by 0.2 m/s “Sural sparing” despite median/ulnar spontaneous activity, large ° SNAP involvement MUAPs and reduced UE: 32 CC No denervation, normal MUAP morphology, reduced recuitment recruitment LE: 30 °CC Myokymia may be present

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Common Sources of Error Common Sources of Error

Age Height Peripheral myelination is complete by age 33--55 Taller individuals often have slower CVs and CVs reach “adult” values Nerves taper in size with length (velocity is After age 60, CV decreases 0.50.5--4.04.0 m/s per proportional to diameter) decade Distal limbs are cooler SNAP amplitudes may drop by 50% by age 70 Most relevant in the measurement of late responses (F(F--waves)waves)

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Electromyography Common Sources of Error Spontaneous Activity Stimulation Errors End Plate Noise Submaximal Stimulation Miniature endend--plateplate potentials that occur spontaneously at The largest fibers have the highest threshold for the NMJ stimulation and thus are evoked last Appear as small, monophasic negative potentials May cause falsely prolonged DL and slowed CV “Hissing” or “seashell” noise CoCo--StimulationStimulation of Adjacent Nerves End Plate Spikes Can lead to spuriously large amplitudes Brief spike morphology & EPS Fib irregular pattern Deflect Neg Pos Wave form may change Initial deflection is negative Firing Irregular Regular “Fat in the frying pan” Sound “Frying” “Rain”

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Electromyography Electromyography

Spontaneous Activity Spontaneous Activity Fibrillations Positive Waves Occurrence of Fibrillations Grading Spontaneous discharge of one 1. Neuropathic Disorders Spontaneous depolarization a 0. None present muscle fiber 2. Inflammatory Myopathies muscle fiber 1+. Persistent single trains (>2-3s) Indicate acute or active 3. Muscular dystrophies Signify active denervation in at least two areas 4. Botulism 2+. Moderate number or potentials denervation Regular pattern in ≥3 areas Initial positive deflection “Dull pop” 3+. Many potentials in all areas Regular rate 4+. Full interference pattern (can “Rain on the roof” occur with trauma, vasculitis and/or infarction) I think it sounds more like a metronome

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Electromyography Electromyography

Spontaneous Activity Spontaneous Activity Complex Repetitive Myotonic Discharges Conditions Associated with Myotonic Discharges Spontaneous discharge of a Discharges muscle fiber Depolarization of a single 1. Myotonic Dystrophy muscle fiber followed by the Can have similar wave form 2. Myotonia Congenita ephaptic spread to adjacent to pp--waveswaves (brief positive 3. Paramyotonia Congenita denervated fibers spike) 4. Myopathies Seen in chronic neuropathic & 1. Acid maltase deficiency myopathic disorders Waxing and waning pattern 2. Polymyositis 3. Myotubular myopathy Can occur in myopathies (vs regular sound of CRDs) 5. Hyperkalemic periodic paralysis associated with denervation, “Revving engine” sound necrosis and inflammation 6. Colchicine myopathy 7. Cyclosporine toxicity Do not occur in acute settings “Machine“Machine--like”like” sound

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Electromyography Electromyography

Spontaneous Activity Spontaneous Activity Fasciculations Myokymic Discharges Benign Fasciculation Syndrome Conditions Associated with Myokymia Spontaneous involuntary Essentially grouped discharge of a single motor • Most common in the eyelids, arms, legs and feet fasciculations (repetitive 1. Radiation induced nerve injury (esp. brachial unit • The tongue can be affected plexus injury following radiation therapy for • No pathologic findings on exam discharges of the same motor breast cancer). Associated with diseases of unit) 2. Facial myokymia occurs in GBS, multiple the anterior horn cell and •Muscle cramping and pain may occur sclerosis and pontine tumors proximal root •AAN Guideline for Symptomatic Treatment “Marching sound” 3. Can be provoked by lowering serum ionized for Muscle Cramps: calcium “Corn popping” sound •Quinine derivatives should be avoided I think it sounds more like for routine use (can be considered on an bursts of machine gun fire individual trial) Doublets & Triplets • Rest tremor can have a Vitamin B complex, Naftidrofuryl, and Similar to fascics (“singlets”) calcium channel blockers are possibly similar sound that is more Characteristically seen in effective continuous tetany from hypocalcemia

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Electromyography Electromyography: MUAP Analysis

Spontaneous Activity Three major components: Neuromyotonia Clinical Presentation Associated with Neuromyotonia High frequency repetitive 1.Generalized stiffness, hyperhidrosis and delayed Morphology discharges of a single motor muscle relaxation after contraction unit 2.Direct muscle percussion does not elicit myotonia Stability (unlike myotonic dystrophy) Rare 3.Activity persists during sleep and during surgery 1. Abolished by curare Firing characteristics “Pinging” sound 4.Neuromyotonic discharges are most commonly seen in acquired myotonia 1. Autoimmune condition associated with voltage-gated potassium channels 2. Can be seen in chronic polio & SMA

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Electromyography: MUAP Analysis Electromyography: MUAP Analysis

Morphology Stability Duration Reflects the number of muscle fibers within a unit MUAPs should appear stable in morphology ••Increases as the number of fibers and the territory ofof a unit increases from potential to potential Correlates with pitch: long durations sound dull & thuddy, short durations sound crisp (like static) Unstable MUAPsoccur when individual Polyphasia muscle fibers are blocked Measure of “synchrony”“synchrony”——thethe extent to which muscle fibers within a unit fire at the same time Indicates an unstable NMJ Calculated by the number of times the baseline is crossed (normal is 22--4)4) Can occur in neuropathic, myopathic or NMJ Polyphasic units have a “clicking” sound disorders Amplitude

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Electromyography: MUAP Analysis Electromyography: MUAP Analysis

Firing Characteristics Duration Phases Amplitude Stability Activation Recruitment Muscles can increase force by: Acute axonal Normal Normal Normal Normal Normal Reduced Increasing the firing rate of motor units Chronic Axonal Prolonged Polyphasic Increased Normal Normal Reduced Firing additional motor units During maximum contraction, multiple units fire Demyelinating Normal Normal Normal Normal Normal Normal

creating an interference pattern, which depends on: Demyelinatng + Normal Normal Normal Normal Normal Reduced Activation: the ability to increase the firing rate Cond. nlock Recruitment: the ability to add units as the firing rate Acute myopathy Short Polyphasic Small Normal Normal Early increases Chronic Normal Normal Prolonged Polyphasic Small Reduced In a healthy person, 55--66 different MUAPs should be myopathy present when fully activated (firing rate of 3030--5050 Hz)

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Electromyography: MUAP Analysis

Neuropathic Myopathic

Specific Patterns

Reduced recruitment of large amplitude MUAPS Early recruitment of small, polyphasic units

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Radiculopathy Radiculopathy Nerve conductions are C5: deltoid, supra & usually normal infraspinatus; lateral upper arm With chronic lesions there sensory loss may be motor axonal loss C6: biceps, brachioradialis, Sensory fibers are almost ECR; thumb/index sensory loss always spared (the lesion is proximal to the DRG) C7: triceps, FCR, finger Neuropathic abnormalities extensors; middle finger in a myotomal distribution C8: intrinsic hand muscles; medial hand sensory loss; can There may be preferential involvement of fascicles be associated with a Horner’s Syndrome

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Plexopathy Spinal Cord—Compressive Plexus lesions usually result in abnormal SNAP responses L2: Hip flexion weakness SideSide--toto--sideside difference of >50% (iliopsoas), anterior thigh in amplitude numbness Medial antebrachialand lateral L3: Knee extension (quadriceps); antebrachial medial thigh numbness Motor studies are less useful L4: Knee extension, foot Needle examination dorsiflexion (Tib anterior, Assessment of the most posterior); medial leg numbness proximal muscles is important L5: Great toe dorsiflexion to evaluate root vsvsplexus (EHL); numbness of the great Absent CMAPs,CMAPs , profuse toe denervation and absent MUAPs is an ominous sign for recovery S1: Plantar flexion; digit 5 & Surgical exploration may be lateral foot considered

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Brachial Plexus Brachial Plexus

ROOTS TRUNKS DIVISIONS SUPRASCAPULAR DORSAL SCAPULAR ANTERIOR C5 UPPER C6 MIDDLE C7

LT C8 LOWER

T1 POSTERIOR Supraclavicular plexopathies are more common and less likely to recover Supraclavicular: Inflammatory lesions, CLAVICLE neoplastic infiltration, trauma (including obstetric); injuries tend to produce deficits in SUPRACLAVICULAR INFRACLAVICULAR myotomal &/or dermatomal patterns Infraclavicular: Radiation, penetrating injuries, axillary arteriograms; tend to produce deficits reflective of mononeuroapthies

Brachial Plexopathy Brachial Plexopathy

Disorders of the Brachial Plexus Disorders of the Brachial Plexus Neuralgic amyotrophy (Parsonage-Turner) Radiation Plexopathy Immune-mediated inflammatory process Symptoms occur from 1 month to 18 years after exposure • One of the most-common plexopathies (other than trauma) May occur in up to 9% of pts Acute onset shoulder and arm pain followed by weakness and sensory loss • 65% of pts have pain at onset; in 90% it is sudden and intense; lasts days to weeks Risks include: higher dose of radiation, # ports, chemotherapy, • Pts keep the arm in an elbow-flexion/shoulder adduction position axillary node dissection • Weakness may lag behind pain by weeks (2 or more) Myokymic discharges on EMG are characteristic • Can be bilateral (30%) No specific treatments have been proven to be helpful • Occur in 63% of pts • Steroids may reduce pain but do not alter the disease • Do not occur in neoplastic plexopathies • Significant improvement in 36% at 1 year, 75% at 2 and 89% at 3 – 2’ local spread; breast, lung, lymphoma • Recurrence in 1-5% – Presence of a Horner’s and high signal on T2 favor neoplastic vs. Hereditary Neuralgic Amyotrophy radiation-induced AD inheritance; recurrent brachial plexopathy No specific treatment proven Typically painful (vs HNPP which is usually painless) • Anticoagulation may be helpful

Mononeuropathies Brachial Plexus Radial Neuropathy Most commonly compressed at the spiral groove (spares the triceps); can also be Posterior Cord (The “STAR”) compressed at the Arcade of Frohse (formed by the supinator muscle; PIN) UPPER Muscles innervated: Radial Nerve (Main Trunk) • Triceps MIDDLE RADIAL • Brachioradialis • ECR Longus • ECR Brevis Posterior Interosseous LOWER THORACODORSAL • Supinator AXILLARY • EDC SUBSCAPULAR POSTERIOR DIVISIONS • ECU (* DO NOT CONFUSE WITH • EPL THE SUPRASCAPULAR!!) • EPB • APL • EIP • Cords are named in relation to the axillary artery • EDM

Brachial Plexus Mononeuropathies

ANTERIOR DIVISIONS CORDS LATERAL Musculocutaneous N. UPPER MUSCULOCUTANEOUS Can be damaged with MIDDLE shoulder dislocation & MEDIAN weight lifting

MEDIAL (including “carpet LOWER ULNAR carrier neuropathy” Muscles Innervated Biceps brachii Brachialis

Mononeuropathies Mononeuropathies

Median Nerve Ulnar Nerve CTS is the most common entrapment neuroapthy Commonly entrapped Muscles Innervated at the elbow (cubital Pronator tunnel) and wrist FCR (Guyon’s canal) Anterior Interosseous • FDP Muscles innervated: • FPL FCU • Pronator Quadratus FDP Lumbricals I & II Opponens Pollicis ADM APB Interossei FPB Lumbricals

Lumbosacral Plexopathy Lumbosacral Plexopathy

Lumbar Plexus Lumbar/Sacral Two Major Nerves: Sciatic Femoral (L2(L2--L4)L4) Tibial Division Iliopsoas Semitendinous Quadriceps Pectineus Semimembranous Sartorius Biceps femorisfemoris,, long head Saphenous (sensory) Peronal Divisino Obturartor Biceps femorisfemoris,, short head Obturator externus Adductor Longus Adductor Magnus Adductor brevis Gracilis

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Neuromuscular Junction Neuromuscular Junction

PrePre--SynapticSynaptic PostPost--SynapticSynaptic Characterized by facilitation of CMAP Baseline, then 11-- amplitudes postpost--exerciseexercise minute of exercise, & highhigh--frequencyfrequency (30Hz) followed by RNS at 1 LEMS: >100% minute intervals for 33--44 facilitation minutes Baseline CMAPs are usually borderline low >10>10--20%20% decrement Botulism: 30% after exercise facilitation Needle exam may PP--waves/fibswaves/fibs are reveal unstable common MUAPs

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Myopathies Question 1

Distal Myopathies Myopathies with Denervating Features A 78 year old female with history of breast cancer 1. Myotonic Dystrophy Type 1 (DM1) 1.Polymyositis 2. FSH Muscular Dystrophy 2.Dermatomyositis presents with left arm weakness. Exam reveal 3. Scapuloperoneal Muscular Dystrophy 3.Inclusion body myositis weakness of left shoulder abduction and forearm 4. Inclusion Body Myositis 4.Sarcoid Myopathy 5.Duchenne’s/Beckers flexion. EMG is notable for myokymic discharges. 6.FSH 7.EDMD What is the most likely mechanism of injury? 8.Oculopharyngeal MD 9.Acid maltase deficiency 1. C5/C6 radiculopathy due to herniated disc Steroid Myopathy 2. PostPost--radiationradiation plexopathy •Risk increases with use 3. Metastatic invasion of the brachial plexus •Typically proximal •Abnormal spontaneous activity is usually not 4. Left axillary neuropathy seen—which may help differentiate from undertreated polymyositis

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Question 1 Question 2

A 34 year old male presents with two weeks of right Answer: PostPost--radiationradiation plexopathy foot weakness. Examination is notable for weakness of right ankle dorsiflexion and inversion. Plantarflexion and eversion are normal. What are Myokymic discharges are virtually pathognomonic the most likely findings on the nerve conduction for postpost--radiationradiation plexopathy. study? 1.1. Absent right superficial peroneal SNAP response 2.2. Absent right sural SNAP response 3.3. Conduction block across the fibular head 4.4. Spontaneous activity in the lumbar paraspinal muscles

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Question 2 Question 3

A 67 year old male present Answer: Spontaneous activity in the lumbar with complaint of slowly paraspinal muscles progressive weakness. Repetive stimulation reveals the following. What is the most likely cause of his This most likely represents a lumbar radiculopathy weakness? (L4(L4--L5).L5). Weakness of ankle inversion occurs withwith 1.1. Presynaptic blockade of involvement of the tibialis posterior (tibial ACh release 2.2. Presynaptic blockade of innervated, L4L4--L5).L5). The peroneus longus (peroneal calcium channels 3.3. Postsynaptic blockade of innervated, L5L5--S1)S1) everts the foot. ACh receptors 4.4. Failure of AChRsto congregate at the NMJ

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Question 3 Question 4

Answer: Presynaptic A 38 year old female presents for progressive blockade of calcium channels difficulty walking and distal numbness. Proximal The patient’s clinical history stimulation of the right tibial and repetitive nerve nerve results in the following stimulation are most CMAP. What is the most consistent with LambertLambert-- likely diagnosis? Eaton myasthenic syndrome, 1. HSMN I (CMT) which is typically associated 2. HSMN II with a P/Q calcium channel 3. Vitamin B12 polyneuropathy antibody. With LEMS, there is >100% facilitation of 4. CIDP CMAP amplitudes on RNS.

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Question 4

Answer: 4. CIDP Answer: 4. CIDP

The image is consistent with temporal dispersion, which is only seen is acquired demyelinating conditions.

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