Peripheral Nerve Trauma: Electrodiagnostic Workup and Indications for Surgical Referral to Limit Pain and Disability Faren H Williams, MD, MS Edward Calkins, M.D. Marci Jones, M.D. Anthony Howley, OTR/L, CHT U of Massachusetts Medical School

Peripheral nerve injuries: Electrodiagnostic Considerations Faren H. Williams, M.D., M.S. Chief and Clinical Professor Physical Medicine and Rehabilitation Dept of Orthopedics and Physical Rehabilitation University of Massachusetts

Peripheral nerve injuries 1167 peripheral nerve injuries – 5.7% sports – 10% traumatic Trauma – Falls, MVA’s, GSW’s UPPER extremities – more mobile –88% upper extremity

Normal Nerve Faren H. Williams, M.D., M.S.4

Nerve Structure Faren H. Williams, M.D., M.S.5

Nerve Physiology Faren H. Williams, M.D., M.S.6

Peripheral Nerve Injury Faren H. Williams, M.D., M.S.7

Electrodiagnostic Testing Information about Integrity of Anterior Horn Cell Dorsal (Sensory) Ganglion –NERVE –NEUROMUSCULAR JUNCTION –MUSCLE Faren H. Williams, M.D., M.S.8

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Nerve Anatomy Axon swelling/ Node of Ranvier Faren H. Williams, M.D., M.S.10

Faren H. Williams, M.D., M.S.11 Overview NCS/ EMG Sensory distal latency –Time required for nerve impulses to travel between The stimulation and recording electrodes Motor distal latency Time required neuromuscular transmission Initiation of Action Potential

Latency Changes over time

Myelinopathies Affects the myelin sheath Intussusception of myelin –occludes –Nodal Gap Latency slowing Profound loss of myelin – –Associated Axonal loss

Neural Intussesception

Nerve Anatomy Single nerve fiber Faren H. Williams, M.D., M.S.15

Faren H. Williams, M.D., M.S.16 Overview NCS/ EMG Amplitude Measures of the number of nerve fibers conducting impulses from the stimulating to the recording points Relative conduction rates along those fibers Distance between muscle/nerve fibers and recording electrodes

Faren H. Williams, M.D., M.S.17 Overview NCS/ EMG Duration –Relative rates in conduction of fibers between Stimulating & recording points –Prolonged vs. dispersed –Motor – duration of negative response

Early NCS’s First week s/p injury –Allows for precise localization of the injury –Distal stump continues to conduct –Impaired conduction across site of major injury –Ability to localize lost after 1 st week as Distal stump ceases to conduct Faren H. Williams, M.D., M.S.18

Faren H. Williams, M.D., M.S.19 Overview NCS/ EMG Conduction block –Amplitude distal to the focal lesion is higher % loss in amplitude – related to % of fibers/ axons lost –After 7-10 days – can’t localize Day 1-2 – can’t differentiate axonal loss from demyelination –Latency is usually slowed across the lesion- Secondary to demyelination

Amplitude changes over time

Early NCSs Lesion – electrophysiologically –Incomplete (Neuropraxia) or Complete –Incomplete lesions – MUAPs voluntarily controlled – Number of MUAPs less with more severe injury – Single MUAP indicates lesion is incomplete – Nerve trunk not disrupted – Better Prognosis Faren H. Williams, M.D., M.S.21

Ulnar Motor Inching Study

Contralateral side NCS’s imperative to determine degree of AXONAL loss – If distal amplitude is same side: side Then lesion is neuropraxic If distal amplitude on affected side is 50% less then 50% axonal loss 50% conduction block – across lesion Faren H. Williams, M.D., M.S.23

Ulnar Inching

NEEDLE EMG RESTING MUSCLE is ELECTRICALLY SILENT with Needle EMG Faren H. Williams, M.D., M.S.25

Faren H. Williams, M.D., M.S.26 Overview NCS/ EMG Needle EMG –Insertional activity Injury potentials mechanically evoked by needle movement Decreased when muscle atrophied, fatty, or fibrotic Increased (muscle membrane activity >300ms) –Non-specific –Can be seen associated with denervation –No diagnosis made based on this finding alone

Abnormal potentials Proximal muscles after days Distal muscles after 3-4 weeks Faren H. Williams, M.D., M.S.27

Abnormal Potentials Faren H. Williams, M.D., M.S.28

Needle EMG Assists in localization Allow sufficient time for Wallerian degeneration Prognosis –Follow changes over time More sensitive for detecting motor loss than NCSs Complete lesion – no MUAPs Incomplete lesion – reduced recruitment (rapid firing)

Faren H. Williams, M.D., M.S.30

Faren H. Williams, M.D., M.S.31 NCS/ EMG Overview

Normal AVI Faren H. Williams, M.D., M.S.32

Needle EMG and NCSs BOTH NEEDED for INTERPRETATION –NCSs -50% axonal loss, 50% conduction block Need data from contralateral (normal) limb –4+ fibs/ positive waves and no MUAPs Doesn’t correlate with percent of axonal loss –Represents neuropraxia and axonotmesis –Not complete axonal lesion Faren H. Williams, M.D., M.S.33

Neurotmesis No motor or sensory potentials – over time Axons and epineurium disrupted MRI neurography – localization Intraoperative electrodiagnosis Surgical repair tenuous

Nerve Regeneration Depends on distance from nerve lesion to muscle Type of Nerve Injury Age of Patient General Health of Patient/ Co-morbities Faren H. Williams, M.D., M.S.35

Faren H. Williams, M.D., M.S.36 Overview NCS/ EMG Motor Unit Analysis –Early reinnervation MUAP’s – Increased polyphasicity and duration –Temporal dispersion –Poor synchronization of muscle fiber discharges –Later Axonal sprouts mature – polyphasicity reduced –Late High amplitude, long duration, occ polyphasic

Distal Wallerian Degeneration Proximal Sprouting Faren H. Williams, M.D., M.S.37

Faren H. Williams, M.D., M.S.38

Regenerating Sprouts Mature Re-myelination Faren H. Williams, M.D., M.S.39

Faren H. Williams, M.D., M.S.40 Polyphasic MUAPs

Faren H. Williams, M.D., M.S.41 Overview EMG/ NCS Polyphasicity – suggests reinnervation –MUAPs with >5 phases –Isolated finding – non-specific –Overreported, Overinterpreted –20-30% polyphasic MUAPs - normal

Faren H. Williams, M.D., M.S.42 Overview NCS/ EMG Recruitment – helpful for prognosis –Reduction in lower motor neuron pool Increased firing rate (fewer vs. more MUAPs) –Poor central effort Effort, Pain inhibition, CNS problem Non-diagnostic

Intrepretation/ Recommendations Diagnosis – type of nerve injury/ Localization –Demyelination, Axonopathy, or both (mixed) Prognosis Recommendations- therapeutic regimen, medications Repeat study to follow/ monitor progress Surgical referral/ intervention Faren H. Williams, M.D., M.S.43

Patient Informatiion History Dominant arm Motor, sensory, reflexes Mechanism of injury Timing s/p Injury Faren H. Williams, M.D., M.S.44

Peripheral nerve injury Physical Examination –Strength –Sensation – dermatomal, peripheral –Reflexes – UMN, LMN –Contralateral limb –Muscle atrophy –Deformities, i.e. Claw hand

Sensation – Ventral Arm

Sensation – Dorsal Arm

Case #1 25 y/o R HD male, with R humerus fx, s/p MVA 2 months prior to EDX study – brachial a. repair PE – triceps 3/5, B-R 2-/5, ECRL 2-/5, FDP to middle, ring and little fingers 2/5, FDP –index 0/5 FPL 0/5, APB ?tr, impaired sensation median n Faren H. Williams, M.D., M.S.48

R Median motor response, s/p MVA Faren H. Williams, M.D., M.S.49

Left median motor Faren H. Williams, M.D., M.S.50

Right radial motor Faren H. Williams, M.D., M.S.51

Left Radial Motor Faren H. Williams, M.D., M.S.52

Motor NCS’s Right median motor –DL – 4.7 ms, ampli – 0.4 K with dispersed waveform Left median motor DL – 3.9 ms, amplitude 7.8 K Right radial motor DL – 3.3 ms, amplitude 0.5 K Left radial motor DL – 3.0 ms, amplitude 2.2 K Faren H. Williams, M.D., M.S.53

Right median –radial sensory Faren H. Williams, M.D., M.S.54

Right radial sensory- snuff box Faren H. Williams, M.D., M.S.55

Sensory NCS’s Right Median – No responses Right Radial – no response from thumb 4.2 ms peak latency, and 14 uV from snuff box Left Median – 2.4 ms peak latency, 68 uV ampl Left Radial (from thumb) -2.6 ms lat, 7.9 uV ampl from snuff box 3.2 peak latency, 40 uV ampli. Faren H. Williams, M.D., M.S.56

Needle EMG- Right Spontaneous activity –APB, EIP, Pronator Teres, Brachioradialis, ECRL –No MUAPs – in APB, and Pronator Teres –Radial innervated muscles – decreased recruitment Discrete recruitment in more distal muscles, all + MUAPs Faren H. Williams, M.D., M.S.57

Interpretation Median nerve injury - > 95% axonal loss, Motor & Sens 0 MUAPs in median innervated muscles Radial nerve injury – 75% axonal loss, motor –Reinnervation – proximal to distal Prognosis- median recovery guarded, radial fair Faren H. Williams, M.D., M.S.58

f/u EDX, 9 mos post-op Right radial motor ampl – 50% greater than ’12 Right median motor (s/p median n graft) –Amplitude 10x’s greater than Nov ‘12 Right median sensory – from thumb and index finger 3-5 uV amplitude –improved from no response in ‘12 Needle EMG – ongoing fibs/ positive waves R APB but with MUAPs with reduced/ discrete recruitment in median innervated muscles. Radial ones polyphasic Faren H. Williams, M.D., M.S.59

Median motor, s/p Nerve Repair Faren H. Williams, M.D., M.S.60

R radial motor, 9 mos post-op Faren H. Williams, M.D., M.S.61

Case #2 24 y/o R HD female, c L distal humerus fx MVA EDX 3 months later – no ulnar motor or sensory Needle study with spontaneous activity in all ulnar innervated muscles, incl FCU 0 MUAPS in 1 st DI and ADM, Recruitment reduced in FCU Faren H. Williams, M.D., M.S.62

EDX 5 mos s/p MVA Left ulnar motor not obtainable Left ulnar dorsal cutaneous not obtainable Left ulnar sensory from little finger not obtainable Needle study with more firing MUAPs in FCU FDP –ulnar, polyphasic MUAPS, reduced recruit 0 MUAPs in 1 st DI and ADM Faren H. Williams, M.D., M.S.63

Polyphasic MUAPs –FDP, ulnar Faren H. Williams, M.D., M.S.64

L Ulnar Motor, 6 mos, s/p MVA Faren H. Williams, M.D., M.S.65

L Ulnar sensory, 6 mos, s/p MVA Faren H. Williams, M.D., M.S.66

Summary- EDX Prognosis Type of Nerve Injury Timing s/p Injury NCS’s in combination with needle EMG –Complete vs Incomplete Lesion Distance from Lesion to Muscles Clinical Correlation with EDX findings Serial Electrodiagnostic Studies Faren H. Williams, M.D., M.S.67

References Campbell, W., Evaluation and Management of Peripheral Nerve Injury, Malikowski, T., Micklesen, P J, Robinson, L., Prognostic Values of Electrodiagnostic Studies, Muscle and Nerve, Sept 2007, p Robinson, L.R., Traumatic Injury to Peripheral Nerves. AAEM Minimonograph #28, p Sahin et al. Correlation of Neurodiagnostics with Recovery. Hand, Faren H. Williams, M.D., M.S.68