This document provides information about performing and interpreting needle electromyography (EMG). It discusses preparing the patient, electrode placement, different muscle contraction techniques, and Johnson's 5 steps for needle examination. It explains what to look for at rest, with minimal/maximal contractions, and different abnormal findings including fibrillation potentials and complex repetitive discharges. Neurogenic and myogenic recruitment patterns are compared. The overall summary is that this document outlines the procedure and analysis of needle EMG examinations.

1. Needle Electromyography
DUMITRU
Chapter 7

2. Preparation
 Patient anxiety
 Do not show needle
 Gauze
 Muscle soreness 1-2 days

3. The examiner
 Disposable glove
 Sodium hypochloride 15-20 min
 Distraction technique for entrance

4. Art of needle EMG
 Place and light and speech tone
 Less painful area with needle tip
 Apply pinching or stretching the skin
 VMUAP: needle in SubQ then isometeric
 Paraspinal :
 Push forehead against examiner hand
 Tighten stomach muscles
 Extensors of forearm : relaxed in more
supinated position

5. Johnson’s 5 step to needle examination
 1. muscle at rest / same
 2. insertional activity / same
 3. minimal muscle contraction / minimal to moderate
 4. maxima muscle contraction/ information synthesis
 5. exploration / impression formulation

6. Muscle in rest
 Sensitivity : 50 micro/ div
 Sweep : 10 ms/div
 Monopolar : reference elect. Close to site
 Quickly insertion through the skin

7. Insertional activity
 Pyramidal space
 0.5- 2 mm insertion
 Several seconds pause
 Needle mechanically
depolarize muscle fibers
 Injury potential

8. Minimal to moderate contraction
 Type I fiber analysis
 500 mv/div
 Think of small contraction
 High amp >5 mv
 Polyphasia >4
 Interference pattern : minimal information
 Pain
 Patient effort
 Ability for resistance
 Exception : type II fiber atrophy (steriod myopathy)
 In maximal contraction normal high amp MUAP are absent.

9. Information synthesis
 EDX examination differ from reading
EKG in isolation from patient.
 Finally impression formulation

10. Electrophysiology
action potential generation
 Membrane potential depolarized from -
80 mV to -50 to -60 mV ( threshold)
 Voltage gated Na channel activated 0.5 ms
 Then depolarization to +40 mV
 Delayed increased K permeability with
inactivation of Na channel 2.0 ms

12. Isopotential lines

14. Needle insertional activity

15. Insertinal activity

16. Insertional activity
 Monopolar :
 Total time of activity: < 230 ms
 After needle cessation 48+/- 18 ms
 Concentric
 Total time :<300 ms
 In animal after denervation: PSW then Fib
 Snap crackle and pop :
 Normal in young men in Gast.
 Variable length of time persisted
 Another normal variant:
 Run of PSW S or C few Fib
 AD inheritance
 So Fib & PSW are not always pathologic

17. Spontaneous activity
 After placing a needle into endplate
 Miniature endplate potential (MEPPs)
 Endplate spike

18. Difference between MEEPs and endplates

19. Innervation ratio

20. Single muscle fiber
 It’s a triphasic wave (+ - +)
 Biphasic (positive-negative) seen in:
 Positive terminal wave is small and lost
 Musculotendinous junction
 Endplate zone

21. MUAPs
Anatomy
 Motor unit definition
 Types:
 Alpha: skeletomotor
 Beta : skeletofusimotor
 Gamma: fusiomotor
 Alpha situated in ventrolateral horn
 Limbs motor units located laterally in comparison with neck and
trunk muscle.
 They have axon collateral to synapse with Renshaw interneourons
and other alpha motor neurons
 One MU may be distributed over 100 muscle fiber
 MUs dos not extended between 2 muscle
 One single fiber innerveted by only one MN
 Sometimes 2 NMJ seen but its from one MN

22.  Electrophysiolgic counting
 Incremental motor unit counting
 Max CMAP divided by mean incremental amplitude
 PAS staining
 Circular region about 20-30% muscle volume
 Higher density in enter of motor unit
 Upper limb MU territory: circular to oval 5-7 mm
 Lower limb MU territory: m7-12 mm

23. Periodic acid shift staining

24. Physiology
 MU classifications
 Fast twitch
 More force innervated by fact conductive neurons
 Slow twitch
 Small force by slow conductive neurons
 Speed of contraction
 Specific contractile proteins
 Rate of calcium uptake
 Fast twitches have
 More extensive sarcoplasmic reticulum
 Richer in Ca-Mg ATPase

25. Motor units classification
 Fast fatigue (FF)
 Readily fatigue
 High tetanus tension
 Fast contraction time
 Slow (s)
 Low tetanus tension
 Long contraction time
 Resistant to fatigue
 Third group
 Moderate tetanic tension
 Fast twitch time
 Relatively fatigue resistant (FR)
 Forth small intermediate population (F int)
 Between FF and FR

26. Histochemical technique
 Fatigue resistant: higher activity of
 Mitochondrial enzymes
 Succinate dehydrogenase
 Fatigue sensitive: higher activity in
 Phosphorylase activity (myosin ATPase

28. Recruitment principles
 Henneman size principle
 First MU activated is weakest
 Then large MUs activated
 So contraction in smooth and
appropriate to need

29. Parameters
 In one territory
 10 MU type I and more than 30 (I&II)
 Interdigited muscle fibers
 Active and inactive fibers
 Muscle tissue act as LPF (HFF)
 Reduce peck amplitude

30. MUAP parameters
figure
 Amplitude
 Rise time
 Duration
 Phase
 Spike duration
 Initial and terminal portion

31. Phase
 Polyphay : 5 or more
 Monopolar:30% nl
 Concentric: 15% nl
 Main spike arise from
 1-12 muscle fiber
 <500 mic m distance
 Distant potential :After filtering
 low frequency initial and terminal
 Small negative spike

32. Instrumentation factor
 Reduction in MUAP amplitude
 Reduced HFF
 Concentric needle
 Large electrode lead off surface
 Rotation on concentric needle
 Removal of Teflon in monopolar

33. Effect of temperature on MUAP
 Controversial
 Authors opinion:
 Reduction of temp
 Increased initially
 More dec. in temp.: AP failure and MUAP decreased
 In >65 Y : MUAP increased

34. MUAP duration
 Duration depend on:
 Width of Endplate Zone
 Lesser: terminal axon conduction velocity
 Inc LFF:
 Deletion of initial and terminal
 Dec. duration
 Concentric needle :
 Reduced duration
 Cooling
 Increased duration

35. Phase
 Synchronocity
 Aging and temperature reducing:
 Increased phase
 Elevating LFF : inc phasicity
 Monopolar have more polyphasic potential

36. Recruitment
 Principles:
 First MUAP : small and slow type I
 Minimal to moderate force needed
 Late type II MUAPs in not simple to analyze
 Subtle pathology my be miss
 Increasing fire rate of first MUAP with more force
 Slow and constant contraction is sufficient for analysis

37. Others
 Equipment :
 LFF: 10-30
 HFF: 10,000 or more
 Sweep speed 20 ms/div
 Techniques :
 Identify first MUAP and measure firing rate

38. Recruitment
 Recruitment frequency:
 Frequency of MUAP A when MUAP B begin fireing
 Recognition:
 Observing for second MU to appear
 Change in sound
 Recruitment interval
 Distance between 2 peaks of MUAP
 Normal muscle
 Recruitment frequency: 10 Hz
 Recruitment interval: 100 ms
 Facial muscles: short interval and high frequency

39. Normal recruitment
1st 2nd 3rd 4th
5 Hz
10 Hz 5 Hz
15 Hz 10 Hz 5 Hz
20 Hz 15 Hz 10 Hz 5 Hz

40. Recruitment ratio
 Recruitment ratio:
 Frequency of fastest MUAP divided by number of
Different MUAP in screen
 Should be close to 5
 If near 10: too few MU presented (neurogenic)
 If below 4 : too many MU existed (myogenic)
 Predicting firing rate:

41. Insertional activity
 Decreased I.A :
 Fibrosis
 Sub Q
 Attack of periodic paralysis
 Improper electrode connection
 Increased IA:
 Muscle denervation
 Other membrane instability

42. Fibrillation potential
 4-6 or longer days
 Threshold level and regularly repetition
 Previous endplate
 Decreased with:
 Decreased temperature
 Ischemia
 D-tubocurarine
 50 % regular
 High pitched: crackling cellophane or rain

43. Positive sharp waves
 Positive wave terminated to base line
 Monophasic
 Same ethiology
 Purely demyelinatig disease have PSWs
but no fibrilation
 Combination of Fib/PSW

44. Clinical findings
 Radiculopathy
 7-10 days : paraspinal
 21 days: limbs
 Persistent : sequestrated muscles
 Amplitude:
 First 2 m : 600 micro v
 End of 3 m: 500 micro v
 At 6 m: 300 micro v
 One year: < 100 micro v
 In period paralysis : no fib between attacks
 No difference in needle types

45. Grading of fibrillation potentials
 0: no fib
 1: unsustained <2 region
 2: moderate in > 2 region
 3: many in all region
 4: CRT obliterate in all region

46. Complex repetitive discharges
 CRD
 Bizarre high frequency or pseudomyotonic
 Heavy machinery or idling motorcycle
 Hallmark : start and stop abruptly
 Not stop with nerve block
 Ephaptical pathway

47. 3 type of CRD

48. Myotonic discharge
 Myotonia:
 Delayed muscle relaxation after contraction
 Percussion myotonia
 Warm up
 Ice effect in paramyotonia congenita
 Decreased CL conductance
 Some patient severity related with K level
 Sound dive bomber ( waxing and waning)
 Seen with or without clinical myotonia

49. Classification
 1+ : last 500 ms in 3 region
 2+ : > ½ needle sites
 3+ : all area

51. Myotonic potential

52. Fasciculation potentials
 Fasciculation :
 visible spontaneous contraction of a portion of muscles
 Arise from anterior horn cell
 Normal in foot intrinsic and GCS
 Aggravation with:
 Anxiety
 Fatigue
 Heavay exercise
 Coffee and smoking

54. Fasciculation potentials show

55. Myokimic discharge
 Vermicular movement movement
 Burst of normal MUAP with interburst silence
 Sound : low power motor boat engine
 Difference with CRD:
 No regularity in burst of MUs
 No typical start and stop abruptly
 They are group of MU but CRD single muscle fiber
 Normal in orbic. Oculi
 Face :
 Fatigue , MS, brainstem neoplasm
 Mechanisms: transaxonal ephaptic activation

57. Myokymic potentials

58. Continuous muscle fiber activity
 CNS and PNS are involved
 Stiff man syndrome:
 CNS: so inhibited with
 Peripheral and NMJ and spinal block
 General anesthesia and sleep
 Diazepam but not phenytion and CMZ
 Isaacs syndrome (neuromyotonia):
 PNS: so inhibited with
 Nm block
 But no peripheral or spinal block or
 General anesthesia or sleep not diminished
 Auto Ab against nerve voltage gated K channels

59. Cramps
 Sustained or painful contraction of multiple MU
 Exercise or malpositioning
 Needle: multiple MU synchronously firing 40-50 or 300 Hz
 Induced by :
 Hyponatremia
 Hypocalcemia
 Vitamin deficiency
 Ischemia
 Arise from peripheral portion of MU
 Cramp with electrical silence
 Mc Ardle’s disease

60. Muscle cramps show

61. Multiplet discharge
 Rapid firing of single MU
 Doublets, triplets or multiplet
 Tetany:
 Muscle twitching or Carpopedal spasm
 Association with:
 Alkalosis
 Hypocalcemia and magnesiumemia
 Hyperkalemia
 Local ischemia
 Chvostek’s sign facial nerve
 Peroneal sign : fibular head
 Trousseau’s sign : limb ischemia

62. Doublet and triplet

63. Neural loss
 2 process after denervation:
 Re-growth 2-3 mm/day
 Collateral sprouting
 Point of node of Ranvier
 Bunds of bunger : remaining Schwan cell sheaths
 Each MN : support 4-5 times
 So 20 % remaining could cover others
 Fiber types grouping
 2 weeks
 MU territory remain unchanged

64. Muscle loss
 Muscle fiber loss
 Muscle fibers approximated but no
electrical summation
 Fiber type grouping also occur

65. MUAP findings in muscle disease
 MUAP duration decreased
 Increase number of phase
 Fiber splitting and slow conduction:
 Satellite potential
 10% in normal
 12 % in neuropathy
 45 % in myopathy
 Responsible for abnormal long duration 60 ms
 Large MUAP: needle near hypertrophic fibers
 Segmental necrosis : Fib/PSW

66. Neurogenic recruitment show
 Decreased recruitmet
 Recruitment ratio : > 5
 Neuropraxia could mimic that
1st 2nd 3rd 4th
20
25 0 0
30 0 0 20

67. Myogenic recruitment show
 Increased MU firing
 Early or increased recruitment
 Recruitment ratio < 3
1st 2nd 3rd 4th 5th
15 15 15 15 15

68. Other entity
 CVA
 First MU 7-8 firing rate
 Second MU 10-15
 50-60 Hz
 EKG 1Hz
 Pacemaker

69. Pain
 Cervical paraspinal
 Lumbosacral paraspinal
 Intrinsic hand muscle

70. Contraindication
 No absolute
 Relative :
 Needle in coagulopathy
 Increased bleeding in:
 Plt < 50.000
 PT & PTT > 1.5 – 2 times nl
 Hemophilia: optimized clotting factors
 Lymphedema:
 Infection : iodine solution use
 Alcohol : questionable
 HIV chance : 0.5 % after needling
 Pneumothorax
 Cervical if needle far from mid line inserted

71. Other entity
 Muscle biopsy
 CK level 1.5 nl return 48 H to base line