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1. NERVE CONDUCTION
VELOCITY

2.  PRINCIPLES
 ACTION POTENTIAL
 AXONAL TRANSPORT
 TYPES OF CONDUCTION
 CMAP
 SNAP
 VARIABLES
BASICS

3. PRINCIPLES
 Proximal and distal rule
 Same nerve roots but different peripheral
nerves to localize the changes to one or the
other
 Until normal values

4. Proximal and Distal Rule
Proximal-distal rule: motor neurons that innervate
distal muscles (e.g., hand muscles) are located
lateral to motor neurons that innervate proximal
muscles (e.g., trunk muscles)

5. TYPES OF CONDUCTION
 ORTHODROMIC:
 Normal physiological direction
 ANTIDROMIC:
 Opposite to normal physiological direction

6. Motor unit

7. VARIABLES AFFCTING NCV
 PHYSIOLOGICAL
 AGE
 TEMPARATURE
 SEX
 DIGIT
CIRCUMFERANCE
 UPPER VERSUS
LOWER LIMB
 TECHNICAL :
 STIMULATION;
 FAULTY LOCATION
OF STIMULATOR
 FAT AND OEDEMA
 BRIDGE
FORMATION
BETWEEN ANODE
AND CATHODE

8. TECH………CONTD…….
RECORDING:
 BREAK IN THE
CABLE
 WRONGLY
CONNECTED
AMPLIFIER
 WRONG SETTINGS
OF GAIN
,SWEEP,FILTER
 INCORRECT
POSITION OF
ACTIVE OR
REFERANCE
IN ADVRETANT
STIMULATION OF
UNWANTED NERVE :
 VOLUME
CONDUCTION
 ANAMOLUS
CONDUCTION

9. NERVE CONDUCTION VELOCITY
 The speed at which the nerve conduct an
impulse

11. TYPES OF NCV
 MNCV
 SNCV
 LATE RESPONSES
 H REFLEX
 F WAVE
 AXON REFLEX
 BLINK REFLEX

12. TYPES
NCV
MNCV SNCV LATE RESPONSES

13. MNCV

14. PRINCIPLES OF MNCV
 Orthodromic
 Motor or mixed nerve is stimulated at least at
two points along it course
 Pulse is adjusted to get CMAP
 A Biphasic action potential should be
recorded
 Supra maximal stimulation should be used

16. ELECTRODE PLACEMENTS
 RECORING :
 PICK UP : Muscle belly (motor points)
 REFERENCE :Tendon(3 cm distal to pick up)
 GROUND : In between pickup and stimulating
 STIMULATING :
 Cathode – active – black - closer to pick up
 Anode – inactive - red

18. MACHINE SETTING
 Square wave pulse
 Duration-0.1ms
 Frequency-1 pulse /sec
 Intensity-5 – 40mA or 100 -300 V
 Diseased nerve-75mA or 500 V
 Filter setting-5HZ – 10KHZ
 Sweep speed-2 -5 ms/div

19. MEASUREMENTS
 Onset latency
 Duration
 Amplitude
 Conduction velocity

20. WAVE FORMS

21. LATENCY
 Time in ms from the stimulus artifact to the
first negative deflection of CMAP
 Measure of fastest conducting motor fibers
 It includes RESIDUAL LATENCY
 Measured in ms

22. AMPLITUDE
 Base line to negative peak
 Peak to peak
 Co relates with the number of nerve fibers
 Measured in mV

23. DURATION
 Initial take off from the base line to final return
to the baseline
 Co relates with the density of small nerve
fibers
 Measured in ms

24. CONDUCTION VELOCITY
 Conduction velocity is determined by dividing
the distance between the two cathodal
stimulation points by the difference between
the two latencies
Conduction distance
 CV =
Proximal –distal latency
 Meters / seconds

25. NORMAL VALUES
 In between 45-70 m/sec
 Upper limbs-60 m/sec (average)
 Lower limbs -50 m/sec (average)

26. SNCV

27. PRINCIPLES OF SNCV
 Orthodromic or Antidromic
 Orthodromic:
 Digital nerve is stimulated and SNAP recorded
at a proximal point along the nerve
 Antidromic:
 The nerve is stimulated at a proximal point
and SNAP recorded distally.

28. ELECTRODE PLACEMENTS
ORTHODROMIC STUDY
 Ring electrodes – Stimulation
 Surface electrodes - recording
 Stimulating :
 Cathode – 1st IP joint
 Anode – 3cm distal
 Recording :
 Pick up – proximal point
 Reference – 3cm proximal
 Ground – in b/w stimulating and recording

30. ANTIDROMIC STUDY (REVERSE)
 Surface electrodes – stimulating
 Ring electrode – recording
 Stimulating :
 Cathode –proximal point
 Anode -3 cm proximal
 Recording :
 Pick up – 1st pip joint
 reference -3 cm distal
 Ground –in b/w stimulating and recording

31. MACHINE SETTINGS
 Filter – 10 Hz – 2kHz
 Sweep speed -1-2ms/div
 Gain – 1-5 µV /div

32. MEASUREMENTS
 Onset latency
 Amplitude
 Duration
 Conduction velocity

33. WAVE FORM

34. ONSET LATENCY
 Stimulus artifact to the initial positive or
subsequent negative peak
 Measured in ms

35. DURATION
 Initial take off from the baseline to final return
to the baseline
 It represents the number of slow conducting
fibers
 Measured in ms

36. AMPLITUDE
 Base line to negative peak or Positive to
negative peak
 It represents the density of nerve fibers
 Measured in mV

37. CONDUCTION VELOCITY
 SNCV is calculated dividing the distance
(mm) between stimulating and recording site
by the latency
Distance
 CV =
latency
 Meters / seconds

38. ABNORMAL NCV
 Degeneration – amplitude reduction
 Demyelination – latency prolongation

39. LATE RESPONSES

40.  Late responses are the potentials
appearing after motor response (M wave)
following a mixed nerve stimulation

41. TYPES
 H reflex
 F wave
 Axon reflex

42. F WAVE

43. F WAVE
It is a late response resulting from Antidromic
activation of alpha motor neuron involving
conduction to and from spinal cord and occurs at
the interface between the peripheral and central
nervous system

44. PHYSIOLOGY OF F WAVE

45. WAVE FORMS

46. HISTORICAL BACKGROUND
 Magladery and mc dougal – 1950 ( CMT )
 Small muscles in the foot
 De afferented man
 Not a reflex
 Proximal motor pathway

47. FACTORS AFFECTING
F WAVE
 Renshaw cell inhibition
 Maximum voluntary contraction
 Tension

48. METHODS
 Supra maximal stimulation ( 25 % )
 Stimulus rate more than 0.5
 Cathode should be proximal to anode
 It is recorded from any distal muscle by
stimulating appropriate nerve

49. RECORDING
 Electrode placements – same as MNCV
Machine settings:
 Amplifier gain – 200 -300 microvolts /division
 Sweep speed – 5-10 ms / division

50. PROCEDURE
 Relaxed
 slight voluntary contraction
 Amplitude of more than 20 micro volts
 10 – 20 responses
 persistence

51. PARAMETERS
 Latency
 Chronodispersion
 Persistence
 Amplitude
 F/M ratio
 Conduction velocity

52. WAVE FORMS

53. LATENCY
 Minimal latency
 Maximal latency
 Mean or median latency
 Age, height, limb length
 31 ms in hand, 61 ms in foot
 Right to left symmetry is more than 2 ms in
hand and 4 ms in foot – abnormal

54. CHRONODISPERSION
 Difference between minimal latency and
maximal latency
 Measure of range of conduction of F wave
 ABP – 3.6 +/- 1.2
 ADM – 3.3 +/- 1.1
 EDB – 6.4 +/- 0.8

55. PERSISTENCE
 Number of occurrence divided by number of
stimuli
 Measure of antidromic excitability of particular
motor neuron pool

56. AMPLITUDE
 Depends on the number and size of the
motor unit
 5 % of M wave
 Mean amplitude
 Excitability of alpha motor neuron

57. F/M RATIO
 Proportion of motor neuron pool activated by
antidromic stimulation
 To use mean rather than maximum F
amplitude for calculating F/M ratio
 ADM – O.8
 Ad H – 0.9

58. CONDUCTION VELOCITY
 stimulus site to C7 spinous process via the
axilla and mid clavicular point
 Stimulus site to T12 spinous process via knee
and greater trochanter of the femur
( 2D )
 FWCV =
( F – M – 1 )

59. CLINICAL APPLICATIONS
 Proximal motor pathway
 Segmental motor neuron excitability
 It is more precise for assessment of
segmental motor neuron excitability than H
and T reflex

60. LMN
latency
 Changes in peripheral nerve and root lesion
F/M ratio
 Increased in both poly neuropathy and spasticity
persistence
 Absent or reduced in GBS, ALS, proximal nerve root
injury
choronodispersion
 Increased in poly neuropathy ( demyelinating )

61. UMN
Amplitude and Persistence
 Initial stage – Decreased
 Chronic stage – Increased
 latency also prolonged while duration and
amplitude increased in UMN

62. H REFLEX

63. H- REFLEX
The H - reflex is a monosynaptic reflex elicited
by sub maximal stimulation of the tibial nerve
and recorded from calf muscles
 Hoffman 1918

64. PHYSIOLOGY OF H REFLEX

65. REFLEX ARC
 1 a fibers
 Spinal cord
 Alpha motor neuron

66.  It does not include muscle spindle
 H reflex is larger at submaximal stimulation
 Inhibited by stronger stimulation
Due to collision of orthodromic impulses by
antidromic conduction in motor axons

67. MODIFYING FACTORS
 Renshaw cell inhibition
 Supraspinal mechanism
 Inhibition by adjacent motor neuron

68. VARIATIONS
 In normal adults – other muscles except small
muscles of hand and feet
 In childrens – below 2 years

69. METHODS

70. ELECTRODE PLACEMENTS
 Position :
Semi reclining or prone
 Recording :
Active - Distal edge of calf
Reference - Tendon
 Stimulating :
popleteal fossa

72. MACHINE SETTINGS
STIMULATION
 Square wave pulse of 1 ms
 Stimuli below 0.1 ms will stimulate motor
axons
 Cathode is kept proximal to anode
 Stimulus frequency should not exceed 1 in 5
seconds

73. PROCEDURE
 The stimuli is adjusted to evoke maximum H
response amplitude
 At this strength a small M response may also
present
 M response – help to monitor the strength of
stimuli
 At least 5 H response required for analysis
 By increasing the stimuli strength to supra
maximal maximum M responses can be
recorded
 3 M responses required for analysis

74. PARAMETERS
 latency
 H - amplitude
 M wave
 H / M ratio
 H - Vibratory inhibition
 H – TA
 Conduction velocity

75. WAVE FORMS

76. NORMAL VALUES
Latency 30.3 +/- 1.7
Amplitude 9.8 +/- 6.1
M wave 24.6 +/- 6.6
H/M ratio 0.4 +/- 0.2
H vib 42.9 +/- 18.2
H - TA 39.9 +/- 31.1

77. LATENCY
 Measured in ms
 Soleus – 35 ms, FCR – 20 ms
 Age, height, limb length
 Right to left asymmetry up to 1.5 ms
 Latency in full term infant is 15.94 +/- 1.45

78. AMPLITUDE
 Base to peak of the negative phase
 Measured in mV
 Alpha motor neuron excitability

79. H / M - RATIO
 The ratio of peak to peak maximum H reflex
to maximum M amplitude
 To estimate the motor neuron pool activation
 Less than 0.7

80. TONIC VIBIRATION REFLEX
VIBIRATORY INHIBITION
 Achilles tendon is vibrated for 1 minute at 100
Hz
 Normal – amplitude decreases
 UMN lesion – there is no decrease in
amplitude
 Due to the vibratory inhibition is less than
normal

81. VIBRATORY INHIBITION

82. RECIPROCAL INHIBITION

83. CONDUCTION VELOCITY
 The distance between knee and T11 by the
latency difference between H reflex and M
response

84. CLINICAL APPLICATIONS
PNS
To evaluate proximal sensory motor pathway
Helpful in plexopathies ,radiculopathies and
neuropathies
latency
 S1 radiculopathy – Absent
 C5 - C6 radiculopathy – Absent
 GBS - absent or delayed or dispersed

85. CNS
 Understanding the patho physiology
 Excitability of alpha motor neuron
 Amplitude, H/M ratio, H - vibratory inhibition,
H - reciprocal inhibition

86. DIFFERENCE
BETWEEN H REFLEX AND F WAVE

87. H reflex F wave
Nature Monosynaptic
reflex
Not a reflex but
due to antidromic
activation of alpha
motor neuron
Best elicited in Soleus, FCR,VM Any distal muscle
Stimulus Sub maximal Supra maximal
Persistence Persistent Variable
Amplitude 50 – 100 % of M
wave
5 % M wave
Useful in Neuropathy,radicul
opathy,spaticity
Neuropathy,radicul
opathy

88. BLINK REFLEX

89. BLINK REFLEX
 The electrical analog of corneal reflex
 Kugelberg in 1952
 To evaluate trigeminal and facial
 Supra orbital nerve
 Orbicularis oculi

90. REFLEX ARC
 Afferent – trigeminal nerve
 Centre – pons
 Efferent – facial nerve

91. PHYSIOLOGY OF BLINK REFLEX

92. METHOD

93. ELECTRODE PLACEMENTS
Recording :
 Recording - bilaterally over orbicularis oculi
 Reference - side of nasal bone
 Ground - over chin
Stimulating :
 Cathode - supra orbital notch over supra
orbital nerve
 Anode - directed somewhat laterally

95. MACHINE SETTINGS
 Gain - 200 – 500 mV/division
 Sweep speed - 10 ms /division
 Stimulus rate - 1 in 3 seconds
 Avoid prolonged studies - R2 Habituated
 Aberrant innervation - lower facial muscles

96. RESPONSES
 Ipsilateral side - R1 and R2
 Contra lateral - R2

97. WAVE FORMS

98. PHYSIOLOGICAL MECHANISM
 R 1 - Monosynaptic pathway
 R2 - Poly synaptic pathway

99. NORMAL VALUES
Ipsilateral side
 R1 – less than 13 ms
 R2 -- less than 40 ms
Contra lateral side
 R2 – less than 41 ms

100. CLINICAL APPLICATIONS
 Abnormal R1 and R2 on the paretic side with
normal contra lateral R2 - ipsi lateral facial
nerve lesion