This document provides information about needle electromyography (EMG), including the types of spontaneous activity and motor unit potentials that can be observed. It discusses normal insertional activity and recruitment patterns and lists various abnormal spontaneous muscle fiber and motor unit potentials that can indicate neurogenic or myopathic conditions. These include fibrillation potentials, positive sharp waves, complex repetitive discharges, and fasciculation potentials among others. The document also describes how to analyze motor unit potential morphology and recruitment.

1. MUHAMMED AJMAL P,NDT,CINM
IONM TECHNOLOGIST
NEUROSURGERY.

2.  Needle EMG involves extracellular recording of muscle
action potentials using either monopolar or concentric needle
electrodes.
 This is a qualitative assessment

3.  It can distinguish myopathic from neurogenic muscle
wasting and weakness
 It can detect abnormalities such as chronic
denervation or fasciculations in clinically normal
muscle
 It can, by determining the distribution of neurogenic
abnormalities, differentiate focal nerve, plexus, or
radicular pathology

4. 1. Insertional activity
2. Spontaneous activity
3. Recruitment Pattern
4. Interference Pattern

5.  Burst of high frequency positive or negative spikes
occurring
 Due to mechanical irritation/injury by the penetrating
needle
 It lasts for about few hundred milliseconds
 At least four to six brief needle movements are made in
four quadrants of each muscle to assess insertional
activity

6.  Its lasts longer than 300 ms
indicates increased
insertional activity
 Increased insertional
activity may be seen in both
neuropathic and myopathic
conditions

8.  The insertion activity can be graded as follows:
 No activity
 Decreased activity
 Normal activity
 Increased activity
 Highly increased activity

9.  All spontaneous activity is abnormal
 exception of potentials that occur in the
muscle endplate zone (i.e., the NMJ).
a) endplate noise
b) endplate spikes

10.  Physiologically, they represent MEPPs.
 It occurs with the release of acetylcholine due to
irritation of intramuscular nerve terminals by the needle
tip at the end plate region
 low-amplitude (10-50μv ), monophasic negative
potentials
 duration of 1-2ms
 Firing Rate 20-40Hz
 “seashell” sound

12.  It occurs due to stimulation of the single muscle fiber
by the tip of the needle at the end plate
 They are biphasic, with an initial negative deflection
 Sound like cracking, buzzing, or sputtering
 It is irregular high amplitude(100-200μv)
 Duration of 3-4ms
 Firing Rate 5-50Hz

15.  ABNORMAL MUSCLE FIBER POTENTIALS
1. Fibrillation Potentials
2. Positive Sharp Waves
3. Complex Repetitive Discharges (CRD)
4. Myotonic Discharges
 ABNORMAL MOTOR UNIT POTENTIALS
1. Fasciculation Potentials
2. Doublets, Triplets, and Multiplets
3. Myokymic Discharges
4. Cramp Potentials
5. Neuromyotonic Discharges
6. Rest Tremor

16. 1. Fibrillation Potentials
 This arise from single muscle fiber.
 Active denervation.
 They typically are associated with neuropathic disorders
(i.e., neuropathies, radiculopathies, motor neuron disease)
 they also may be seen in some muscle disorders (especially
the inflammatory myopathies and dystrophies)
 rarely in severe diseases of the NMJ (especially botulism).

17. Morphology:
 A brief spike with an initial
positive deflection
 1 to 5 ms in duration
 low in amplitude (typically
10–100 μV).
 The firing pattern is very
regular
 0.5 to 10 Hz, occasionally
up to 30 Hz
 sound like “rain on the roof

19. 2. Positive Sharp Waves
 spontaneous depolarization of a muscle
fiber
 active denervation.

20.  A brief initial positivity
followed by a long
negative phase
 sound like a dull pop
 (usually 10–100 μV,
occasionally up to 3
mV).
 Regular Pattern
 0.5-10Hz (30Hz)
 early in denervation.

21.  0 None present
 +1 Persistent single trains of potentials (>2–3 seconds)
in at least two areas
 +2 Moderate number of potentials in three or moreV
areas
 +3 Many potentials in all areas
 +4 Full interference pattern of potentials

22. 3.Complex Repetitive Discharges
 depolarization of a single muscle fiber
followed by ephaptic spread to adjacent
denervated fibers
 direct spread from muscle membrane to
muscle membrane).

23. Pathophysiology of a complex repetitive:
discharge (CRD). A spontaneous depolarization occurs from
ephaptic transmission from one denervated muscle fiber to an
adjacent one. If the original pacemaker is reactivated, a circus
movement is formed without an intervening synapse. In neuropathic
conditions, the pathologic correlate is grouped atrophy, wherein
denervated fibers lie next to other denervated fiberS.

24.  high-frequency
(typically 5–100 Hz)
 repetitive discharges
 abrupt onset and
termination.
 machine-like sound
 Perfectly regular
 They occur in both
chronic neuropathic and
myopathic disorders

26. 3.Myotonic Discharges
 spontaneous discharge of a muscle fiber
 similar to fibrillation potentials and positive sharp
waves
 waxing and waning of both amplitude and frequency
 20–150 Hz
 “revving engine” sound on EMG,

27.  myotonic dystrophy, myotonia congenita, and paramyotonia
congenita.
 also occur in other myopathies (acid maltasecdeficiency,
polymyositis, myotubular myopathy), hyperkalemic periodic
paralysis,
 rarely, in denervation of any cause.
 A single brief run of myotonic discharges may occur in any
denervating disorder

28.  1. Fasciculation Potentials
 A fasciculation potential is a single, spontaneous,
involuntary discharge of an individual motor unit
 The source generator of fasciculation potentials is the
motor neuron or its axon, prior to its terminal branches
 Stimulus can originate at any level from anterior horn
cell to axon terminal

29.  corn popping
 Low (0.1–10 Hz)
 generally fire very
slowly and irregularly,

30. 2. Doublets, Triplets,
and Multiplets
 Spontaneous MUAPs
that fire in groups of
two are known as
doublets
 Same fasciculation
potentials
 Horse trotting
 Variable (1–50 Hz)

31.  Fasciculations are associated with numerous
disease processes affecting the lower motor
neuron
◦ Motor neuron disease, such as amyotrophic lateral
sclerosis,
◦ radiculopathies, polyneuropathies, and entrapment
neuropathies.

32. 3. Myokymic Discharges
 The are rhythmic, grouped, spontaneous repetitive
discharges of the same motor unit (i.e., grouped
fasciculations).
 1–5 Hz (interburst)
 5–60 Hz(intraburst)
 Marching soldiers
 The origin -spontaneous depolarization of or ephaptic
transmission along demyelinated segments of nerve.

34.  Disorders Commonly Associated with Myokymic
Discharges:
 Radiation injury (usually brachial plexopathy)
 Guillain–Barré syndrome (facial)
 Multiple sclerosis (facial)
 Pontine tumors (facial)
 Hypocalcemia
Occasionally seen in
 Guillain–Barré syndrome (limbs)
 Chronic inflammatory demyelinating polyneuropathy
 Nerve entrapments
 Radiculopathy

35.  involuntary contractions
of muscle
 Cramps are painful,
 high-frequency
discharges
 usually 40–75 Hz
 Cramps may be benign
(e.g., nocturnal calf
cramps, post-exercise
cramps)

36.  maybe associated with a wide range of
neuropathic,endocrinologic, and metabolic
conditions.

38.  decrementing, repetitive discharges of a single motor unit
 high-frequency (150–250 Hz)
 “pinging” sound
 Autoimmune channelopathy
 Clinically
 Stiffness
• Hyper hidrosis
• Delayed muscle relaxation after contraction.

40.  Tremor is recognized as a synchronous bursting pattern
of MUAPs separated by relative silence
 Marching soldiers
 1–5 Hz (interburst)
 Bursting –synchronous bursting of many different
motor unit potentials

43.  The motor unit refers to
the motor neuron cell
body, motor axon, and all
innervated muscle fibres.
 The motor unit potential
(MUP ) is the sum of
activity from muscle
fibres of one motor unit
 Components:
•Amplitude
•Duration
 •Rise time
 •Phases

46.  It is measured from peak to
peak of the MUAP.
 amplitude100 μV- 2 mV
 MUAP amplitude reflects
only those few fibers nearest
to the needle (only 2–12
fibers).

47.  Measured from the
initial deflection from
the base line to the
final return to the base
line
 Duration-5 to 15 ms
 It depends primarily on
the number of muscle
fibers within the motor
unit

48.  Increased age -increased duration
 Decreased temperature -increased duration
 Proximal and bulbofacial muscles- shorter duration

49.  Polyphasia
◦ Is a measure of synchrony
◦ muscle fibers within a motor unit fire more or less
at the same time
◦ may be abnormal in both myopathic and
neuropathic disorders
◦ calculated by counting the number of baseline
crossings of the MUAP and adding one
◦ Normally, MUAPs 2-4 Phases.
◦ >4 it is called polyphasic

51.  also called turns
 changes in the direction
of the potential that do
not cross the baseline

52.  seen in early
reinnervation
 late spike distinct
from main potential
 time locked to the
main potential
 Latency can rage
from 8-32ms

53.  It is the time lag from
the initial positive peak
to the subsequent
negative peak of the
MUP.
 It reflects the distance
between the recording
electrode and the
muscle fibres of the
motor unit
 Rise time <500μs

54.  It depends on the number of muscle fibres
with in 2mm radius of the recording electrode
 Movement of the electrode has significant
effect on area
 Helps to differentiate neuropathy from
myopathy

55. Activation
 Refers to the ability to increase firing rate.
 This is a central process.
 Poor activation may be seen in diseases of the central
nervous system (CNS) or as a manifestation of pain,
poor cooperation, or functional disorders.

56. Recruitment
 the ability to add motor unit action potentials as the
firing rate increases.
 Recruitment is reduced primarily in neuropathic
diseases
 although rarely it may also be reduced in severe end-
stage myopathy
 Normal ratio of firing frequency to the number of
motor units is 5:1
 Maximum firing rate of a motor unit is about 30-50HZ

57. Normal recruitment:
 the pattern of recruitment is normal for that
muscle, with an adequate number of MUAPs
being recruited for the frequency of firing
present.
 If maximal effort can be obtained, a full
interference pattern is seen.
 It should obey the 5:1 Ratio

59. Reduced recruitment
 Reduced recruitment is characteristic of neurogenic
disorders in which axonal loss or conduction block is
the pathophysiologic mechanism
 severe or end stage myopathic disorders, reduced
recruitment may also occur due to the loss of all muscle
fibers within a motor unit.

60. Rapid /Early recruitment
 increased number of motor units relative to the force of
contraction
 early recruitment pattern is typically seen in muscle
disorders and in some disorders of the NMJ.

61.  During the maximum contraction of muscle several motor units get
activated simultaneously resulting in the over lap of MUPs creating an
interference pattern

63.  Equipment
 •Electrodes
 •Amplifier
 •Filter
 •Display method

64.  Electrodes
 For clinical Electromyography following
Needle electrodes are used

65.  Amplifiers
 Bioelectrical potentials recorded will be in the range of
1μV to 1mV these signals need to be amplified by
1million to thousand times for deflection of 1cm in
1v/cm recording
 Differential amplifiers increases the amplitude of the
desired response while rejecting unwanted noise
 Amplifiers ability to reject common signals is known as
its common mode rejection ratio (CMRR).
 The higher the CMRR, the better the rejection

66. Gain
 Amplifier gain describes the extent to which the
input signal is increased in voltage.
 Display sensitivity
 Describes the visible waveform and is expressed
as volts per division or volts per centimeter
 Usually kept at 50-200μV/cm
Filters
 They are used to selectively attenuate the noise
preserving the signal Band pass filters extending
from 10HZ to 10KHZ is
 commonly used

67. Preparing the patient
 Prior to the test Patient should be briefly
explained about the procedure and insertion
of needle would cause some discomfort
 Wipe the skin over the each puncture site
with spirit beforenneedle is inserted
 Though most patients tolerate the pain some
may require oral analgesic

68. Selecting the muscle
 It is done on the basis of clinical indication
 Ideally muscle selected should be superficial,
easily palpated, Located away from major
blood vessels and nerve trunks