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Brad 4th Ed Part 1 > Ch. 10 Electrodiagnostic medicine II: Clinical Evaluation & Findings > Flashcards

Ch. 10 Electrodiagnostic medicine II: Clinical Evaluation & Findings Flashcards

1
Q

What is an H-reflex?

A

Electrophysiologically recorded Achilles muscle stretch reflex

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2
Q

How is an H-reflex generated?

A

Recording over the gastroc and soleus muscles and stimulating the tibial nerve in the popliteal fossa

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3
Q

Describe the stimulus needed to generate an H-reflex

A

Stim duration of 1 ms
Inc by 3-5 mA increments
Freq of <1/second

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4
Q

What does an abnormal H-reflex indicate?

A

Lesions alone sciatic nerve, lumbosacral plexus or S1 nerve root

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5
Q

What is a F-wave?

A

Late responses involving motor axons and axonal pool at the spinal cord level

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6
Q

How are F-waves elicited?

A

With maximal stim of the median, ulnar, peroneal or tibial nerves

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7
Q

What are the four types of needle examination during EMG?

A
  1. Insertional activity
  2. Spontaneous activity
  3. Morphology and size of motor units
  4. Motor unit recruitment
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8
Q

How is insertional activity examined?

A

Briefly inserting needle through muscle and observing amount and duration of electrical activity

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9
Q

When is decreased insertional activity seen?

A

In atrophied muscle or fatty tissue

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10
Q

What is considered increased insertional activity?

A

Activity lasting >300 ms after needle stops advancing

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11
Q

What is spontaneous activity?

A

Electrical discharges occurring after needle movement has stopped

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12
Q

Describe the appearance of an end-plate potential

A 
Biphasic 
Initial negative (upward) deflection
Fire irregularly
Sputtering sound
Assoc w/ pain
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13
Q

Describe the shape of a PSW

A

Biphasic

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14
Q

Describe the shape of a fibrillation potential

A

Triphasic

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15
Q

Describe grade 1+ spontaneous potentials

A

Transient but reproducible trains of discharges after moving the needle in more than one site or quadrant

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16
Q

Describe grade 2+ spontaneous potentials

A

Occasional spontaneous potentials >2 diff quadrants

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17
Q

Describe grade 3+ spontaneous potentials

A

Spontaneous potentials present in all quadrants

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18
Q

Describe grade 4+ spontaneous potentials

A

Abundant spontaneous potentials nearly filling the screen in all 4 quadrants

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19
Q

What is a polyphasic potential?

A

> 4 phases

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20
Q

What is a serrated potential?

A

Same clinic relevance as polyphasic with many turns that do not cross baseline

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21
Q

What are polyphasic potentials associated with?

A

Reinnervation of denervated motor units when duration is inc or myopathies and NMJ d/o when duration is short

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22
Q

What is seen on EMG with full force muscle contractions?

A

Screen filled w/ overlapping motor units making it impossible to assess individual motor units

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23
Q

What is seen on EMG with low force muscle contractions?

A

1 or 2 units firing at ~10Hz

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24
Q

What is reduced recruitment?

A

Firing ratio of highest firing rate to number of motor units in 100 ms is >10

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25
Q

What does reduced recruitment indicate?

A

Motor axonal loss or function drop out from conduction block

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26
Q

What is early or myopathic recruitment?

A

Many motor units recruited to generate a low level of force

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27
Q

What does early recruitment indicate?

A

Myopathy or NMJ disorder

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28
Q

What diseases are complex repetitive discharges seen in?

A 
Polymyositis
Limb girdle dsytrophy
Myxedema
Schwartz-Jampel synd
Spinal muscular atrophy
Amyotrophic lateral sclerosis
Hereditary and chronic neuropathies
Carpal tunnel synd
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29
Q

Which normal muscles are complex repetitive discharges seen in?

A

Iliopsoas

Biceps brachii

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30
Q

What diseases are Myokymic discharges seen in?

A 
Multiple sclerosis
Brainstem neoplasm
Polyradiculopathy
Bell pasly
Radiaton plexopathy
Chronic nerve compression
Rattlesnake venom
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31
Q

What do complex repetitive discharges sound like?

A

Machine-like discharge

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32
Q

What do myokymic potentials sound like?

A

Marching soldiers

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33
Q

What do myotonic potentials sound like?

A

Diver bombers

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34
Q

What diseases are myotonic potentials seen in?

A 
Myotonic dystrophy
Myotonia congenita
Paramyotonia
Polymyositis
Acid maltase def
Hyperkalemic periodic paralysis
Chronic radiculopathy/peripheral polyneuropathy
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35
Q

When should single fiber EMG’s be performed?

A

Neuromuscular disorders
Myasthenia gravis
Lambert-Eaton synd

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36
Q

What is a hallmark finding of Lambert-Eaton synd?

A

Marked facilitation of the CMAP >400% of baseline amp after brief contraction

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37
Q

What is Martin-Gruber anastomosis?

A

Branch from median nerve, usually the AIN joins the ulnar nerve in the forearm

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38
Q

What is seen with Martin-Gruber anastomosis on Median nerve NCS?

A

Median CMAP is smaller with wrist stimulation than w/ proximal stimulatio

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39
Q

What is seen with Martin-Gruber anastomosis on Ulnar nerve NCS?

A

Larger amp w/ wrist stim than w/ below or above elbow stim

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40
Q

What is an accessory deep peroneal nerve?

A

Part of the deep peroneal nerve that remains with the superficial peroneal nerve and innervates the EDB after passing behind the lateral malleolus

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41
Q

What is seen on EDB NCS with an accessory deep peroneal nerve?

A

Stim at the fibular head yields a higher CMAP than ankle stim when recorded over EDB

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42
Q

How can an accessory deep peroneal nerve be stimulated?

A

Stim behind the lateral malleolus

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43
Q

What type of stimulating probe is needed for pediatric EDX?

A

Pediatric bipolar stimulating probe

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44
Q

What type of EMG needle should be used for pediatric patients?

A

Monopolar

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45
Q

What skin surface temperature is needed in pediatric EDX?

A

36-37 degrees C

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46
Q

Which children are at risk for malignant hyperthermia?

A

Children with neuromuscular diseases who are given halogenated anesthesia

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47
Q

Which muscles should be tested for spontaneous activity in infants?

A

Extensor muscles and intrinsic hand and foot muscles

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48
Q

Describe motor units in pediatric patients

A

Bi or triphasic
Amp 100-700 uV
Short duration 5-9 ms

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49
Q

Which muscles should be examined for motor unit morphology and recruitment in pediatrics?

A

Flexor muscles

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50
Q

What is repetitive nerve stimulation used to evaluate?

A

Pre and postsynaptic neuromuscular disorders

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51
Q

What is the MCC of generalized hypotonia?

A

Central nervous system d/o

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52
Q

What is the MC neuromuscular dx in hypotonic infants?

A

Spinal muscular atrophy

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53
Q

What obstetric causes are related to brachial plexopathies at birth?

A

Duration of labor

Shoulder dystocia

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54
Q

What is involved in Erb pasly?

A

Upper plexus and C5 or C6 roots

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55
Q

What is involved in Kumpke palsy?

A

Lower trunk, C8 or T1 roots

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56
Q

What are anatomic risk factors for brachial plexus injury?

A

Supracostoclavicular space narrowing with cervical ribs or fibrous bands

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57
Q

What is the MC entrapment neuropathy?

A

Carpal tunnel synd

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58
Q

What are causes of CTS?

A

Repetitive trauma
Obesity
Pregnancy
Lupus

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59
Q

What are sx of CTS?

A

Aching pain in the forearm and wrist
Insidious onset of tingling, parasthesias of thumb, index and long finger
Thenar weakness
Nocturnal pain

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60
Q

What is mild CTS?

A

Prolonged SNAP and/or slightly reduced SNAP amp

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61
Q

What is moderate CTS?

A

ABN median SNAP plus prolonged motor latency

62
Q

What is severe CTS?

A

Prolonged motor and sensory distal latencies plus either absent SNAP or low amp or absent CMAP
EMG shows fibs in thenar muscles

63
Q

What is pronator synd?

A

Entrapment of the median nerve b/w heads of the pronator teres and beneath FDS arch at forearm

64
Q

What are causes of pronator synd?

A

Repetitive overuse
Tight casting
Penetrating injuries (IV catheter)
“Grocery bag neuropathy” carrying a bag w/ arm flexed

65
Q

What are sx of pronator synd?

A 
Aching pain in volar forearm
Hand numbness
Sx worse w/ repeated pronation
Loss of dexterity
Flexor muscle and thenar muscle wasting if severe
Tender pronator muscle
66
Q

What is ABN on NCS in pronator synd?

A

CMAP reduced if motor axonal loss present

NCV slowed across pronator area or conduction block

67
Q

What is ABN on EMG in pronator synd?

A

Reduced recruitment in median innervated muscles

Pronator teres spared

68
Q

What is Kiloh-Nevin synd?

A

Entrapment of AIN at forearm

69
Q

What are the causes of AIN synd?

A 
Direct trauma
Inflam
Strenous exercise
Fx
Brachial neuritis
Compression by fibrous bands
70
Q

What are the sx of AIN synd?

A 
Pure motor synd
Pain in forearm and elbow
Weak FPL adn FDP of index and long finger
Weak pronator quadratus
Fingers pinch with OK sign
71
Q

What is ABN on EDX with AIN synd?

A

Slowed median NCV to pronator quadratus

Findings on EMG to FPL, PQ and FDP to index and long fingers

72
Q

What causes median nerve entrapment beneath the ligament of struthers?

A

Trauma
Inflam
Fibrous band from supracondylar process to medial epicondyle

73
Q

What are the sx of median nerve entrapment beneath the ligament of struthers?

A 
Weak grip
Wrist flexor weakness
Deep aching pain in forearm
Numbness of 1-3 digits
Weak hand pronation
2nd and 3rd digit flexion weakness
Wasting of APB
74
Q

What is the ligament of struthers?

A

CT from the supracondylar process of the humerus (also known as avian spur) to the medial humeral epicondyle

75
Q

What is seen on NCS of median nerve entrapment beneath the ligament of struthers?

A

Dec or absent SNAP
Red motor NCV or conduction block across this segment
Dec CMAP from APB

76
Q

What is seen on EMG of median nerve entrapment beneath the ligament of struthers?

A

Findings in median nerve muscles including pronator teres

77
Q

What are causes of radial nerve entrapment at the axilla?

A

Improper use of crutches

Falling asleep w/ arm over sharp chair back

78
Q

What are sx of radial nerve entrapment at the axilla?

A

Weakness in all radial innervated muscles including triceps

Dec sensation in posterior arm and forearm

79
Q

What seen on NCS of radial nerve entrapment at the axilla?

A

Reduced or absent SNAP and CMAP

Conduction block across axilla

80
Q

What seen on EMG of radial nerve entrapment at the axilla?

A

Findings in radial innervated muscles including triceps

81
Q

What are causes of radial nerve entrapment at the spiral groove?

A

Prolonged compression of the nerve at humerus from someone sleeping on the arm (honeymoon palsy)
Assoc w/ alcohol use
Injection
Compression with tourniquet

82
Q

What are sx of radial nerve entrapment at the spiral groove?

A

Involves all radial innervated muscles except the triceps and aconeus
Wrist and finger extension weakness
Sensory loss over dorsal hand and posterior forearm

83
Q

What seen on EMG of radial nerve entrapment at the spiral groove?

A

Findings in radial innervated muscles except triceps and aconeus

84
Q

What is radial tunnel synd?

A

Entrapment of the PIN by fibrous bands at radial head or tendinous margin of the ECRB

85
Q

What is PIN or supinator synd?

A

PIN entrapped by origin of supinator muscle at aracde of Frohse

86
Q

What are causes of radial nerve with PIN compression?

A 
Radial tunnel, PIN or supinator synd
Elbow dislocation
Monteggia fx
FOOSH 
Surgical resection of radial head
Mass lesions
87
Q

What is a Monteggia fx?

A

Fx of the proximal third of the ulna with dislocation of the proximal head of the radius

88
Q

What are sx of radial nerve with PIN compression?

A

Deep pain at elbow
Wrist extension weakness
Weakness of MCP extension w/ preserved ability to extend IP joints d/t interossei
No sensory loss

89
Q

What is seen on NCS of radial nerve with PIN compression?

A

Normal superficial radial sensory response
Slowed motor conductive across the elbow
Low CMAP over EIP

90
Q

What is seen on EMG of radial nerve with PIN compression?

A

Findings in PIN innervated muscles

Brachioradialis and ECRL spared

91
Q

What is Wartenberg synd?

A

Radial nerve entrapment at the wrist

92
Q

What are causes of radial nerve entrapment at the wrist?

A

Handcuff or bracelet neuropathy
Ganglions
Over use synd

93
Q

What are sx of radial nerve entrapment at the wrist?

A

Numbness, parasthesias of dorsoradial aspec of hand and dorsum of 1-3 digits
Tender to palpation in this area
No motor weakness

94
Q

What is seen on NCS of radial nerve entrapment at the wrist?

A

Superficial radial sensory response delayed in latency or low in amp

95
Q

What are causes of ulnar nerve compression at Guyon’s canal?

A

Chronic pressure from using tools
Bicycling riding
Ganglion
RA

96
Q

What is affected in Type 1 ulnar nerve compression at Guyon’s canal?

A

Hypothenar and deep ulnar branch

97
Q

What is affected in Type 2 ulnar nerve compression at Guyon’s canal?

A

Deep ulnar branch

98
Q

What is affected in Type 3I ulnar nerve compression at Guyon’s canal?

A

Superficial ulnar sensory branch

99
Q

What sx of ulnar nerve compression at Guyon’s canal?

A

Numbness
Parasthesia
Intrinsic muscle atrophy
Nocturnal pain

100
Q

What is seen on EMG of ulnar nerve compression at Guyon’s canal?

A

Fibs or motor unit changes in hand intrinsics but not thenar muscles

101
Q

What are causes of ulnar nerve entrapment at the elbow?

A 
Trauma
Cubitus valgus
Bony spurs
Tumors
Overuse
Previous fx
Arcade of struthers
FCU
102
Q

What are sx of ulnar nerve entrapment at the elbow?

A 
Vague aching dull forearm pain
Intermittent parasthesia
Hypoesthesia on ulnar side of hand
Weakness of abduction of 5th finger
Ulnar claw when severe
Wasting of FDI and hypothenar eminence
Wasting of ulnar border of forearm
103
Q

What is seen on NCS of ulnar nerve entrapment at the elbow?

A

Ulnar sensory/motor or dorsal ulnar cutaneous nerve amp absent or reduced
NCV > 10 m/s slower across elbow

104
Q

What are causes of femoral neuropathy?

A

Trauma
Retroperitoneal hematoma
Cardiac cathererizations

105
Q

What are sx of femoral neuropathy?

A

Weak quads and knee extension
Absent knee jerk
Groin pain
Dec sensation over medial and anterior thigh and lower leg in saphenous nerve distribution

106
Q

What is seen on NSC in femoral neuropathy?

A

Red amp or absent saphenous nerve response

Red CMAP over rectus femoris

107
Q

What is meralgia parasthetica?

A

Lateral femoral cutaneous nerve entrapment at the thigh

108
Q

What are causes of lateral femoral cutaneous nerve entrapment at the thigh?

A

Repeated trauma
Obesity
Pregnancy
Tight clothing over lateral inguinal ligament

109
Q

What are sx of lateral femoral cutaneous nerve entrapment at the thigh?

A

Pure sensory synd
Parasthesias, burning or dull ache in lateral thigh
Aggravated by prolonged standing or walking

110
Q

What is seen on NCS of lateral femoral cutaneous nerve entrapment at the thigh?

A

Red amp in lateral femoral cutaneous nerve

111
Q

What are causes of peroneal nerve entrapment at the fibular head?

A 
Fx
Casting
Tight stockings
Excessive weight loss
Farm work
Tumors
Crossing legs or improper positioning
112
Q

What are sx of peroneal nerve entrapment at the fibular head?

A

Foot drop
Weakness of eversion
Numbness of dorsum of the foot
Pain

113
Q

What is seen on NCS of peroneal nerve entrapment at the fibular head?

A

CV reduces in fibular head segment by >10 m/s compared to leg segment

114
Q

What are causes of tibial nerve entrapment at the tarsal tunnel?

A 
Compression from shoes
Casting
Post traumatic fibrous
Overuse
Ganglion cysts
115
Q

What are sx of tibial nerve entrapment at the tarsal tunnel?

A

Pain in foot and ankle
Wasting and weakness in feet
Sensory impairment at toes and sole of foot

116
Q

What is seen on NCS of tibial nerve entrapment at the tarsal tunnel?

A

Prolonged latencies or low amp of plantar nerves and tibial motor across tarsal tunnel

117
Q

What is seen clinically with traumatic plexopathy with nerve root avulsion?

A

Profound weakness
CMAP low or absent
SNAPs preserved

118
Q

What is a radiculopathy?

A

Pathologic process involving a spinal nerve root

119
Q

Why are SNAPs preserved in most radiculopathies?

A

Nerve root is affected proximal to the dorsal root ganglion

120
Q

How is a radiculopathy diagnosed on EMG?

A

ABN in >2 muscles of the same nerve root with normal muscles of adjacent nerve roots

121
Q

What does spontaneous activity in paraspinal muscles indicate?

A

Pathology at the root level

122
Q

How many muscles should at least be screened when looking for a radiculopathy?

A

Paraspinal muscles and at least 6 peripheral muscles

123
Q

When can surgical exploration of traumatic nerve injuries be considered?

A

If no clinical improvement and no motor or sensory responses seen on EDX 3 weeks after injury

124
Q

What does temporal dispersion suggest?

A

Acquired demyelinating polyneuropathy

125
Q

What are F-waves important for diagnosing?

A

Diabetic polyneuropathy

Acute and chronic inflammatory demyelinating polyradiculoneuropathy

126
Q

What is seen on NCS in AIDP?

A

Prolonged distal latencies or F-waves, temporal dispersion or slowed conduction velocity in >2 nerves

127
Q

What indicates a poor prognosis with AIDP on EDX?

A

Ulnar and median innervated muscles are 10-20% of normal values

128
Q

What is the clinical presentation of multifocal motor neuropathy?

A

Asymmetric weakness in a single body region (hand MC) w/o sensory sx w/ progression over many years

129
Q

What is seen on NCS in multifocal motor neuropathy?

A

Normal sensory studies
Multiple motor nerve conduction blocks in sites not prone to entrapment
Distal motor latencies and amp usually normal

130
Q

What is alcoholic polyneuropathy?

A

Axonal loss disorder affecting both sensory and motor nerves

131
Q

What is typically seen before presenting signs of alcoholic polyneuropathy?

A

Weight loss

132
Q

What are characteristics of HSMN type 1?

A

Hypertrophic variety with onion bulb formation and axonal atrophy

133
Q

What is seen clinically with HSMN type 1?

A

Sx in 1st 2 decades

Markedly reduced nerve conduction velocities w/o temporal dispersion

134
Q

What is seen clinically with HSMN type 2?

A

Presents in adult life

Severe distal muscle atrophy and weakness

135
Q

What is seen on EDX with HSMN type 2?

A

NCS showes mild slwoing

EMG reveals large, reorganized MUAPS w/ fibs and PSWs

136
Q

What is HSMN type 3 or Dejerine-Sottas?

A

Severe type of neuropathy appearing in infancy w/ delayed motor development
NCV <10 m/s

137
Q

What are the most sensitive diagnostic studies for detecting distal symmetric polyneuropathy?

A

Sural sensory and peroneal motor NCS

138
Q

What can be seen on EMG in acute inflammatory myopathies?

A

Fibs, PSWs, CRDs
Early or inc recruitment
Short duration, polyphasic and low amp MUAPs

139
Q

What are the presynpatic NMJ disorders?

A

Lambert-Eaton

Botulism

140
Q

What is the postsynpatic NMJ disorder?

A

Myasthenia gravis

141
Q

What is Myasthenia gravis?

A

Autoimmune d/o caused by Abs directed at Ach receptors of skeletal muscle

142
Q

What is seen with repetitive nerve stim in Myasthenia gravis?

A

Decreemeting responses

143
Q

What is seen clinically with Lambert-Eaton synd?

A

Weakness and fatigability of proximal muscles w/ sparing of ocular muscles
Hyporeflexia
Normal sensation

144
Q

What is Lambert-Eaton associated with?

A

Oat cell carcinoma of the lung

145
Q

What is seen with repetitive nerve stim in Lambert-Eaton synd?

A

Postactivation inc in CMAP of >200%

146
Q

What syndromes can have inc jitter on single fiber EMG?

A

Lambert-Eaton synd
Myasthenia gravis
ALS

147
Q

What is botulism caused by?

A

Potent toxin of Clostridium botulinum through oral ingestion or wound infection

148
Q

What is seen clinically with botulism?

A

Rapid-onset paralysis of eye muscles followed by rapid spread to other muscles

149
Q

What does the botulinium toxin do?

A

Irreversibly blocks Ach release from presynaptic nerve terminals

150
Q

What is seen on EDX with botulism?

A

Low CMAPs

Decrementing response on 2 Hz repetitive nerve stim

151
Q

What is seen on NCS in ALS?

A

Normal sensory NCS

Normal motor NCS unless CMAP <30% of mean then CV must not be <70% of normal

152
Q

What is seen on EMG in ALS?

A

PSWs and/or Fibs in 3 limbs or 2 limbs and bulbar muscles

Reduced recruitment and altered MUAP duration and amp

Brad 4th Ed Part 1 (36 decks)

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