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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

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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
What does reduced recruitment indicate?
Motor axonal loss or function drop out from conduction block
26
What is early or myopathic recruitment?
Many motor units recruited to generate a low level of force
27
What does early recruitment indicate?
Myopathy or NMJ disorder
28
What diseases are complex repetitive discharges seen in?
``` Polymyositis Limb girdle dsytrophy Myxedema Schwartz-Jampel synd Spinal muscular atrophy Amyotrophic lateral sclerosis Hereditary and chronic neuropathies Carpal tunnel synd ```
29
Which normal muscles are complex repetitive discharges seen in?
Iliopsoas | Biceps brachii
30
What diseases are Myokymic discharges seen in?
``` Multiple sclerosis Brainstem neoplasm Polyradiculopathy Bell pasly Radiaton plexopathy Chronic nerve compression Rattlesnake venom ```
31
What do complex repetitive discharges sound like?
Machine-like discharge
32
What do myokymic potentials sound like?
Marching soldiers
33
What do myotonic potentials sound like?
Diver bombers
34
What diseases are myotonic potentials seen in?
``` Myotonic dystrophy Myotonia congenita Paramyotonia Polymyositis Acid maltase def Hyperkalemic periodic paralysis Chronic radiculopathy/peripheral polyneuropathy ```
35
When should single fiber EMG's be performed?
Neuromuscular disorders Myasthenia gravis Lambert-Eaton synd
36
What is a hallmark finding of Lambert-Eaton synd?
Marked facilitation of the CMAP >400% of baseline amp after brief contraction
37
What is Martin-Gruber anastomosis?
Branch from median nerve, usually the AIN joins the ulnar nerve in the forearm
38
What is seen with Martin-Gruber anastomosis on Median nerve NCS?
Median CMAP is smaller with wrist stimulation than w/ proximal stimulatio
39
What is seen with Martin-Gruber anastomosis on Ulnar nerve NCS?
Larger amp w/ wrist stim than w/ below or above elbow stim
40
What is an accessory deep peroneal nerve?
Part of the deep peroneal nerve that remains with the superficial peroneal nerve and innervates the EDB after passing behind the lateral malleolus
41
What is seen on EDB NCS with an accessory deep peroneal nerve?
Stim at the fibular head yields a higher CMAP than ankle stim when recorded over EDB
42
How can an accessory deep peroneal nerve be stimulated?
Stim behind the lateral malleolus
43
What type of stimulating probe is needed for pediatric EDX?
Pediatric bipolar stimulating probe
44
What type of EMG needle should be used for pediatric patients?
Monopolar
45
What skin surface temperature is needed in pediatric EDX?
36-37 degrees C
46
Which children are at risk for malignant hyperthermia?
Children with neuromuscular diseases who are given halogenated anesthesia
47
Which muscles should be tested for spontaneous activity in infants?
Extensor muscles and intrinsic hand and foot muscles
48
Describe motor units in pediatric patients
Bi or triphasic Amp 100-700 uV Short duration 5-9 ms
49
Which muscles should be examined for motor unit morphology and recruitment in pediatrics?
Flexor muscles
50
What is repetitive nerve stimulation used to evaluate?
Pre and postsynaptic neuromuscular disorders
51
What is the MCC of generalized hypotonia?
Central nervous system d/o
52
What is the MC neuromuscular dx in hypotonic infants?
Spinal muscular atrophy
53
What obstetric causes are related to brachial plexopathies at birth?
Duration of labor | Shoulder dystocia
54
What is involved in Erb pasly?
Upper plexus and C5 or C6 roots
55
What is involved in Kumpke palsy?
Lower trunk, C8 or T1 roots
56
What are anatomic risk factors for brachial plexus injury?
Supracostoclavicular space narrowing with cervical ribs or fibrous bands
57
What is the MC entrapment neuropathy?
Carpal tunnel synd
58
What are causes of CTS?
Repetitive trauma Obesity Pregnancy Lupus
59
What are sx of CTS?
Aching pain in the forearm and wrist Insidious onset of tingling, parasthesias of thumb, index and long finger Thenar weakness Nocturnal pain
60
What is mild CTS?
Prolonged SNAP and/or slightly reduced SNAP amp
61
What is moderate CTS?
ABN median SNAP plus prolonged motor latency
62
What is severe CTS?
Prolonged motor and sensory distal latencies plus either absent SNAP or low amp or absent CMAP EMG shows fibs in thenar muscles
63
What is pronator synd?
Entrapment of the median nerve b/w heads of the pronator teres and beneath FDS arch at forearm
64
What are causes of pronator synd?
Repetitive overuse Tight casting Penetrating injuries (IV catheter) "Grocery bag neuropathy" carrying a bag w/ arm flexed
65
What are sx of pronator synd?
``` 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
What is ABN on NCS in pronator synd?
CMAP reduced if motor axonal loss present | NCV slowed across pronator area or conduction block
67
What is ABN on EMG in pronator synd?
Reduced recruitment in median innervated muscles | Pronator teres spared
68
What is Kiloh-Nevin synd?
Entrapment of AIN at forearm
69
What are the causes of AIN synd?
``` Direct trauma Inflam Strenous exercise Fx Brachial neuritis Compression by fibrous bands ```
70
What are the sx of AIN synd?
``` 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
What is ABN on EDX with AIN synd?
Slowed median NCV to pronator quadratus | Findings on EMG to FPL, PQ and FDP to index and long fingers
72
What causes median nerve entrapment beneath the ligament of struthers?
Trauma Inflam Fibrous band from supracondylar process to medial epicondyle
73
What are the sx of median nerve entrapment beneath the ligament of struthers?
``` 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
What is the ligament of struthers?
CT from the supracondylar process of the humerus (also known as avian spur) to the medial humeral epicondyle
75
What is seen on NCS of median nerve entrapment beneath the ligament of struthers?
Dec or absent SNAP Red motor NCV or conduction block across this segment Dec CMAP from APB
76
What is seen on EMG of median nerve entrapment beneath the ligament of struthers?
Findings in median nerve muscles including pronator teres
77
What are causes of radial nerve entrapment at the axilla?
Improper use of crutches | Falling asleep w/ arm over sharp chair back
78
What are sx of radial nerve entrapment at the axilla?
Weakness in all radial innervated muscles including triceps | Dec sensation in posterior arm and forearm
79
What seen on NCS of radial nerve entrapment at the axilla?
Reduced or absent SNAP and CMAP | Conduction block across axilla
80
What seen on EMG of radial nerve entrapment at the axilla?
Findings in radial innervated muscles including triceps
81
What are causes of radial nerve entrapment at the spiral groove?
Prolonged compression of the nerve at humerus from someone sleeping on the arm (honeymoon palsy) Assoc w/ alcohol use Injection Compression with tourniquet
82
What are sx of radial nerve entrapment at the spiral groove?
Involves all radial innervated muscles except the triceps and aconeus Wrist and finger extension weakness Sensory loss over dorsal hand and posterior forearm
83
What seen on EMG of radial nerve entrapment at the spiral groove?
Findings in radial innervated muscles except triceps and aconeus
84
What is radial tunnel synd?
Entrapment of the PIN by fibrous bands at radial head or tendinous margin of the ECRB
85
What is PIN or supinator synd?
PIN entrapped by origin of supinator muscle at aracde of Frohse
86
What are causes of radial nerve with PIN compression?
``` Radial tunnel, PIN or supinator synd Elbow dislocation Monteggia fx FOOSH Surgical resection of radial head Mass lesions ```
87
What is a Monteggia fx?
Fx of the proximal third of the ulna with dislocation of the proximal head of the radius
88
What are sx of radial nerve with PIN compression?
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
What is seen on NCS of radial nerve with PIN compression?
Normal superficial radial sensory response Slowed motor conductive across the elbow Low CMAP over EIP
90
What is seen on EMG of radial nerve with PIN compression?
Findings in PIN innervated muscles | Brachioradialis and ECRL spared
91
What is Wartenberg synd?
Radial nerve entrapment at the wrist
92
What are causes of radial nerve entrapment at the wrist?
Handcuff or bracelet neuropathy Ganglions Over use synd
93
What are sx of radial nerve entrapment at the wrist?
Numbness, parasthesias of dorsoradial aspec of hand and dorsum of 1-3 digits Tender to palpation in this area No motor weakness
94
What is seen on NCS of radial nerve entrapment at the wrist?
Superficial radial sensory response delayed in latency or low in amp
95
What are causes of ulnar nerve compression at Guyon's canal?
Chronic pressure from using tools Bicycling riding Ganglion RA
96
What is affected in Type 1 ulnar nerve compression at Guyon's canal?
Hypothenar and deep ulnar branch
97
What is affected in Type 2 ulnar nerve compression at Guyon's canal?
Deep ulnar branch
98
What is affected in Type 3I ulnar nerve compression at Guyon's canal?
Superficial ulnar sensory branch
99
What sx of ulnar nerve compression at Guyon's canal?
Numbness Parasthesia Intrinsic muscle atrophy Nocturnal pain
100
What is seen on EMG of ulnar nerve compression at Guyon's canal?
Fibs or motor unit changes in hand intrinsics but not thenar muscles
101
What are causes of ulnar nerve entrapment at the elbow?
``` Trauma Cubitus valgus Bony spurs Tumors Overuse Previous fx Arcade of struthers FCU ```
102
What are sx of ulnar nerve entrapment at the elbow?
``` 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
What is seen on NCS of ulnar nerve entrapment at the elbow?
Ulnar sensory/motor or dorsal ulnar cutaneous nerve amp absent or reduced NCV > 10 m/s slower across elbow
104
What are causes of femoral neuropathy?
Trauma Retroperitoneal hematoma Cardiac cathererizations
105
What are sx of femoral neuropathy?
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
What is seen on NSC in femoral neuropathy?
Red amp or absent saphenous nerve response | Red CMAP over rectus femoris
107
What is meralgia parasthetica?
Lateral femoral cutaneous nerve entrapment at the thigh
108
What are causes of lateral femoral cutaneous nerve entrapment at the thigh?
Repeated trauma Obesity Pregnancy Tight clothing over lateral inguinal ligament
109
What are sx of lateral femoral cutaneous nerve entrapment at the thigh?
Pure sensory synd Parasthesias, burning or dull ache in lateral thigh Aggravated by prolonged standing or walking
110
What is seen on NCS of lateral femoral cutaneous nerve entrapment at the thigh?
Red amp in lateral femoral cutaneous nerve
111
What are causes of peroneal nerve entrapment at the fibular head?
``` Fx Casting Tight stockings Excessive weight loss Farm work Tumors Crossing legs or improper positioning ```
112
What are sx of peroneal nerve entrapment at the fibular head?
Foot drop Weakness of eversion Numbness of dorsum of the foot Pain
113
What is seen on NCS of peroneal nerve entrapment at the fibular head?
CV reduces in fibular head segment by >10 m/s compared to leg segment
114
What are causes of tibial nerve entrapment at the tarsal tunnel?
``` Compression from shoes Casting Post traumatic fibrous Overuse Ganglion cysts ```
115
What are sx of tibial nerve entrapment at the tarsal tunnel?
Pain in foot and ankle Wasting and weakness in feet Sensory impairment at toes and sole of foot
116
What is seen on NCS of tibial nerve entrapment at the tarsal tunnel?
Prolonged latencies or low amp of plantar nerves and tibial motor across tarsal tunnel
117
What is seen clinically with traumatic plexopathy with nerve root avulsion?
Profound weakness CMAP low or absent SNAPs preserved
118
What is a radiculopathy?
Pathologic process involving a spinal nerve root
119
Why are SNAPs preserved in most radiculopathies?
Nerve root is affected proximal to the dorsal root ganglion
120
How is a radiculopathy diagnosed on EMG?
ABN in >2 muscles of the same nerve root with normal muscles of adjacent nerve roots
121
What does spontaneous activity in paraspinal muscles indicate?
Pathology at the root level
122
How many muscles should at least be screened when looking for a radiculopathy?
Paraspinal muscles and at least 6 peripheral muscles
123
When can surgical exploration of traumatic nerve injuries be considered?
If no clinical improvement and no motor or sensory responses seen on EDX 3 weeks after injury
124
What does temporal dispersion suggest?
Acquired demyelinating polyneuropathy
125
What are F-waves important for diagnosing?
Diabetic polyneuropathy | Acute and chronic inflammatory demyelinating polyradiculoneuropathy
126
What is seen on NCS in AIDP?
Prolonged distal latencies or F-waves, temporal dispersion or slowed conduction velocity in >2 nerves
127
What indicates a poor prognosis with AIDP on EDX?
Ulnar and median innervated muscles are 10-20% of normal values
128
What is the clinical presentation of multifocal motor neuropathy?
Asymmetric weakness in a single body region (hand MC) w/o sensory sx w/ progression over many years
129
What is seen on NCS in multifocal motor neuropathy?
Normal sensory studies Multiple motor nerve conduction blocks in sites not prone to entrapment Distal motor latencies and amp usually normal
130
What is alcoholic polyneuropathy?
Axonal loss disorder affecting both sensory and motor nerves
131
What is typically seen before presenting signs of alcoholic polyneuropathy?
Weight loss
132
What are characteristics of HSMN type 1?
Hypertrophic variety with onion bulb formation and axonal atrophy
133
What is seen clinically with HSMN type 1?
Sx in 1st 2 decades | Markedly reduced nerve conduction velocities w/o temporal dispersion
134
What is seen clinically with HSMN type 2?
Presents in adult life | Severe distal muscle atrophy and weakness
135
What is seen on EDX with HSMN type 2?
NCS showes mild slwoing | EMG reveals large, reorganized MUAPS w/ fibs and PSWs
136
What is HSMN type 3 or Dejerine-Sottas?
Severe type of neuropathy appearing in infancy w/ delayed motor development NCV <10 m/s
137
What are the most sensitive diagnostic studies for detecting distal symmetric polyneuropathy?
Sural sensory and peroneal motor NCS
138
What can be seen on EMG in acute inflammatory myopathies?
Fibs, PSWs, CRDs Early or inc recruitment Short duration, polyphasic and low amp MUAPs
139
What are the presynpatic NMJ disorders?
Lambert-Eaton | Botulism
140
What is the postsynpatic NMJ disorder?
Myasthenia gravis
141
What is Myasthenia gravis?
Autoimmune d/o caused by Abs directed at Ach receptors of skeletal muscle
142
What is seen with repetitive nerve stim in Myasthenia gravis?
Decreemeting responses
143
What is seen clinically with Lambert-Eaton synd?
Weakness and fatigability of proximal muscles w/ sparing of ocular muscles Hyporeflexia Normal sensation
144
What is Lambert-Eaton associated with?
Oat cell carcinoma of the lung
145
What is seen with repetitive nerve stim in Lambert-Eaton synd?
Postactivation inc in CMAP of >200%
146
What syndromes can have inc jitter on single fiber EMG?
Lambert-Eaton synd Myasthenia gravis ALS
147
What is botulism caused by?
Potent toxin of Clostridium botulinum through oral ingestion or wound infection
148
What is seen clinically with botulism?
Rapid-onset paralysis of eye muscles followed by rapid spread to other muscles
149
What does the botulinium toxin do?
Irreversibly blocks Ach release from presynaptic nerve terminals
150
What is seen on EDX with botulism?
Low CMAPs | Decrementing response on 2 Hz repetitive nerve stim
151
What is seen on NCS in ALS?
Normal sensory NCS | Normal motor NCS unless CMAP <30% of mean then CV must not be <70% of normal
152
What is seen on EMG in ALS?
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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