61. Electrotherapy diagnostics online multiple choice Question and Answer- 4

61.The accessory peroneal nerve:
A) Is noted when the amplitude at the fibular head is larger than at the ankle
B) Innervates the extensor digitorum hallucis muscle
C) Is a branch of the deep peroneal nerve
D) All of the above

62.You are performing an electromyography (EMG) on a patient and notice that the sensory and motor amplitudes are low throughout, latencies are prolonged throughout, and conduction velocities are slow throughout. The most likely conclusion is:
A) Alcoholic neuropathy
B) Paraneoplastic syndrome
C) Diabetic neuropathy
D) Guillain-Barré syndrome

63.On needle electromyographic (EMG) testing, myotonic discharges are characterized by:
A) Involuntary group repetitive discharge of the same motor unit action potential with a high-frequency pattern within the burst and a slow-frequency between the burst
B) Spontaneous discharge of a single motor unit potential at very high frequencies, with a notable decrementing response
C) Action potentials of muscle fibers firing in a prolonged fashion that wax and wane in both amplitude and frequency
D) Spontaneous action potentials of single muscle fibers that are fi ring autonomously in a regular fashion

64.Which muscle is innervated solely by the C5 root?
A) Serratus anterior
B) Rhomboids
C) Supraspinatus
D) Biceps brachii

65.What type of neuropathy is critical illness neuropathy?
A) Sensorimotor demyelinating
B) Sensorimotor axonal
C) Motor axonal
D) Sensory demyelinating

66.Which of the following has the poorest prognosis of nerve recovery?
A) Axonotmesis
B) Conduction block
C) Demyelination
D) Neurapraxia
E) Neurotmesis

67.What is the difference between an unmyelinated nerve and a demyelinated nerve?
A) The location of the sodium channels
B) The resting transmembrane potential
C) The way the sodium-potassium pump operates
D) The ions that are required

68.In a brachial plexopathy, the sensory nerve action potentials (SNAPs):
A) Would be affected as the lesion is distal to the dorsal root ganglion
B) Would not be affected as the lesion is distal to the dorsal root ganglion
C) Would be affected as the lesion is proximal to the dorsal root ganglion
D) Would not be affected as the lesion is proximal to the dorsal root ganglion

69.What type of neuropathy is usually seen on electrodiagnostic testing in diabetic neuropathy?
A) Axonal sensory neuropathy
B) Demyelinating sensory motor neuropathy
C) Axonal and demyelinating sensory motor neuropathy
D) Axonal sensory motor neuropathy

70.In electrodiagnostic testing, the ideal minimal distance between the active and the reference electrode in a sensory nerve study is:
A) 1 cm
B) 4 cm
C) 1 in.
D) 2 cm

71.In a sensory nerve (as opposed to a motor nerve), the conduction velocity can be calculated from the distance from the stimulator to the active electrode because:
A) The sensory nerve pickup is more distal than a motor nerve pickup
B) The sensory nerve has no myoneural junction
C) Sensory nerves are more superfi cial
D) This is not true; a conduction velocity can be calculated in a motor nerve by knowing the distance from the stimulator to the active electrode

72.What gain would you typically use for a sensory nerve conduction study?
A) 10 mcV
B) 100 mcV
C) 1 mV
D) 10 mV

73.A good way to differentiate between an upper trunk and a lateral cord brachial plexopathy is the fi nding of decreased amplitude in the:
A) Musculocutaneous nerve compound motor action potential (CMAP) to the biceps muscle
B) Axillary nerve CMAP to the deltoid muscle
C) Lateral antebrachial nerve sensory nerve action potential (SNAP)D) Median nerve SNAP

74.The Riche-Cannieu anastomosis:
A) Is a communication between the deep branch of the ulnar nerve and the recurrent branch of the median nerve in the hand
B) Can result in an all ulnar hand
C) May have denervation in the abductor pollicis brevis (APB) with an ulnar nerve lesion at the elbow
D) All of the above

75.You are performing an electromyography (EMG)/nerve conduction study (NCS) of the upper extremities to evaluate for carpal tunnel syndrome and notice that the sensory and motor, median, and ulnar latencies are delayed. One possible mistake that you may have made that could have resulted in this finding would be:
A) Your anode and cathode were reversed on the stimulator
B) You did not use maximal stimulation
C) You did not stimulate over the nerve
D) There was too much electrical interference

76.One of the common findings in ulnar neuropathy is the Froment’s sign, which is demonstrated by:
A) Difficulty in abducting the fourth and fifth digits
B) Pain and numbness in dorsal aspect of the hand
C) Weakness of the flexor digitorum profundus muscle to the fourth and fifth digits D) Substitution of the flexor pollicis longus muscle for a weakened adductor pollicis

77.How does limb temperature cooling affect electrodiagnostic fi ndings?
A) No change in conduction velocity, decreased amplitude
B) No change in conduction velocity, no change in amplitude
C) Decreased conduction velocity, increased amplitude
D) Increased conduction velocity, decreased amplitude

78.A typical amplitude of a compound muscle action potential (CMAP) is:
A) 10 msec
B) 10 mcV
C) 10 mV
D) 10 mcsec

79.Which of the following does the nerve conduction component of the neurodiagnostic study fail to assess or give information about?
A) Autonomic nerve
B) Integrity of myelin
C) Motor nerve
D) Sensory nerve
E) Speed of transmission

80.When is it most appropriate to perform F-waves?
A) For the evaluation of radiculopathy
B) For the evaluation of peroneal neuropathy at the fibular head
C) For the evaluation of possible acute inflammatory demyelinating polyneuropathy
D) For the evaluation of peripheral neuropathy

Electrotherapy diagnostics online multiple choice Question and Answer- 4

61. A) The accessory peroneal nerve is a branch from the superficial peroneal nerve. It travels posterior to the lateral malleolus and innervates the lateral portion of the extensor digitorum brevis (EDB) muscle. The anomaly is usually noted when the amplitude of the compound motor action potential (CMAP) at the fibular head is larger than the CMAP amplitude at the ankle. With stimulation behind the lateral malleolus, a CMAP is produced. Usually, the amplitude of the CMAP at the ankle combined with the amplitude of the CMAP posterior to the lateral malleolus equals the amplitude of the CMAP obtained at the fibular head.
62. C) Diabetic neuropathy usually presents as sensory and motor, axonal and demyelinating peripheral polyneuropathy. Alcoholic neuropathy is usually a sensory motor axonal neuropathy. Paraneoplastic syndrome is usually a sensory axonal neuropathy. Guillain-Barré syndrome usually presents with segmental demyelination.
63. C) Choice (A) describes myokymic discharges. It is often noted to sound like “soldiers marching” and is often seen in conditions such as multiple sclerosis, Bell’s palsy, and polyradiculopathy. Choice (B) refers to neuromyotonic discharges. Generalized neuro myotonia is usually an autoimmune disease characterized by widespread muscle stiffness and delayed muscle relaxation after voluntary movement. Choice (D) refers to fibrillation potentials, which are usually triphasic in nature. Myotonia is clinically seen as delayed relaxation of a muscle after contraction. Potentials tend to fi re at a variable rate, waxing and waning in appearance, and its variation causes a characteristic “dive bomber” sound.
64. B) The serratus anterior is innervated by the long thoracic nerve (roots C5, C6, and C7), which helps to protract the scapula and rotate the glenoid upward. The supraspinatus is innervated by the suprascapular nerve (roots C5, C6), which helps in shoulder abduction and external rotation. The biceps brachii is innervated by the musculocutaneous nerve (roots C5, C6) and assists in elbow flexion and forearm supination. The rhomboids are innervated by the dorsal scapular nerve (solely C5 root) and help to elevate and retract the scapula as well as rotate the glenoid downward.
65. B) Critical illness neuropathy is a sensorimotor axonal neuropathy. On nerve conduction studies, sensory and motor amplitudes are low. Three extremities should be tested and temperature should be maintained at 32°C in the upper extremities and 30°C in the lower extremities. Latencies and conduction velocities remain normal to borderline normal. (If the fastest axons are affected, latency may be mildly increased, and conduction velocities mildly decreased. However, the axonal loss (amplitude) is out of proportion to the slowing.) Critical illness neuropathy is seen in the critical care setting and is most commonly associated with sepsis, systemic inflammatory response syndrome (SIRS) and multiorgan failure. Patients who have abnormal weakness (out of proportion to their disease) should be considered for electrodiagnostic testing.
66. E) Neurotmesis is a complete disruption of the axon, myelin, and all supporting connective tissues. Complete nerve regeneration is unlikely, as there is no path for the nerve to follow when trying to connect to the distal muscles.
67. A) A myelinated nerve has sodium channels located only at the nodes of Ranvier. An unmyelinated nerve has sodium channels throughout the length of the nerve. Therefore, if a myelinated nerve loses its myelin (becomes demyelinated), the sodium channels are still located at distinct intervals throughout the nerve. If saltatory conduction cannot occur (because the myelin has been lost), the action potential cannot propagate along the nerve. Therefore, conduction block will occur. Conduction block does not occur in an unmyelinated nerve because the lesion in a conduction block is myelin.
68. A) In a brachial plexopathy, the lesion is distal to the sensory nerve body (the dorsal root ganglion). As such, the continuity between the cell body and the end organ has been affected. Therefore, the SNAP would be affected. Conversely, in a radicular lesion, there is continuity between the dorsal root ganglion and the end organ (the sensation over the hand or foot), so the SNAP is not affected.
69. C) The peripheral neuropathy seen in diabetic neuropathy is usually axonal and demyelinating sensory motor neuropathy. This means that low-amplitude sensory nerve action potentials (SNAPs) and compound motor action potentials (CMAPs) would be noted with slowing of nerve conduction velocities (both sensory and motor) and increased latencies.
70. B) There should be at least 4 cm between the active and the reference electrodes. If the electrodes are placed too close together, the sensory nerve action potential (SNAP) amplitude could falsely decrease (resembling an axonal lesion). This has to do with the rise time of the SNAP. The electrodiagnosis (EMG) machine will “subtract” the recorded action potential of the reference electrode from the recorded action potential of the active electrode. If the action potential reaches the reference electrode during the rise time of the action potential seen by the active electrode, the EMG machine will subtract one from the other, resulting in a decreased SNAP amplitude.
71. B) Because the sensory nerve has no myoneural junction, the speed (V = D/T) can be directly calculated if the distance and the time (latency) is known. Motor nerves, on the other hand, have a myoneural junction. As it is not known how long it takes for the action potential to cross the myoneural junction and for conduction in the muscle, the conduction velocity in a motor nerve must be calculated using the formula V = change in distance/change in time. Therefore, two stimulations must be performed (one proximal and one distal) to assess velocity. The difference in distance is divided by the difference in latency.
72. A) Sensory amplitudes are generally about 10 to 20 mcV. These are much smaller than compound motor action potential (CMAP) amplitudes, where the gain is usually 1,000 mcV. Remember that the gain is the Y-axis and is also called the sensitivity. Therefore, a lower number (10 mcV) represents a higher sensitivity than a higher number (1 mV). The waveform is the same. What differs is how much the waveform is “blown up” so that it can be visualized.
73. B) The axillary nerve comes off at the trunk level. With either an upper trunk or a lateral cord lesion, the musculocutaneous CMAP to the biceps, the lateral antebrachial SNAP, and the median SNAP will all be affected.
74. D) The Riche-Cannieu anastomosis is a communication between the deep branch of the ulnar nerve and the recurrent branch of the median nerve in the hand. It can produce an all-ulnar hand. Therefore, if the ulnar nerve is injured proximally, the muscles normally innervated by the median nerve (but now innervated via the ulnar nerve anastomosis) may show signs of injury. Conversely, if the patient has a complete laceration of the median nerve at the wrist, he or she may still retain thenar function via the anastomosis.
75. A) If the anode and cathode were reversed on the stimulator, there would be an extra 3 to 4 cm in length between the stimulator and the active electrode. The longer the distance that the stimulation has to travel, the longer the latency. If maximal stimulation were not used, the sensory and motor amplitudes may be decreased. If you did not stimulate over the nerve, the sensory and motor amplitudes may be decreased as well. If there was too much electrical interference, the baseline would not be flat.
76. D) Froment’s sign is often found in ulnar neuropathy. It is demonstrated by having the patient grasp a piece of paper between the thumb and the radial side of the second digit. As the examiner tries to pull the paper out of the patient’s hand, the patient will try to substitute his or her median-innervated flexor pollicis longus muscle for a weakened ulnarly innervated adductor pollicis muscle.
77. C) Cooling results in a longer time for the action potential to proceed down the axon. This is in part due to a change in protein configuration of the Na+ channels as its structure is changed by temperature change. Cooling can cause slow opening and even slower closing of Na+ channels, which slows the propagation of action potentials in axons. For every 1°C drop in temperature, there is an approximate 5% decrease in conduction velocity. Amplitude is increased along with the duration of the action potential because of prolonged opening times of the sodium channels.
78. C) The typical amplitude of a compound muscle action potential (CMAP) is above 4 mV. A millivolt is one thousandth of a volt. A microvolt is a thousandth of a millivolt (or a millionth of a volt)—this is a typical amplitude of a sensory nerve action potential (SNAP). The other choices are measures of time, not amplitude. Amplitude is on the Y-axis, whereas time is on the X-axis of the electromyography (EMG) screen.
79. A) Except for somatosensory-evoked potentials, electrodiagnostic testing only assesses the peripheral nervous system. Testing is possible of both the motor and the sensory fibers. Assessment can be made about the integrity of the myoneural junction, the axon, and the myelin. However, the autonomic nervous system is not evaluated by conventional nerve studies and electrodiagnosis (EMG).
80. C) F-waves are low-amplitude late responses thought to be due to antidromic activation of motor neurons. They have variable latency and configuration with variable responses. They are indicated to assess proximal conduction in conditions such as AIDP (also known as Guillain-Barré syndrome). F-waves are reported to be among the earliest electrodiagnostic findings in AIDP. F-waves should not be used routinely to assess for radiculopathy. The most commonly assessed parameter of F-waves is the shortest F latency. F-waves evaluate a very long neural pathway, are nonspecific, and can be affected by anything that would slow the pathway (ie, peripheral neuropathy and focal slowing). The exact location of the slowing cannot be assessed, so to use an F-wave to say the slowing is at the root level is faulty. In addition, because the active electrode is over a muscle that would have multiple root innervations and because the F-wave only assesses the fastest fibers, in theory the F-wave should be normal in a radiculopathy. Radiculopathies may affect the axon, and the F-wave is a test of latency. If there is slowing of the neural path in a radiculopathy, the area of slowing is small compared with the length of the pathway assessed with an F-wave. Finally, as the F-wave latency is extremely variable, multiple stimulations must be performed to find the shortest latency. The number of stimulations, therefore, has to be high (more than 10) and even then, the electromyographer is never sure that the shortest latency has been recorded.

Electrotherapy diagnostics online multiple choice questions and answers-4

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