electrotherapy mcqs with answers and electrotherapy diagnostics online multiple choice questions and answers-6

101. The only muscle that is innervated by the common peroneal (fibular) nerve is:
     A) Tibialis anterior
     B) Short head of the biceps femoris
     C) Peroneus longus
     D) Long head of the biceps femoris
102. The sartorius muscle is innervated by which nerve?
     A) Superior gluteal nerve
     B) Inferior gluteal nerve
     C) Sciatic nerve
     D) Femoral nerve
103. The common peroneal nerve splits at the fibular head into the superficial and deep peroneal nerve. Which muscle is innervated by the superficial peroneal nerve?
     A) Tibialis anterior
     B) Extensor digitorum brevis
     C) Extensor hallucis longus
     D) Peroneus brevis
104. During repetitive nerve stimulation in a patient with myasthenia gravis, what should be seen?
     A) Incremental increase in amplitude of the compound motor action potential (CMAP) from the first to the fifth stimulation
     B) Greater than 10% decrease in amplitude of the CMAPs from the first to the fifth stimulation
     C) Greater than 10% decrease in latency of the CMAPs from the first to the fifth stimulation
     D) None of the above
105. The amplitude of the compound motor action potential (CMAP) you have obtained is very small, and you are unable to assess where the takeoff is. In order to see the takeoff more clearly, you should:
     A) Increase the sweep speed
     B) Decrease the sweep speed
     C) Increase the gain
     D) Decrease the gain
106. During electrodiagnostic testing, how can you tell if an accessory peroneal nerve is present? A) There is decreased compound motor action potential (CMAP) amplitude when the peroneal nerve is stimulated at the ankle, and normal CMAP amplitude with stimulation at the fibular head
     B) There is decreased CMAP amplitude when the peroneal nerve is stimulated at the fibular head, and normal CMAP amplitude with stimulation at the ankle
     C) There is unusually slowed conduction velocity in the peroneal nerve
     D) There is unusually fast conduction velocity in the peroneal nerve
107. The normal gain for a sensory nerve study is:
     A) 100 mcV/division
     B) 1,000 mcV (1 mV)/division
     C) 10 mV/division
     D) 20 mcV/division
108. In electrodiagnostic testing, increased firing frequency refers to:
     A) A firing rate of more than 10 Hz before the next motor unit is recruited
     B) Increased recruitment
     C) A myopathic process
     D) Fibrillations and positive sharp waves (PSWs)
109. When performing needle electromyography (EMG) with a monopolar needle, the best location for the reference electrode is:
     A) Over nonmuscle distal to the needle
     B) Over nonmuscle but close to the needle
     C) Over a muscle innervated by the same nerve as the muscle you are testing
     D) Over the same muscle and close to the needle
110. When noted during electrodiagnostic testing, all of the following indicate a chronic (more than 6 months) process except:
     A) Polyphasicity
     B) Complex repetitive discharges
     C) Fibrillations and positive sharp waves
     D) Large amplitude motor units
111. When performing the needle portion of an electrodiagnostic test examination, it is important for the muscle to be at rest. This is best accomplished by:
     A) Putting a pillow under the muscle
     B) Activating the antagonist muscle
     C) Having the patient use imagery
     D) Activating the agonist muscle
112. A patient presents for electrodiagnostic testing for left-sided low-back pain. The study is normal except for a prolonged left H-reflex. What is your diagnosis?
     A) Left S1 radiculopathy
     B) Polyneuropathy
     C) Lumbar plexopathy
     D) None of the above
113. The motor unit action potential below was taken using a monopolar needle in the quadriceps muscle.
     50 uV 10 ms images…….

What can you determine about the amplitude of the motor unit?
A) Normal
B) Decreased amplitude
C) Increased amplitude
D) Mixed increased and decreased amplitude

114. The sural nerve is made up of sensory fibers from:
     A) Femoral nerve
     B) Peroneal nerve
     C) Tibial nerve
     D) Tibial and peroneal nerves
115. Which of the following muscles has dual innervation?
     A) Pronator quadratus
     B) Flexor carpi ulnaris (FCU)
     C) Flexor digitorum profundus (FDP)
     D) Rhomboids
116. In alcohol-induced polyneuropathy, what kind of findings would you expect to see on nerve conduction studies (NCS)?
     A) Increased compound motor action potential (CMAP) amplitude, increased sensory nerve action potential (SNAP) amplitude, decreased conduction velocity
     B) Increased CMAP amplitude, decreased SNAP amplitude, decreased conduction velocity
     C) Decreased CMAP amplitude, decreased SNAP amplitude, decreased conduction velocity
     D) Decreased CMAP amplitude, decreased SNAP amplitude, normal conduction velocity
117. All the following are true regarding F-wave studies except:
     A) F-waves are obtained using supramaximal stimulation, initiating an antidromic motor response to the anterior horn cells in the spinal cord
     B) The F-wave is a pure motor response that does not represent a true reflex
     C) The latency of the F-wave is constant
     D) In some chronically injured nerves, an A-wave may be seen
118. Assuming correct timing of performing the complete neurodiagnostic study, which of the following conditions would most likely result in a normal electromyographic (EMG)/nerve conduction studies (NCS) test?
     A) Bell’s palsy
     B) Brachial plexopathy (eg, medial cord)
     C) Botulism
     D) Myofascial pain
     E) Ulnar nerve impingement at elbow
119. Which of the following is not an indication that a Martin-Gruber anastomosis is present? A) An initial positive deflection of the median compound motor action potential (CMAP) when stimulating the median nerve at the antecubital fossa
     B) Slowed median nerve conduction velocity in the forearm
     C) Decreased amplitude of the median CMAP with distal stimulation as compared with proximal stimulation
     D) An excessively fast median nerve forearm conduction velocity when carpal tunnel is present
120. Complex repetitive discharges (CRDs) are most likely seen in:
     A) Radiculopathy of 4 weeks duration
     B) Carpal tunnel syndrome of 1 year duration
     C) Lumbar radiculopathy of 1 week duration
     D) Sensory axonal peripheral neuropathy of 2 years duration

Electrotherapy diagnostics online multiple choice questions and answers-6

101. B) The short head of the biceps femoris is the only nerve that is innervated by the common peroneal (fibular) nerve. It is also the only muscle innervated by the peroneal nerve that is above the popliteal fossa. Therefore, it is a very important muscle to test to determine the location of a lesion. The tibialis anterior muscle is innervated by the deep peroneal (fibular) nerve. The peroneus longus is innervated by the superficial peroneal (fibular) nerve, and the long head of the biceps femoris is innervated by the tibial nerve.
102. D) The sartorius is innervated by the femoral nerve. The femoral nerve also innervates the pectineus, iliopsoas, and quadriceps muscles.
103. D) The superficial peroneal nerve innervates the peroneus brevis and peroneus longus muscles. These muscles help to plantarflex and evert the foot. This nerve provides cutaneous sensation to the lower lateral aspect of the leg and dorsum of the foot with the exception of the first web space between the great and the second toes (innervated by the deep peroneal nerve). Choices (A), (B), and (C) are all innervated by the deep peroneal nerve along with the peroneus tertius and the extensor digitorum longus.
104. B) In repetitive nerve stimulation, a greater than 10% decrease in CMAP amplitude from the fi rst to the fi fth stimulation is considered signifi cant for pathology at the neuromuscular junction.
105. C) Increasing the gain is equal to increasing the sensitivity. By increasing the gain from 1,000 mcV (1 mV)/division to 500 mcV/division, each “box” on the Y-axis will portray a smaller percentage of the waveform. If the CMAP amplitude is 2,000 mcV in amplitude, and if the gain is 1,000 mcV (1 mV)/division, the waveform will be two boxes high. If the gain is increased to 500 mcV/division, the waveform will be four boxes tall (hence amplifi ed). The sweep speed is represented on the X-axis and is measured in milliseconds per division.
106. A) An accessory peroneal nerve is a branch from the superficial peroneal nerve that travels posterior to the lateral malleolus and can innervate the lateral portion of the extensor digitorum brevis (EDB) muscle. The fi bers from the accessory branch are not activated with ankle stimulation and therefore cannot contribute to the distal CMAP amplitude. These fibers are activated with proximal stimulation. If the accessory branch is stimulated posterior to the lateral malleolus (with pickup on the EDB), a waveform will be obtained. Usually, this CMAP amplitude, when added to the CMAP amplitude of the ankle stimulation, will equal the CMAP amplitude of stimulation at the fibular head.
107. D) The gain is the Y-axis on the screen. Normal sensory nerve amplitudes are between 10 and 20 mcV/division. If the gain is set too low, the sensory nerve action potential (SNAP) will be merely a blip on the screen (oscilloscope). (Remember that gain means sensitivity. A low gain would be 1,000 mcV/division or 1 mV/division.) Compound motor action potentials, which have an amplitude of about 5 mV, can be visualized on a gain of 1 mV/division.
108. A) An increased fi ring frequency is frequently reported as “decreased recruitment.” Both mean that a single motor unit fi res faster than normal before a second motor unit is recruited. Muscles can increase their strength in one of two ways: they can recruit more motor units, or the motor units that are there can fi re faster. In a neuropathic process, there are not more motor units that can be recruited. Therefore, the remaining motor units have to fi re faster to increase the strength of the contraction. One motor unit may fi re at 20 Hz (cycles per second) or faster. If the sweep is set at 10 msec/division, and there are 10 divisions per screen, then the screen represents 1/10 of a second. Therefore, if a motor unit fi res twice in a screen, it is fi ring at about 20 Hz.
109. D) To decrease interference and make the baseline as quiet as possible, the reference electrode should be placed over the same muscle that is being tested. The EMG machine will “subtract” the electrical activity of the reference electrode, therefore getting rid of any excess noise.
110. C) Fibrillations and positive sharp waves are seen in acute processes (either neuropathic or myopathic). Polyphasicity and long duration motor units are noted with reinnervation and asynchronous fi ring of the individual muscle fibers that make up a motor unit. Complex repetitive discharges are noted in chronic processes as well.
111. B) It is very difficult to have the patient relax a muscle during needle testing. The best way to do this is to have the patient activate the antagonist muscle. This will automatically relax the muscle that you are testing. For example, if the needle is in the biceps muscle (which fl exes the elbow and supinates), have the patient extend the elbow and pronate. It is important to know the function of each muscle. As described, simply extending the elbow will often not be enough to relax the biceps, as it also functions as a supinator.
112. D) You cannot state that the patient has an S1 radiculopathy based solely on a prolonged H-refl ex. Many conditions can lead to a prolonged H-reflex. To definitively state that the patient has a radiculopathy, there must be findings of denervation in the corresponding paraspinal muscle as well as two limb muscles innervated by the same root level, but different peripheral nerves.
113. B) The gain is set at 50 mcV. Therefore, the largest motor unit is 200 mcV in amplitude. This is considered a small-amplitude potential, as normal amplitude of a motor unit using a monopolar needle is about 1 to 7 mV in amplitude.
114. D) The sural nerve receives sensory branches from both the tibial and the peroneal (fibular) nerves.
115. C) The FDP is innervated by the median nerve (anterior interosseous branch) and the ulnar nerve. The median nerve innervates the FDP to digits 2 and 3, whereas the ulnar nerve innervates the FDP to digits 4 and 5. The pronator quadratus is innervated by the anterior interosseous nerve via the median nerve. The ulnar nerve innervates the flexor carpi ulnaris. The dorsal scapular nerve innervates the rhomboids.
116. D) Alcohol abuse can lead to axonal injury to the nerves, involving both sensory and motor nerves. Thus, both CMAP and SNAP amplitudes would be expected to be decreased. As the myelin is usually not affected, the conduction velocity and latency should not be affected.
117. C) F-waves are a delayed pure motor response. They are triggered by antidromic activation of motor neurons from peripheral stimulation of a nerve. This stimulation travels antidromically to the anterior horn cell. From there, it proceeds orthodromically to the muscle fiber. This backfiring of the axon is thought to represent a small portion (about 5%) of the orthodromically generated motor response (M-wave) that first occurs with stimulation. F-waves vary in their waveforms and latency and thus are averaged over multiple trials (usually 10). A-waves are seen in chronically injured nerves and represent regeneration or collateral sprouting of a nerve, as the orthodromic response is diverted along a collateral neural branch to circumvent the conventional path. This alternative path has a constant latency and is seen between the M- and the F-wave, with submaximal stimulation.
118. D) Myofascial pain does not lead to changes in the nerves or muscles that are quantifiable by electrodiagnostic testing. In general, changes to the sensory or motor nerve (axonal, demyelinating, or both), the neuromuscular junction, or the muscle itself can lead to electrophysiological changes that can be quantifiable by electrodiagnostic testing.
119. B) Martin-Gruber anastomosis is a median to ulnar nerve anastomosis in the forearm. Most commonly these are ulnar fibers that are destined for the ulnarly innervated hand muscles that travel with the median nerve proximally and then cross over to the ulnar nerve in the forearm (usually from the anterior interosseous nerve). When the active electrode is placed over the abductor pollicis brevis (APB) muscle (median nerve study), and the median nerve is stimulated at the antecubital fossa, the ulnarly innervated adductor pollicis muscle is stimulated as well (from the ulnar fibers that travel with the median nerve). Remember, in the forearm, these fibers switch over to again travel with the ulnar nerve. Because these fibers do not have to go through the carpal tunnel, the action potential reaches the adductor pollicis muscle before the median fibers get to the APB muscle. Therefore, there is an initial positive (downward) deflection with stimulation of the median nerve in the antecubital fossa (this occurs because the active electrode is not over the motor point of the muscle being activated, the active electrode is over the APB muscle, not the adductor motor point). There is decreased amplitude of the median CMAP with distal stimulation as compared with proximal stimulation, because distal stimulation only activates the median-innervated APB muscle. Proximal stimulation activates the median-innervated APB muscle as well as the nearby ulnar-innervated adductor pollicis muscle. The excessively fast median forearm conduction velocity noted with a Martin-Gruber anastomosis when carpal tunnel is present is due to the proximal stimulation of ulnar fibers (which do not have to travel through the carpal tunnel). This leads to a spuriously decreased latency with proximal stimulation compared with the increased latency of the distally stimulated median nerve.
120. B) CRDs are usually noted in longstanding disorders (of more than 6 months). They represent groups of spontaneously firing action potentials with an affected area of muscle electrically stimulating an adjacent muscle fiber. This produces a local muscular arrhythmia. The patterns repeat regularly with a frequency of 10 to 100 Hz. They have the sound of a motorboat misfiring. They can be seen in chronic neurogenic or myopathic disorders. As the needle study would be normal in a sensory neuropathy (only the motor fibers are tested with needle testing), CRDs would not be noted in a sensory peripheral neuropathy.

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