21. Which is the worst nerve injury, according to the Seddon classification of nerve injuries?
D) Conduction block
22. All of the following muscles usually receive at least some innervation from the C7 nerve root except:
A) Extensor carpi radialis
B) Opponens pollicis
C) Pronator teres
D) Flexor carpi radialis
23. During nerve conduction testing, dispersion of the compound motor action potential (CMAP) is noted in which of the following:
A) Axonal injury
B) Focal nerve slowing
C) Conduction block
D) Segmental demyelination
24. What are the clinical symptoms of a patient with anterior interosseous nerve (AIN) syndrome?
A) Impairment of all median nerve–innervated muscles
B) A dull, achy sensation in the distal forearm along with weakness in grip strength and wrist fl exion
C) Numbness and paresthesias radiating to the fi rst, second, third, and fourth lateral digits of the hand
D) Abnormal “okay” sign, diffi culty forming a fi st, inability to approximate the thumb and index fi nger
25. Which one of the following muscles is not dually innervated?
A) Flexor pollicis brevis
C) Biceps femoris
D) Lumbricals of the hand
26. Myokymic discharges are usually seen in:
A) Radiation plexopathy
B) Acute carpal tunnel syndrome
C) Myasthenia gravis
D) Myotonic dystrophy
27. Conduction block in the forearm would present with:
A) Decreased compound motor action potential (CMAP) amplitude with proximal stimula-tion and distal stimulation
B) Decreased CMAP amplitude with proximal stimulation but not distal stimulation
C) Decreased CMAP amplitude distally but not proximally
D) Slowing of conduction velocity across the lesion
28. In a healthy adult, from what muscle can an H-reflex be obtained?
B) Flexor carpi radialis
D) Extensor digitorum
29. A lumbar plexopathy affecting the posterior division will affect all of the following muscles except:
B) Rectus femoris
C) Adductor longus
30. The best way to localize whether a lesion is in the plexus or a radiculopathy is:
A) Assess sensory nerve action potential (SNAP) amplitude
B) Look for denervation in the extremity muscles
C) Assess compound motor action potential (CMAP) amplitude
Electrotherapy diagnostics online quiz-2
31. The anterior interosseous nerve innervates all of the following muscles except:
A) Flexor digitorum profundus to digits 2 and 3
B) Pronator quadratus
C) Flexor digitorum superfi cialis to digits 1 and 2
D) Flexor pollicis longus
32. When performing an electromyography (EMG), 60-cycle interference can be reduced by:
A) Turning on the notch fi lter
B) Moving the reference electrode closer to the active electrode during nerve conduction studies
C) Moving the ground to the opposite limb
D) Changing to a sensory setting (from a motor setting)
33. Hereditary neuropathies are usually:
A) Segmental demyelinating
B) Uniform demyelinating
D) Mixed sensory and motor axonal and demyelinating
34. The connective tissue that surrounds bundles or fascicles of nerve fibers is called the:
35. All of the following muscles are innervated by the posterior cord of the brachial plexus except: A) Triceps
36. What is the best way to ensure that the biceps muscle is electrically silent during electrodiagnostic testing?
A) Extend the elbow
B) Supinate the forearm
C) Extend the elbow and pronate the forearm
D) Flex the elbow and supinate the forearm
37. What are the areas of median nerve entrapment?
A) Ligament of Struthers (LOS), bicipital aponeurosis, cubital tunnel, anterior interosseous nerve, carpal tunnel
B) Arcade of Struthers, bicipital aponeurosis, pronator teres syndrome, Guyon’s canal, carpal tunnel
C) LOS, cubital tunnel, carpal tunnel
D) LOS, bicipital aponeurosis, pronator teres, anterior interosseous nerve, carpal tunnel
38. A patient who underwent a pelvic surgery is noted to have an impingement of the obturator nerve. Which muscle would you least suspect to show signs of denervation on electrodiagnostic testing?
B) Adductor longus
C) Adductor brevis
D) Adductor magnus
39. Electrodiagnostic fi ndings in patients with critical illness myopathy (CIM) most commonly include:
A) Low amplitude sensory nerve action potentials (SNAPs)
B) Denervation potentials (fi brillations and positive sharp waves) in proximal muscles
C) Low amplitude compound motor action potentials (CMAPs)
D) Decreased motor conduction velocities
40. To determine whether an ulnar nerve lesion is at the wrist or the elbow, it is important to:
A) Test conduction velocity across the elbow
B) Needle test the fi rst dorsal interosseous muscle
C) Test the dorsal ulnar cutaneous nerve
D) Test the ulnar motor response to the fi rst dorsal interosseous muscle
Electrotherapy diagnostics online quiz-2Question and Answer Online Multiple choice Question
- B) Neurotmesis is complete transection of the nerve and involves the axon, the myelin, and all supporting tissue (connective tissue including the epineurium). There is complete disruption of any pathway, and nerve action potentials cannot propagate. There is little chance for regeneration (collateral sprouting or axonal regrowth) because of the loss of a pathway of connective tissue for the axon to follow. Neurapraxia is the same thing as conduction block. This is a focal area of severe demyelination. The demyelination is so severe that the action potential cannot propagate. As remyelination takes place, the myelin is immature. Therefore, with remyelination, there will be slowing of the segment where the conduction block occurred. Axonotmesis is damage to the axon itself. However, the connective tissues and Schwann cells are intact, so recovery can take place.
- B) The extensor carpi radialis is innervated by the radial nerve (C6/C7). The pronator teres is innervated by the median nerve (C6/C7). The fl exor carpi radialis is innervated by the median nerve (C6/C7). However, the opponens pollicis is innervated by the median nerve (C8/T1).
- D) Dispersion is noted when the various components of the action potential travel at different speeds. Uneven degrees of demyelination and remyelination in the different nerve fi bers make the entire CMAP waveform of lower amplitude and longer duration. This is frequently seen in segmental demyelination. The area under the entire waveform is not decreased. The sum of all of the nerve fi bers contributes to the shape of the CMAP. If some of the fi bers are traveling at 30 m/sec, some at 40 m/sec, and some at 50 m/sec, the duration of the waveform will be prolonged (and the amplitude decreased). This can be confused with an axonal injury if the clinician only assesses amplitude, and not duration. In axonal injury, the amplitude is decreased, but the duration of the waveform is normal. Focal nerve slowing will present with a normal CMAP amplitude, but with conduction velocity slowing across the involved area. With conduction block, the CMAP amplitude distal to the lesion will be normal, but the CMAP amplitude will be decreased with stimulation across the lesion.
- D) The AIN is a motor nerve branch of the median nerve. An injury to this nerve results in a pure motor syndrome with no sensory defi cits. The muscles innervated by the AIN are the fl exor pollicis longus (FPL), pronator quadratus, and the fl exor digitorum profundus (FDP) to digits 1 and 2. The FPL is usually the fi rst muscle to be affected. As a result of the muscle impairments, patients are unable to approximate the thumb and index fi nger or give an “OK” sign.
- B) All the muscles listed are dually innervated except for the gracilis. The fl exor pollicis brevis is innervated by the median and ulnar nerves. The lumbricals are supplied by the median and ulnar nerves. The long head of the biceps femoris is innervated by the sciatic tibial division, whereas the short head of the biceps femoris is innervated by the common peroneal nerve. Only the gracilis is innervated by one nerve—the obturator nerve.
- A) Myokymic discharges are spontaneous motor unit action potentials that fi re repetitively and have the sound of “marching soldiers.” They have a regular rate and rhythm. These single or paired discharges fi re at a rate of 5 to 10 Hz. They may be seen in chronic nerve lesions, radiation plexopathy, facial muscles in Bell’s palsy, multiple sclerosis, and chronic polyradiculopathy.
- B) Conduction block is an area of focal demyelination that is so severe that the action potential cannot propagate. If the conduction block were located in the forearm, stimulation distal to the conduction block would be normal. When stimulation occurred across the area of conduction block, some of the action potentials could not propagate. This would lead to a drop in CMAP amplitude (with proximal stimulation). Choice (D) is incorrect because slowing of conduction velocity is actually the result of a conduction block with subsequent remyelination. The immature myelin conducts slower than normal myelin, leading to a slowing of conduction velocity.
- B) In healthy adults, an H-reflex can be obtained in the fl exor carpi radialis muscle and can therefore be useful in the assessment of C6/C7 radiculopathies. In the healthy adult, an H-refl ex elicited in any muscle besides the gastrocnemius-soleus or the fl exor carpi radialis is considered pathological and may indicate an upper motor neuron lesion.
- C) The adductor longus muscle is innervated by the obturator nerve, which comes off of the anterior division. The other muscles are innervated by the femoral nerve, which comes off of the posterior division.
- A) If a lesion is in the plexus, it will be postganglionic (ie, distal) to the dorsal root ganglion. Therefore, the SNAP amplitudes will be affected. If a lesion is at the root level, it will be preganglionic (ie, proximal to the dorsal root ganglion). Therefore, the SNAP amplitudes will not be affected. In both cases, there may be denervation in the extremity muscles. In a radiculopathy, there may be denervation in the paraspinal muscles as well. F-wave abnormalities are nonspecifi c and may indicate that the problem is between the stimulation point and the spinal cord. This would include both plexopathy and radiculopathy, and so does not distinguish between the two.
- C) The anterior interosseous nerve is a motor branch of the median nerve that innervates the fl exor digitorum profundus to digits 2 and 3, the fl exor pollicis longus, and the pronator quadratus. Its function can be tested by asking the patient to make the “okay” sign, which uses these muscles. When testing for anterior interosseous nerve injury, the nerve conduction studies are usually normal, as the active electrode is over the abductor pollicis brevis muscle. Needle electromyography (EMG) fi ndings of denervation limited to the three muscles listed would be diagnostic of an anterior interosseous nerve (AIN) lesion.
- A) A 60-cycle (60-Hz) interference happens frequently and is usually caused by electrical sources near the EMG machine. Turning on the notch fi lter will get rid of all components of the waveform that have 60-cycle components. Although this is usually a good thing (making the baseline fl atter), the electromyographer must remember that just like all fi lters, you may be removing parts of the waveform that you want to see. Turning on the notch fi lter will remove part of the waveform, which may affect amplitude, latency, and conduction velocity as well as motor unit action potential (MUAP) morphology. Eliminating extraneous electrical currents and ensuring better electrical contacts may be a better solution.
- B) Hereditary neuropathies are usually uniform-demyelinating neuropathies. They will therefore show uniformly slowed conduction velocity without temporal dispersion. Temporal dispersion would be seen in segmental demyelination, where some fi bers are conducting much slower than others.
- C) The perineurium is a protective connective tissue that surrounds fascicles of myelinated and unmyelinated nerve fi bers. The endoneurium is connective tissue that surrounds each individual axon and its myelin sheath. The epineurium is the loose connective tissue that surrounds the entire nerve.
- C) The triceps and brachioradialis are innervated by the posterior cord via the radial nerve. The deltoid is innervated by the posterior cord via the axillary nerve. The biceps is innervated by the lateral cord via the musculocutaneous nerve.
- C) The biceps is an elbow fl exor, but it is also a strong supinator. To relax the biceps muscle, it is important to extend the elbow and pronate the forearm.
- D) The median nerve is known to have fi ve classic areas of possible impingement. The LOS is a rudimentary ligament seen in only 1% of the population. It connects the medial epicondyle to a 2-cm bone spur that is a few centimeters proximal to the epicondyle. The median nerve, along with the brachial artery, can become entrapped under this ligament. The bicipital aponeurosis is a thickening of the antebrachial fascia, which attaches the biceps to the ulna and spreads over the median nerve in the forearm. The median nerve then travels between the two heads of the pronator teres muscle (where it can become entrapped) and runs below the fl exor digitorum superfi cialis. In pronator teres syndrome, the pronator teres muscle is usually not affected as the muscle receives its nerve innervation proximal to the nerve entering the two heads of the muscle. The anterior interosseous nerve, a motor branch of the median nerve, can be injured by a fracture of the forearm, compression, or laceration. Finally, the carpal tunnel syndrome is the most common site of median nerve compression.
- D) The only muscle listed here that is not solely innervated by the obturator nerve is the adductor magnus. This muscle has dual innervation from both the obturator nerve and the tibial division of the sciatic nerve. Adductor part: Obturator nerve (L2-L4)
Ischiocondylar part: Tibial division of sciatic nerve (L4) Mnemonic: African Mouse Sneaks Out (refers to Adductor Magnus Sciatic Obturator)
- B) CIM affects predominantly proximal muscles. Sensory responses should not be affected. Although CMAP amplitudes may be affected, they are usually normal to borderline normal as the pickup is over a distal muscle (and proximal muscles are affected in CIM). Electrodiagnostic fi ndings include denervation potentials (fi brillations and positive sharp waves) in proximal muscles as well as low amplitude, short duration, polyphasic motor units with early recruitment.
- C) The dorsal ulnar cutaneous nerve is a sensory branch of the ulnar nerve that supplies the dorsum of the hand. It can easily be obtained (and compared with the nonaffected hand). The dorsal ulnar cutaneous nerve branches above the wrist. Therefore, in lesions at the wrist, the dorsal ulnar cutaneous nerve will be spared. Decreased amplitude of the dorsal ulnar cutaneous nerve indicates that the ulnar nerve lesion is above the wrist.
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