Electrodiagnostics

Question 1

A physician orders electrodiagnostic testing on a football player who sustained a stinger in a football game. The player has upper extremity weakness. You tell the referring physician which of the following?

Answer 1

Serial testing can provide information on the presence and extent of recovery.

Question 2

What outcome can an athlete experiencing an axonotmesis nerve injury (Grade 2 Seddon) expect?

Answer 2

Good rate of recovery with significant improvement

Question 3

Needle electromyography of a patient with symptomatic lumbar spinal stenosis with neurogenic claudication may show a higher specificity with inclusion in which of the following muscle(s)?

Answer 3

Lumbar paraspinals

Question 4

In patients with co-existent cervical and lumbar spinal stenosis with myeloradiculopathy, the clinical picture often contains both upper and lower motor neuron signs mimicking amyotrophic lateral sclerosis (ALS). In patients with co-existent cervical and lumbar spinal stenosis, normal electromyographic findings in what muscle groups helps to rule out ALS?

Answer 4

thoracic paraspinals

Question 5

Which of the following explains post-exercise facilitation that is seen in Lambert-Eaton myasthenic syndrome?

Answer 5

Calcium influx into the nerve terminal

Question 6

Single fiber EMG testing is most helpful in order to:

Answer 6

Rule out a neuromuscular junction disorder (high sensitivity)

Question 7

Measurement of F-wave minimal latencies are a useful part of the electrodiagnostic workup for:

Answer 7

demyelinating neuropathy

Question 8

A patient in the ICU for 23 days developed bilateral flaccid paraparesis, areflexia and non-radicular sensory loss. Nerve conduction studies showed bilateral sural and ulnar sensory nerve action potentials with normal peak latencies and reduced amplitudes. Bilateral tibial, peroneal, left ulnar motor studies demonstrated normal distal latencies and low-normal conduction velocities but significantly low amplitudes and no conduction block. Needle EMG showed fibrillation potentials and neuropathic recruitment in bilateral tibialis anterior, medial gastrocnemius, quadriceps, and deltoid muscles. What is the electrophysiologic diagnosis most consistent with these findings?

Answer 8

critical illness polyneuropathy

Question 9

A variation in the interpotential interval between paired action potentials of the same motor unit is defined as:

Answer 9

jitter

Question 10

Compared to a limb at 32o C, the compound muscle action potential (CMAP) recorded from a limb at 29o C will be:

Answer 10

Larger in amplitude and longer in duration

Question 11

Which of the following is a feature of a complex repetitive discharge?

Answer 11

Arises from ephaptic activation of muscle fibers

Question 12

Myotonic discharges produce a distinctive sound on electromyography (EMG). This sound results from:

Answer 12

Spontaneous firing of muscle fibers

Question 13

A 40-year-old with pain and paresthesias in the lateral foreleg has weakness of ankle dorsiflexion and eversion and decreased sensation over the dorsum of foot including first web space. Which nerve conduction study results would be most expected?

Answer 13

Reduced sensory and motor amplitudes involving the fibular (peroneal) nerve

Question 14

Which of the following electrodiagnostic findings can distinguish a C8 radiculopathy from an ulnar neuropathy?

Answer 14

Ulnar SNAP amplitude

Question 15

When performing a nerve conduction study, which of the following patterns of neuropathy would prompt consideration of a nerve biopsy?

Answer 15

Mononeuropathy multiplex

Question 16

In evaluating a femoral mononeuropathy, nerve conduction studies should include:

Answer 16

saphenous nerve

Question 17

A 7-year-old boy present with bilateral hand intrinsic muscle atrophy, toe-walking, and pes cavus. Nerve conduction study and EMG will likely show:

Answer 17

Uniform slowed conduction velocity (CMT)

Question 18

What is the correct statement for delayed or absent H reflexes and F waves findings in a patient with Guillain-Barré syndrome (GBS)?

Answer 18

Observed even if peripheral conduction studies are normal

Question 19

Needle electromyographic study of a patient with steroid myopathy and type II fiber atrophy usually reveals motor unit action potentials with:

Answer 19

Normal amplitude and normal duration

Question 20

In order to distinguish between axonotmesis and neurapraxia, how much time needs to pass?

Answer 20

10 days

Question 21

Which of the following needle EMG patterns would be consistent with a suprascapular neuropathy at the level of the suprascapular notch?

Answer 21

Abnormal supraspinatus, abnormal infraspinatus

Question 22

Which of the following techniques is commonly used to reduce stimulus artifact while performing nerve conduction studies?

Answer 22

Place ground between stimulator and recording electrodes

Question 23

Which of the following findings on an electrodiagnostic study would help diagnose Myasthenia Gravis?

Answer 23

Post-activation exhaustion 2-4 minutes after exercise

Question 24

Critical illness polyneuropathy is most often a(n):

Answer 24

Axonal sensory-motor polyneuropathy

Question 25

In Lambert-Eaton myasthenic syndrome (LEMS), slow repetitive nerve stimulation (RNS) after 10 seconds exercise would show the following abnormality:

Answer 25

Low amplitude and CMAP increment of 1000% before and after 10 seconds exercise

Question 26

Which technical error can artificially increase (prolong) distal sensory latency when performing antidromic sensory nerve conduction studies?

Answer 26

reversing anode and cathode

Question 27

Which of the following is most characteristic of radiation plexopathy?

Answer 27

Involuntary, grouped firing of motor unit potentials on electromyography (usually is painless)

Question 28

What is the best electrodiagnostic evidence of a myopathic process?

Answer 28

Reduced duration motor unit potentials are specific for myopathies along with small amplitude, polyphasic and early recruitment.

Question 29

Which of the following electrodiagnostic studies is most useful in the evaluation of a Stiff Person Syndrome?

Answer 29

Dual channel electromyography of antagonist muscles

Question 30

Which of the following characteristics helps to identify inherited demyelinating neuropathy?

Answer 30

Uniform, symmetric slowing of conduction