Electrodiagnostics Flashcards
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?
Serial testing can provide information on the presence and extent of recovery.
What outcome can an athlete experiencing an axonotmesis nerve injury (Grade 2 Seddon) expect?
Good rate of recovery with significant improvement
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)?
Lumbar paraspinals
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?
thoracic paraspinals
Which of the following explains post-exercise facilitation that is seen in Lambert-Eaton myasthenic syndrome?
Calcium influx into the nerve terminal
Single fiber EMG testing is most helpful in order to:
Rule out a neuromuscular junction disorder (high sensitivity)
Measurement of F-wave minimal latencies are a useful part of the electrodiagnostic workup for:
demyelinating neuropathy
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?
critical illness polyneuropathy
A variation in the interpotential interval between paired action potentials of the same motor unit is defined as:
jitter
Compared to a limb at 32o C, the compound muscle action potential (CMAP) recorded from a limb at 29o C will be:
Larger in amplitude and longer in duration
Which of the following is a feature of a complex repetitive discharge?
Arises from ephaptic activation of muscle fibers
Myotonic discharges produce a distinctive sound on electromyography (EMG). This sound results from:
Spontaneous firing of muscle fibers
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?
Reduced sensory and motor amplitudes involving the fibular (peroneal) nerve
Which of the following electrodiagnostic findings can distinguish a C8 radiculopathy from an ulnar neuropathy?
Ulnar SNAP amplitude
When performing a nerve conduction study, which of the following patterns of neuropathy would prompt consideration of a nerve biopsy?
Mononeuropathy multiplex
In evaluating a femoral mononeuropathy, nerve conduction studies should include:
saphenous nerve
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:
Uniform slowed conduction velocity (CMT)
What is the correct statement for delayed or absent H reflexes and F waves findings in a patient with Guillain-Barré syndrome (GBS)?
Observed even if peripheral conduction studies are normal
Needle electromyographic study of a patient with steroid myopathy and type II fiber atrophy usually reveals motor unit action potentials with:
Normal amplitude and normal duration
In order to distinguish between axonotmesis and neurapraxia, how much time needs to pass?
10 days
Which of the following needle EMG patterns would be consistent with a suprascapular neuropathy at the level of the suprascapular notch?
Abnormal supraspinatus, abnormal infraspinatus
Which of the following techniques is commonly used to reduce stimulus artifact while performing nerve conduction studies?
Place ground between stimulator and recording electrodes
Which of the following findings on an electrodiagnostic study would help diagnose Myasthenia Gravis?
Post-activation exhaustion 2-4 minutes after exercise
Critical illness polyneuropathy is most often a(n):
Axonal sensory-motor polyneuropathy
In Lambert-Eaton myasthenic syndrome (LEMS), slow repetitive nerve stimulation (RNS) after 10 seconds exercise would show the following abnormality:
Low amplitude and CMAP increment of 1000% before and after 10 seconds exercise
Which technical error can artificially increase (prolong) distal sensory latency when performing antidromic sensory nerve conduction studies?
reversing anode and cathode
Which of the following is most characteristic of radiation plexopathy?
Involuntary, grouped firing of motor unit potentials on electromyography (usually is painless)
What is the best electrodiagnostic evidence of a myopathic process?
Reduced duration motor unit potentials are specific for myopathies along with small amplitude, polyphasic and early recruitment.
Which of the following electrodiagnostic studies is most useful in the evaluation of a Stiff Person Syndrome?
Dual channel electromyography of antagonist muscles
Which of the following characteristics helps to identify inherited demyelinating neuropathy?
Uniform, symmetric slowing of conduction
