EDT EDT EMG Waveform Analysis 3

Question 1

Which EMG pattern is most consistent with Lambert-Eaton Myasthenic Syndrome (LEMS) on repetitive nerve stimulation?

Accepted Answer

Incremental response >100% at high-frequency (20–50 Hz) stimulation or post-exercise

Answer

LEMS shows a markedly incremental CMAP response (>100%) at high-frequency stimulation or after brief exercise because calcium accumulation enhances ACh vesicle release.

Question 2

Neuromyotonia (Isaacs syndrome) is characterized on EMG by:

Accepted Answer

Continuous high-frequency spontaneous MUP discharges that persist after nerve block

Answer

Neuromyotonia shows continuous high-frequency spontaneous discharges that persist even after nerve block, indicating the abnormality is at the nerve terminal membrane level.

Question 3

When performing needle EMG of the first dorsal interosseous (FDI), the main clinical purpose is to evaluate:

Accepted Answer

Ulnar nerve and/or C8/T1 roots

Answer

The FDI is innervated by the ulnar nerve (deep branch) and reflects C8/T1 myotomal innervation, making it useful for evaluating ulnar nerve or C8/T1 pathology.

Question 4

The insertional activity on needle EMG is normally:

Accepted Answer

A brief burst of electrical activity lasting only as long as needle movement

Answer

Normal insertional activity is a brief burst of electrical potentials generated by mechanical irritation of muscle fibers that stops immediately when needle movement ceases.

Question 5

In evaluating a patient with suspected ALS, EMG evidence of active denervation must be found in how many body regions to meet El Escorial criteria?

Accepted Answer

3 regions

Answer

Definite ALS by El Escorial criteria requires EMG evidence of lower motor neuron involvement (fibrillations, large MUPs, reduced recruitment) in at least 3 of 4 body regions.

(EDT) Electrodiagnostic Technician Certification Practice Test

(EDT) Electrodiagnostic Technician Certification Practice Test

EDT EDT EMG Waveform Analysis 3