Electrodiagnostic Technician (EDT) Certification — Questions and Answers

Question 1: For an F-wave study, how should sweep speed typically be adjusted compared to a standard distal motor latency recording?

Increased to 100 ms/div or more (Correct answer)
Decreased to 1 ms/div
Kept identical at 5 ms/div
Set to 10 ms/div regardless of nerve tested

Correct answer: Increased to 100 ms/div or more

F-waves travel to the spinal cord and back, requiring a longer time window (100 ms or more) to capture the late response.

Question 2: Which EMG pattern is most consistent with Lambert-Eaton Myasthenic Syndrome (LEMS) on repetitive nerve stimulation?

Decremental response at 3 Hz stimulation
Incremental response >100% at high-frequency (20–50 Hz) stimulation or post-exercise (Correct answer)
Decremental response only at high frequencies
No change in CMAP amplitude at any stimulation frequency

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

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

Question 3: Which SSEP finding indicates a lesion between the cervical spinal cord and the cortex?

Prolonged peripheral conduction time with a normal central conduction time
Absent Erb's point potential with a normal cortical N20 response
Preserved subcortical N13 response with absent or delayed cortical N20 response (Correct answer)
Increased amplitude of the cortical response with normal latency

Correct answer: Preserved subcortical N13 response with absent or delayed cortical N20 response

Preservation of the subcortical generator (N13) combined with loss or delay of the cortical response (N20) localizes dysfunction to the pathway between those two levels.

Question 4: A blink reflex study evaluates which nerve and pathway?

Facial motor nerve only
Vagus nerve and brainstem
Optic nerve and occipital cortex
Trigeminal sensory and facial motor pathways (Correct answer)

Correct answer: Trigeminal sensory and facial motor pathways

The blink reflex evaluates the trigeminal afferent (V1) and facial efferent pathways, with R1 and R2 components reflecting brainstem and pontine circuitry.

Question 5: For EDX evaluation of a patient with obesity (BMI >40), a key technical adjustment is:

Decreasing stimulus intensity to prevent discomfort
Using only bipolar surface electrodes for EMG
Increasing stimulus intensity and potentially needle electrode placement for NCS to achieve supramaximal stimulation through thick tissue (Correct answer)
Avoiding all sensory nerve studies

Correct answer: Increasing stimulus intensity and potentially needle electrode placement for NCS to achieve supramaximal stimulation through thick tissue

Increased subcutaneous fat in obese patients attenuates electrical stimulation; higher intensities are needed to depolarize deep nerves, and near-nerve needle stimulation may be necessary.

Question 6: Wartenberg syndrome (superficial radial nerve entrapment) is confirmed on EDX by:

Absent ulnar sensory response
Reduced or absent superficial radial sensory SNAP (Correct answer)
Absent median motor response
Prolonged radial motor distal latency

Correct answer: Reduced or absent superficial radial sensory SNAP

Wartenberg syndrome involves compression of the superficial radial sensory nerve at the forearm; EDX confirmation requires reduced or absent superficial radial SNAP.

Question 7: Infection control protocols in the EDX laboratory require that reusable needle electrodes:

Be sterilized using approved sterilization methods or replaced with single-use disposable needles between patients (Correct answer)
Be wiped with alcohol between patients
Be stored in a dry container for 24 hours between uses
Be discarded only if visually contaminated

Correct answer: Be sterilized using approved sterilization methods or replaced with single-use disposable needles between patients

Single-use disposable needles are the standard of care in most modern labs; if reusable needles are used, rigorous sterilization per facility policy is mandatory to prevent infection transmission.

Question 8: Needle gauge selection for EMG affects recordings because smaller gauge needles:

Record from a larger territory and capture more motor units
Record from a smaller territory, are less painful, but may have higher impedance (Correct answer)
Are more durable and preferred for all studies
Produce higher amplitude MUPs due to proximity

Correct answer: Record from a smaller territory, are less painful, but may have higher impedance

Smaller gauge needles have a smaller recording territory (reduced uptake area), causing less patient discomfort but potentially higher impedance and smaller recorded MUP amplitudes.

Question 9: When performing EDX studies in a patient with suspected acute Guillain-Barré syndrome within the first week of symptom onset, results may be:

Consistent with a pure axonal pattern immediately
Always dramatically abnormal from day one
Initially normal or show only subtle F-wave abnormalities, as demyelination evolves over days to weeks (Correct answer)
Show marked denervation on needle EMG within 24 hours

Correct answer: Initially normal or show only subtle F-wave abnormalities, as demyelination evolves over days to weeks

In early GBS, EDX changes lag behind clinical presentation; absent or prolonged F-waves may be the only early finding, with full demyelinating pattern emerging over 1–4 weeks.

Question 10: A technician is about to perform H-reflex studies and notes the patient's record indicates a history of DVT in the same leg. What is the safest approach?

Cancel the entire study and refer back to the ordering physician
Switch to the contralateral limb without notifying anyone
Proceed normally; H-reflex studies pose no DVT risk
Consult with the referring physician before applying pressure from electrode straps or positioning maneuvers to the affected limb (Correct answer)

Correct answer: Consult with the referring physician before applying pressure from electrode straps or positioning maneuvers to the affected limb

Pressure from electrode straps or limb positioning could theoretically dislodge a thrombus; notifying the referring physician to clarify safety constraints is the appropriate step before proceeding.

Question 11: A patient with hepatitis C is scheduled for needle EMG. What is the correct needle handling protocol?

Sterilize the needle in alcohol between muscles to save costs
Reusable needles are acceptable if autoclave-sterilized between patients
Wear double gloves but standard disposal in regular waste is acceptable
Use disposable single-use needles and discard in an approved sharps container immediately after use (Correct answer)

Correct answer: Use disposable single-use needles and discard in an approved sharps container immediately after use

Single-use disposable needles eliminate cross-contamination risk and must be discarded immediately into a puncture-resistant sharps container per OSHA bloodborne pathogen standards.

Question 12: What is the primary reason for using a concentric needle electrode rather than a monopolar needle in EMG recording?

Concentric needles record from a larger area of muscle tissue
Concentric needles deliver electrical stimulation simultaneously
Concentric needles are self-referencing, providing built-in differential recording with less noise (Correct answer)
Concentric needles allow deeper tissue penetration

Correct answer: Concentric needles are self-referencing, providing built-in differential recording with less noise

The concentric needle has its reference within the cannula, creating a differential recording pair that rejects common-mode noise without a separate surface reference.

Question 13: Performing EDX studies in a patient with active skin infection or open wounds over the target area requires:

Applying conductive gel directly into the wound
Proceeding normally as infection does not affect results
Using higher stimulus intensity to penetrate the wound
Deferring the study if possible or avoiding electrode placement in infected areas and using alternative sites to prevent spreading infection (Correct answer)

Correct answer: Deferring the study if possible or avoiding electrode placement in infected areas and using alternative sites to prevent spreading infection

Placing electrodes in or near infected or open wound areas risks spreading infection; the study should be modified to use alternative sites or deferred until the skin is healed.

Question 14: Fibrillation potentials on needle EMG represent:

Spontaneous discharge of individual denervated muscle fibers (Correct answer)
Voluntary firing of normal motor units
Normal insertional activity
Fasciculation of an entire motor unit

Correct answer: Spontaneous discharge of individual denervated muscle fibers

Fibrillation potentials represent spontaneous discharges of single denervated muscle fibers that have become hyperexcitable after losing their nerve supply.

Question 15: Which finding on repetitive nerve stimulation (RNS) at 3 Hz indicates a postsynaptic neuromuscular junction defect such as myasthenia gravis?

Incremental response >100% with high-frequency stimulation
No change in CMAP amplitude
Decremental response >10% in CMAP amplitude (Correct answer)
Markedly prolonged CMAP duration

Correct answer: Decremental response >10% in CMAP amplitude

A decremental response greater than 10% in CMAP amplitude at 3 Hz stimulation is the hallmark of postsynaptic NMJ disorders like myasthenia gravis.

Question 16: In evaluating a patient with vasculitic neuropathy, EDX findings typically demonstrate:

Diffuse uniform demyelination
Normal NCS with myopathic EMG
Asymmetric, multifocal axonal sensorimotor neuropathy (mononeuritis multiplex pattern) (Correct answer)
Symmetric length-dependent polyneuropathy identical to diabetic neuropathy

Correct answer: Asymmetric, multifocal axonal sensorimotor neuropathy (mononeuritis multiplex pattern)

Vasculitic neuropathy causes ischemic axonal injury to individual nerves in a random multifocal pattern (mononeuritis multiplex), resulting in asymmetric axonal sensorimotor findings on EDX.

Question 17: When performing needle EMG of the first dorsal interosseous (FDI), the main clinical purpose is to evaluate:

Ulnar nerve and/or C8/T1 roots (Correct answer)
C6 nerve root
Radial nerve in the forearm
Median nerve at the wrist

Correct answer: Ulnar nerve and/or C8/T1 roots

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 18: Satellite potentials seen on needle EMG are:

Independent discharges of denervated single fibers
Late components of MUPs linked to the main potential, indicating reinnervation (Correct answer)
Normal findings in younger patients
Artifacts from nearby muscle activity

Correct answer: Late components of MUPs linked to the main potential, indicating reinnervation

Satellite potentials are small late components time-locked to the main MUP, reflecting slow-conducting newly reinnervated muscle fibers linked to the same motor unit.

Question 19: The recruitment pattern in a myopathic process typically shows:

Reduced recruitment with large MUPs
Early recruitment with small, short-duration MUPs (Correct answer)
Absent voluntary activity
Discrete pattern at maximal effort

Correct answer: Early recruitment with small, short-duration MUPs

Myopathies reduce the force-generating capacity of individual muscle fibers, requiring more motor units to fire early to compensate, producing early recruitment of small MUPs.

Question 20: When performing upper extremity somatosensory evoked potentials (SEPs), the recording electrode placed at Erb's point (EP) primarily monitors:

Brainstem response at the dorsal column nuclei
Cortical response at the primary somatosensory area
Peripheral nerve volley at the brachial plexus level (Correct answer)
Spinal cord response at C3–C4

Correct answer: Peripheral nerve volley at the brachial plexus level

The Erb's point electrode records the peripheral nerve action potential as the volley passes through the brachial plexus, serving as the peripheral reference for SEP interpretation.

Question 21: Positive sharp waves (PSWs) on EMG are considered abnormal when:

They occur only with needle insertion
They appear during voluntary contraction
They are seen only in paraspinal muscles
They persist beyond needle movement and occur spontaneously at rest (Correct answer)

Correct answer: They persist beyond needle movement and occur spontaneously at rest

PSWs are abnormal when they occur spontaneously at rest beyond the area of needle insertion, indicating denervation or muscle membrane instability.

Question 22: When a patient's CMAP or SNAP amplitude is unexpectedly low, the first technical factor to assess is:

Whether the repetition rate is too fast
Whether the filter bandwidth is set to 20 Hz–10 kHz
Whether the sweep speed is set correctly
Whether the recording electrodes have adequate skin contact and low impedance (Correct answer)

Correct answer: Whether the recording electrodes have adequate skin contact and low impedance

High electrode impedance due to poor skin contact is one of the most common technical causes of reduced CMAP or SNAP amplitude and should be checked before concluding pathology.

Question 23: Which type of artifact most frequently contaminates evoked potential recordings and is the most common technical challenge?

DC electrode drift
60 Hz power line interference
Cardiac R-wave artifact
Muscle (EMG) artifact from patient tension or movement (Correct answer)

Correct answer: Muscle (EMG) artifact from patient tension or movement

Muscle artifact from patient tension or involuntary movement has a broad frequency spectrum overlapping with evoked potentials, making it the predominant source of technical interference.

Question 24: In evaluating a patient with chemotherapy-induced peripheral neuropathy (CIPN), EDX typically shows:

Length-dependent axonal sensory-predominant polyneuropathy affecting distal SNAP amplitudes earliest (Correct answer)
Proximal demyelinating polyneuropathy
Multifocal motor neuropathy
Normal NCS with myopathic EMG

Correct answer: Length-dependent axonal sensory-predominant polyneuropathy affecting distal SNAP amplitudes earliest

Most chemotherapy agents (taxanes, platinum compounds, vinca alkaloids) cause length-dependent axonal sensory-predominant neuropathy, with sural SNAP amplitude reduction being an early and sensitive finding.

Question 25: In needle EMG, the term 'reduced recruitment' means:

Too many motor units firing for the level of force exerted
Fewer motor units than expected are available to fire, reflecting motor unit loss (Correct answer)
Absence of all voluntary activity
Motor units that fire irregularly

Correct answer: Fewer motor units than expected are available to fire, reflecting motor unit loss

Reduced recruitment indicates fewer functioning motor units than expected for a given level of voluntary effort, a hallmark of neurogenic disease.

Question 26: During a nerve conduction study, increasing the stimulus intensity beyond the supramaximal level will have what effect on the CMAP amplitude?

Amplitude decreases due to co-stimulation of inhibitory fibers
Amplitude remains stable (plateau) because all fibers are already activated (Correct answer)
Amplitude fluctuates unpredictably
Amplitude continues to increase proportionally

Correct answer: Amplitude remains stable (plateau) because all fibers are already activated

Once all axons are depolarized at supramaximal stimulation, additional intensity cannot recruit more fibers, so amplitude plateaus.

Question 27: During a facial nerve NCS, a patient becomes distressed and reports eye pain after a surface electrode is placed near the orbit. What should the technician do immediately?

Reduce stimulator output and continue to save procedural time
Remove the electrode, inspect for electrode gel contact with the eye, and address the complaint before proceeding (Correct answer)
Place a cotton eye pad over the area and proceed with recording
Reassure the patient that orbital discomfort is normal and continue the study

Correct answer: Remove the electrode, inspect for electrode gel contact with the eye, and address the complaint before proceeding

Electrode gel near or in the eye can cause corneal irritation or chemical injury; the electrode must be removed, the eye assessed, and the patient's comfort ensured before any further testing.

Question 28: A needle EMG finding of increased polyphasia (>20% polyphasic MUPs) in a muscle indicates:

Isolated peripheral nerve injury
Normal voluntary activity in trained athletes
Definitive diagnosis of ALS
Possible pathology suggesting reinnervation or myopathy causing desynchronized fiber firing (Correct answer)

Correct answer: Possible pathology suggesting reinnervation or myopathy causing desynchronized fiber firing

Increased polyphasia reflects desynchronized firing of muscle fibers within a motor unit, seen in both neurogenic (reinnervation) and myopathic conditions.

Question 29: Absent sural sensory response with preserved peroneal motor response is consistent with:

L5 radiculopathy
Sacral plexopathy
Common peroneal neuropathy
Sciatic neuropathy distal to the short head of the biceps femoris (Correct answer)

Correct answer: Sciatic neuropathy distal to the short head of the biceps femoris

The sural nerve (sensory) and peroneal nerve (motor) share the sciatic nerve; absent sural with preserved peroneal suggests a lesion distal to where sural branches off, or affecting sural preferentially.

Question 30: The absolute refractory period of a nerve fiber corresponds to which channel state?

The membrane is at its resting potential
K⁺ channels are maximally closed
All Na⁺ channels are open
Na⁺ channels are in the inactivated (closed) state (Correct answer)

Correct answer: Na⁺ channels are in the inactivated (closed) state

During the absolute refractory period, voltage-gated Na⁺ channels are inactivated and cannot reopen regardless of stimulus strength, preventing a new action potential.

Question 31: Which of the following best describes the role of the differential amplifier in electrodiagnostic equipment?

It filters high-frequency noise above 10 kHz
It converts analog signals to digital without amplification
It amplifies the difference between E1 and E2, rejecting signals common to both (Correct answer)
It amplifies only the signal at E1 while ignoring E2

Correct answer: It amplifies the difference between E1 and E2, rejecting signals common to both

A differential amplifier subtracts the E2 signal from E1, amplifying the desired potential while rejecting common-mode interference.

Question 32: What is the purpose of nerve conduction studies (NCS)?

To monitor heart rate
To assess nerve function (Correct answer)
To detect brain tumors
To record muscle spasms

Correct answer: To assess nerve function

Nerve conduction studies (NCS) are diagnostic tests that measure how fast and how well electrical signals travel along a nerve. They are used to evaluate the function of motor and sensory nerves, helping to identify nerve damage or dysfunction, such as carpal tunnel syndrome or neuropathy.

Electrodiagnostic Technician (EDT) Certification

The EDT certification validates the knowledge and skills of technicians who perform electrodiagnostic studies including electromyography (EMG) and nerve conduction studies (NCS), covering device operation, waveform interpretation, quality assurance, and patient safety across diverse populations.

Questions

35 min

Time Limit

70%

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