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What is the primary ion responsible for the depolarization phase of a peripheral nerve action potential?

Sodium (Na+) influx through voltage-gated channels

Potassium (K+) efflux through voltage-gated channels

Calcium (Ca2+) influx through voltage-gated channels

Chloride (Cl-) influx through ligand-gated channels

to track

2026 Statistics

Key Facts: ABEM (EDX) Exam

~200

Exam Questions

ABEM/AANEM

$950-$1,050

Registration Fee

AANEM 2026

4 months

Minimum EDX Training

ABEM Requirements

200 + 100

Studies Required

Training + post-training

3,500+

Physicians Certified

ABEM/AANEM

10 years

Certification Cycle

ABEM CoreComp

Important: this is the American Board of Electrodiagnostic Medicine (ABEM) exam — the physician board certification in electrodiagnostic medicine (EMG and nerve conduction studies). It is NOT the American Board of Emergency Medicine. The exam has approximately 200 multiple-choice questions including waveform images and video-based EMG/NCS identification. It is administered annually at Pearson VUE testing centers. Candidates must hold board certification (or candidacy) in Neurology or Physical Medicine & Rehabilitation and must document at least 4 months of supervised EDX training (200 studies) plus 8 months of post-training experience with 100 additional evaluations. The registration fee is $950 (early) or $1,050 (regular), with a $525 subsequent-attempt fee. ABEM is operated under the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM), though AANEM membership is not required to certify. More than 3,500 physicians are currently ABEM-certified.

Sample ABEM (EDX) Practice Questions

Try these sample questions to test your ABEM (EDX) exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What is the primary ion responsible for the depolarization phase of a peripheral nerve action potential?

A.Sodium (Na+) influx through voltage-gated channels

B.Potassium (K+) efflux through voltage-gated channels

C.Calcium (Ca2+) influx through voltage-gated channels

D.Chloride (Cl-) influx through ligand-gated channels

Explanation: The rapid depolarization (upstroke) of a peripheral nerve action potential is mediated by voltage-gated sodium channels opening and allowing Na+ to rush into the axon, driving the membrane potential toward the sodium equilibrium potential (+55 mV). Voltage-gated potassium channels open more slowly and mediate repolarization, while calcium channels are critical at the presynaptic terminal for neurotransmitter release, not axonal conduction.

2Saltatory conduction in myelinated peripheral nerves refers to which phenomenon?

A.The jumping of action potentials from one node of Ranvier to the next

B.Continuous propagation along the entire axolemma

C.Antidromic conduction along sensory fibers

D.Propagation exclusively through the myelin sheath itself

Explanation: Saltatory conduction describes how action potentials in myelinated nerves 'jump' from one node of Ranvier to the next, where sodium channels are densely clustered. Between nodes, the internodal myelin prevents current loss and acts as an insulator, allowing faster conduction with less energy expenditure than continuous propagation along unmyelinated fibers. Loss of myelin (demyelination) slows or blocks this process.

3Which peripheral nerve fibers have the fastest conduction velocity?

A.Large myelinated A-alpha fibers (12-20 micrometers diameter)

B.Small myelinated A-delta fibers

C.Unmyelinated C fibers

D.Small myelinated B fibers (preganglionic autonomic)

Explanation: A-alpha fibers are the largest (12-20 micrometers) and most heavily myelinated peripheral nerve fibers, with conduction velocities of 70-120 m/s. They subserve motor function and proprioception (Ia and Ib afferents). Conduction velocity in myelinated nerves is approximately proportional to fiber diameter (roughly 6 × diameter in micrometers). Unmyelinated C fibers are the slowest at 0.5-2 m/s and carry pain and temperature information.

4The biceps brachii muscle is primarily innervated by which nerve and spinal root?

A.Musculocutaneous nerve, C5-C6

B.Axillary nerve, C5-C6

C.Median nerve, C6-C7

D.Radial nerve, C6-C8

Explanation: The biceps brachii is innervated by the musculocutaneous nerve, which arises from the lateral cord of the brachial plexus and carries fibers primarily from the C5 and C6 roots. This muscle is commonly sampled during needle EMG for suspected C5-C6 radiculopathy, upper trunk plexopathy, or musculocutaneous neuropathy. The axillary nerve innervates deltoid and teres minor.

5A Martin-Gruber anastomosis refers to what anatomical variant?

A.A communicating branch from the median to the ulnar nerve in the forearm

B.A communicating branch from the ulnar to the median nerve in the hand

C.A connection between the median and radial nerves in the upper arm

D.A tibial-to-peroneal communication in the leg

Explanation: Martin-Gruber anastomosis is a common anatomical variant (present in 15-30% of the population) in which motor fibers cross over from the median nerve (typically from the anterior interosseous branch) to join the ulnar nerve in the forearm. This can cause unusual NCS findings such as a positive initial deflection on ulnar motor studies when stimulating the median nerve at the wrist, or apparent conduction block in the forearm segment. Riche-Cannieu is the opposite — an ulnar-to-median connection in the hand.

6In a standard median motor nerve conduction study recording from the abductor pollicis brevis (APB), which statement about the expected distal motor latency is most accurate?

A.Normal distal motor latency is typically less than approximately 4.4 ms with a standard 8 cm distance

B.Normal distal motor latency is typically less than 2.0 ms

C.Normal distal motor latency has no upper limit as long as amplitude is preserved

D.Normal distal motor latency should exceed 6 ms in healthy adults

Explanation: In routine median motor NCS recording from APB with an 8 cm wrist-to-APB distance, the upper limit of normal distal motor latency is approximately 4.2-4.4 ms in most laboratories (Preston & Shapiro). Prolongation beyond this is a key finding in carpal tunnel syndrome. Each lab should establish its own reference values based on technique, distance, and temperature.

7Temperature significantly affects nerve conduction studies. Cooling a limb below the recommended range will typically produce which changes?

A.Prolonged latencies, slower conduction velocities, and increased CMAP/SNAP amplitudes

B.Shortened latencies, faster conduction velocities, and decreased amplitudes

C.No change in latencies but decreased amplitudes only

D.Prolonged latencies and decreased CMAP/SNAP amplitudes

Explanation: Cold temperature slows the kinetics of voltage-gated sodium channels, prolonging latencies and slowing conduction velocity by approximately 1.5-2.5 m/s per degree Celsius below normal. Paradoxically, amplitudes are increased in cold limbs because slowed sodium channel inactivation prolongs the action potential duration and increases the area under the curve. Standard guidelines recommend warming the hand to at least 32°C and the foot to at least 30°C before testing.

8A 52-year-old woman presents with nocturnal paresthesias in the first three digits of the right hand. Median motor NCS shows a distal latency of 5.8 ms (upper limit 4.4 ms) recording APB with 8 cm distance. Median sensory NCS shows absent SNAP at the wrist. Ulnar studies are normal. What is the most likely diagnosis?

A.Moderate to severe carpal tunnel syndrome (median neuropathy at the wrist)

B.C6 radiculopathy

C.Pronator teres syndrome

D.Brachial plexopathy of the lateral cord

Explanation: Prolonged median distal motor latency (5.8 ms) with absent median SNAP at the wrist and normal ulnar studies is a classic pattern for carpal tunnel syndrome, specifically moderate to severe based on Stevens/AANEM grading (absent SNAP categorizes as severe). C6 radiculopathy would affect non-median innervated C6 muscles and typically spare sensory nerve action potentials because the lesion is proximal to the dorsal root ganglion. Pronator syndrome would affect median forearm muscles.

9In evaluating ulnar neuropathy at the elbow (cubital tunnel), what degree of focal slowing across the elbow is typically considered diagnostically significant?

A.A drop in conduction velocity of more than 10 m/s across the elbow segment compared to the below-elbow segment

B.A drop of more than 2 m/s across the elbow segment

C.A conduction velocity below 60 m/s anywhere along the ulnar nerve

D.Any latency difference greater than 0.1 ms

Explanation: AANEM guidelines for ulnar neuropathy at the elbow recommend diagnosing focal slowing when the across-elbow conduction velocity drops by more than 10 m/s compared to the below-elbow segment. The elbow should be flexed 70-90 degrees with at least a 10 cm across-elbow measurement to minimize technical error. Additional supportive findings include conduction block (>20% amplitude drop) across the elbow and focal slowing with a short inching technique.

10Which of the following is considered abnormal spontaneous activity indicating active denervation on needle EMG?

A.Fibrillation potentials and positive sharp waves

B.End-plate noise and end-plate spikes

C.Insertional activity lasting approximately 200-300 ms

D.Motor unit action potentials with voluntary activation

Explanation: Fibrillation potentials (brief, regular spontaneous discharges from single denervated muscle fibers) and positive sharp waves are the classic findings of active denervation, typically appearing 2-3 weeks after nerve injury. End-plate noise and end-plate spikes are normal findings near the neuromuscular junction region. Normal insertional activity is brief (typically <300 ms) and represents mechanical muscle membrane depolarization from needle movement.

About the ABEM (EDX) Exam

The ABEM Certification Exam is the only U.S. board exam certifying physicians in electrodiagnostic (EDX) medicine — nerve conduction studies and needle EMG. It is administered by the American Board of Electrodiagnostic Medicine (ABEM), which operates under AANEM. It is NOT the American Board of Emergency Medicine. Candidates are typically neurologists or physiatrists (PM&R) who have completed supervised EDX training.

Questions

200 scored questions

Time Limit

Full-day computer-based exam

Passing Score

Scaled criterion-referenced passing score

Exam Fee

$950 early / $1,050 regular (American Board of Electrodiagnostic Medicine)

ABEM (EDX) Exam Content Outline

18-20%

Anatomy

Peripheral nerve, plexus, and root anatomy; muscle innervation; anomalous innervations (Martin-Gruber, Riche-Cannieu)

18-20%

Nerve Conduction Studies

Motor, sensory, and mixed NCS technique, F-waves, H-reflex, blink reflex, repetitive stimulation, waveform analysis

18-20%

Needle EMG

Insertional/spontaneous activity, MUAP analysis (amplitude, duration, phases), recruitment patterns

18-20%

Clinical

History, examination, localization, and clinical correlation of EDX findings in neuromuscular disease

13-15%

Pathology

EDX patterns in radiculopathy, polyneuropathy, myopathy, NMJ disorders, motor neuron disease, focal entrapments

8-10%

Instrumentation

Electrodes, amplifiers, filters, gain, sweep, stimulators, electrical safety, artifact recognition

2-4%

Ethics

Professionalism, informed consent, reporting standards, conflicts of interest

~1%

Autonomic

Basic autonomic nervous system testing (sympathetic skin response, QSART fundamentals)

How to Pass the ABEM (EDX) Exam

What You Need to Know

Passing score: Scaled criterion-referenced passing score
Exam length: 200 questions
Time limit: Full-day computer-based exam
Exam fee: $950 early / $1,050 regular

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

ABEM (EDX) Study Tips from Top Performers

1Master the normal values — distal motor latencies, conduction velocities, SNAP/CMAP amplitudes, and F-wave latencies for commonly tested nerves (median, ulnar, radial, tibial, peroneal, sural)

2Practice waveform interpretation daily — MUAP duration, amplitude, phases, and recruitment patterns distinguish neurogenic from myopathic disease

3Understand temperature effects — cold limbs slow conduction and increase amplitude; warm to at least 32°C upper limb / 30°C lower limb before studies

4Know the anomalous innervations cold — Martin-Gruber anastomosis (median-to-ulnar in forearm) and Riche-Cannieu (ulnar-to-median in hand) create characteristic NCS patterns

5Differentiate axonal from demyelinating polyneuropathy — demyelinating features include slowed CV (<75% LLN), prolonged distal latency (>130% ULN), prolonged F-waves, conduction block, and temporal dispersion

6Practice radiculopathy localization — know which muscles are innervated by which root and when paraspinal fibrillations confirm the localization

7Review repetitive stimulation protocols — 3 Hz decrement for MG, post-exercise increment for LEMS (>100% CMAP increase is pathognomonic)

8Study the Preston & Shapiro, Kimura, or Dumitru EDX textbook cover to cover — these are the canonical references

Frequently Asked Questions

Is the ABEM exam the same as the American Board of Emergency Medicine?

No. There are two organizations that use the acronym ABEM. This page covers the American Board of Electrodiagnostic Medicine — the physician board certification in nerve conduction studies and needle EMG, operated under AANEM. The American Board of Emergency Medicine is a separate organization (abem.org) that certifies emergency physicians. These are completely distinct credentials and exams.

Who is eligible to take the ABEM Electrodiagnostic exam?

Candidates must be diplomates (or active candidates) of the American Board of Psychiatry and Neurology (neurology), American Board of Physical Medicine and Rehabilitation, or the osteopathic/Canadian equivalents. You must document at least 4 months of full-time supervised EDX training with 200 studies (150 with active participation), plus 8 months of independent post-training experience with 100 additional complete EDX evaluations.

What is the ABEM exam format?

The ABEM Certification Exam is a computer-based exam administered at Pearson VUE testing centers every spring. It contains approximately 200 multiple-choice questions including waveform items, static images, and video-based questions that require candidates to identify motor unit action potentials, spontaneous activity, nerves, muscles, and physical examination findings.

What score do I need to pass the ABEM exam?

ABEM uses a criterion-referenced scaled passing score determined through standard-setting methodology. The passing score is not expressed as a simple percentage. Historical first-time pass rates are approximately 70-85% based on AANEM exam result summaries. Written and video items are combined into a single score.

How much does the ABEM exam cost?

Registration is $950 for early registration and $1,050 for regular registration. Subsequent attempts cost $525. AANEM membership is not required to certify, though members often receive discounts on study materials. Total preparation cost including textbooks and courses typically ranges from $1,200 to $2,500.

How long should I study for the ABEM exam?

Most candidates study 200-400 hours over 6-12 months. Preparation usually combines textbook review (Preston & Shapiro, Kimura, or Dumitru), AANEM/ABEM sample questions, waveform identification practice, and clinical EDX experience. Your EDX fellowship or training volume is the single strongest predictor of success.

What content is on the ABEM exam?

The blueprint covers Anatomy (18-20%), Nerve Conduction Studies (18-20%), Needle EMG (18-20%), Clinical (18-20%), Pathology (13-15%), Instrumentation (8-10%), Ethics (2-4%), and Autonomic (~1%). Auditory, visual, and somatosensory evoked potentials are explicitly excluded. Waveform interpretation and MUAP analysis are emphasized heavily in the video portion.

How do I maintain ABEM certification?

ABEM uses a 10-year continuous certification cycle. To maintain certification, diplomates must earn 150 Category 1 CME activities within the 10-year cycle, pay an annual fee, and successfully complete yearly CoreComp self-assessment questions. No decennial recertification exam is required as long as the self-assessment and CME requirements are met.