Start with the motor unit
Motor unit & electrophysiology
Identify whether you are recording a nerve response, a muscle response or one motor unit.
3 learning sections✓ Read
NCV / EMG LEARNING
Electrodiagnostic learning center
Connect nerve and muscle anatomy with waveforms and clinical localization. Choose a question and start learning.
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Measure latency, amplitude and velocity
Latency, amplitude & conduction velocity
Reproducible measurements require explicit cursors, distances and units.
3 learning sections✓ Read
Exclude technical artifacts first
Temperature, distance & artifacts
Rechecking distance and limb temperature often improves interpretation more than another test.
3 learning sections✓ Read
Median nerve
Median nerve
Nocturnal radial-digit paresthesia suggests carpal tunnel involvement. Forearm weakness or thenar skin sensory loss warrants a proximal assessment.
C6–T1; some references include C5✓ Read
Anterior interosseous nerve
Anterior interosseous nerve · AIN
Weak thumb IP and index DIP flexion produces a flattened tip-to-tip pinch or incomplete OK sign.
Predominantly C8–T1✓ Read
Ulnar nerve
Ulnar nerve
A reproducible focal across-elbow abnormality supports elbow localization. Dorsal ulnar sensory sparing can help assess a Guyon canal lesion.
C8–T1; possible C7 contribution✓ Read
Reference limits need context
Method-matched reference limits
Match the population and technique before consulting a numerical limit.
3 learning sections✓ Read
The four phases of needle EMG
Insertion, rest, activation, recruitment
Structure the examination around insertion, rest, slight contraction and increasing effort.
3 learning sections✓ Read
Recognize activity at rest
Spontaneous activity
Describe regularity, morphology and firing pattern before assigning pathological meaning.
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Compare neurogenic and myopathic patterns
MUAP morphology & recruitment
Relate motor-unit morphology and number to the force being produced.
3 learning sections✓ Read
Understand the time course of injury
Timing & reinnervation
EDX is a snapshot of an evolving process. Early preserved responses do not exclude injury.
3 learning sections✓ Read
Separate axonal and myelin features
Axonal loss vs demyelination
Interpret low amplitude and slowing within the complete pattern.
3 learning sections✓ Read
Conduction block and temporal dispersion
Conduction block & temporal dispersion
Compare amplitude, area and duration when assessing proximal and distal responses.
3 learning sections✓ Read
F waves and H reflexes
F waves & H reflex
Late responses assess long pathways but rarely localize a single lesion alone.
3 learning sections✓ Read
Localize median slowing at the wrist
Carpal tunnel syndrome
Use comparisons under the same hand conditions to identify focal median abnormalities.
3 learning sections✓ Read
Ulnar nerve: elbow, wrist or C8–T1?
Ulnar localization
Cross-check the across-elbow segment, DUC and non-ulnar muscles.
3 learning sections✓ Read
A localization pathway for foot drop
Foot drop: fibular, sciatic or L5
Connect dorsiflexion, eversion, inversion and hip abduction.
3 learning sections✓ Read
Build a case for radiculopathy
Cervical & lumbosacral radiculopathy
A myotomal pattern across peripheral nerves supports root localization.
3 learning sections✓ Read
Distinguish plexus and root lesions
Brachial & lumbosacral plexopathy
Combine sensory responses, muscles across nerves and paraspinal findings.
3 learning sections✓ Read
Brachial Plexopathy
Brachial Plexopathy
An overview of plexus anatomy, electrodiagnostic localization, lesion patterns and common causes.
12 learning sections✓ Read
Classify polyneuropathy patterns
Polyneuropathy patterns
Organize findings by distribution, fiber type, time course and physiology.
3 learning sections✓ Read
Recognize a myopathic pattern
Electrodiagnosis of myopathy
Understand what recruitment and distribution reveal, and what EMG cannot name alone.
3 learning sections✓ Read
Motor neuron disease and its mimics
Motor neuron disease & mimics
Integrate lower motor neuron evidence with progression and upper motor neuron signs.
3 learning sections✓ Read
Repetitive stimulation and the NMJ
Repetitive nerve stimulation
A stable baseline CMAP is essential before interpreting decrement or increment.
3 learning sections✓ Read
Jitter and single-fiber EMG
Jitter & single-fiber EMG
High sensitivity does not imply disease specificity.
3 learning sections✓ Read
Acquired demyelinating neuropathies
Acquired demyelinating neuropathies
Use formal criteria to avoid overcalling minor slowing.
3 learning sections✓ Read
EDX during an acute GBS course
Guillain–Barré syndrome
Early and follow-up findings may differ. One negative study must not stop clinical assessment.
3 learning sections✓ Read
Recognize anomalous innervation
Anomalous innervation
An anatomical variant can explain a CMAP pattern that otherwise looks pathological.
3 learning sections✓ Read
Safety and informed participation
Safety & informed participation
Balance the question being asked with risk and the person's willingness to participate.
3 learning sections✓ Read
Write a clinically useful report
From findings to an impression
Separate measurements, inferences and limitations.
3 learning sections✓ Read
Choose muscles that test localization
Hypothesis-driven muscle sampling
Each sampled muscle should answer a distinct anatomical question.
3 learning sections✓ Read
Facial, blink and respiratory studies
Facial, blink reflex & respiratory studies
Understand the questions specialized techniques can answer and their limits.
3 learning sections✓ Read
Use ultrasound alongside EDX
Neuromuscular ultrasound
Combine structural and dynamic information with physiological localization.
3 learning sections✓ Read
Small-fiber disease with normal NCS
Small-fiber neuropathy
Know the scope of routine testing before interpreting a negative result.
3 learning sections✓ Read
Neuropathy and myopathy in the ICU
Critical illness polyneuropathy & myopathy
Find useful information despite edema, cold and limited participation.
3 learning sections✓ Read
Myotonia and peripheral nerve hyperexcitability
Myotonic vs neuromyotonic discharges
Similar names can describe activity from different physiological sources.
3 learning sections✓ Read
Dorsal ulnar cutaneous nerve
Dorsal ulnar cutaneous nerve · DUC
Guyon canal lesions usually spare this branch; an abnormal response may suggest a more proximal lesion.
C8–T1✓ Read
Radial nerve
Radial nerve
Wrist drop with brachioradialis involvement suggests a lesion above the PIN. Triceps helps assess a still more proximal level.
C5–T1✓ Read
Posterior interosseous nerve
Posterior interosseous nerve · PIN
Finger extension weakness with preserved skin sensation. Wrist extension may remain, often with radial deviation.
Predominantly C7–C8✓ Read
Superficial radial nerve
Superficial radial sensory nerve
Radial dorsal hand paresthesia after wristband compression or local injury, without wrist or finger extension weakness.
Predominantly C6–C8✓ Read
Musculocutaneous nerve
Musculocutaneous nerve
Weak elbow flexion and supination with lateral forearm sensory changes.
C5–C7✓ Read
Lateral antebrachial cutaneous nerve
Lateral antebrachial cutaneous nerve · LABC
Adds sensory information when assessing musculocutaneous, lateral-cord or upper-trunk lesions.
Predominantly C5–C6✓ Read
Medial antebrachial cutaneous nerve
Medial antebrachial cutaneous nerve · MABC
Provides non-ulnar sensory information in lower-trunk or medial-cord assessment.
C8–T1, predominantly T1✓ Read
Axillary nerve
Axillary nerve
Weak shoulder abduction and lateral shoulder numbness after dislocation.
C5–C6✓ Read
Suprascapular nerve
Suprascapular nerve
Isolated infraspinatus involvement may suggest the spinoglenoid notch; both muscles suggest a more proximal site.
C5–C6✓ Read
Long thoracic nerve
Long thoracic nerve
Medial scapular winging during a wall push may indicate serratus anterior weakness.
C5–C7✓ Read
Spinal accessory nerve
Spinal accessory nerve · CN XI
Shoulder droop, weak shrug or lateral scapular winging after neck surgery.
Spinal accessory motor nucleus; not a single brachial root✓ Read
Dorsal scapular nerve
Dorsal scapular nerve
Weak scapular retraction; provides information from a proximal root branch when comparing root and plexus lesions.
Mainly C5✓ Read
Sciatic nerve
Sciatic nerve
Fibular-division involvement is often more prominent and may resemble an isolated foot drop.
L4–S3✓ Read
Common fibular nerve
Common fibular (peroneal) nerve
Weak dorsiflexion and eversion with relatively preserved inversion supports a fibular localization.
L4–S2✓ Read
Deep fibular nerve
Deep fibular (peroneal) nerve
A distal anterior ankle lesion may affect EDB and first-web sensation while sparing proximal TA.
Predominantly L4–S1✓ Read
Superficial fibular nerve
Superficial fibular (peroneal) nerve
Eversion weakness with dorsal foot sensory changes; a distal cutaneous lesion may be sensory only.
Predominantly L5–S1✓ Read
Tibial nerve
Tibial nerve
Calf involvement helps distinguish a proximal tibial lesion from distal tarsal tunnel disease.
L4–S3✓ Read
Sural nerve
Sural nerve
A commonly tested sensory nerve in length-dependent polyneuropathy assessment.
Predominantly S1–S2✓ Read
Medial plantar nerve
Medial plantar nerve
Focal plantar symptoms may involve distal tibial branches or the tarsal tunnel.
Tibial branch; assess the target-muscle myotome✓ Read
Lateral plantar nerve
Lateral plantar nerve
A distal branch lesion may cause focal plantar symptoms; compare with broader tibial involvement.
Predominantly S1–S2✓ Read
Femoral nerve
Femoral nerve
Weak knee extension and a reduced knee reflex, with relatively preserved hip adduction.
L2–L4✓ Read
Saphenous nerve
Saphenous nerve
Helps evaluate femoral or lumbar plexus lesions and may be injured locally after surgery.
L3–L4✓ Read
Lateral femoral cutaneous nerve
Lateral femoral cutaneous nerve · LFCN
Meralgia paresthetica is a sensory syndrome without primary muscle weakness.
L2–L3✓ Read
Obturator nerve
Obturator nerve
Hip adduction weakness suggests involvement of obturator-supplied muscles.
L2–L4✓ Read
Superior gluteal nerve
Superior gluteal nerve
Weak hip abduction or a Trendelenburg sign adds non-fibular information about L5.
L4–S1✓ Read
Inferior gluteal nerve
Inferior gluteal nerve
Hip extension weakness provides proximal L5–S2 information outside the sciatic nerve.
L5–S2✓ Read
Facial nerve
Facial nerve · CN VII
Facial motor conduction and blink reflexes provide information about different parts of the pathway.
Facial motor nucleus in the pons✓ Read
Phrenic nerve
Phrenic nerve
Unexplained respiratory weakness or weaning difficulty may prompt specialist assessment of nerve, muscle and NMJ causes.
C3–C5, predominantly C4✓ Read
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