Understanding Your EMG/NCS Results: Complete Guide to Reading Your Report

Decoding Your EMG and Nerve Conduction Test Results, Normal Values, and What Abnormalities Mean

Published: February 2026 Read Time: 10-12 minutes

You've had your EMG/NCS test, and now you're looking at the report. The terminology might seem overwhelming—words like "latency," "amplitude," "motor unit potentials," "denervation," and "conduction velocity." What does it all mean? This article explains how to read your EMG/NCS report in language that makes sense.

EMG/NCS Report Structure

[1] Most EMG/NCS reports follow a similar format:

1. Patient information: Your name, date of birth, test date
2. Clinical information: Why the test was ordered, your symptoms
3. Procedure description: Which nerves and muscles were tested
4. NCS results: Numerical data for each nerve tested
5. EMG findings: Description of muscle electrical activity
6. Impression: The physician's clinical interpretation
7. Recommendations: Suggested next steps

NCS Values Explained

[2] NCS results include several key measurements for each nerve tested.

Conduction Velocity (CV)

What it is: How fast the nerve signal travels (measured in meters per second, m/s)

Normal range: Typically 40-70 m/s depending on the nerve

What it means:

• Normal: Nerve is conducting signals at normal speed
• Slow: Suggests demyelination (damage to nerve insulation) or some types of neuropathy
• Very slow: Significant nerve disease

Amplitude

What it is: Strength of the nerve's electrical response (measured in millivolts, mV)

Normal range: Varies by nerve, typically 5-50 mV for motor nerves, 10-30 microvolts for sensory nerves

What it means:

• Normal: Good number of functioning nerve fibers
• Low: Suggests nerve fiber loss (axonal damage)
• Very low/absent: Severe nerve damage or complete nerve block

Latency

What it is: Time for signal to travel from stimulus point to recording point (measured in milliseconds, ms)

Normal range: Varies by nerve and distance, typically 2-8 ms

What it means:

• Normal: Signal travels at appropriate speed
• Prolonged: Suggests slowing of conduction, often from demyelination
• Very prolonged: Significant slowing indicating nerve disease

EMG Findings

Insertional Activity

What it is: Electrical activity that occurs when the needle is inserted into the muscle

Normal: Brief burst of activity that quickly stops

What abnormalities mean:

• Decreased: Suggests muscle disease or denervation
• Increased: Suggests irritable muscle (inflammation or denervation)

Spontaneous Activity at Rest

What it is: Electrical activity when the muscle is completely relaxed

Normal: No electrical activity (electrical silence)

Abnormal patterns:

• Fibrillations: Small involuntary muscle contractions, suggests denervation or muscle disease
• Fasciculations: Larger visible muscle twitches, can indicate nerve disease or motor neuron disease
• Other spontaneous activity: Various patterns indicating muscle or nerve problems

Motor Unit Action Potentials (MUAPs)

What it is: Electrical patterns produced when you contract the muscle

Normal: Patterns that are appropriate for the muscle being tested

What abnormalities mean:

• Polyphasic: Abnormal, complex patterns suggesting denervation or neuromuscular disease
• Small amplitude: Low-voltage patterns suggesting muscle disease
• Long duration: Patterns lasting longer than normal, can indicate denervation or reinnervation
• Reduced recruitment: Fewer motor units activating than expected for force applied

Normal Ranges (Examples)

[3] Here are example normal ranges for common nerves tested. Your lab may have slightly different normal values, so always compare to the reference values listed on YOUR report:

Nerve	CV (m/s)	Amplitude (mV)	Latency (ms)
Median Motor	50-70	7-15	2.5-3.5
Ulnar Motor	50-70	7-15	2.0-3.0
Tibial Motor	40-60	5-15	3.0-5.0
Median Sensory	45-65	15-30 microV	2.0-3.5

Abnormal Patterns and What They Suggest

Demyelinating Pattern

Findings: Significantly slowed conduction velocity, prolonged latencies, relatively preserved amplitudes

Suggests: Damage to nerve insulation (myelin). Examples: Guillain-Barré syndrome, some inherited neuropathies

Axonal Pattern

Findings: Reduced amplitudes, normal or mildly slowed conduction velocities

Suggests: Nerve fiber loss (axonal damage). Examples: Diabetic neuropathy, toxin-related neuropathy

Conduction Block

Findings: Drop in amplitude between two stimulation points on same nerve

Suggests: Nerve compression or demyelination at specific location. Examples: Carpal tunnel, nerve entrapment

Motor Neuron Disease Pattern

Findings: Denervation on EMG, normal or near-normal NCS results

Suggests: Problem at motor neuron level. Examples: ALS, motor neuropathy

Myopathic Pattern

Findings: Small amplitude, polyphasic motor units, early recruitment on EMG; normal NCS

Suggests: Primary muscle disease. Examples: Muscular dystrophy, inflammatory myopathy

Interpretation and Impression

[1] This is the most important part of your report—the physician's clinical conclusion.

Possible Conclusions

"Normal EMG/NCS": No abnormalities detected. Your nerves and muscles are functioning normally.

"Abnormal EMG/NCS": Abnormalities present. The report should specify what type (demyelinating, axonal, etc.) and what it indicates.

"Consistent with [specific diagnosis]": Findings match a particular condition. Example: "Consistent with moderate carpal tunnel syndrome"

"Suggestive of [diagnosis]": Findings support but don't definitively prove a diagnosis.

"Cannot exclude": Findings don't rule out a diagnosis; further testing may be needed.

Common Phrases Explained

Phrase	What It Means
Denervation	Loss of nerve-muscle connection; nerve fibers have died or been separated from muscle
Demyelination	Damage to nerve insulation (myelin); slows signal conduction
Axonal damage	Damage to the actual nerve fiber (axon); reduces signal amplitude
Focal abnormality	Problem at one specific location on the nerve
Generalized/diffuse	Problem affecting multiple nerves throughout the body
Mild/moderate/severe	Degree of nerve or muscle abnormality
Clinical correlation recommended	Results should be interpreted alongside your symptoms and physical exam

Questions to Ask Your Doctor

When you review your results with your doctor, consider asking:

• "Are my results normal or abnormal?"
• "What do these findings mean for my diagnosis?"
• "Do these results confirm what you suspected?"
• "What does [specific term from report] mean?"
• "Do I need further testing?"
• "What treatment do you recommend based on these results?"
• "What is the prognosis with these findings?"
• "Will I need repeat EMG/NCS in the future?"