An EMG/NCS (Electromyography / Nerve Conduction Study) is a diagnostic test that evaluates the health of muscles and the nerves controlling them. The two components are usually performed together:
Nerve Conduction Study (NCS)
Small electrical pulses are applied to the skin over a nerve, and sensors measure how fast and how strongly the signal travels. This assesses:
Conduction velocity (how fast the nerve fires)
Amplitude (signal strength)
Latency (delay time)
It's particularly good at identifying demyelinating vs. axonal nerve pathology.
Electromyography (EMG)
A fine needle electrode is inserted into specific muscles to record electrical activity at rest and during contraction. Abnormal findings include:
Fibrillations and positive sharp waves (signs of denervation)
Fasciculations
Polyphasic or giant motor unit potentials (signs of reinnervation or myopathy)
What it diagnoses
Peripheral neuropathies (diabetic, compressive, toxic)
Radiculopathy (cervical or lumbar nerve root compression)
Carpal tunnel and other entrapment syndromes
Plexopathies (brachial or lumbosacral)
Neuromuscular junction disorders (myasthenia gravis, Lambert-Eaton)
Myopathies and muscular dystrophies
ALS and other motor neuron diseases
Clinical relevance in pain management
For your practice, EMG/NCS is particularly valuable in objectively confirming radiculopathy, distinguishing it from peripheral neuropathy or plexopathy, and guiding procedural planning — for instance, confirming which nerve root is compromised before an epidural steroid injection or nerve block.