Needle electromyography (EMG) studies are used to assess the health or dysfunction of the neuromuscular system by recording and evaluating the electrical activity in skeletal muscles both at rest and during contraction and the nerve fibers that control the muscles. During EMG testing, a small needle electrode is inserted into a muscle and records the electrical activity in that muscle both a rest and during contraction. Your provider will then assess if there is any abnormal spontaneous electrical activity when the muscle is at rest, activity that isn't present in healthy muscle. The muscle will then contract, and the electrical activity during contraction will be evaluated.
EMG is used to diagnose conditions that affect peripheral nerves, such as peripheral polyneuropathy, nerve compression syndromes such as carpal tunnel syndrome, issues that affect the spinal nerve roots, muscle disorders such as myopathies and muscular dystrophies, motor neuron disorders such as polio and amyotrophic lateral sclerosis (ALS) and conditions that affect the connection between the nerves and muscles such as myasthenia gravis.
