Electroneuromyography

Electroneuromyography (ENMG) is a diagnostic procedure that assesses the health of muscles and the nerve cells that control them (motor neurons). Motor neurons transmit electrical signals that cause muscles to contract. An ENMG translates these signals into graphs, sounds, or numerical values that a specialist interprets. The procedure is composed of two main components: nerve conduction studies (NCS) and electromyography (EMG). NCS measures the speed and strength of signals traveling between two or more points, while EMG measures the electrical activity of muscles at rest and during contraction.

Indications

Electroneuromyography is used to diagnose conditions that affect muscle function and nerve pathways. These conditions include:

• Peripheral neuropathy – damage to the peripheral nerves
• Muscular dystrophy – a group of diseases that cause progressive weakness and loss of muscle mass
• Amyotrophic lateral sclerosis (ALS) – a condition that affects the motor neurons, leading to severe muscle weakness
• Carpal tunnel syndrome – a condition caused by pressure on the median nerve
• Radiculopathy – nerve pain that radiates from the spine to the extremities

Procedure

The ENMG procedure is typically performed by a neurologist or a physiatrist, specialists in the nervous system and physical medicine and rehabilitation, respectively. The procedure involves two main tests:

Nerve Conduction Studies

During NCS, electrodes are placed on the skin over the nerves to be tested. A small electric shock is passed through the nerve to measure the strength and speed of nerve signals.

Electromyography

For EMG, a thin needle electrode is inserted through the skin into the muscle. The electrical activity detected by this electrode is displayed on a monitor and may also be heard through a speaker. This activity is analyzed to determine the health of the muscle and the nerve supplying it.

Risks and Complications

Electroneuromyography is generally safe. Patients may experience temporary discomfort or pain during the insertion of the EMG needle. There is a minimal risk of bleeding, infection, or nerve injury.

Interpretation of Results

Abnormal ENMG results may indicate nerve or muscle damage. Decreased electrical activity in muscles can suggest a problem with the nerves supplying the muscle. Conversely, abnormal spontaneous activity might indicate a muscle disorder. The results must be interpreted in the context of the patient's symptoms and medical history.

Conclusion

Electroneuromyography is a valuable diagnostic tool for assessing diseases that impair muscle function and nerve pathways. It provides critical information that can guide the diagnosis, treatment, and management of neuromuscular disorders.