To begin the procedure, the patient typically sits or lies down comfortably. The area being examined is exposed, and the skin is cleaned to ensure good electrical contact. A fine needle electrode, called an intramuscular electrode, is then inserted into several muscles of interest. These electrodes are like tiny, hollow, stainless steel needles and are typically placed through the skin into the muscle belly. The needle electrode is connected to recording equipment via a thin wire, which allows for the detection and amplification of the electrical activity within the muscle.
Once the electrodes are in place, the patient is instructed to relax and then perform specific muscle contractions. The neurologist or electromyographer will ask the patient to perform simple movements, such as lifting a leg or arm, clenching a fist, or even walking. The needle electrodes record the electrical signals generated by the muscles during these actions.
During rest, a healthy muscle should show no electrical activity or “silent” baseline. However, if there is abnormal electrical activity present, it may indicate muscle asymmetry or spontaneous activity, which could be a sign of underlying nerve or muscle dysfunction. When the patient contracts the muscle, the electromyographer can observe the muscle’s response and analyze the recruitment pattern and waveform characteristics of the electrical signals produced. This information can help assess the muscle’s strength, coordination, and integrity.
The procedure can be uncomfortable as the needle electrodes penetrate the skin and muscles. However, the discomfort is typically mild and brief. Patients may experience a sensation similar to a small pinch or muscle twitching when the needle is inserted in the muscle. The length of the procedure varies depending on the number of muscles being examined, but it usually takes around 30 minutes to an hour.
In some cases, a nerve conduction study (NCS) is performed alongside EMG. NCS measures the speed and strength of electrical signals as they travel through the nerve. During this part of the procedure, flat, adhesive electrodes are placed on the surface of the skin overlying the nerve being evaluated. Small electrical currents are then applied to stimulate the nerve, and the resulting responses are recorded and analyzed. Combining EMG and NCS can provide comprehensive information about both the muscle and nerve health.
Electromyography is generally considered a safe procedure with minimal risks. Occasionally, patients may experience minor bruising or bleeding at the electrode insertion sites. Rarely, an infection may occur, but this is highly unlikely with proper sterile techniques. Patients with certain bleeding disorders or taking blood-thinning medication should inform their healthcare provider prior to the procedure.
In conclusion, electromyography is a diagnostic tool that can provide valuable insights into the health and function of muscles and nerves. By evaluating the electrical signals produced by the muscles during rest and contraction, electromyography helps identify nerve and muscular abnormalities. Although it may cause temporary discomfort, the information gained from the procedure can be critical in and managing various neuromuscular conditions.