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Single fiber electromyography assesses the delay between the contractions of individual muscle fibers within a motor unit and is a sensitive test for dysfunction of the neuromuscular junction caused by drugs, poisons, or diseases such as myasthenia gravis.
Electromyography is the measurement and analysis of the electrical activity in skeletal muscles. This technique is useful for diagnosing the health of the muscle tissue and the nerves that control them. [8] EMG measures action potentials, called Motor Unit Action Potentials (MUAPs), created during muscle contraction.
For example, a doctor may insert a catheter containing an electrode into the heart to record the heart muscle's electrical activity. Another example of clinical electrophysiology is clinical neurophysiology. In this medical specialty, doctors measure the electrical properties of the brain, spinal cord, and nerves.
Using their broader training, physicians in electrodiagnostic medicine, often perform more detailed evaluations which may include laboratory tests, CT or MRI scans, genetic evaluation, biopsy of nerve, skin, or muscle, or perform neuromuscular ultrasound. A more complete listing of disorders and testing can be found under neuromuscular medicine.
Motor NCS are obtained by stimulating a nerve containing motor fibers and recording at the belly of a muscle innervated by that nerve. The compound muscle action potential (CMAP) is the resulting response and depends on the motor axons transmitting the action potential, the status of the neuromuscular junction, and muscle fibers.
The technique has been used for the purpose of evaluating neuromuscular diseases both for their diagnosis and for their ongoing assessment of progression or with therapeutic intervention. Muscle composition and microscopic structure change with disease, and EIM measures alterations in impedance that occur as a result of disease pathology.
The compound muscle action potential (CMAP) or compound motor action potential is an electrodiagnostic medicine investigation (electrical study of muscle function). The CMAP idealizes the summation of a group of almost simultaneous action potentials from several muscle fibers in the same area.
Muscle fibers of people with MG are easily fatigued, which the repetitive nerve stimulation test can help diagnose. In single-fiber electromyography, which is considered to be the most sensitive (although not the most specific) test for MG, [20] a thin needle electrode is inserted into different areas of a particular muscle to record the action ...