It is a needle EMG method in which electrical activities obtained from a single muscle fiber are recorded.
Technically, it is a method whose application requires time, practice, and experience. It is a method essentially called the motor endplate, which is more commonly used in diseases of the transition region (neuromuscular junction) between muscles and motor neurons. A needle electrode is inserted into a selected muscle and you are asked to contract that muscle very lightly. Meanwhile, the electrical activities of the synchronously contracting muscle fibers are recorded, and the firing time variability between the fibers is measured. If this variability is greater than 55 microseconds, depending on the muscles, it is expressed as “Increased Jitter”. If high jitter values are obtained in more than 10% of the muscle fibers in the examined muscle, it means that the motor endplate function is impaired in that muscle. Functional impairment in the motor endplate leads to fatigue and weakness during sequential muscle activities.
It is especially important in the diagnosis of the disease called “Myasthenia Gravis”. However, a defective single fiber EMG test does not always indicate Myasthenia Gravis. Increased jitter may also be found in some neuropathies and motor neuron diseases. Therefore, the diagnosis of the disease is not made only on the basis of single fiber EMG results; the diagnosis should be reached by evaluating the clinical findings, various antibody levels in the blood, and other parameters such as repetitive stimulation tests.