Electromyography (EMG) and Nerve Conduction Velocity (NCV) - My Child Has - Children's Hospital Boston

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Electromyography (EMG) and Nerve Conduction Velocity (NCV)

A number of illnesses primarily involve the peripheral portions of the nervous system and/or the muscles. These neuromuscular processes affect variable anatomic structures including the cells in the spinal cord from which the various nerve roots are derived. Alternatively, the plexus of nerves in the axilla and pelvis, or the individual nerves that control the muscles in the extremities as well as transmit sensory information from the arms and legs to the brain, may be damaged. Lastly, certain disease processes primarily affect either the neuromuscular junction between the nerves and muscles, or the muscles themselves.

EMG is indicated for the evaluation of specific neuromuscular processes including the spinal muscular atrophies such as Werdnig-Hoffmann disease, plexopathies as exemplified by Erb's palsy, congenital or acquired neuropathies including the Guillain-Barre syndrome, defects in neuromuscular transmission such as myasthenia gravis and infantile botulism, and the various myopathies. These include acquired diseases of muscle including polymyositis or those of genetic origin such as some congenital disorders or muscular dystrophies where gene testing is not available or has not confirmed a specific diagnosis. Children with these illnesses may variably complain of numbness and tingling or muscle weakness, in one or more extremities.

An EMG is actually a two-part test consisting of nerve conduction studies (NCS) and electromyography (EMG). Initially the electromyographer performs the nerve conduction studies by stimulating the various nerves along their course. Recordings are made from the muscles for motor nerves or over the nerve itself when testing sensory function. Children will experience a sensation similar to a mild static charge from a wool rug in the winter months. The actual speed of nerve conduction can be calculated. Subsequently, in the electromyography part, the physician inserts tiny electrodes into the muscles. These act like a microphone allowing us to listen to the muscle's electrical activity. We also observe the responses on a oscilloscope-like screen similar to a personal computer. At the onset the patient experiences a tiny pinch. The electrodes are similar in size to those utilized for acupuncture. The physician listens to the responses while observing the screen. Children often offer their ideas as to what the muscle sounds like such as rain on the roof, a lobster boat or a motor cycle! In general EMG is well tolerated by children, especially when their parents are in our lab with them. On occasion with toddlers who do not understand or with very complicated cases requiring extensive study, the EMG is performed in the day surgery center with the help of our anesthesia colleagues.
Electromyography (EMG) and Nerve Conduction Velocity (NCV) - My Child Has - Children's Hospital Boston