Electrodiagnosis

electrodiagnosis [i¦lek·trō‚dī·əg′nō·səs]

(medicine)

Diagnosis of disease states by recording the spontaneous electrical activity of tissue or organs, or by the response to stimulation of electrically excitable tissue.

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Electrodiagnosis 

a method of investigating the conductivity of motor nerves and the excitability of muscles by stimulation with an electric current. Electrodiagnosis is used to detect diseases or injuries to peripheral nerves and muscles. Both alternating and direct current are used.

There are certain points on the surface of the body that correspond to the most electrically excitable points on each nerve and muscle. An active electrode in the form of a rod is attached to these points, and a passive electrode in the form of a wide lead plate is placed on the sternum or lower back. The threshold of excitability is determined from the minimum current intensity capable of inducing visible muscle contraction first on the healthy side and then on the affected side; quantitative changes are subsequently noted. The absence of a muscle reaction to strong stimulation implies that the nerve or muscle is dead. Nerve regeneration after an injury is judged from the restoration of excitability.

Electrodiagnosis permits early detection of tetanus, myasthenia, myotonia, and other diseases. Chronaximetry is a means of electrodiagnosis whereby the electroconductivity of tissues is measured, taking into account the type and duration of current needed to evoke a response. In poliomyelitis, for example, considerable time is required to provoke a muscle response to stimulation. Electrodiagnosis is also used to diagnose some ear, eye, and internal disorders.

Electro-odontodiagnosis is a method of examining sensory nerves of teeth by stimulating them with an electric current. It is used in dentistry to diagnose painful changes in the pulp or periodontium.