EMG INSTRUMENTATIONS EMG Instrumentations

EMG instrementations

Introduction

Electromyography (EMG) is a diagnostic procedure that is used to determine the health of muscles, along with the nerve cells that control these muscles, or what are called motor neurons. In purpose, the EMG is an electrical recording of muscle activity that aids in the diagnosis of neuromuscular disease. The EMG scan, sometimes also called a myogram, is used to identify the electrical signals that originate from these motor neurons (which cause the muscles to move. These electrical signals identified by the EMG allows the medical specialist to interpret such signals in order to diagnosis any problems within the muscles and the nerves that control them (Haig, 2009, 210).

Purpose

Muscles are stimulated by signals from nerve cells called motor neurons. This stimulation causes electrical activity in the muscle, which in turn causes contraction. An electrode, which consists of a very small, solid needle (pin), is inserted through the skin and into the muscle. It is connected to a recording device that detects this electrical activity. When a needle is used the process is called a needle EMG, or simply an EMG. The needle electrode and recorder pair is called an electromyography machine, which includes a monitor called an oscilloscope. A speaker is included, which provides crackling sounds as the electrical intensity rises and falls.

EMG can determine whether a particular muscle is responding appropriately to stimulation, and whether a muscle remains inactive when not stimulated. Thus, during the test, the patient will be asked to contract particular muscles, such as those in the leg. The electrical wave produced on the EMG machine will determine the condition of the muscle and nerves as it responds to the contraction. Usually a nerve conduction velocity (NCV) test (or nerve conduction study) is also performed at the same time as an EMG. This test consists of two electrode being placed apart on the surface of the skin. One electrode is activated so that a muscle is electronically simulated. The second electrode senses the activity (electrical impulse) of the muscle as it moves. The NCV test measures the intensity and speed at which electrical signals pass between two points.

The EMG procedure is performed most often to help diagnose different diseases causing weakness. Although EMG is a test of the motor system, it may help identify abnormalities of nerves or spinal nerve roots that may be associated with pain or numbness. Other symptoms for which EMG may be useful include numbness, tingling, atrophy, stiffness, fasciculation (twitch), pain or cramping, deformity, and spasticity (abnormal muscle performance, such as muscle weakness). EMG results can help determine whether symptoms are due to a muscle disease or a neurological disorder, and, when combined with clinical findings, usually allow a confident diagnosis.

EMG can help diagnose many muscle and nerve disorders, including (but not restricted to) the following:

muscular dystrophy or polymyositis

congenital myopathies

myasthenia gravis

mitochondrial myopathies

metabolic myopathies

myotonias

peripheral neuropathies

radiculopathies

nerve lesions

amyotrophic lateral sclerosis

polio

spinal muscular atrophy

Guillain-Barre´ syndrome

ataxias

myasthenias

Discussion and Analysis

Swallowing is a complicated process that involves many neck muscles, including the ...