|  | Conditions Treatments | Wounds Injuries

Emg Negative Traumatic Brachial Plexus Injuries

The brachial plexus is a nerve complex located in the neck and under the arm. Damage to this complex---known as brachial neuropathy---has a number of potential causes, including traumatic injury, viral infection, surgical complications and autoimmune response. An electromyogram (EMG), also referred to electromyography, is a standard test used to detect brachial plexus injuries. However, improper timing of an EMG test can produce negative results when an injury is actually present.

  1. The Facts

    • An EMG procedure for brachial damage involves the use of electrode needles that are inserted into the muscles controlled by the brachial plexus. These needles record electrical activity inside the muscles, and translate that activity into waves that can be read on an instrument called an oscilloscope. Doctors conducting an EMG look to record the levels of activity when the muscles are contracted and at rest. Abnormal responses on an EMG indicate damage to the brachial plexus.

    Significance

    • In some cases, the brachial nerves are only stretched, and over time any loss of sensation or movement will return. In more serious circumstances, where nerves in the plexus are cut or torn, injury may be both significant and permanent. EMG tests are a critical tool in determining the full extent of a brachial plexus injury and the future course of treatment.

    Additional Tests

    • EMG tests are performed as part of a full-spectrum approach for detecting nerve damage. In addition to physical examination, this process includes a nerve conduction test, which measures the strength of nerve signals sent from the brain and spinal cord to the rest of the body. However nerve conduction only tests the response of the fastest nerves that are still functioning, and can produce good results even when significant nerve damage is present. EMG tests reveal this underlying damage.

    Considerations

    • According to Wheeless' Textbook of Orthopaedics, from Duke University, the true extent of nerve damage takes quite some time to become manifest. If an EMG is performed in the first week after a brachial plexus injury, it will typically produce negative results, whether or not serious brachial damage is present. For this reason, the standard minimum time period for an EMG is seven to 10 days after the injury occurs. Since EMG tests performed further removed from the time of injury can reveal greater detail about the damage present, three to four weeks is considered an optimum amount of time to wait for testing.

    Outcomes

    • If an EMG test performed within 10 days after injury is negative, the test should be repeated at a more appropriate time. If the results of an EMG performed during the optimum window are also negative, it is likely that no permanent damage has occurred. However, a positive EMG result indicates the presence of a potentially permanent injury that will require further treatment.

Wounds Injuries - Related Articles