Nerve Conduction Studies

Nerve Conduction Studies

That is what it may seem like to anyone who has ever undergone a nerve conduction study with electromyography (NCS/EMG). For those who have no idea what I am talking about, please allow me to elaborate. The NCS/EMG is a test that assesses the status of specific nerves and muscles in the body. It can be used to diagnose simple conditions like carpal tunnel syndrome, or life threatening conditions such as Lou Gehrig’s Disease (ALS) or Guillain Barre Syndrome (AIDP). There are two parts to the test. During the nerve conduction portion, electrodes are placed on the skin and specific nerves are stimulated using a small amount of electricity. The nerves are very similar to wires, essentially carrying electrical signals to various parts of the body. The time it takes for this stimulation to reach the electrodes combined with the amount of electricity that reaches the electrodes are used to assess the health and continuity of the nerve. The second portion of the test involves inserting small pin electrodes into specific muscles. This is literally nothing more than an antenna which picks up the electrical activity within the muscle. There are many patterns that can be found which are associated with various neuromuscular diseases, hence the requirement for specialized training prior to performing this test.

Unfortunately, a certain degree of this testing can be subjective and the interpretation can vary within physicians. In addition, this test also has the potential to be over utilized. From a personal perspective, I have seen many studies reported in a substandard fashion and diagnosis made on insufficient criteria. This is detrimental to both the patient and medical field. While I currently do not perform NCS or EMG studies, I am trained to do so and have performed approximately 500 of them during my career.

So, how do you know if your study was done and interpreted correctly? Unfortunately, this is almost impossible to do as a patient unless you have extensive knowledge of neuroanatomy and neurophysiology. I do have some recommendations, however, to help determine if your study was performed in a comprehensive manner:

  • Is the study being performed by a physician or a technician? While there is a specific type of technician who can perform the nerve conduction portion of the study, a physician must perform the EMG portion of the study. In addition, I personally prefer to perform the nerve conduction portion of the study myself as valuable information can be obtained by actually doing the study vs. just reviewing the results.
  • Is more being done than necessary? If you are being evaluated for carpal tunnel syndrome, it is not always necessary to test both arms AND both legs.
  • Is the physician board certified in Physical Medicine and Rehabilitation (Physiatry) or Neurology?
  • Do they have a full NCS/EMG machine, or a hand held device with pre-fabricated electrodes? A true EMG machine has many more features and can offer more detailed analysis than the hand held units.
  • This test is not a ‘one size fits all’, and should be tailored to the specific condition and/or findings discovered during the test. Often, I started a test with one possible diagnosis in mind, but wound up discovering unexpected abnormal findings which lead to an alternate diagnosis. This lead to a modification of my intended testing procedure. I would be weary of a clinician who performs a set amount of studies, regardless of the condition being tested.

The purpose of this blog is not to discredit anyone who performs electrodiagnostic testing, but rather to inform you of how the test should be conducted and what to look for when having one done.

Citations

  • Wang H, Cui F, Yang F, Huang D, Wang X, Chen Z, Ling L, Huang X. [Clinical, magnetic resonance imaging and neuroelectrophysiological characteristics of 14 patients with lumbosacralradiculitis]. Zhonghua Yi Xue Za Zhi. 2014 Oct 28;94(39):3062-5. PubMed PMID: 25549678

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