In the midst of these changing times, it is apparent that the substantiation and documentation of testing follow an orderly diagnostic process. The following is a brief explanation of when one would want to order electrodiagnostic testing.

More specifically a needle EMG

The explosive field of neurobiology has taken off especially in this decade of the brain (1900-2000). This knowledge has given reason for concepts about neural organization and function and has opened new therapeutic avenues for afflication of the brain and spinal cord.

I believe the original premise on which this profession was founded was correct. The nervous system is the master system and we as chiropractors have the unique ability to manipulate (excuse the pun) a persons physiology to bring about change. Advances within the last 10-15 years in the basic sciences are now explaining what we've been seeing clinically for many years and just didn't have the knowledge to explain it.

Studying the electrical activity of muscle and nerves has become a very useful tool in neurology and chiropractic. The determination of whether to do a test or not is based solely on your clinical impression. The tests may be of benefit in showing the extent of the lesion (qualitatively and quantitatively) and the probability of recurrence. Understanding the response of the nerve cell to injury, its capability and time frame of regeneration (3-4/,o) will give you some predictive outcomes to your diagnosis. This will also help document the need for serial studies.

The sequencing of events is imperative to the diagnostic process. If you don't have an idea of what's going on (your clinical impression) then you have not established medical necessity for performing the test (you're fishing). Who wants the embarrassment of appearing clinically incompetent? It all falls back on your clinical skills (history & exam). This will prevent a lot of unsubstantiated, unnecessary, costly test with negative results. There is no standard examination for any patient referred for EMG and nerve conduction studies. Every condition is unique. The clinical problem is considered and a combination of muscle sampling and nerve studies are performed appropriate to the situation.

What does one look for clinically when suggesting the possibility of performing a needle EMG?

Basically from paresis to paralysis, atrophy, fasiculations (maybe), axonopathy, myopathy, myelopathy (ventral horn disease), etc. It is beyond the scope of this article to explain how each of these entities is determined clinically. However, I can only stress the importance in perfecting your clinical skills (history & exam). Which should never cease.

Electromyography (EMG) is carried out by the insertion of a twin core needle electrode into the muscle and the electrical potentials are observed on an oscilloscope. The readings are taken at three different times.

1. During needle insertion
2. With the muscle at rest
3. During full contraction

In general, mildly affected muscles are preferred to severely affected muscles as there may be so few surviving muscle fibers left in the severely affected muscles. Also in some diseases the fastest conducting fibers seem to be affected first so that the maximal findings of denervation are in the periphery of the muscle. A particular fracture of motor neuron disease.

Essentially this can be broken down into two different abnormalities:

1. Denervation
2. Myopathic changes

With denervation what has happened is the nerve supply to a muscle has been affected. This may be damage to or disease of the ventral horn cell, nerve root or peripheral nerve known as "chronic partial denervation". A unique feature of these axons inherent in their ability to undergo plastic changes is that surviving neurones are capable of branching and taking over adjacent denervated muscle fibers and re-enervating them by enlarging the size of the surviving units.

Myopatic changes presents us with quite a different situation. The disease process affects all or some muscle fibers in an entirely random way without regard to motor units. Examples are necrotic myopathies like: polymyositis, Pompe's disease, Myotonia and Myastheaia Gravis.

This is not exhaustive by any means and only represents an introduction. My hopes in sharing with you is that there is a method to this madness and that with perseverance you will succeed.