David S. Klein, M.D.

Electrodiagnosis

The electrodiagnostic medicine examination is useful in localizing the site of the neuromuscular lesion, determining the pathogenic basis of the disease process, and occasionally identifying the specific disorder. Occasionally, an electrodiagnostic medicine consultant may detect abnormalities not suspected by the referring physician because of the nature of the disease only manifesting electrically at the time of the patient’s presentation, or suggest an entirely different list of disorders.

DIABETIC NEUROPATHY

One of the most common complications of diabetes is diabetic neuropathy. Neuropathy means damage to the nerves that run throughout the body, connecting the spinal cord to muscles, skin, blood vessels, and other organs.

Diabetic neuropathy can be painful and disabling. Fortunately, severe forms do not occur often. And many times, symptoms go away after several months.

What is Neuropathy?Diabetic neuropathy is actually a group of nerve diseases.All these disorders affect the peripheral nerves, that is, the nerves that are outside the brain and spinal cord.

There are three types of peripheral nerves: motor, sensory, and autonomic. Motor nerve fibers carry signals to muscles to allow motions like walking and fine finger movements. Sensory nerves take messages in the opposite direction. They carry information to the brain about shape, movement, texture, warmth, coolness, or pain from special sensors in the skin and from deep in the body.

Autonomic nerves are nerves that are not consciously controlled. These nerves have functions such as controlling the pace of heartbeats, maintaining blood pressure and controlling sweating.

Some symptoms of neuropathy occur when the nerve fibers are lost. If the loss of nerve fibers affects the motor fibers, it can cause muscular weakness. If the loss of nerve fibers affects the sensory fibers, it can cause loss of feeling. And if the loss of nerve fibers affects autonomic fibers, it can cause loss of functions not normally under conscious control, like digestion.

Neuropathy symptoms can also be caused by nerves that are damaged or are healing.These symptoms include prickling, tingling, burning, aching, or sharp jabs of needlelike pain. These are signs of the increased nerve activity that occurs in damaged or healing nerves.

Different types of symptoms can occur together. It is common to have pain even though many fibers have been lost.

What Causes Neuropathy?

Researchers do not yet know what causes diabetic neuropathy. Glucose control seems to play a role. Neuropathy is more likely to affect people who have had diabetes for a long time or whose glucose control is poor.

But no one is sure how high glucose levels must be before nerve damage happens. Glucose probably does not hurt nerve cells directly. Instead, it may affect other systems of the body, which in turn affect the nerves.

Neuropathy can be prevented, at least in some cases. The Diabetes Control and Complications Trial studied complications in people on tight glucose control and those using regular diabetes treatment. Only one-third as many people in the tight-control group got neuropathy as in standard-treatment group.

In addition, avoiding alcohol and cigarettes will probably help protect your nerves from damage.

People with diabetes should be aware that other diseases can also cause neuropathy. These include disorders of the immune system, infectious disease, and poor nutrition.

How Is Neuropathy Diagnosed?Your symptoms are one way of diagnosing neuropathy. Your doctor will ask you to describe your symptoms. Also, the doctor will ask whether your muscles feel weak (not tired); how often you get muscle cramps; whether you keep having prickling, numbness, or pain; whether you have been fainting or vomiting; and whether your bladder control and sexual ability are normal.

Another way to diagnose neuropathy is with a neurological evaluation. The doctor performs several simple and painless tests. These may measure muscle strength, autonomic nerve function, and sensation (such as whether you can feel a pinprick or a vibration).

A third approach I an NCV examination. In this test, a small electric shock is applied to the nerves. A machine reads and records the voltage from the shocks. In neuropathy, the speed of the impulse along the nerve gets slower, shoving something is wrong. Most people do not find the shocks uncomfortable.

Median motor nerve conduction studies

The first report of the usefulness of median motor nerve conduction studies (NCSs) in the diagnosis of CTS was done in 1956. >Median motor nerve latencies are prolonged across the carpal tunnel but nerve conduction is usually normal or faster proximal and distal to the transverse carpal ligament. Even though less sensitive than other diagnostic methods listed below, motor nerve stimulation still plays an important role in the documentation of motor fiber involvement and can be used to localize the lesion when no sensory potentials can be recorded.

SOMATOSENSORY EVOKED POTENTIAL TESTING

The SOMATOSENSORY EVOKED POTENTIAL (SSEP) test is used to evaluate nerve function. The SSEP is a particularly sensitive medical test that is used to determine the presence or absence of nerve injury or dysfunction. The SSEP helps us diagnose problems that involve nerve pathways, such as herniated lumbar, thoracic or cervical disc, arthritis of the spine, as well as degenerative diseases such as multiple sclerosis (MS), Charcot-Marie-Tooth Disease, and diabetic polyneuropathy.

Approximately 1/3 of the adult population will show signs of spinal disk herniation or "bulge" on MRI or CAT scan, and not experience pain at all!! Unfortunate, indeed, is the patient with an asymptomatic herniated disk, probably there for years, who then pulls a muscle and experiences referred pain to the leg.

If the "herniated" or "bulging" disk is actually causing the patient to experience pain, surgery might be of some benefit. If the SSEP is negative, it is far more likely that spinal surgery will be ineffective. Due to the sensitivity of the SSEP, findings of spinal nerve root irritation will be evident, if the disk is truly causing pain due to nerve root compression.

Given the fact that 1/3 of spinal surgery patients get worse after surgery, and only 1/3 get better, it is essential to be certain to avoid a rushed decision for surgery. Once the back is operated upon, it is never the same again.

Before spinal surgery, it is imperative to get all of the information before an irreversible or irreparable consequence.

SSEP is particularly useful to confirm the presence of DIABETIC neuropathy, and Multiple Sclerosis.

David S. Klein, MD, FACA, FACPM, FACMIMS
Director, Pain Center of Orlando
www.suffernomore.com