#4 EMG Experts Don’t Understand Pain Physiology

By James Hedgecock, PhD, Inventor of F-EMG EDx.

Around 2015 insurance giants, Gieco and State Farm, hired neurology professors and presidents of EMG organizations to explain in court filings why functional Pain Fiber F-NCS can’t work. This backfired, revealing these “experts” know little about pain fiber physiology and zero concerning functional electrodiagnosis.

It will be noted that Gieco and State Farm “experts” repeated the same ridiculous statements. To follow are typical statements. These were specifically made by an ex-president of the American Association of Neuromuscular Electrodiagnostic Medicine. His initials (Dr. T) precede his statements in bold font. My answers are in normal font preceded by my initials (Dr. H):

Dr. H: I looked up Dr. T and found that upon becoming president of the AANEM he made this statement. “The field of medicine is in a state of flux, and the AANEM has always done an admirable job in educating and advocating for its members so that they can better adapt to these changes.”

Dr. H: I think one can substitute for “better adapt to these changes” with “better adapt to threats to our practices.”

Dr. T: Hedgecock reports that the A-delta fiber test only tickles, but if these fibers could be stimulated by an electrical current the patient could only feel pain, because that is the only sensation these fibers transmit.

Dr. H: Next to Dr. T’s statement is inserted a Guyton & Hall’s Physiology textbook chart of nerve function from. The chart (right) clearly shows A-delta fibers (Sensory Class III) transmit not only pain, but hair receptor sensations, deep pressure, touch, cold and warmth. Also, studies have found that A-delta in combination with C-Type fibers create itch sensation.

As for Dr. T’s assertion that A-delta fibers cannot be stimulated by electricity, this is laughable. What does Dr. T think he and his colleagues are using when they send a signal through the skin (transcutaneous) to a nerve during NCV? It’s electricity. I suggested Dr. T. stick his thumb in a light socket and let me throw the switch to see if the electricity passes to a nerve and he feels it.

Electricity is used in standard EDx. The electrical stimulus is passed through the skin over a nerve trunk. In the case of the F-NCS voltage passes directly to the nerve fibers and activates the voltage-gated channels. A potentiometer detects the action potential amplitude electrical surge that verifies the minimum voltage causing the action potential. This minimum voltage produces a tickling sensation.

Dr. T:

After careful review and analysis of the information, I have concluded that the A-Delta F-NCS is NOT capable of selectively stimulating and recording A-delta fast pain sensory nerve fibers. If you did activate the A-delta (Fast Pain) fibers the patient would only feel pain and pull away from the stimulus (Withdrawal Reflex).

Dr. H:

Dr. T repeats the same nonsense. I refer again to the Guyton’s chart in Dr. T’s report, which clearly shows A-delta fibers transmit many sensations other than pain.

• skin hairs receptors sensations

• deep pressure

• light touch

• hot

• cold

• stretch

• pricking pain

Dr. T:

In Segen’s Medical Dictionary

1. First Pain (redirected from Epicritic Pain), one of 2 components of acute pain over the skin surface, which is A-delta fiber mediated and characterized as a sharp, pricking, well localized sensation.

2. Physiology pain: Fast pain is a protective and useful response, enabling the individual to accurately localize and withdraw from the pain stimulus to avoid or reduce tissue damage; caused by stimulation of high-threshold thermo/mechanical nociceptors, and transmitted along fast-conduction A-delta fibers.

Dr. H:

Nothing Dr. T is saying here argues that A-delta voltage stimulation is ineffective. He is simply repeating what’s in a medical dictionary about acute skin surface pain and deeper high threshold pain. I am sure, however, that he is unaware he’s pointed out two salient factors, which I underlined. A weak stimulus, such as produced by placing the F-NCS test electrode on the skin, does NOT cause pain or activate High-Threshold Thermo/Mechanical Receptors. The electrode’s sensation becomes baseline within a few seconds and is ignored, while the voltage stimulus is then easy to discern when the current passes through the skin to the underlying nerve and the selective frequency activates the A-delta fibers voltage-gated channels. A large number of A-delta fibers must be excited to cause a Reflex Withdrawal. Dr. T thinks A-delta fibers only transmit pain; therefore, any stimulation causes a Reflex Withdrawal.

Complex Regional Pain Syndrome (CRPS) /Sympathetic Mediated Pain (SMP) cause pain when a patient is simply touched by clothing, sun light or wind. It has been noted that instead of the minimum A-delta F-NCS threshold stimulus causing a tickling sensation, in CRPS/SMP patients the experience is that of severe pain and Reflex Withdrawal. Therefore, an added advantage of A-delta Pain Fiber F-NCS is that it can detect the earliest stages of CRPS/SMP, long before skin, muscle or bone atrophy begins. EMG-type EDx cannot test pain fibers, so therefore they have zero ability to detect early or chronic CRPS/SM. This leaves the diagnosis to be solely based on late stage symptoms and signs.

Skin Mechanoreceptors:

• Designates those receptors thought to be associated with A-delta fibers. * Ruffini’s end organs (skin stretch and joint position) * Krause end-bulbs (cold) * Meissner’s corpuscle (texture, slow vibrations) * Pacinian corpuscle (deep pressure, fast vibrations) * Free nerve endings

• Thermo-receptor

• Nociceptor

• Bulboid corpuscles (end bulb of Krause receptor)

• Chemoreceptor

Dr. T:

One cannot use electricity to stimulate sensory nerves since there are no electrical skin receptors.

Dr. H:

Here we go again with electricity not passing through the skin? This statement is idiotic. Certainly Dr. T wasn’t thinking clearly when he wrote this, because Dr. T and his colleagues use pass electricity through the skin when performing standard NCV. They place the stimulus electrode on the skin over/near a nerve and give the nerve an electric shock. If one takes Dr. T at his word, then he is saying his electricity is different from that used for F-NCS and F-EMG.

It should be noted that researchers have found electric receptors in the skin. From a practical level the mild A-delta F-NCS electric current is not felt until it breaks through the skin’s impedance and directly activates the voltage-gated channels of the nerve’s A-delta fibers. This results in the patient feeling a sensation, which is verified by the potentiometer detecting an electrical amplitude surge. Then the stimulus is turned down, but not off, otherwise the skin’s impedance will need to be again breached. Since the strength of the break though is probably somewhat higher than the minimum threshold stimulus, the patient is told the next sensation will be much weaker. The patient is then allowed to be in silence for a few seconds. Then the stimulus is turned up. After a series of tests the minimum stimulus causing perception of the threshold is found. Next, without having turned the stimulus back to zero or breaking the electrode’s contact with the skin the patient is tested a last time, while the examiner watches the potentiometer to records the objective amplitude jump.

EMG is subjective and not objective

The 1944 EMG, which hasn’t changed since the early 1960s, involves a short shock being increased until the patient subjectively judges he feels a muscle twitch. After the patients feels the muscle twitch, the shock is increased and the examiner subjectively judges the sound of the muscle’s electrical activity, and subjectively judges the oscilloscope waveform.

In the F-NCS the threshold is verified objectively by recording the potentiometer amplitude jump of electricity emanating from the voltage-gated channels.

Dr. T:

The recording electrode needs to be exactly over the nerve.

Dr. H:

Not true. The AMA Electrophysiology Guideline state: “The stimulus and recording electrode is placed near the nerve.” The fact is that electricity follows the path of least resistance. Since nerves carries electrical signals they have less electrical resistance than the surrounding body tissue, therefore, electricity travels to the closest nerve, so one need only to place the electrode near the nerve being tested.

Dr. T:

The A-delta F-NCS graph and standard EMG motor EDx is different.

Dr. H:

Why would a method for detecting gross large fiber damage use the same type of graph as one assessing small pain fiber function? The F-NCS is capturing the naturally generated electrical amplitude released by the A-delta fibers. Motor NCV is measuring speed of a shock passing along large fibers to measure slowing that suggests tissue damage, not functional impairment.

The F-NCS is painless and quick, so the function of all the major nerves in a region can be recorded. This allows the patient to act as his own control using his Bell-Shaped Curve. Therefore, results are independent of race, age and genders. 1944 EMG compares gross damage measures to population averages, so poor sensitivity is built in its analysis.

Dr. T:

There is no support for different types of nerve fibers being selectively responsive to various frequencies.

Dr. H

It is mystifying why many so-called experts can’t wrap their heads around the concept that a certain range of electrical frequency selectively initiates action potentials. There are so many examples. EMG uses frequency ranges between 0 and 150 Hz. and this is never questioned. In 1800 William Herschel discovered invisible infrared light using a prism and thermometers. This eventually led to the understanding that light has vibrations/frequencies and the retina picks up these frequencies and the brain creates colors. Likewise, auditory hair cells selectively sense specific frequencies to produce different sound pitches. It seems intuitive that nerves react to specific vibrations ranges - frequencies. As I once explained to a Harvard neurophysiology researcher; We can’t be certain that 150 Hz to 300 Hz will selectively activate A-delta pain fibers, but one thing is certain; one can find the threshold of this frequency for all the major nerves in region, such as the cervical or lumbosacral regions, and the nerve requiring the strongest voltage at that mid frequency range (250 Hz) is the injured nerve with 100% statistical accuracy.

Dr. T:

Hedgecock’s theory that the skin’s impedance shifts is wrong. The skin’s impedance is fixed and unchanging.

Dr. H:

The body’s electrical impedance is not fixed. I guess Dr. T has never heard of the Polygraph/Lie Detector which has measured shifting skin impedance since 1924.

Dr. T:

Hedgecock’s analysis does not use population averages by age, race or gender.

Dr. H:

Dr. T thinks that the analysis used in EMG-type EDx is superior to all others, but he is way off base. In standard 1018-1944 EDx a single nerve or two is tested and the results are compared with population averages for age, race and gender. I little thought reveals the best possible accuracy using a population average analysis is around 60% accuracy on a bell-shaped curve.

F-NCS is painless, which means function of all the major nerves in a region can be measured. Obviously, in the vast majority of cases a patient has one of two nerve roots involved, so if one averages all the measures of an individual, the result is that patient’s unique bell-shaped curve. The higher measures require more than average voltage to initiate an action potential, while the lowest require less than average voltage. Therefore, results are as close to 100% as possible and independent of age, race and gender.