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NJ Electrotherapy in Physical Therapy

Patients present with a myriad of symptoms. While the primary purpose of a chiropractic adjustment is to balance the nervous system and correct the underlying cause of the symptoms, adjunct therapies such as electrotherapy may help achieve the desired results in less time. Electrotherapy is effective for the following symptoms: pain, spasm, edema, and muscle weakness.

The theoretical principles that support the use of electrotherapy for the treatment of pain will be explicated. This therapy will only decrease the patient’s perception of pain and should only be used in conjunction with a chiropractic adjustment. At no time should these therapies be used as a substitute for manipulation.

Nociceptors

What stimulates a nociceptor? The common response to this question is pain. But pain is not a stimulus—it is a perception that results from the stimulation of a nociceptor. So what is the stimulus necessary for causing a nociceptor to send an impulse to the brain? The answer is tissue destruction or the potential for tissue destruction. These specialized mechanoreceptors have a high threshold for stimulus and therefore will be stimulated only when a tissue is injured or is about to be injured.

Once a nociceptor is stimulated, the impulse must be carried to the spinal cord, which requries that each nociceptor be connected to a peripheral neuron. There are two types of peripheral neurons that carry pain to the spinal cord, which are classified by how fast they transmit the impulse. The A delta neuron carries fast pain resulting from the mechanical deformation of a nociceptor.

The C neuron carries slow pain resulting from chemical irritation of a nociceptor. This is the slow, dull, aching pain that results from inflammation to a tissue. Both the A delta and the C fibers will carry the impulse from the nociceptor to the dorsal horn of the spinal cord where it will synapse with a neuron that carries the impulse in spinal cord tracts up to the brain. These synaptic connections can be found throughout lamina 1–6 of the dorsal horn however, most are found in lamina 2—also known as the substantia gelatinosa. Understanding the neurology of these dorsal horn synapses is imperative to the understanding of how electrotherapy is effective in decreasing pain perception.

Spinal cord pain tracts begin at the dorsal horn at each level of the spinal cord and receive impulses from the A delta and C fibers. The A delta fibers will synapse with the neurons that become part of the Spinothalamic tract and the C fibers will synapse with neurons that become part of the Spinoreticular tract. Therefore, the Spinothalamic tract will carry fast types of pain to the brain and the Spinoreticular tract will carry the slower types of pain to the brain. Each of these tracts will specifically terminate at the thalamus, which integrates all sensory stimuli (except smell) before it reaches the cortex. Impulses that reach the cortex will be perceived as pain.

To summarize the pain pathway, we begin at the nociceptor, which when stimulated by tissue destruction or the potential for tissue destruction, will send impulses by way of A delta (fast) and C (slow) neurons to the dorsal horn of the spinal cord. There the impulses may be passed along important synaptic connections to spinal tract neurons that take the impulses to the thalamus. Once in the thalamus, the impulses are integrated and sent to the cortex where they are perceived as pain. These impulses can be modified at the level of the dorsal horn so the cortex never receives the information and thus never perceives the pain. These inherent modifications can be activated through electrotherapy protocols resulting in a decrease in the patients’ perception of pain. What are these inherent modifications and what protocols can be used to activate them?

Pain Modification Theories

Gate control theory: The gate theory of pain control was postulated by Melzack and Wall in 1965 and is still a strong influence on our understanding of pain today. It states that the dorsal horn synapses can be inhibited by increased activity of the larger A-beta fibers coming into the cord. These larger fibers carry impulses received from mechanoreceptors other than nociceptors. Movement, massage, vibration, adjustments, and exercise can stimulate these mechanoreceptors. As they are stimulated, the A beta fiber input to the cord is increased and the dorsal horn pain synapses are inhibited. According to this theory, by increasing A-beta fiber input to the cord, transmission of pain is inhibited. Electrotherapy is an extremely effective therapy for achieving this result, however correct protocols must be used.

When using an electrical current to take advantage of this inherent pathway, correct frequency and intensity settings must be used. These settings can be used with these electrical currents: high volt, low volt, interferential, pre-mod, sinusoidal, and variable muscle stimulation (VMS).

The settings are designed to stimulate the A beta fiber directly, thereby increasing A-beta fiber input to the cord. To optimize the effect, the pads should be placed around the point of pain, the frequency should be set to sweep between 70 and 150 Hz, and the intensity should be set to patient comfort. The patient’s perception should be that of a comfortable paresthesia. The sweeping of the frequency is used to prevent accommodation to the stimulus. If your machine does not permit you to sweep, then set it to a fixed amount between 70 and 150 Hz and check on the patient every 5–7 minutes to see if the patient is still perceiving the stimulus. If not, then change the frequency to a higher setting until sensed. The optimal treatment time for this protocol is 20 minutes and it can be performed up to three times per day.

Descending inhibitory pathway theory: This is a more advanced theory that describes descending neurons from the brain stem that when activated, can presynaptically inhibit the same dorsal horn pain synapses that have been previously mentioned. These descending neurons are believed to originate in the periaqueductal gray matter (PAG) of the brain stem. Stimulation of the PAG causes descending neurons to release inhibitory neurotransmitters in the dorsal horn, thus inhibiting pain synapses and decreasing the patient’s perception of pain. The question is what stimulates the PAG?

According to this theory, three types of stimuli can stimulate the PAG: large fiber mechanoreceptor input to the cord, nociceptive bombardment, and power of suggestion.

The same electrical currents described for the gate control theory can be used in this protocol as well. The frequency and intensity settings, however, will be different. The electrical current is designed to stimulate the PAG through nociceptive bombardment of the spinal cord, meaning the current must be optimized to stimulate the smaller A-delta and C fibers. These fibers will be stimulated with frequencies sweeping between 1 and 10 Hz with intensities that the patient describes as painful or uncomfortable. Sometimes the intensities will be high enough to cause muscle contractions. Once again, the pads should be around the point of pain and the treatment time should be twenty minutes. Because this therapy is so uncomfortable, it should not be performed more than once per day.

In what situation should the gate theory protocols or descending theory protocols be utilized? There are no rules set in stone. They are both effective protocols, however, in my experience, some patients respond to one but not the other; therefore you need to experiment between the two. Typically, I begin the more acute patients with the gate control theory protocols and chronic patients with the descending theory protocols. However, I will switch protocols when I feel the patient is no longer responding.

The electrotherapies are only as effective as the doctor using them. Electrotherapy devices require the proper settings in order to achieve desired results. There are other protocols that are used for reducing edema and spasm, and still other protocols for strengthening and reeducating muscles. Too many doctors use electrotherapy without following the correct protocols and as a result, it is not producing the expected outcomes and the therapy is blamed for the failure. An unfortunate conclusion considering the results that are achievable when the machines are used correctly.