Meridian Phenomena

In recent decades, an increasing number of American patients have embraced acupuncture therapy. At the same time, more and more clinical studies have confirmed the therapeutic effects of acupuncture. Acupuncture is widely used to treat pain, as well as disorders of the cardiovascular, digestive, respiratory, urinary, dermatological, endocrine, neurological, and immune systems. Moreover, since acupuncture is much less expensive compared to Western medical treatments, many Health Maintenance Organization (HMO) insurance plans in the United States now cover acupuncture therapy.

Why can acupuncture treat such a wide variety of conditions? In other words, what is the mechanism behind acupuncture’s effects?

Traditional Chinese Medicine (TCM) believes that diseases resulted from blockage of qi and block circulation and imbalance of yin and yang. The efficacy of acupuncture is achieved by unblocking the flow of qi and blood in the meridians and balancing the yin and yang of the body. The effect of acupuncture depends on selection of the acupoints and the techniques of needling.

What are meridians? 

Meridians are channels through which qi and blood circulate, connecting the internal organs with the body surface and various tissues such as bones and muscles throughout the body. They form a regulatory system for bodily functions. The main channels are called jing (meridians), while their branches are known as luo (collaterals). Meridian theory is one of the most distinctive aspects of TCM and serves as the theoretical foundation for acupuncture, massage, and Qigong.

Over the past half-century, scholars around the world, primarily in China, have been researching the mysterious meridians. Research has mainly focused on two areas: the phenomena of meridians and the substance of meridians. Here, I will briefly introduce the phenomena of meridians based on the content of Experimental Acupuncture Science.

Meridian phenomena refer to various physiological and pathological manifestations that appear along the pathways of the meridians due to certain factors. These phenomena include propagated sensations along the meridians (PSM), skin vascular reactions along meridians, skin disorders along meridians, and sensory disturbances along meridians.

Propagated Sensation Along Meridians (PSM)

This refers to the special sensations—such as soreness, numbness, or distension—that occur when an acupoint is stimulated by needling or other methods, which then propagate along the course of the meridian.

The nature, speed, depth, width, and direction of the propagated sensation vary depending on the acupoint. In other words, not all acupoints produce obvious sensations after needling. Generally speaking, acupoints located on the back and abdomen tend to produce weaker sensations, whereas those on the limbs and lower back often evoke stronger sensations, and needling fingers and toes tends to be more painful. This is because different nerves are stimulated, resulting in different sensations.

For example:

• Needling Zu-san-li (ST36) often produces a distinct soreness and numbness because it stimulates the lateral sural cutaneous nerve and the saphenous nerve.

• Needling Nei-guan (PC6) frequently causes an electric-like sensation radiating to the fingers due to stimulation of the median nerve.

• Needling Huan-tiao (GB30) can cause a radiating sensation to the calf because it stimulates the sciatic nerve.

  
  

Commonly used acupoints with a high rate of reported sensations include Huant-iao, Nei-guan, Zu-san-li, Zhong-ji, Guan-yuan, San-yin-jiao, and Taixi, etc. Some patients mistakenly believe that no sensation when needling means the doctor is highly skilled—this is not necessarily true.

The occurrence of sensations is also related to the depth of needling. Nowadays, some doctors use shorter, thinner needles to reduce patient discomfort, but different depths of needling can lead to different therapeutic outcomes.

The occurrence of propagated sensation depends on the thickness of the needle, the depth of insertion, and the intensity of stimulation (needling technique)—in other words, it is related to the doctor's selection and technique. On the other hand, each person’s pain threshold differs, meaning their sensitivity to pain varies: the same doctor, using the same needle and technique on the same acupoint, may elicit different sensations in different patients. Aside from deliberate strong stimulation, propagated sensation occurs in only a minority of people—about 12–25%. The propagated sensation described here is commonly referred to as deqi in acupuncture.

Skin Vascular Reactions Along Meridians

This refers to changes in the vascular function of the skin accompanying propagated sensations, such as the appearance of red lines, white lines, rashes, papules, or subcutaneous bleeding. These are physiological changes in the skin’s vasculature. Such reactions are generally short-lived, self-resolving, and leave no obvious sequelae. Occasionally, in patients with sensitive skin, redness may appear at the acupoint after needling. If a subcutaneous blood vessel is punctured, bruising may occur.

Sensory Disturbances Along Meridians

This refers to spontaneous abnormal sensations, such as pain, appearing along the course of a meridian, and is considered a pathological state. Common examples include:

• Finger numbness caused by cervical spondylosis or carpal tunnel syndrome

• Arm pain caused by frozen shoulder (adhesive capsulitis)

• Leg pain caused by hip arthritis

• Posterior thigh pain caused by sciatic nerve compression

  
  

Many of these pains can be explained by modern anatomy and physiology. Loss of sensation or clumsiness in the limbs following a stroke also falls into this category. Experienced acupuncturists can locate the site of illness based on the area and type of pain described (e.g., dull pain, stabbing pain, intermittent pain) rather than simply needling where the patient points, known as the Ashi point.

Skin Disorders Along Meridians

These are skin conditions distributed in a band-like pattern along the course of a meridian due to genetic factors or external/internal stimuli. The most common acquired meridian-related skin disorder is herpes zoster (shingles). Others include scleroderma, eczema, and allergic purpura.

Locating tender points, nodules, or abnormal discolorations along the meridians can be an effective aid in diagnosis and treatment.