CHAPTER 2 Dynamic Pathophysiology of Acupoints

INTRODUCTION

Acupoints in different parts of the human body have different anatomic characteristics. All acupoints, however, have one element in common: they are able to become sensitive, tender, or even painful when exposed to a pathologic disorder. The process of sensitizing is still a puzzle to scientists and clinicians. Recent research data and clinical observations related to muscle pain ¹ help to explain more clearly some of the characteristics of acupoints.

It is important to clarify confusion regarding the differences between acupoints and trigger points.

1. The definition of acupoints is neurogenically oriented, whereas the definition of trigger points is myofascially defined. A trigger point is classically defined as an exquisitely tender spot in the muscle.² By contrast, an acupoint can form anywhere in the body. In this book a tender acupoint is defined as any anatomic structure associated with sensitized sensory nerves. This neurogenic definition suggests that acupoints may appear on any part of the body where there is a sensory nerve. Sensory nerves are distributed all over the body, which means that acupoints may appear anywhere in the body, such as in the muscles, tendons, joints, at bone foramina, and in the suture lines of the skull. About 70% of classic acupoints are also trigger points because muscles constitute a large proportion of the body. Acupuncture therapy and trigger point therapy are different by both definition and clinical practice.

2. Tender acupoints gradually develop when homeostasis declines. These tender acupoints, therefore, are defined as homeostatic acupoints (HAs) in this book. As a rule, homeostatic acupoints develop symmetrically in the human body because the distribution of peripheral nerves is bilaterally symmetrical. By contrast, most trigger points are activated directly by the pain symptoms and are not necessarily symmetrical. Trigger points share some, but not all, characteristics of acupoints, which means that trigger points have some inclusive but not exclusive parameters of acupoints. Acupoints share all the characteristics of trigger points. Thus not all acupoints are trigger points, but all trigger points are acupoints. Note that trigger points correspond to symptomatic acupoints in our Integrative Neuromuscular Acupoint System (INMAS).

One of the most important concepts of acupuncture is that acupoints are pathophysiologically dynamic entities. The degree of their sensitivity changes when homeostasis (the yin-yang balance) changes. Most acupoints show practically no sensitivity when the homeostasis is optimal. Acupoints become tender when homeostasis declines or the body is insulted by pathologic factors. Thus the number of tender HAs can be the quantitative indicator of the homeostasis status of the body. The more tender the HAs detected in the body, the more imbalanced the homeostasis is. Once the homeostasis declines, the health deteriorates.

Then the chain reaction follows: the immune function is suppressed, self-healing capability is impaired, and different pathological disorders may be developed. Patients with more tender acupoints in their bodies need more treatments than those with less tender acupoints.

An understanding of acupoint physiology is important for clinical practice because at the practical level such understanding enables a practitioner to perform quantitative acupuncture evaluation to obtain a reliable prognosis of acupuncture treatment, to predict how many treatment sessions will be needed, and to achieve maximal pain relief in more than 90% of pain patients.

DYNAMIC PHASES OF ACUPOINTS

Dr. H.C. Dung described three phases of acupoints: latent, passive, and active.³ Generally in healthy people some acupoints are neither sensitive nor tender. These nonsensitive acupoints are referred to as latent acupoints.

Under the influence of pathophysiologic disturbances, such as chronic pain or disease, nonsensitive (latent) acupoints are gradually transformed into sensitive or passive acupoints. Almost everyone has a number of passive (tender) acupoints, but people are not consciously aware of them until an experienced practitioner palpates these acupoints with a certain amount of pressure, at which acupoint a person may feel tender or sore at the palpated locations. Most acupoints encountered in acupuncture practice are passive acupoints.

As pathologic disturbances continue to insult the body, pain becomes more intense, and finally passive acupoints become active acupoints. Patients feel painful active acupoints without any palpation and are able to show the precise location of these points and areas to their doctors.

Latent acupoints represent normal tissues. Neurologically passive acupoints have a lower mechanical threshold than normal tissues do and start to fire impulses to the spinal cord and brain under normal mechanical pressure. The same amount of pressure will not induce impulses on latent points. Active acupoints have the lowest mechanical threshold; they may continuously fire impulses to the brain, even without being submitted to external mechanical pressure, and may finally sensitize the neurons in the spinal cord and brain. As the mechanical threshold decreases, the physical size of a sensitized acupoint increases. The phase transition from latent to passive or from passive to active is a continuous process without any clear demarcation; so there is no quantitative measurement for differentiating acupoints of different phases. Table 2-1 provides some criteria, based on our clinical experience, to differentiate the three phases of acupoints. The pressure used to palpate the acupoints is about 2 or 3 pounds. In the clinic we use the thumb to press the points. The pressure is about 2 or 3 pounds when the thumbnail turns from pinkish to whitish. The pressure used to palpate may need to be adjusted because some patients tolerate less pressure if their acupoints are very sensitive or even painful.

Table 2-1 Three Pathophysiologic Phases of an Acupoint