Definition

Nerve-tracing is that branch of palpation by which the tenderness of irritated spinal nerves is discovered and their paths demonstrated.

Organ-Tracing

Organ-tracing is that branch of palpation which deals with the outlining of the boundaries and surface markings of a tender organ or part.

Palpaters frequently confuse tenderness of one of the parenchymatous viscera for the tenderness of interlaced and branching nerve filaments, especially in the abdominal region. The fact that the tender area takes on the characteristic shape of one of the viscera is conclusive evidence that an organ, and not nerves, have been traced.

What Nerves Traceable

Any spinal nerve may be traceable for at least a part of its course. The cranial nerves are made inaccessible to palpation by their location, except the spinal portion of the spinal accessory and the terminal portions of the nerves to the face. Likewise the sympathetic trunks, except perhaps in the neck, are untraceable.

Nerve-tracing is comparatively easy in the upper and lower extremities, neck and back. The superficial nerves of the scalp are hard to follow on account of the hair. The superficial nerves of thorax, abdomen, and pelvis are accessible under the conditions mentioned below; the deep or visceral branches, never.

Of those nerves mentioned as traceable, only such as are irritated and consequently swollen and tender, can be followed. If a nerve is very heavily impinged, especially if the impingement be chronic, it is partially or wholly paralyzed and not traceable. If the heavy impingement be acute, or if there be a light impingement serving as a mechanical irritant, nerve-tracing is a real aid to diagnosis.

Proportion of Cases with Traceable Nerves

About one-half of all the cases which visit Chiropractors for adjustment are susceptible of nerve-tracing. In the remaining half it is absolutely impossible to acquire any information in this way. Of the half who are at all susceptible, it is possible in perhaps four-fifths of all cases to secure some accurate or reliable information.

The patient in whom all accessible nerves seem tender to light palpation is hyperesthetic and unavailable for tracing.

In the usual case one or two nerves will be found easily traceable, while the rest exhibit no tenderness on pressure. Such a case furnishes the most reliable information securable by this method and the tender nerves may be considered as lightly or acutely impinged.

Preconception of Nerves Essential

Knowledge of the anatomy of the nervous system is a part of the necessary equipment of the Chiropractor who would trace nerves and this knowledge should be so thorough as to enable the palpater to recognize each tender line found as an anatomically described nerve-path or an error on his part. The examiner must know the paths of all nerves and be able to predict from the first tender points discovered the probable course which the tenderness will follow, so as to direct his search along that probable path.

He must be able to detect unconscious deception on the part of the patient through his knowledge of the anatomical impossibility of the apparent tracing. For instance, if for any reason he may appear to have traced a nerve upward beside the spinal column from D 10 to the eye by way of the vertex, he must know that this is an illusion—because such nerves do not exist and cannot be anatomically demonstrated—or accept the well merited ridicule of any educated person who discovers his absurdity.

Because of the difficulty of determining whether the tender structure found be muscle, nerve, or viscus, and because of the natural suggestibility of both palpater and patient, nerve-tracing cannot be so reliable a guide to nerve-paths as is dissection. It should not be necessary to state this obvious truth but the calm acceptance, by many, of the weird conclusions based upon a belief in the infallibility of nerve-tracing testifies that it is necessary.

Nerve-tracing is valuable only where the nerve-path outlined as being tender corresponds to the known path of some nerve.

Suggestion

Paradoxically, knowledge of nerve-paths may lead to error. By the law of expectancy, we are prone to find what we look for and if we hold too strongly to the belief that because we have found one or two points of tenderness we must find a series of points extending along a mentally pictured nerve-path, we may search until we falsely believe that we have found this series.

Likewise the patient, having been carefully informed as to the manner of procedure and knowing what we expect to discover, may unconsciously deceive us by feeling tenderness in response to suggestion, where no real impingement exists.

Place in Diagnosis

The value of nerve-tracing in diagnosis has been much overestimated by many, though the tendency of the profession seems to be toward rationalism along that line.

Whereas, in palpation of the spine every real subluxation gives evidence of disease, or tendency to disease, while every normally aligned pair of vertebrae furnish proof that no disease can exist in the area of distribution of the nerve emerging between them, nerve-tracing is much less reliable. If the tender nerve be traceable to a vertebral subluxation it may be taken as additional evidence that the effect of that subluxation is disease, rather than tendency to disease, truly an important distinction, but scarcely broad enough to support a diagnosis without aid.

The absence of tenderness from nerves does not negative a disease in any instance, whereas the absence of subluxation does. Like all other expedients for the selection of vertebrae for adjustment without admitting the necessity for first acquiring much skill by much labor, nerve-tracing has a great weakness. Only irritated nerves are tender and the effects of subluxation may be either irritation or paralysis.

If accurately done, sources of error carefully eliminated, and the results of nerve-tracing found to correspond with the condition of the spine and the other symptoms, this method of demonstrating to the patient the connection between the vertebrae and the diseased region of his body is valuable. It aids in convincing him of the validity of the Chiropractic theory.

TECHNIC OF NERVE TRACING

Where to Begin

The palpater, having made his vertebral palpation, may begin at some point in the body indicated by the symptoms as diseased and, finding tenderness, follow the path of a nerve back to the spinal column where the nerve may be fairly presumed to enter the intervertebral foramen.

Or he may use his palpation record as a guide and follow the tender nerves outward to their periphery. This is the better method.

Palpation as Guide

When palpation has been made, remember that the impinged nerve is usually found on the side opposite to the direction of the spinous process in its departure from the median line. With a left subluxation the tenderness is usually, though not always, on the right side. If in the Lumbar, and the subluxation a rotation, the impinged nerve will be found below the transverse process of the subluxated vertebra. In the Cervical and Dorsal regions the tender nerve is usually below, but may be either above or below, the transverse of the subluxated one.

Examine the nerves having exit from the foramina of each subluxated vertebra in turn from above downward. When a tender point is found about an inch from the mid-spinal line, attempt to follow the nerve and palpate until it has been traced as completely as possible.

Where to Expect Tenderness

The region immediately surrounding the spinous process of the subluxated vertebra may be tender because of impingement of the axons of the posterior primary division of that spinal nerve which emerges below the vertebra. Such tenderness is more common with anterior subluxations than with others. It is not to be confused with the soreness which often appears after adjustment and is due to bruising or straining of the tissues.

Nerve tenderness may be discovered at a little distance from the mid-spinal line and at a level slightly lower than the emergence of the nerve. If a nerve is irritated, the finger inserted between the ribs near their articulation with the transverse processes will elicit tenderness. The discovery of tender points along the spine is the most important part of nerve-tracing.

Nerve-Paths

Detailed description of the paths of all the spinal nerves may be studied from any standard work on anatomy and will not be included here, but it may be well to remind the reader of certain general tendencies.

The spinal nerves do not cross the median line in front except perhaps fine interlacing fibres.

In the Dorsal region the nerves are usually found following the interspaces until the lower ones debauch upon the abdominal wall anteriorly. There are, however, some Dorsal and lower Cervical nerve bundles which pass obliquely downward and outward to innervate back muscles.

Reference to the section on Spino-Organic Connection will make clear the tissues supplied by each nerve.

Slight deviations from the usual course of nerves are common; marked deviations very infrequent.

Use of Fingers

Use second finger of either hand for the palpating finger, choosing the hand which can be most conveniently used as determined by the position of patient and the part of the body to be examined. There is no set rule. Reinforce this second finger by the pressure upon it of the first and third and, if desired, by pressing thumb against it. (See Fig. 5.)

Apply the tip of the palpating finger to the nerve with a motion such that it crosses the path of the nerve at right angles back and forth. Meanwhile the probable path of the nerve must be kept in mind. As the finger crosses the nerve-path it makes steady and even pressure upon any structures passing beneath it. The motion of the hand is almost a rolling motion, the finger tip probing, as it were, for a tender spot.

Tenderness—How Recognized

The irritated condition of the nerve which has thus been rolled beneath the finger may be recognized in one of three ways; the patient may involuntarily flinch, betraying the hurt; or he may inform the palpater of the hurt; or the swollen, cord-like nerve may be felt.

The two former are the reliable guides, while the latter is only occasionally possible. In children and in feeble-minded, insane, or mute adults, the first mentioned method must be relied upon entirely. Muscular contraction is the unconscious or reflex response to pain and often occurs independently of the intelligence or state of mind of the subject.

Of all the three methods the one most commonly relied upon is the second—the statements of the patient.

Instruction to Patient

The patient should be informed of your intentions when palpation is begun and should be asked to answer every time you apply your finger, saying, “Yes,” if the spot is tender and, “No,” if not. He should speak promptly each time so as to avoid self-deception which might come with reasoning upon his sensations. Occasionally vary the steady rhythm of your movements by omitting one and note if the patient responds mechanically when you do not press.

At times during the tracing, it is well to depart from the probable nerve-path and to touch again a point marked as tender, to see if the patient’s information may be relied upon. Whenever you leave the nerve-path his answer should be, “No,” immediately changing to, “Yes,” when you re-cross the tender line.

Marking Tender Points

At each tender point noted a small mark should be made with an eye-brow pencil or other grease-paint, which leaves a distinct but easily removable mark. These tender points should be noted and marked at intervals of about an inch.

Connecting Line

When the entire nerve-path has been traversed in this way, draw a line with the eye-brow pencil, passing through all the marks indicating points of tenderness. This line should be a sufficiently accurate rough outline of the nerve-path to make clear the spinal connection with the diseased area. The significance of this connection will be better understood when the section on Spino-Organic Connection has been studied.

Common Findings

In muscular rheumatism, neuralgia, neuritis, or in case of a local boil or abscess indicating local disturbance of the trophic influence of nerves, clear and definite tracings are common. Muscular spasm, such as wry-neck, usually has a very tender nerve associated. Localized painful disease of any kind is likely to be associated with a very definite nerve tenderness, as is the case frequently with appendicitis, ovaritis, hepatic colic, etc.

The painless disorders, or various disorders of spleen, diaphragm, heart, lungs, etc., though they be of a very serious nature, seldom are discoverable by nerve-tracing unless their serous membranes are involved. Tracings may be made from D 2 or 3 to anterior thoracic walls in heart or lung disease but are not common.

Any spinal nerve may be traceable at times through at least a part of its course.

Sources of Error

Several of these have been mentioned, such as the natural suggestibility of both examiner and patient. Among others are: failure in the back, thigh, or leg to reach the really tender nerve because of the interposition of several muscle layers between it and the finger, ignorance of nerve-paths, failure to apply equal pressure to all parts of a nerve, application of such heavy pressure that muscle tissue is bruised and hurt, and failure of full co-operation on the part of the patient. Let us consider these in turn.

If several muscle layers interpose themselves between the searching finger and the nerve, it is proper to push aside the intervening layers, using a twisting and rolling movement until the finger feels underneath the muscles. This done, and a tender nerve found underneath several muscle layers, the same amount of overlying tissue must be pushed aside each time the finger searches for the nerve. Only exhaustive study of the anatomy of the typical nervous system will enable the examiner to know exactly at what point a nerve will become more or less superficial. Unless he does know this it is best to follow the neutral rule that nerves tend to follow the long axes of ribs and limbs and to maintain their depth beneath the surface throughout their course. This statement is too general for accuracy.

Care should be taken that equal pressure be made on all points palpated on one nerve. If the nerve pass over a bone, less force is needed to exert the same pressure than if it overlie muscle or other soft structure. The force used varies constantly as the hand moves from place to place, according to the density and hardness of the structures overlying and underlying a nerve.

Sufficiently heavy pressure will elicit tenderness in all except anaesthetic patients. But if a nerve be irritated it will be tender without heavy pressure, when the finger really makes a close contact with it.

If the patient willfully attempts to deceive the palpater, nerve-tracing might as well be abandoned except in those extreme cases where the patient will flinch against his will on account of extreme sensitiveness.

Use of Second Hand

As far as possible, the second hand is placed opposite the tracing hand and steadily supports the body; its position changes with changes in the position of the first. If the arm is to be examined it had best be held away from the body, and the part to be examined held between the two hands.

Position of Patient

For tracing nerves in the neck, back, and upper extremities, the patient should sit easily. For lumbar, abdominal, or pelvic tracing, or for tracing in the lower extremities, have patient lie on side or back. Do not hesitate to change the position of the patient as often as is necessary to secure easy access to the part to be examined and relaxation of the patient’s muscles. Never allow the assumption of a strained position during tracing; the sensation of cramped muscles may be confused with sensations of nerve tenderness.