Principles of Osteopathy
Dain L. Tasker, D. O.
CHAPTER V - The Segmentation of the Body
The Lesion as a Guide in Diagnosis. - Since the spinal
lesion may be either cause or effect, i.e., a trauma or an expression of the
body's protective reaction, we need certain fundamental facts upon which to
base judgment. No matter whether the lesion is cause or effect the physician
must recognize it as a guide for the unraveling of a series of phenomena which
are quite sure to be present in any case. It is a well recognized fact
that effects become causes and thus a cycle of reflexes become established making
it difficult to recognize where the series began. Any diagnosis worthy
the name must be based on structure and function. Much of the phenomena
we are called upon to interpret is difficult to understand, unless we know not
only normal structure but the development processes whereby this present structural
formation was achieved.
The Spinal Segment. - The far reaching influence
of a cervical lesion can readily be understood when we study the embryological
development of cervical structures. To mention a nerve to a diagnostician
should instantly bring to his mind all the structural associations of that
nerve, its origin and distribution. The thought of its origin and
distribution would naturally bring to mind an association of all the tissues
depending on it for innervation. We would thus have a picture of
a localized community of interests. Considering the similar distribution
on the opposite side of the body we have pictured a sort of transverse
division of the body. Every pair of spinal nerves, with the tissues
directly under their influence, should form in our minds an entity, a mechanism
in which reactions tend to take place independent of all other segments.
Although we may think of a segment as a unit, the development of the body
has coalesced its various structures in such a way as to locate the nervous
control of any one structure, such as a muscle, in more than one segment
of the spinal cord, hence the controlling nerve to a muscle usually contains
fibers from more than one segment.
It is readily seen that there is an element of protection
in this fact. A slight central lesions i.e., an injury to the spinal
cord, its membranes; or a pressure lesion due to disease of the bone, as
in Pott's disease, might not produce complete loss of function in any single
muscle because the governing nerve to that muscle is made up of fibers
from two or more cord segments.
Injury of a Single Nerve. Example: Posterior
Thoracic. - Complete paralysis of a single muscle is indicative of
serious injury to its governing nerve at some point exterior to the central
nervous system; in fact, beyond the point of coalescence of the fibers
which form it. As an example of injury of a single nerve we may take
a case of paralysis of the Serratus Magntis. This large muscle which
acts to hold the posterior border of the scapula close to the thorax, when
one is pushing with the hand or when taking a deep inspiration, is innervated
by the posterior thoracic nerve which is made up of fibers from the upper
portion of the brachial plexus, fifth, sixth and seventh cervicals.
Evidently an injury capable of involving all the fibers of the posterior
thoracic nerve and no others must be peripheral to the point of junction
of its fibers from the fifth, sixth and seventh cervicals.
A patient came to me in 1901 complaining of a peculiar
loss of power of the right arm. He was a large, powerfully built
young man whose occupation, as a lumber shover, unloading lumber on the
San Pedro docks, was lost as a result of his condition. He gave a
history of perfect health at all times. Said that two days previous,
on Sunday he had erected a tent for himself and as he was tightening the
guy ropes he felt a sharp pain under his right shoulder blade, which was
immediately followed by an inability to push with the right arm.
The pain was of short duration. He described his position as a somewhat
awkward one, i.e., he was kneeling on his right knee facing one of the
tent guy rope pegs. With his right hand grasping the wooden clamp
on the guy rope, he attempted to draw the guy rope taut. His great
strength enabled him to do this, even though his right hand was considerably
behind him. Figs. 4 and 5 show the effects of the paralysis of the
Serratus Magnus in this case.
A second case presenting exactly the same symptoms
was seen in the clinic of the Pacific College of Osteopathy a short time
later. A telephone lineman, while engaged in stringing wire from
pole to pole, made a vigorous awkward pull with the right hand some distance
back of his hip. His legs were entwined about the crosspieces of
the pole. At the time of greatest effort he felt a severe pain under
the right shoulder, followed by a profound sense of weakness in the shoulder
and arm. The scapula immediately took a wing position and the patient
could not shove with the right arm.
These cases serve to give us a picture of the influence
of position and motion of the shoulder as governed by one nerve taking
origin from three cervical segments. The lesion was not a spinal
one, i.e., such as we have before described, neither was it one involving
the cells of origin of this nerve in the spinal cord. The awkward
position of the patients and their naturally great strength operated to
injure them in much the same way as the various nerve holds practiced by
the jiu-jitsu wrestler. The pressure where the nerve crossed the
ribs became too great and, hence, caused a severe trauma of the nerve.
A Unilateral Cervical Spinal Lesion. - The
foregoing cases present the classical first symptoms of a severed motor
nerve. In order to present the symptoms accompanying a cervical lesion
of the spinal lesion type we will describe a case which has been under
observation for a long time. A woman, 41 years of age, has been under my
professional care for three years. At the time of my first examination
she appeared to be constitutionally ill, but careful examination failed
to discover any organic disease. Functional rhythm seemed discordant
everywhere, hence our first efforts were to see that environment was fairly
normal. Rest, nutritious diet and an optimistic atmosphere served
to eliminate many of the irritating symptoms.
The first examination of the spinal area discovered
a lesion between the sixth and seventh cervical vertebrae. There
was muscular ankylosis controlling this articulation and any attempted
movement of the whole cervical area, sufficient to make demand on this
joint, caused pain of a sharp neuralgic character to radiate into the left
shoulder and arm. This pain could be produced most easily by either
voluntary or passive rotation of the head to the left. A persistent
effort to rotate the head in this direction caused the hand and arm to
become numb. The hand would become bloodless, cold and moist; power
to pick up a book or cup was greatly lessened. These symptoms would
wear off in twenty-four to thirty-six hours, but the pain would leave her
in almost a state of collapse. Massage of the arm and hand would
bring no reaction; heat also failed to stimulate circulation.
These attacks had been brought on by any sort of
housework, at first only sweeping or such work as required arm leverage.
Later it seemed as though the attacks came without any mechanical reason.
They were accompanied by severe headache, tachycardia, meteorism, cold
extremities and subnormal temperature. As might be expected in such
a case the spinal lesion picture was a mixed one and it seemed, in view
of so many symptoms of autointoxication, as though the mid dorsal lesions
were more nearly primary than the others. The sensitiveness of this
spinal column was so great and so many compensations were in evidence that
it was deemed best to attempt at first merely to simplify the symptom complex
as much as possible by giving the spinal column physiological rest.
The patient was kept in bed, thus reducing the demand on the weight carrying
function of the spine. This, and the psychological influence of trying
a new plan under optimistic circumstances, served to reduce the number
and complexity of symptoms, but in no wise changed the character, or viciousness,
of the reactions arising from any disturbance of the articulation between
the sixth and seventh cervical vertebrae.
Treatment. - Direct extension, slowly and
gentle, was attempted with marked success. Great care had to be exercised
when releasing the extension, else the closure of the cervical articulations
acted as though a nerve had been caught by direct pressure. Gradually
the muscular tension around this joint was decreased and a slight degree
of rotation toward the lesion, i.e., in this case the left side, could
be accomplished without arousing severe pain. Digital pressure made
against the left side of the sixth cervical spine would always cause a
severe reaction. It was not possible to use any quick leverage or
thrusting movements in this case for correction of the lesion until about
eighteen months after we gave our initial treatment. A fairly wide
range of movement is now possible. The patient can voluntarily rotate
the head to the left, but the sensitiveness on the left side of the cervical
spine has never entirely disappeared. She lives a normal existence
as a busy housewife. She has gained thirty pounds in weight.
In this case the lesion is nearer center, i.e., closer
to the spinal cord. The symptoms it presents are nearer in character
to those of true central origin, except that they are unilateral.
The local symptoms, pain, muscular tension, anaesthesia and vaso-constriction,
are manifested in the area of distribution of the brachial plexus.
Although the spinal muscles, whose tension constituted an ankylosis of
the articulation between the sixth and seventh cervical vertebrae, are
innervated by branches of the posterior division of the lower cervical
nerves, the reflexes, through the cells of origin of the lower cervical
nerve trunks in the spinal cord, were manifested in all divisions of the
brachial plexus, not only in the plexus but overflowed into the sympathetics,
as shown by the vaso-motor disturbance and rapid heart action.
There is a history of accident in this case which
classes this lesion as traumatic. We have its effects shown in the
reaction of the cerebro-spinal and sympathetic systems. In other
words, the somatic and splanchnic structures, innervated by nerves from
the lower cervical group, act and react upon each other in an effort to
adapt themselves to this lesion. As time went on the whole body was
engaged in a losing effort at adaptation, simply because the lesion area
was never given physiological rest, i.e., eliminating all demand on the
weight carrying and balancing functions of the joint. The manipulation
of this spinal joint was also in the nature of physiological rest because
it reduced the hypertension and gradually reestablished normal functional
Involvement of the Central Nerve Cells. -
The next step in severity in lesions is the involvement of the contents
of the spinal canal, either through direct invasion of the tissues of the
cord, or by pressure due to destruction of sections of the spinal column.
The point we wish to illustrate is that the diagnostician must, in order
to do scientific work, make a diagnosis based on the facts of anatomy as
interpreted by embryology. If symptoms were noted and interpreted
with the same precision with which the trouble man on a telephone system
works out his problems we would not find so many fantastic medical theories.
It is, in large measure, the failure to teach the fundamentals of anatomy,
physiology and pathology in a thorough manner that is responsible for the
vagaries in medical practice. We are not forgetting the fact that the public
is not educated to this view and, therefore, the one who attempts to act
irrespective of the public's state of education has a hard row to hoe.
Cervical Muscles. - In the first case described,
wherein the Serratus Magnus was paralyzed, we noted that it receives its
innervation from the cervical region. This makes it a cervical muscle.
In this same sense the trapezium and latissimus dorsi are cervical muscles
and will necessarily enter into any reactions involving the segments of
the spinal cord which give origin to their nerves. In order to bring
to your attention some of these peculiar changes which have taken place
in the development of the body, we will review a few of the most notable
which will aid its in the interpretation of the effects of lesions.
Embryology. - Embryology is the "histology
of very young beings." We may question here what contribution the
study of embryology has made wwhich has practical significance in the diagnostic
and therapeutic work of our practitioners. Since we have a "division
of labor," as evidenced by a variety of tissues having special functions,
and since self-preservation for purposes of perpetuating organisms of a
similar character is a prime requisite of life, groups of tissues are associated
into mechanisms. Comparative embryology has helped us to recognize,
in part, these mechanisms. The recognition of the segmental arrangement
of the body is one of the great contributions of embryologists.
Segmentation. - Early in the development of
the embryo the mesodermic cells on either side of the longitudinal groove
show transverse divisions which form a series of segments called protovertebrae
or mesodermic somites. With out our going into a lengthy description
of the arrangement of the mesodermic cells to form the spinal column and
its muscles, we want this early series of divisions kept in mind.
"The appearance of the mesodermic somites is an important
phenomenon in the development of the embryo, since it influences fundamentally
the future structure of the organism. If each pair of mesodermic
somites be regarded as an element and termed a metamere or segment, then
it may be said that the body is composed of a series of metameres, each
more or less resembling its fellows, and succeeding one another at regular
intervals. Each somite differentiates, as has been stated, into a
scleratome and a myotome, and, accordingly, there will primarily be as
many vertebrae and muscle segments as there are mesodermic somites, or,
in other words, the axial skeleton and the voluntary muscles of the trunk
are primarily metameric. Nor is this all. Since each metamere
is a distinct unit, it must possess its own supply of nutrition, and hence
the primary arrangement of the blood vessels is also metameric, a branch
passing off on either side from the main longitudinal arteries and veins
to each metamere. And further, each pair of muscle segments receives
its own nerves, so that the arrangement of the nerves, again, is distinctly
"This metamerism is most distinct in the neck and
trunk regions, and at first only in the dorsal of these regions, the central
portions showing metamerism only after the extension into them of the myotomes.
But there is clear evidence that the arrangement extends also into the
head and that this, like the rest of the body is to be regarded as composed
of metameres. There is reason, therefore, for believing that the
fundamental arrangement of all parts of the body is metameric, but though
this arrangement is clearly defined in early embryos, it loses distinctness
in latter periods of development. But even in the adult the primary
metamerism is clearly indicated in the arrangement of the nerves and of
parts of the axial skeleton, and careful study frequently reveals indications
of it in highly modified muscles and blood vessels.
"Although the dermal mesenchyme is unsegmental in
character, yet the nerves which send branches to it are segmental, and
it might be expected that indications of this condition would be retained
by the cutaneous nerves, even in the adult. A study of the cutaneous
nerve-supply in the adult realizes to a very considerable extent this expectation,
the areas supplied by the various nerves forming more or less distinct
zones and being, therefore, segmental. But a considerable commingling
of adjacent areas has also occurred. Thus, while the distribution
of the cutaneous branches of the fourth thoracic nerve, as determined experimentally
in the monkey (Macacus), is distinctly zonal or segmental, the nipple lying
practically in the middle line of the zone; the upper half of its area
is also supplied or overlapped by fibers of the third nerve and the lower
half by fibers of the fifth, Fig. 14, so that any area of skin in the zone
is innervated by fibers coming from at least two segmental nerves (Sherrington).
And furthermore, the distribution of each nerve crosses the mid-ventral
line of the body, forming a more or less extensive crossed overlap.
"And not only is there a confusion of adjacent areas,
but an area may shift its position relatively to the deeper structures
supplied by the same nerve, so that the skin over a certain muscle is not
necessarily supplied by fibers from the nerve which supplies the muscle.
Thus, in the lower half of the abdomen, the skin at any point will be supplied
by fibers from higher nerves than those supplying the underlying muscles
(Sherrington), and the skin of the limbs may receive twigs from nerves
which are not represented at all in the muscle supply (second and third
thoracic and third sacral)."
Widespread Influence of a Spinal Lesion. -
No skin area (or individual muscle) is supplied wholly by fibers from one
segment of the spinal cord, but, in fact, is innervated by a nerve made
up of fibers from two or more segments. A spinal lesion of traumatic
origin, granting that only one articulation is involved, will influence,
in some cases, widely separated structures. For example: A lesion
between the fourth and fifth cervical vertebrae might influence the diaphragm,
latissimus dorsi and trapezius, and through the spinal accessory the muscles
of the larynx. Such apparently widely separated structures must be
kept in mind when considering a lesion at the location under discussion.
Nor is this enough, because skin areas must be reckoned with.
To learn these tissue associations, through the study
of anatomy, is quite possible, but embryology furnishes an interpretation
which tends to keep them in one's mind. When we know that the diaphragm,
trapezius and latissimus dorsi are essentially cervical muscles which have
migrated but remain under the control of cervical nerves, we cease to think
of one as the dividing wall betweem thorax and abdomen, a great muscle
of respiration; the others as constituting the first layer of dorsal muscles.
Association of Muscles Innervated by the Same
Segment. - Such structures, as we have just mentioned, have migrated
far from their original segments and have taken on functions and are concerned
in reactions which are no longer segmental but have for their aim the preservation
of the whole body, hence any injury to one, or all, of them would tend
to produce a reflex localized in the segment from which they received their
innervation. Compare with these migrated structures a segmental muscle
of primitive character like the intertransversalis or interspinalis.
The influence of these primitive muscles is wholly on the one articulation,
but they are part of the mechanism supplied from the same segment as the
migrated muscles. These small muscles, which are the intrinsic muscles
of the spinal arthrodial joints, are important prime movers in the effort
to maintain the erect position, i.e., they enter into the weight carrying
and balancing functions of the spinal column. In case of their injury,
a spinal lesion, the lost motion in the joint causes widespread influences,
as heretofore mentioned. The fifth layer of dorsal muscles, according
to Gray, consists of a network of small muscles, the deepest of which extend
between portions of two adjoining vertebrae; more superficially placed
layers extend greater distances so as to influence the movements between
more than two vertebrae. The next layer of muscles, consisting of
the erector spinae and its continuations, influence a greater number of
vertebrae and bring rib positions under the influence of cervical nerves.
The splenius capitis et colli, of the third layer, and the rhomboids, of
the second layer, are likewise supplied by cervical nerves. Thus
we find the nerve which takes its exit between the fifth and sixth cervical
vertebrae supphes a series of over-lapping muscles, the first one supplied,
intertransversalis, being wholly intrinsic to the spine and the one on
the surface of the body, the latissimus dorsi, having a very widespread
Effect of Sectioning Single Spinal Nerve.
- To cut the fifth cervical nerve at its exit from the intervertebral foramen
would not paralyze any but the intrinsic spinal muscles between the fifth
and sixth cervical vertebrae. All muscles beyond that point would
be weakened in proportion to the number of fibers their governing nerves
received from that cut trunk. In other words, it appears probable
that the severing of the pair of nerves, the fifth cervical, could weaken
the gross movements made by muscles innervated by them, but since only
the intrinsic spinal muscles of one intervertebral articulation are wholly
supplied by them there would be no complete muscular paralysis apparent.
The sixth cervical nerves innervate about twenty-eight pairs of muscles
in the neck, chest, shoulders and upper extremities and back, and the diaphragm.
Developmental Changes in Muscles. - This gives
us some idea of the great changes that have been consummated in the development
of the body. The many changes in position and direction of fibers
are recognized through the fact that they remain under the nerve control
of the one segment. The various changes in the development of muscles
are thus described by McMurrich: "It may be seen that the changes which
occur in the myotomes may be referred to one or more of the following processes:
"1. A longitudinal splitting into two or more portions, a process well
illustrated by the trapezium and sternomastoid, which have differentiated
by the longitudinal splitting of a single sheet and contain, therefore,
portions of the same myotomes. The sterno-hyoid has also differentiated
by the same process, and indeed, it is of frequent occurrence.
"2. A tangential splitting into two or more layers. Examples
of this are also abundant and are afforded by the muscles of the fourth,
fifth and sixth layers of the back, as recognized in English textbooks
of anatomy, by the two oblique and transverse layers of the abdominal walls,
and by the intercostal muscles and the transversus of the thorax.
"3. A fusion of portions of successive myotomes to form a single
muscle, again a process of frequent occurrence, and well illustrated by
the rectus abdominis (which is formed by the fusion of the ventral portions
of the last six or seven thoracic myotomes) and by the superficial portions
of the erector spinae.
"4. A migration of parts of one or more myotomes over others.
An example of this process is to be found in the latissimis dorsi whose
history has already been referred to, and it is also beautifully shown
by the serratus anterior and the trapezium, both of which have extended
far beyond the limits of the segments from which they are derived.
"5. A degeneration of portions or the whole of a myotome. This
process has played a very considerable part in the evolution of the muscular
system in the vertebrates. When a muscle normally degenerates, it
becomes converted into connective tissue, and many of the strong aponeurotic
sheets which occur in the body have their origin to this process.
Thus, for example, the aponeurosis connecting the occipital and frontal
portions of the occipito-frontalis is due to this process and is muscular
in such forms as the lower monkeys, and a good example is also to be found
in the aponeurosis which occupies the interval between the superior and
interior serrati postici, these two muscles being continuos in lower forms.
The strong lumbar aponeurosis of the oblique and transverse muscles of
the abdomen are also good examples.
"Indeed, in comparing one of the mammals with a member
of one of the lower classes of vertebrates, the greater amount of connective
tissue compared with the amount of muscular tissue in the former is very
striking, the inference being that these connective-tissue structures (fasciae,
aponeurosis, ligaments) represent portions of the muscular tissue of the
lower form (Bardelben). Many of the accessory ligaments occurring
in connection with diarthrodial joints, apparently owe their origin to
a degeneration of muscle tissue, the fibular lateral ligament of the knee
joint, for instance, being probably a degenerated portion of the peroneous
longus, while the sacro-tuburous ligament appears to stand in a similar
relation to the long head of the biceps femoris (Sutton).
"Finally, there may be associated with any of the
first four processes a change in the direction of the muscle-fibers.
The original antero-posterior direction of the fibers is retained in comparatively
few of the adult muscles and excellent examples of the process here referred
to are to be found in the intercostal muscles, and the muscles of the abdominal
walls. In the musculature associated with the branchial arches the
alteration in the direction of the fibers occurs even in the fishes, in
which the original direction of the muscle-fibers is very perfectly retained
in other myotomes, the bronchial muscles, however, being arranged parallel
with the bronchial cartilages or even passing dorso-ventrally between the
upper and lower portions of an arch, and so forming what may be regarded
as a constrictor of the arch. This alteration of direction dates
back so far that the constrictor arrangement may well be taken as the primary
conditions in studying the changes which the branchial musculature has
undergone in the mammalia."
Please note that, "since the relation between a nerve and
the myotome belonging to the same is established at a very early period of development
and persists throughout life, no matter what changes of fusion, splitting or
migration the myotome may undergo, it is possible to trace out more or less
completely the history of the various myotomes by determining their segmental
innervation." In view of this the clinician ought to be well versed in
the knowledge of anatomy, i.e., the gross structures innervated from the same
segment of the cord. Much of the physical diagnostic work of the osteopath
is based on the fundamental facts of embryology and anatomy, i.e., metamerism.