Ambrose L[oomis] Ranney.

The applied anatomy of the nervous system, being a study of this portion of the human body from a standpoint of its general interest and practical utility online

. (page 31 of 43)
Online LibraryAmbrose L[oomis] RanneyThe applied anatomy of the nervous system, being a study of this portion of the human body from a standpoint of its general interest and practical utility → online text (page 31 of 43)
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posterior columns of the cord be involved, complete ansBsthe-
sia may also exist in the parts supplied with motor power by
the sciatic nerve. The condition of the paralyzed muscles,
as to their electrical reactions, and the presence or absence of
the evidences of increased reiiex excitability will dei)end
greatly upon how much damage has been done to the gray
matter of the lumbar enlargement. If the gray matter be so
destroyed as to impair its function, the reflex movements will
be absent ; and, if the trophic function of the cord be affected
by changes in the ganglion cells of the gray matter, the para-
lyzed muscles will undergo atrophy. The sense of constric-
tion, or *' band feeling," will usually be referred, in this le-
sion, either to the ankle, leg, or thigh.

FOCAL LESIONS CONFINED TO THE LATERAL HALF OF THE SPINAL

CORD.

In discussing the focal lesions of the cord, we have de-
scribed the clinical points which are afforded by destruction,
to a greater or less extent, of the substance of the cord in both
of its lateral halves ; hence, the motor and sensory symptoms
have been usually referred to both sides of the body. It was
necessary to thus describe them, since focal lesions, unless
traumatic, are seldom confined to one lateral half of the
cord ; but, in some cases which may be presented to your
notice, where a tumor, a fractured vertebra, a hsemorrhage,
a severe contusion, or some other localized lesion exists, the
injury done to the spinal cord may be confined exclusively
to one lateral half, resulting in one of two named conditions,
viz., "spinal hemiplegia" and ''hemi-paraplegia." Before
proceeding to the special consideration of either of these
conditions, it may prove of advantage to review some few
points in the physiology of the cord, and to again direct your
attention to the two plates upon the blackboard, which are
already familiar to you.

This plate ' shows you that any lesion of a lateral half of
the spinal cord must produce anaesthesia in the opposite side
of the hody^ since all the sensory nerves decussate and enter

' See Fig. 120 of this Tolume.



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FOCAL LESION OF A 'LATERAL HALF OF THE CORD. 349

the gray matter of the cord, which serves as a conducting
medium tpr sensory impressions, while the motor symptoms
produced by the same lesion must be confined to the same
side of the body as the lesion^ since no decussation probably
occurs in the spinal cord (these fibers decussating only in the
medulla oblongata).

This second diagram* will further
assist you to appreciate the fact that
lateral lesions, as well as those which
affect the entire cord, are modified, as
regards their symptomatology, by the
height of the lesion in the cord ; since
the motor nerves, and the special cen-
ters which are situated in the cord itself,
will only be aflfected when they lie below
the seat of the lesion or are directly in-
volved in the destructive process. It
wiU, therefore, be unnecessary to enter
again into detail as to the fuU bearings '''''' ^^1^ ^ZTf ^e
of the plate, since they are probably motor and sen^jyjKUhs
fresh in your memory. (Brown-s^quard.)

When the focal lesion is placed high d, deoissation of pyramids;

^ ^ M, motor paths ; S, sen-

up in the substance of the spinal cord, the sory paths,
motor paralysis affects one side only of
the body (provided the lesion is confined to a lateral half), and
the term '' spinal hemiplegia " is applied to this form of paral-
ysis in contradistinction to a hemiplegia of cerebral origin.' If
the spinal lesion be situated in the dorsal region and be con-
fined to the lateral half of the cord, a motor paralysis of one
half of the same side of the body below the seat of the lesion
is developed, a condition to which the term *'hemi-paraple-
gia" is commonly applied. In closing the clinical aspects of
lesions of the spinal cord, it will be necessary, therefore, for
us to consider the essential features of these two remaining
conditions.

* The reader is referred to page 807 of this vohime for details as to the utility of this
figure in the study of spinal affections.



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350



THE SPINAL CORD,



SPINAL HEMIPLEGIA.

In order to produce a typical case of this condition, it is
necessary to have a lateral focal lesion of the cord in its upper-
most part (in or above the cervical enlargement of the cord). If
we suppose, then, that such a lesion be present, let us see what
we might reasonably expect, on purely physiological grounds,
would be the result We can then examine the clinical rec-



Medalk.




nth D. V. <;



12th D. V,



<



1 L V. <^

2L.7. <;



Ilypo-gloeaal N.

rneumogastric N.
Phrenic N.

Brachial plexas.
Ulnar nerve.



Crural N.



Sciatic N.



Fig. 128. — A diagram to show the relation of the spinous processes of tfie verteb}*€e to spi-
nal nerves. (Malgaigne * and Seguin.)

ords of such cases, and either confirm our deductions or gain
some additional information. Such a lesion would, in the first
place, shut oflf all motor impulses sent out from the brain to
parts below the lesion, on the same side as the lesion, since

* "Tmit6 d* Anatomic Chirurgicale."



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SPINAL HEMIPLEGIA, 351

the decussation of the motor fibers has already taken place in
the medulla ; hence motor paralysis should, theoretically, oc-
cur in the arm and leg of the side of the body corresponding
to the seat of the exciting lesion, and the trunk should also be
paralyzed upon that side. This we find, clinically, to be true,'
with the exception that the intercostal nerves often retain
their motor power when the nerves of the arm and leg are no
longer capable of carrying motor impulses. In the second
place, we should expect to find that the sensation of the side
of the body opposite to the seat of the lesion would be de-
stroyed or greatly impaired, since the sensory nerves decus-
sate throughout the entire length of the cord. This we also find
confirmed by clinical facts ; and so perfect is this anaesthesia
that the line can often be traced to the mesial line of the body
exactly, and upward to the limit of the exciting lesion. In
the third place, the situation of the cilio-spinal center in the
cervical region of the cord would naturally suggest some effects
upon the pupil,' and the circulation and temperature of the
face, neck, and ear of the same side. This is also confirmed, as
the pupil does not respond to light, but it still acts in the ac-
commodation of vision for near objects, and the skin of the
regions named becomes red and raised in temperature. Fi-
nally, the presence of vaso-motor centers in the cord might
occasion a rise in temperature in the paralyzed muscles ; and,
strangely confirmatory of this fact, we often find the tempera-
ture of the paralyzed side of the body hotter than that of the
anaesthetic side.

In some exceptional cases, the face, arm, and trunk are
alone paralyzed, the legs seeming to escape, and often giving
evidence of reflex spasm (perhaps most commonly on the
anaesthetic side). This must be explained as the result of
incomplete destruction of the lateral half of the cord.

* The researcbeB of Brown-S^quard, as early as 1849, and his published memoirs
(1863-'5 and 1868, 1869), have probably done more to clear up this field and to place it
upon a positive foundation than those of any other observer.

' The reader is referred to pages 114 and 135 of this volume.



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352 THE SPINAL CORD.

HEMI-PAEAPLEGIA.

This condition is the result of some focal lesion of the
spinal cord in the dorsal region^ which involves only its lateral
half. The results of such a lesion differ but little from those
of one causing spinal hemiplegia, as regards the motor and
sensory symptoms, excepting that the situation of the excit-
ing cause is below the cervical enlargement, where the nerves
to the upper extremity are given oflf, and where the cilio-
spinal center is situated. For that reason the muscles of the
upper extremity are not paralyzed, nor are the effects ui)on
the pupil and the skin of the face, ear, and neck (mentioned
as present in spinal hemiplegia) produced. The muscles be-
low the seat of the lesion are paralyzed on the side of the body
corresponding. to the exciting cause, and the skin is sometimes
rendered hypersesthesic upon that side ; * while the integu-
ment of the side opposite to the lesion is deprived of sensi-
bility. The bladder and rectum may be paralyzed in some
instances. The sense of constriction, or '*band feeling," will
vary with the seat of disease in the spinal cord. The amount
of reflex irritability and the presence or absence of muscvZar
atrophy in the parts paralyzed will depend upon the depth
of the lesion in the spinal cord and the changes which have
been produced in the gray matter. The same increase of tem-
perature in the paralyzed limb, which was mentioned as oc-
curring in spinal hemiplegia, may also be present in this vari-
ety of paralysis.

Should the side affected with anaesthesia give any evidence
of motor paralysis or muscular weakness, or symptoms of
anaesthesia appear upon the side where the motor paralysis
is present, you may regard either one as conclusive evidence
that the exciting lesion is progressing, and that the opposite
lateral half of the cord is being involved to a greater or less
extent.

' This is probably due to some imtation of the gitiy matter of the cord.



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THE SPINAL NERVES.

THEIR ORIGIN, DISTRIBUTION, FUNCTIONS, AND
CLINICAL IMPORTANCE.



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THE SPINAL NERYES.



We have now considered the general points in the con-
struction of the cerebro-spinal axis, and the clinical facts
which pertain to the brain and spinal cord. We have also
separately discussed those nerves which are connected with
the brain, and have noted all the peculiarities in their distri-
bution and anastomoses, which seem to shed a light upon
their physiological action or the clinical features which each
of them presents. ' It now remains for us to investigate those
ner\'es of the neck, trunk, and the extremities which are con-
nected with the spinal cord, and are called '^ spinal nerves,"
in contradistinction from the nerves of cranial origin, or
those of the sympathetic.

The spinal nerves comprise thirty-one pairs, which escape
from each side of the spinal cord by two roots, called the
anterior or "motor root," and the posterior or "sensory
root." These two roots join with each other, in every in-
stance, to form one nerve, which is named in accordance with
its situation and the region of the vertebral column from
which it escapes ; since the nerves, so formed, pass through
foramina between the pedicles of the vertebrae, throughout
the entire length of the spinal column. Thus we have eight
pairs of cervical nerves^ escaping upon either side of the
cervical vertebrae ; twelve pairs of dorsal nerves^ bearing the
same relation to the dorsal region of the spine ; five pairs of
lumhar nerves on each side ; five pairs of sacral nerves^



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356 THE SPINAL NERVES.

escaping from the foramina of that bone ; and one pair of
coccygeal nerves.

As mentioned in the lectures upon the construction of the
spinal cord, the anterior roots of the spinal nerves are con-
nected with the gray matter of the anterior horns ; while the
posterior roots are connected with the posterior horns of the



Fig. 129. — Cervical por- Fio. 130. — Dorsal par- Fig. 181. — Inferior por-

tion of the spinal cord. tion of the spinal cord, tion of the spinal cord^

(Uirschfcld.) (Hirschfeld.) a7id cauda equina.

(Hirschfeld.)
1, antero-inferior wall of the fourth ventricle ; 2, superior peduncle of the cerebellum ;
8, middle peduncle of the cerebellum ; 4, inferior peduncle of the cerebellum ; 5, in-
ferior portion of the posterior median columns of the cord ; 6, glosso-pharyngeal
nerve ; 7, pneumogastric ; 8, spinal accessory nerve ; 9, 9, 9, 9, dentated ligament ;
10, 10, 10, 10, posterior roots of the npinal nerves ; 11, 11, 11, 11, postet^or lata'ol
ffroove ; 12, 12, 12, VI ^ ganglia of the posterior roots of tJie nerves ; 13, 13, an^i'or
roots of the net^es ; 14, division of the nerves into two oranchcs ; 15, lower extremity
of the cord ; 16, 16, coccygeal ligament ; 17, 17, cauda equina ; I — VIII, cei-vical nerves ;
I, II, III, IV — XII, dorsal nerves ; I, II — V, lumbar nerves ; 1 — V, saci'al nerves.

gray matter. Like all sensory neves, the posterior roots have
a ganglionic enlargement * developed upon them, while the

* The presence of a ganglion upon a cercbro-spinal nerve is always an evidence of its
sensory character.



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THE MOTOR AND SENSORY ROOTS, 357

anterior roots, being motor in function, do not. The roots of
the first cervical nerves are small, short, directed horizontally,
and the anterior is the larger of the two ; those of the remain-
ing cervical nerves become larger, longer, and more oblique
as you descend the cord, and the posterior root is consider-
ably larger than the anterior. In the dorsal region, the first
dorsal nerve resembles the lower cervical nerves as to the
actual and relative size of its roots, but the roots of the re-
maining dorsal nerves are smaller than those of the cervical
region, and more nearly equal in their relative size. The
roots of the lumbar and upper sacral nerves again increase
in size from above downward. Finally, the lower sacral and
the coccygeal nerves show a gradual decrease in the size of
their roots, the last sacral and the coccygeal nerves having
the smallest roots of any of the spinal nerves. As regards
the relative size of the anterior and posterior roots, the lum-
bar, sacral, and coccygeal nerves exhibit but little difference.

The length and inclination of the roots of the spinal nerves
increase from the first to the last ; hence the place of escape
of a spinal nerve does not indicate its seat of origin. As the
spinal cord does not descend beyond the first lumbar verte-
bra, the length of the roots of the lumbar, sacral, and coccy-
geal nerves increases, from nerve to nerve, by the thickness
of one vertebra.

The trunk of each spinal nerve, after its escape from the
vertebral canal, immediately divides into an anterior and a
posterior primary division.

In treating of the spinal nerves, I will first direct your
attention to the four upper cervical nerves, since they enter
into the formation of the cervical plexus ; then to the remain-
ing cervical and the first dorsal nerves, since they enter into
the formation of the brachial plexus ; and, later on, the
dorsal, lumbar, sacral, and coccygeal nerves will be separately
considered. By this method of subdivision, which is the one
usually followed by all authors upon anatomy, the nerves can
be more satisfactorily traced from their origin to their termi-
nal distribution than if each nerve were treated of separately.



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368 THE SPINAL NERVES,

since some enter into the formation of plexuses, and thus lose
their individuality.

The axioms regarding the distribution of nerves to the
muscles, joints, and skin, which I quoted in the first lecture
of this winter's course, will be so constantly of use in the
study of the spinal nerves that they will again bear repetition.
The substance of my remarks in that lecture was about as
follows :

It is claimed by John Hilton * that, if we trace the distri-
bution of the nerve filaments from any special nerve trunk to
the muscles, we shall find that only those muscles are supplied
by each of the individual nerves which are required to render
complete the performance of the functions for which that
nerve was designed ; and that, if muscles were classified on a
basis of their nerve supply, instead of in groups of mere rela-
tionship as to locality, a self-evident physiological relation
would be shown which would tend greatly to simplify a
knowledge of the muscular system in its practical bearings,
and to prove a design on the part of the Creator.

Thus, he says, we frequently find muscles close together
and still supplied by separate nerves, one of which has possi-
bly to go a long way out of a direct course to reach it, which
is contrary to the usual method of Nature, who always uses
the simplest means to accomplish her designs ; but, if we ex-
amine the action of these two muscles, we will find that each
one acts in unison with the other muscles supplied by the
same nerve, and that, to produce this perfect accord. Nature
takes what, to a hasty glance, would seem to be a needless
step.

He also lays down certain axioms, pertaining to the dis-
tribution of nerves and the diagnostic value of pain, which
have been often repeated in these lectures, and can not but be
most profitable to those who use them as a guide. They are
as follows :

''Superficial pains on both sides of the hody^ which are
symmetrical^ imply an origin or cause^ the seat of which is

» " Rest and Pain," London, 1876 (New York, 1879).



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THE AXIOMS OF NERVE DISTRIBUTION. 359

central or bilateral; while unilateral pain implies a seat of
origin^ wMch is one-sided^ and^ as a rule^ exists on the same
side of the body as thepainJ^^

The bearings of this first axiom will be rendered very ap-
parent when the regions of the neck and trunk are considered,
since the symptom of local pain is of the greatest value in
connection with diseases affecting the bones of the spinal col-
umn and the spinal cord which they invest; but that the
same rule may be applied to any of the cranial nerves, with a
degree of certainty which seldom admits of error, has been
shown in cases quoted in connection with the motor oculi,
trigeminus, facial, and other nerves.

The second axiom is as follows :

" The same trunks of nerves^ whose branches supply the
groups of muscles moving a joints furnish also a distribu-
tion of nerves to the skin over the insertions of the same mus-
cles ; and the interior cf the joint moved by these muscles
receives a nerve supply from the same source.^

By this axiom, a physiological harmony is shown between
these various cooperating structures. Thus, any joint, when
inflamed, may, by a reflex act through motor branches from
the same trunk by which it is itself supplied, control the mus-
cles which move it, and thus insure the rest and quiet neces-
sary to its own repair.

Spots of local tenderness in the cutaneous surface may,
for this reason, likewise be often considered as a guide to a
source of irritation of some of the structures supplied by the
same nerve, viz., the muscles underneath it, or the joints
which are moved by them ; and, thus, even remote affections
can be accurately determined, which, were this axiom not
used as a guide, might escape recognition till an advanced
stage of the disease had been reached.

It is well, however, to quote one other axiom, laid down
by the same author, before leaving the subject of the diag-
nostic value of the cutaneous nerves as indicators of existing
disease of other organs, viz. :

^^ Every fascia of the body has a muscle or muscles at-



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360 THE SPINAL KERVES.

tached to it ; and ecery fascia must he considered as (me of
the points of insertion of the muscles connected to it^''^ in fol-
lowing the previous axiom as to the cutaneous distribution
of nerves.

This guide is especially important in case the rule be ap-
plied to the extremities (arms and legs) where these fascice
extend over large surfaces, more or less remote from, and ap-
parently unconnected with, the muscles attached to them ; but
it is mentioned in this connection for the especial object of
calling the attention of the reader to those general rules which
govern the distribution of the nerves in their entirety, before
proceeding to apply them in all their individual bearings :

Without this nervous association between the muscular
structures and those composing the joints, there could be no
intimation given by the internal parts of their exhaustion or
fatigue. Again, through the medium of this same association
between the skin and the muscles, great security is given to
the joints, by the muscles being made aware of the point of
contact of any extraneous force or violence. Their involun-
tary contraction instinctively makes the tissues surrounding
the joints tense and rigid, and this brings about an improved
defense for the subjacent joint structures.

From the conclusion of his great work, in which Hilton en-
deavors to prove that mechanical rest may be used as a cure
for most of the surgical disorders, the following sentences are
quoted, since they can not be too often rei)eated :

"I have endeavored to impress upon you the fact thai
every pain has its distinct and pregnant signification if we
will but carefully search for it.

"In the pain which follows the intrusion of a particle of
dust on to the conjunctiva, and the closure of the eyelid for
the security of rest, up to the most formidable diseases which
we have to treat — pain the monitor, and rest the cure — are
starting points for contemplation, which should ever be pres-
ent to the mind of the surgeon."

Now, if you will thoroughly grasp these axioms, not- only
as mere words, but as grand principles^ which can be used



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PROPER USE OF TABLES OF NERVES. 361

by you in your every -day experience as counselors of the
sick, you will be better able to appreciate the tables of
nerve distribution which I am constantly presenting to you
upon the blackboard, so that you can record them in your
note-books. These tables enable you, at a glance, to see to
what muscles each separate nerve sends filaments of distribu-
tion, and thus innumerable problems are being constantly
suggested to you of this character : Why does this nerve sup-
ply the muscles mentioned and omit those in the immediate
vicinity \ What is the common physiological function which
these muscles are destined to perform ? How may this nerve
be classed from its physiological action ?

It is only by such a system of self -inquiry and self-examina-
tion that you are enabled to become the master of the science.
The nerves are then no longer mere cords, running without a
plan, and serving only as a tax upon the memory, but electric
wires, placed with a system which we, as yet, can not begin
to understand in its wonderful adaptability to the demands of
the body, but which a little study will show is remarkable for
its simplicity of distribution, if we but seek for the function
of each nerve. To a student of this character, the nerves be-
come a source of never-ending delight, since they serve as the
key to many problems in anatomy which had previously been
involved in obscurity. We thus learn the action of the mus-
cles^ since the nerves which supply any special group enable
you at once to tell that those have a similarity of function
which are supplied from the same source, while those sup-
plied from different sources are not only dissimilar in their
action, but have some bond of sympathy with other muscles
(possibly far distant) which are similarly supplied. I believe
that the day is not far off when the nervous supply vf'iSl consti-
tute the universally recognized basis upon which muscles will
be divided into groups ; and, when that day comes, the labor
of the student will be greatly lessened, and his grasp of the sub-
ject be of a higher and more comprehensive order. We will now
pass to the consideration of the upper four cervical nerves, and
the cervical plexus which is formed by their anterior branches.



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362



THE SPINAL NERVES.



THE UPPER CERVICAL NERVES.
A CHART OF THE NERVES OF THE CERVICAL REGION. '



FiBST Ceryical
Nerve
(Sub-oedjntal).



' Posterior division.



^ Anterior division.



Second Cervical

Nerve.



Posterior division
(very large in
size).



Anterior division.



r Posterior division. -



Brancli to posterior division of second cervical.
Branches to the posio-ior eranio-vertdfral set of

muscles,
Branch to oomplexus muscles.
Branch to integument o/oceiput.
Branch to rectus cap. ant. major,
Branch to rectus cap. ant. minor,
Branch to rectus cap. lateralis.

(Second cervical,
Pneumogastric,
Hypo-glossal,
Superior cervical ganglion.
Branch to oocipito-atloid articulation.
' Splenius,

Cervicalis ascendens,
Transversalls colli,
Trachelo-mastoid,



External branch
(supplying) '^



Internal branch



Online LibraryAmbrose L[oomis] RanneyThe applied anatomy of the nervous system, being a study of this portion of the human body from a standpoint of its general interest and practical utility → online text (page 31 of 43)