malarial and syphilitic infection, etc.
(_d_) As to the condition of important organs: of the eye in
connection with headaches and vertigo; of the ear in relation to
vertigo and epileptiform attacks; of the heart (and arterial tension)
in various head-symptoms; of the sexual organs in hysteria,
hypochondriasis, epilepsy, etc.
A serious stumbling-block in this last line of inquiry is the
ever-recurring question as to the causal relation between the symptoms
observed. Is the asthenopia the cause of the headache, or does the
neurasthenia, giving rise to the headache, cause the asthenopia? Does
the extremely slow action of the heart in a given case produce the
epileptoid attacks, or are both due to a lesion of the medulla? Does
ovarian hyperæsthesia and neuralgia (with or without organic changes)
cause the hystero-epilepsy, or is the ovaria one of the numerous
peripherally projected sensory symptoms of the hysteric state? Does
the lithæmia, oxaluria, azoturia, or phosphaturia found in a patient
give rise to the nervous symptoms complained of, or are they (the
morbid excretions) the result of defective innervation? The candid
neurologist, looking at his cases from the standpoint of the general
physician rather than from the loophole of narrow specialism, must
admit that these questions vex him daily, and that they are often not
to be resolved in the present state of knowledge except by a
recurrence to the therapeutic test.
For this extremely difficult diagnosis of the pathology of functional
nervous affections we would obtain much immediate assistance if
observers had the courage to publish their cases in continuous series,
instead of giving us successful cases, which often only serve to
mislead. For example, how greatly would the question of the relation
between ovarian symptoms and epilepsy (also hystero-epilepsy) be
advanced if we had the final results of all cases of removal of the
ovaries for these diseases at a period not less than one year after
the operation! And so with the attempts made to cure headaches by the
correction of errors of refraction and weakness of the interni. The
profession has a right to demand a frank and full report of the
experience of those who practice and teach in these directions.
{65}
THE LOCALIZATION OF LESIONS IN THE NERVOUS SYSTEM.
BY E. C. SEGUIN, M.D.
There are two ways in which this important subject may be treated. Of
these, the more interesting and logical would be to systematically
expose the results of anatomical researches and of physiological
experiments which tend to demonstrate the organic independence and the
functions of various parts of the nervous system, and to give a
classified series of results of autopsies bearing on localization.
This would be all the more satisfactory because the questions
involved, although of much importance in practice, are in reality
physiological. The localization of functions being known, the
physician could from the symptoms (_i.e._ perverted or abolished
functions) present make a deductive diagnosis of great exactness. A
treatise on medicine, however, cannot allow the space necessary for
such a treatment of the topic which is best suited for monographic
writing. The other method of exposition, the one we will follow, is
that of summary statement of the association of the symptoms with
definite lesions, with occasional anatomical and physiological
explanations. This will, after all, be a series of diagnostic
propositions stated as concisely and classified as practically as
possible. With this end in view we divide the subject into five parts:
The localization of lesions in the peripheral nervous system
(including the cauda equina);
The localization of lesions in the spinal cord;
The localization of lesions in the medulla oblongata;
The localization of lesions in the encephalon.
Cranio-cerebral topography.
I. Localization of Lesions in the Peripheral Nervous System.
In general terms, it may be said that lesions of peripheral
(cerebro-spinal) nerves give rise to various sensory symptoms in the
area of cutaneous distribution of the affected nerves, and to a
flaccid atrophic paralysis in muscles supplied by the same nerves.
These muscles almost always exhibit the De R. in varying degrees, and
other trophic and vaso-motor symptoms are common. Many of these
symptoms also occur in cerebral and spinal diseases, so that, after
all, the diagnosis of peripheral localization depends largely on a
correct knowledge of the course and {66} distribution of nerves; of
the relative distribution of the sensory and motor filaments of
nerve-trunks; and of the frequent anomalies which occur. The subject
of collateral innervation at the periphery must also receive
attention, as involving a source of error.
Of extreme importance is the law of the relative distribution of motor
and sensory filaments derived from one nerve-trunk. This, Van der
Kolk's law,[1] has hardly received the attention it deserves from
practical neurologists. Briefly stated, it is that of the two sorts of
fibres in a mixed nerve the sensory filaments go to those parts which
are moved by muscles innervated by the motor filaments of the same
nerve. The reader can verify for himself the exactness of this law by
making sketches of an extremity and tracing the motor and sensory
distribution of its various nerves. There are partial and apparent
exceptions to the formula, but this objection applies to almost all
our medical laws. In the cranial system of nerves it is necessary to
consider the trigeminus as the sensory companion of the six anterior
motor nerves; the pneumogastric as the associate of the spinal
accessory (in part).
[Footnote 1: Van der Kolk, _On the Minute Structure and Functions of
the Spinal Cord, etc._, p. 7, New Sydenham Soc. transl., London, 1859;
Hilton, _On Rest and Pain_, p. 101, Am. ed., N. Y., 1879.]
(_a_) Irritative lesions of nerves, as tumors, punctured wounds,
perineuritis, moderate pressure, etc., are indicated by pain,
numbness, and other paræsthesiæ in their cutaneous distribution, and
of spasm or cramp with paresis only, in the associated muscles. Pain
is the most prominent symptom by far, and many cases of so-called
neuralgia belong to this category. As a rule, there is no anæsthesia,
and the electrical reactions of nerves and muscles remain normal, or
at least they do not present De R. In some cases vaso-motor spasm
(coldness, white or bluish appearance of parts) shows itself in the
most peripheral distribution of the nerve. The cutaneous and tendinous
reflexes are variable, but usually preserved.
(_b_) Destructive lesions of nerves, by section, severe pressure, true
neuritis, etc., are characterized by anæsthesia with or without
paræsthesiæ, by motor and vaso-motor paralysis, and by loss of
superficial and deep reflexes. Later, there occurs degenerative
atrophy of the paralyzed muscles with fully-developed De R., and
dystrophic changes in the skin, etc. supplied by the sensory filaments
of the injured nerve. In these anæsthetic parts ulceration is easily
caused by traumatism and want of cleanliness.
The abnormal electrical reactions of the paralyzed muscles are of much
importance for the diagnosis of the amount of injury done to the nerve
and for the purpose of prognosis. They may be summarized as follows,
assuming a case of complete section of a nerve-trunk:
_α_. The Faradic Reactions diminish rapidly in degree in both nerve
and muscles from the third or fourth day, and in the nerve they are,
as a rule, completely lost at the end of from ten to fifteen days. In
the muscles complete loss of faradic reaction is noted only somewhat
later, and is absolute. A return of musculo-faradic contractility is a
most positive sign of recovery of the nerve.
_β_. The Galvanic Reactions.—In the nerve, distal of the lesion, the
result is similar to that stated above—viz. after a few days (from
five to fifteen) all reaction disappears. The anatomical cause of the
complete {67} loss of the faradic and galvanic reactions in the nerve
is its disintegration by the Wallerian degeneration. In the attached
muscles the phenomena are widely different, and present interesting
and complicated variations. In the first place, during a variable
number of days there is increased excitability—_i.e._ the paralyzed
muscles, deprived of innervation, contract to a much weaker current
then do the homologous normal muscles. This is best shown in cases of
peripheral facial paralysis (Bell's palsy) in the second and third
weeks, by placing the electrodes in the median line, one upon the
cervical vertebræ, the other (a small testing interrupting electrode)
on the chin; on closing a very weak current of from four to eight
elements it will be seen that the muscles on the paralyzed side of the
face (the lower muscles) contract distinctly, while those on the
normal side remain quiet. In the course of time, many weeks usually,
the excitability diminishes, and falls below the normal, and in some
cases ultimately disappears. These are known as the quantitative
changes in musculo-galvanic reactions. During the long period
preceding recovery, or without it, various qualitative changes are
also observed in the reaction. The normal general formula of
CaCC > AnCC (with rapid, jerking and full contractions of the muscle)
becomes CaCC = AnCC or CaCC < AnCC. Often, too, distinct opening
contractions occur, usually AnOC. The muscular contractions also tend
to the tonic type or tetanus, expressed as CaDT or AnDT, etc.
The form of the contractions obtained is much altered. Throughout a
practically endless period in some cases, or until regeneration of the
nerve takes place in others, it is observed that musculo-galvanic
contractions are delayed, are slower, less jerking, or assume an
undulating wave-like character, easily passing into tetanus. This
change from the rapid, jerky, and full normal muscular contraction to
one which is slow and wave-like we consider to be the most positive
and reliable evidence of neuro-muscular degeneration and of the
cutting off of the spinal-cord influence. Fig. 4 shows the characters
of a human degenerative myogram contrasted with a normal one, Fig. 3.
[Illustration: FIG. 3. Contraction of Normal Abductor Indicis, CaCC,
with strong current (Amidon[2]).]
[Illustration: FIG. 4. Contraction of Paralyzed Muscle on thirty-first
day of Bell's palsy of the face. CaCC. 20 El. (Amidon). Shows retarded
contraction and slow contraction, with tendency to tetanus.]
[Footnote 2: “The Myography of Nerve-degeneration in Animals and Man,”
_Archives of Medicine_, viii., No. 1, 1882.]
In the period of recovery or regeneration of the nerve the
musculo-galvanic reactions slowly reacquire their normal characters;
the normal suddenness and completeness of the contractions gradually
appear, and faradic excitation causes slight responses. Lastly, the
nerve also begins to exhibit excitability under galvanism and
faradism. These various abnormal electrical reactions, also frequently
observed in diseases of the spinal cord, constitute the so-called
reaction of degeneration, or De R. The subject is one of much
practical importance, and for details the reader is referred to the
treatises on electro-therapeutics of Erb and De Watteville.
Just as we depend upon the De R. to prove interruption of motor
nerve-fibres (or, in other cases, destruction of ganglion cells in the
anterior horns of the cord), so do we rely upon the demonstration of
complete anæsthesia to prove interruption of sensory fibres. In
seeking for the area of anæsthesia several points must be borne in
mind: (1) The normal {68} distribution of the principal nerve-trunks
as taught by ordinary anatomical works; (2) the remarkable anomalies
of distribution which sometimes occur; (3) that many nerves near their
endings exchange filaments in very variable numbers; loops for
collateral innervation, which will supply some sensibility to parts
which, judging by ordinary anatomical rules, should be made anæsthetic
by section of a given nerve-trunk; (4) another consideration is the
degree of anæsthesia. Before pronouncing upon the complete and fatal
division of a nerve-trunk (by injury or by disease), absolute
anæsthesia should be demonstrated in its area of principal and
isolated distribution. Ordinary tests are not, as a rule, sufficient
for this purpose. The best means in our experience consists in the use
of a very strong induction (faradic) current, as follows: The skin of
the suspected region to be thoroughly dried and rubbed with chalk or
powdered starch; one pole, consisting of an ordinary wet electrode, to
be applied just above the part to be tested, and the other pole,
consisting of a single wire, with which different parts of the
anæsthetic area are to be touched. By this means partially insensible
regions, not responding to pricking and burning, may be made to yield
reaction, and the area of absolute anæsthesia be thereby much reduced.
Malingering may also be readily exposed by this test, which presents
another advantage—viz. of not causing local injury or scars as burning
will.
It follows from the preceding statements that in cases of limited
atrophic paralysis with De R. the diagnosis between a central lesion
(destruction of ganglion cells of the anterior horns of the cord) and
a strictly peripheral (or neural) lesion is to be chiefly based upon
two considerations: (1) The distribution of the paralysis, which in
the first case affects muscles which are physiologically grouped or
associated, while in the second case the simple law of anatomical
associations or grouping is observed; (2) by the state of sensibility,
which is normal in disease of the anterior horns of the cord, and is
frequently impaired or abolished in nerve lesions.
Lesions affecting the cauda equina cause all the above-mentioned
symptoms of peripheral lesions in a limited (partial) paraplegic
distribution. If the lesion or injury be in the sacro-coccygeal
region, the symptoms will, as a rule, be found confined to parts below
the knee, occasionally also involving the muscles on the posterior
aspect of the thigh (flexors of the leg). Below the knees we find an
atrophic paralysis with De R., anæsthesia of the foot and part of the
leg, loss of plantar and achillis reflexes, and the sphincter ani will
be paralyzed. The patellar reflex is {69} preserved or exaggerated. In
case the lesion be in the lumbar region, below the first lumbar
vertebræ, the symptoms will be found to extend as high as the groin,
involving also the buttocks and sphincter ani; state of the bladder
variable. All reflexes will be lost in the paralyzed extremities,
except in some cases the cremasteric reflex.
Strange as it may appear, physicians do not always remember that there
is practically no lumbar spinal cord (vide Fig. 2), and that injuries,
etc. of the lumbar vertebræ and dura tend to affect nerves, and not a
nervous centre.
II. Localization of Lesions in the Spinal Cord.
Diseases of the spinal cord are distinguished by the following general
characters, positive and negative:
Positive Characters.—Tendency to primary bilateral or paraplegic
distribution of all the symptoms. In the majority of cases
preservation of electro-muscular excitability, and in one well-defined
group of cases De R. more or less typically developed in the paralyzed
parts. Frequent vesical and rectal paralysis, either of the retaining
or of the ejecting apparatus. Pains and other paræsthesiæ in the
extremities, the pains often possessing the electric or fulgurating
character. Anæsthesia of paraplegic distribution. Sensations of
constriction or cincture about a limb or about the body at various
levels. Occurrence of ataxia without paralysis. Progressive muscular
atrophy without actual paralysis. Easy production of eschars
(bed-sores).
Negative Characters.—Absence of typical hemiplegic or monoplegic
distribution of symptoms. Rarity of head symptoms, as headache,
vertigo, mental disturbance; of lesions of the optic nerve. Absence of
epileptiform convulsions. Absence of such grouping of motor and
sensory symptoms as would exactly correspond to the area of
distribution of one or more large nerve-trunks.
The above symptomatic indications are, of course, of the most general
meaning only, and are liable to exceptions and subject to varying
conditions.
The DIAGNOSIS of the exact localization of lesions in the spinal cord,
considered from the clinical standpoint, is perhaps best arrived at by
following an anatomical and physiological order of subdivision of the
problem into three questions, as follows:
FIRST QUESTION.—BEING GIVEN SYMPTOMS INDICATING DISEASE LIMITED TO ONE
OR MORE SYSTEMS OF THE SPINAL CORD, TO DECIDE WHICH ARE AFFECTED.
Physiology and the results of embryological and pathological
researches justify us in making a general division of the spinal cord,
for purposes of diagnosis, into two great systems, whose limits are
fairly well known—viz. the æsthesodic or sensory system, and the
kinesodic or motor system. The following outline diagram (Fig. 5) of
section through the spinal cord exhibits the ascertained limits of the
two systems.
[Illustration: FIG. 5. Diagram of a Transverse Section of the Spinal
Cord through the Cervical Enlargement: The æsthesodic system is
shaded, the kinesodic system unshaded. Parts of the æsthesodic system:
(1) Posterior nerve-roots; (2) posterior gray horns; (3) fasciculi
cuneati (columns of Burdach, inclusive of posterior root-zones); (4)
fasciculi graciles (columns of Goll or posterior median columns); (5)
ascending cerebellar fasciculi; (6) columns of Clarke. Parts of the
kinesodic system: (7) Anterior roots; (8) anterior columns (inclusive
of anterior root-zones); (9) anterior gray horns; (10) crossed
pyramidal fasciculi; (11) direct pyramidal fasciculi (columns of
Türck); [10 and 11 are the intraspinal prolongation of the cerebral
motor tract]; (12) lateral columns, of ill-defined limits and unknown
functions; P. R., posterior roots; P. S., posterior septum; A. R.,
anterior roots; A. F., anterior fissure.]
A. Lesions of the Æsthesodic System.—Limits of the Æsthesodic
System.—By this term we mean that combinations of ganglion-cells and
nerve-fibres whose functions are locally sensory, and of those fibres
which transmit impressions centripetally (frontad) to the encephalon.
The {70} following are the recognized parts of this system, as
outlined on the diagram: (1) the posterior (dorsal) nerve-roots and
attached ganglia; (2) the posterior gray horn and central gray
substance to an unknown distance ventrad; (3) the fasciculi cuneati
(columns of Burdach), whose lateral parts are more particularly
designated as posterior root-zones; (4) the fasciculi graciles
(columns of Goll) or posterior median columns; (5) the fasciculi ad
cerebellum; (6) the vesicular columns of Clarke (most developed in the
dorsal part of the cord). All of these parts have sensory functions,
or at least transmit impressions centripetally, and they undergo
secondary (Wallerian) degeneration toward the encephalon—_i.e._
frontad of a transverse lesion of the cord.[3]
[Footnote 3: There are some results of physiological experiments and a
few isolated pathological facts which would seem to point to the
existence of other sensory (centripetal) fasciculi in the lateral
columns, but it would be wholly premature to make use of these facts
in a practical consideration of the subject.]
At the present time there is only one lesion of the æsthesodic system
which can be diagnosticated during the patient's life from positive
symptoms.
(_a_) Lesions of the fasciculi cuneati (posterior root-zones, 3). The
symptoms of lesion (usually sclerosis) in this region are wholly
sensory {71} and ataxic. At an early stage acute pains, fulgurating
pains, occur in the extremities; later paræsthesiæ, anæsthesia, and
ataxia. The fulgurating pains caused by the slowly-progressive lesion
of the posterior root-zones are very peculiar, and almost
pathognomonic (vide preceding article for their description). In some
cases paræsthesiæ precede the pains, which inversion of the usual
order must be due to a difference in the starting-point of the
sclerosis within the large fasciculi cuneati. Tendinous reflexes
(especially the patellar) are lost at an early period in the disease,
and by noting the disappearances of the different reflexes we can
trace with some accuracy the longitudinal extension of the sclerosis
(vide Fig. 2). In many cases the pupillary reflex is also abolished,
constituting the Argyll-Robertson pupil.
As negative characters of lesions of the posterior root-zones (and of
the rest of the æsthesodic system) we note absence of paralysis,
contracture, atrophy, and De R.
In the present state of our knowledge of spinal physiology and
pathology we think that a lesion in this location should be recognized
by the physician early and positively—in some cases years before
ataxia and other grosser symptoms make the diagnosis of locomotor
ataxia obvious even to a layman's eye.
(_b_) Lesions of the fasciculi graciles (column of Goll, 4) cannot, we
believe, be recognized directly by positive symptoms. There are a few
cases on record of primary (?) sclerosis of these columns, in which
during life vague sensory symptoms had been noted, but we cannot build
upon such data. Indirectly, however, we can in many cases
diagnosticate degeneration of these fasciculi, reasoning from the data
of pathological anatomy. Thus, for example, in advanced cases of
sclerosis of the fasciculi cuneati (posterior spinal sclerosis) we
know that in the dorsal and cervical regions of the cord the columns
of Goll are in a state of secondary degeneration. After complete
transverse division of the cord by injury, extreme pressure, or focus
of myelitis, etc. the same (centripetal) degeneration exists above the
lesion.
The same remarks apply fairly to our clinical knowledge of the
remaining parts of the æsthesodic system, columns of Clarke (6), and
fasciculi ad cerebellum (5). We know absolutely nothing of lesions of
the posterior horns (2) in their clinical and diagnostic relations.
B. Lesions of the Kinesodic System.—Limits of the Kinesodic System.—In
general this includes the antero-lateral parts of the cord. In a
trans-section of the cord (vide Figs. 5 and 6) the following columns
and fasciculi are recognized, their location and limits being made
known to us by embryology, descriptive and pathological anatomy: (7)
The anterior (ventral) nerve-roots emerging from (8) the true anterior
columns or anterior root-zones; (9) the ventral (anterior) gray horns
with their groups of ganglion cells; (10) the crossed pyramidal
fasciculus, which is the caudal continuation of the cerebral motor
tract of the opposite hemisphere; (11) the direct pyramidal column
(column of Türck), which is the caudal continuation of the cerebral
motor part of the hemisphere on the same side; (12) the antero-lateral
column. Fasciculi 10 and 11 bear an inverse relation to each
other—_i.e._ 11 is larger in proportion as 10 is smaller.