the term employed and by the absence of ataxia. This is well
illustrated in those rare cases in which the muscular sense is
impaired or lost: in such a case volitional movements, such as placing
the fore finger on an object or fastening a button, are fairly well
done with the aid of sight, but without it the hand and fingers grope
almost or quite hopelessly about the object. It is important to note
that persistent trying to do the act does not aggravate the disorder,
but that, on the other hand, success is often achieved after feeling
about. In certain cases of blindness irregular movements of the
eyeball are observed, due to semi-voluntary efforts to look or to
direct the eyeballs in the direction of a person or object. In states
of cutaneous anæsthesia when the eyes are closed the same disorder
appears in muscular movements. Claude Bernard many years ago showed
that section of the posterior roots of spinal nerves in an animal was
followed, not by ataxia, but by vague inco-ordination and staggering.
In human cases we find that where the sensibility of one hand is lost
or greatly impaired, without paralysis, there is extreme awkwardness
and uncertainty in delicate muscular movements, but no ataxia. The
staggering exhibited by patients having plantar anæsthesia is largely
of this type: they stand fairly well while their eyes are open, but
oscillate or {49} fall when they are closed. This variety of
inco-ordination may result from toxic conditions (alcohol),
peripheral, neural, or central nervous disease. A few cases are on
record which would seem to show that there is a centre for muscular
sense in the cortex of the brain, in a part intermediate between the
caudal sensory area and the central motor one—viz. in the inferior
parietal lobule, supramarginal gyrus (and angular gyrus?). It has also
been shown (by Spitzka and others) that there is a conduction tract
for muscular sense, dorsad of the pyramidal tract in the pons and
oblongata (in the stratum intermedium and interolivary tract), lesions
of which produce inco-ordination (ataxia?) without marked paralysis or
anæsthesia.
(_d_) Titubation, or staggering, is the inability to stand erect or
walk straight because of impaired equilibrium. There is neither tremor
nor ataxia present, and paralysis and anæsthesia are not necessary
factors. It is distinguished from vertigo and dizziness by absence of
subjective sensations of movement. Staggering may show itself in a
general way or in the shape of latero-, retro-, or propulsion (disease
of the internal ear, paralysis agitans). A well-defined variety of
staggering is the wrongly-termed cerebellar ataxia. In this the
patient, having disease of the cerebellum involving its vermis
superior, stands with feet widely separated to increase his base of
support; the body is bent somewhat forward, and the arms and hands are
used as balancing-rods to maintain a sort of equipoise. In walking,
this attitude is exaggerated, and if the feet be bare it will be seen
that the toes are unconsciously clutching the floor for support; there
is no outward jerk of the leg or stamp of the heel as in the ataxic
gait, and closing the eyes does not aggravate the attitude or walk.
Besides, if the extremities be separately tested, it is found that
with closed eyes the patient can perfectly well place his fore-finger
on his nose or one heel on the opposite patella (lying down). The
proper term for the disorder is cerebellar titubation. Yet it must be
remembered that titubation also occurs from disease of the oblongata
and pons, from lesions of the base of the brain in general, and from
alcoholic, etc. intoxication. In many cases titubation occurs in
connection with vertigo or dizziness.
(_e_) Inco-ordination more or less of the ataxic form often affects
the muscles of articulation, phonation, and deglutition, giving to the
symptoms dysarthria, dysphonia, and dysphagia. Dysarthria and
dysphagia are probably often caused by lesions of the insula and
subjacent white substance, as well as by those affecting the
oblongata. There are two recent autopsies which would indicate that
there may be a cerebral cortical centre for phonation laryngeal
movements: in the ventral extremity of the right third frontal gyrus—a
part homologous to the speech centre on the left side of the brain. In
some cases, however, dysphonia and aphonia indicate a lesion of the
laryngeal nerves or of the oblongata (nucleus of NN. x. and xi.).
(_f_) Doubtless the internal muscular organs and the blood-vessels are
frequently the seat of inco-ordinate or quasi-ataxic movements, but
our present knowledge of these conditions amounts to very little.
It may be permissible to consider vertigo under the general head of
inco-ordination, because it usually finds a motor expression, either
actual or subjective. Subjective vertigo consists in a sense of
whirling or horizontal movement which is clearly referred to the brain
by the patient. The {50} sensation is variously expressed: in some the
head seems to whirl around; in others external objects seem to whirl
about the patient horizontally or vertically; in others still there is
a sensation of falling in a given direction or of dropping into a
hole. Dizziness is a minor degree of subjective motion conjoined with
more or less confusion and other paræsthesiæ in the head. Static
vertigo is that form in which there is actual loss of equilibrium, or
falling. It is observed more especially in diseases of the internal
auditory apparatus, and it may be produced artificially by
galvanization of the brain. If the electrodes are placed exactly on
the median line, and the current passed fronto-caudad through the
brain, no loss of equilibrium or vertigo is produced. If, however, the
current is passed transversely through the brain, there is produced at
the moment of the closure and opening of the circuit a distinct
tendency to fall or an actual fall to one side: in closing the current
the fall is always away from the negative pole or cathode. The
greatest amount of disturbance is produced when the electrodes are
placed on the mastoid processes or near them. Whether the disturbance
of equilibrium is caused by a change in electrotonus in the
hemispheres, or by a change in the vascular supply of the hemispheres
(in one anæmia, in the other relative hyperæmia), is uncertain. A
third explanation is equally plausible—viz. that the vertigo is caused
by unequal excitation of the internal acoustic organs and the two
halves of the cerebellum. This view would be supported by the fact
that in animals and man a lesion of the acoustic nerve and of the
processus ad pontem on one side produces strong rotary movements about
the long axis of the body.
ABNORMAL REFLEX MOVEMENTS.—Some reference has already been made to
absence or exaggeration of reflexes in the preceding paragraphs, but
the importance of these symptoms demands that they should be
separately considered.
A reflex action, in its simplest conception, is a movement (muscular,
vascular, or psycho-motor) or a secretion which is the result of the
transformation of a centripetal impression into a centrifugal impulse.
The apparatus required for the accomplishment of the reflex action
consists essentially of a sensitive surface of skin or mucous
membrane, of tendinous or other deep structure, to receive the
impression; a sensory afferent nerve to convey it; a nervous centre of
the simplest structure (one or two ganglion cells) to receive and
transform it; a motor or efferent nerve to transmit the resulting
impulse to a common muscle, to the vascular wall of a vessel or
viscus, or to a gland. These various terminal organs execute their
normal functions in response to the centrifugal impulse, and thus give
external or tangible evidence that the reflex action or reflex is
completed. This mechanism, the reflex arc, is illustrated by the
diagram (Fig. 1), which will also serve for the explanation of many of
the morbid reflex states.
[Illustration: FIG. 1. Diagram illustrating the Arc for Reflex Action.
The centripetal and centrifugal paths, the receptive and terminal
organs of the arc, are shown connected with the spinal centre, which
is a portion of central gray matter containing ganglion cells. The
inhibitory cerebral influence is constantly exerted in health to
moderate reflexes.]
In the healthy animal body many important functions are performed
under the law of reflex action; for example, many organic or secretory
functions, the movements of hollow viscera, vascular movements,
muscular tonus, defensive and expressive muscular movements. In the
process of education many acts which at first must be learned by
oft-repeated efforts, such as walking, playing upon musical
instruments, etc., later become habitual and automatic, and are then
largely executed by reflex {51} action unconsciously, co-ordinated by
the spinal (?) apparatus. Much of our intellectual activity is
governed by the same law operating between the psycho-sensory and the
psycho-motor apparatus.
Reflex actions are only to a moderate extent under the control of
volition—indeed, most of them are subconscious—but a strong
restraining action is unconsciously exerted by the cerebrum (vide Fig.
1) upon the spinal reflex centres. This is the so-called inhibitory
cerebral influence. The existence of such an influence is shown by
experiments upon animals, and by human cases in which, the cerebral
activity being reduced or abolished, we observe a great increase in
the frequency and extent of reflex movements, particularly in the
common muscular apparatus.
Clinically, we distinguish cutaneous or superficial, tendinous or deep
reflexes, according to the seat of the original excitation or
testing-point. Cerebral or psychic reflexes are, however, also to be
borne in mind. These reflexes may be abolished or increased.
(_a_) Diminution and abolition of reflex action are frequent symptoms
of disease of the nervous system. The fault or break may be anywhere
in the reflex arc, so that each case must be analyzed by itself. Let
us consider the phenomena as exhibited by two widely distant and
different apparatuses.
First, in the eye. In case of atrophy of the optic nerve the pupillary
reflex is lost, the reflex action failing because the receptive
surface and efferent nerve are injured. In certain cases of spinal
disease (posterior spinal sclerosis) the same pupillary immobility is
observed (the {52} Argyll-Robertson pupil); and in this case the
lesion either affects indirect efferent spinal fibres destined for the
iris, or it is situated in the centre for the reflex action—viz. the
gray matter of the lobus opticus. There may be loss of pupillary
reflex due to injury of the direct efferent fibres of the arc
(paralysis of the motor oculi, N. iii.). Lastly, the iris itself may
be so diseased as to be incapable of contracting, though it receive
the reflex impulse properly; the lesion is then in the terminal organ
of the arc.
Second, the patellar tendon reflex. In a healthy individual, sitting
at ease with one leg thrown over the other (knee over knee), upon
tapping the ligamentum patellæ of the overhanging or free leg a
contraction of the quadriceps muscle occurs, causing a visible forward
movement of the leg and foot. This is the well-known patellar reflex
or knee-jerk. The arc in this case consists of the ligamentum patellæ
with its included sensory fibres as receptive organs, sensory
(afferent) fibres of the crural nerve, a segment of the lumbar gray
matter of the cord as centre, motor (efferent) fibres of the crural
nerve, supplying the quadriceps extensor femoris, which is the
terminal organ. Theoretically (vide Fig. 1), we can conceive of
numerous abnormal conditions of parts of this arc which would lead to
abolition of the patellar reflex, but in practice the following are
the principal lesions to be thought of: Disease (sclerosis) of the
posterior root-zones of the lumbar enlargement of the cord, as
exhibited in the pre-ataxic stage of tabes; disease of the posterior
roots themselves through meningitis or meningo-myelitis, as in
diphtheritic ataxia; lesion of the nervous centre, as is frequently
observed in cases of infantile poliomyelitis; a lesion of the crural
nerve, involving its efferent or afferent fibres, or both sets of
fibres, would produce the same result, as would also, lastly, a severe
myositis or cancerous infiltration of the quadriceps muscle.
It is therefore evident that there is, or can be, nothing
pathognomonic in the loss of a given reflex: it simply indicates a
break in the reflex arc, the seat and nature of which remain to be
determined in each case. The topographical study of reflexes in
disease is of very great importance, more especially as a help to the
correct location and extent of neural and spinal diseases. To assist
this study, and for use more especially in connection with the ensuing
sections on localization, Gowers's excellent diagram and table are
reproduced in Fig. 2.
[Illustration: FIG. 2. Diagram and Table showing the Approximate
Relation to the Spinal Nerves of the Various Sensory and Reflex
Functions of the Spinal Cord (after Gowers).]
(_b_) Exaggeration of reflex actions. This is due, theoretically, to
any condition which increases the excitability of the reflex arc, but
practically and usually the cause of the increase is more or less
complete removal of the inhibitory supraspinal or cerebral influence.
The reflex arc itself remains structurally sound, but its function is
abnormally active. Thus, we meet with the most exquisite exhibition of
exaggerated reflexes in the paralyzed part after a transverse lesion
of the dorsal part of the cord. The lesion cuts off all communication
between the lumbar enlargement and the brain; no sensations pass to
consciousness, and no volitional influence can be exerted upon the
legs; yet the legs are abnormally active, the least touch on or
pricking of the skin, tapping a tendon, handling a joint, the pressure
of feces in the rectum, etc., produce more or less violent spasmodic
movements of mixed clonic and tonic forms (spinal epilepsy). Increased
knee-jerk, foot-clonus, and epileptoid trepidation are also present.
Other proofs that removal of the inhibitory cerebral influences is the
chief cause of increase of spinal reflexes are given by the {53} {54}
history of various cerebral diseases. Thus, in hemiplegia with
secondary contracture the cutaneous and tendinous reflexes on the
paralyzed side are much exaggerated; in dementia paralytica, as a
rule, the patellar reflex is increased on both sides; and in cerebral
neurasthenia all reflexes are often extremely great.
A variety of increased tendon reflex is known as clonus—a series of
rhythmic clonic muscular contractions set up by stretching the body
and tendon of a muscle. This is best studied at the ankle. By holding
the patient's leg nearly extended upon our left hand, and rather
suddenly forcing back the foot (dorsal flexion) by pressing under the
ball of the foot with our right hand, a series of oscillations or
to-and-fro movements of the ankle-joint are produced for a few moments
(ankle- or foot-clonus). Sometimes the same rhythmic clonic
contractions may be produced in the quadriceps by quickly pulling down
the patella with the leg semi-extended.
In some instances, together with great increase of tendon reflex, we
observe a transfer of the centrifugal impulse to other nerves of the
same extremity, or across the spinal cord to nerves and muscles of the
homologous limb.
Another interesting manifestation of morbid reflex movements is the
defensive tonic spasm of muscles about a diseased joint (of the
hip-muscles in coxitis, of vertebral muscles in Potts' disease). This
constitutes a valuable symptom for the differential diagnosis between
articular and neural diseases in certain cases.
Clinically, increase of reflex action is not as valuable an indication
as its absence, many healthy persons having high reflexes. Still, when
studied comparatively as to topography (comparing the two sides of the
body) and as to variations at different times in a given case, the
symptom is of considerable assistance.
IV. Trophic Symptoms.
Our present knowledge of this great group of symptoms of nervous
disease is in a somewhat chaotic state; and although we possess a
large accumulation of facts of this category, their classification is
incomplete and their explanation is for the most part theoretical and
unsatisfactory. The following subdivisions may be made to include all
the phenomena, and is sufficient for clinical purposes:
1. DEGENERATIVE ATROPHY, as distinguished from the simple atrophy of
insufficient nutrition, of disuse of the parts, and of retarded
growth, includes all those trophic symptoms in which, under the
influence of nervous disease, the solid tissues exhibit histological
and chemical alterations as well as reduction of volume. The principal
factor of this group is—
(_a_) Muscular atrophy due to lesions of some part of the nervous
apparatus (thus excluding directly traumatic or inflammatory atrophy),
as seen in the course of progressive muscular atrophy, of various
forms of poliomyelitis, of lead paralysis, of neuritis, and injuries
of nerves. These muscular atrophies are characterized by reduction in
the size of the affected muscles, by altered electrical reactions, and
by histological {55} changes. Reduction in size may affect one muscle
or a muscular group shortly after paralysis (as in poliomyelitis, lead
paralysis, affections of nerve-trunks), or without evident paralysis
it may involve only small fasciculi of a muscle at a time (as in
progressive muscular atrophy); so that we speak of diffused and
fascicular atrophy, of secondary (post-paralytic) and primary atrophy.
In some cases the wasting proceeds to such a degree that apparently no
muscular tissue remains, and the skin seems to rest directly on the
bones; in others the reduction in bulk is moderate, and is compensated
by increase in the intra- and extra-muscular fat (thus in stout
children the atrophy of severe poliomyelitis may be quite masked to
the eye); in still another category the increase in connective tissue
with fatty accumulation overbalances the muscular wasting, and we have
the pseudo-hypertrophic condition. Alterations in electro-muscular
contractility are most important signs of impaired muscular
innervation and nutrition. They present numerous and somewhat
complicated variations of value for diagnosis and prognosis, but which
cannot here be noticed at length. The general principle underlying
these variations is this: that a muscle deprived of its normal
innervation (centrifugal or motor) soon loses its capacity to respond
to the induced (faradic) current, and reacts in an abnormal way to the
galvanic current. This constitutes the reaction of degeneration of
Erb.[6] The chief abnormality in the galvanic reaction of a paralyzed
and diffusely atrophied muscle is its slow or wave-like contraction,
which on a graphic, or even to the observer's eye, presents a striking
contrast to the sharp, jerking, complete contraction of a healthy
muscle. Besides, the reactions to the two poles become equal, or even
reversed, so that we may obtain in testing by the polar method such
formulas as CaCC = AnCC, or CaCC < AnCC. With reference to the failure
of atrophied muscles to respond to the induced or faradic current,
this qualification must be added: If the poles are applied on the
moistened skin, as usual in testing or treating cases, no reaction
occurs even with most intense currents; but if a needle be made one
pole of the battery and inserted into the affected muscle, slight and
limited contractions may be obtained with a moderate current for many
months. Of this we have repeatedly satisfied ourselves in cases of
poliomyelitis, lead paralysis, and traumatic peripheral paralysis. In
the later stages of diffused paralytic atrophy, after an uncertain
number of years, no reaction can be obtained with either electrical
current. In fascicular non-paralytic muscular atrophy (as in
progressive muscular atrophy) the loss of faradic contractility is
only demonstrable in the affected fasciculi, good contractions being
obtained in adjacent healthy fasciculi of the same muscle. The amount
or extent of contraction varies pari passu with the progress of the
atrophy. The galvanic reactions of this form of muscular atrophy are
not yet well established. Muscles and muscular groups in a condition
of impaired nutrition exhibit at an early period an interesting
condition—viz. that they no longer contract by reflex excitation. Thus
in a case of infantile poliomyelitis with paralysis of the muscles of
the leg, these muscles no longer contract when the sole of the foot is
tickled, and if the thigh-muscles are affected even so slightly as to
appear of normal size and consistence, the patellar reflex is found
wanting. In these and in traumatic cases the {56} reflex act is
prevented by lesion of the centrifugal motor nervous apparatus, and
perhaps also by the associated muscular trophic alterations.
[Footnote 6: Conveniently expressed by the symbol De R.]
Histological changes in atrophied muscles vary somewhat in character
in different diseases, and vary much in degree at different periods of
the atrophy. An early appearance is the presence of proteinaceous and
of fatty granules or molecules in the sarcous substance. Later, the
muscular fibres become reduced in size, lose their striation, and show
inequalities; the interstitial connective tissue becomes active and
increases in amount, at the same time that fat is deposited. The fatty
change in some cases, in others the granular or proteinaceous
transformation, ultimately completely destroys the muscular substance,
so that in the place of a muscle we find abnormal connective and fatty
tissues, blood-vessels, fatty and proteinaceous débris, the whole
presenting a pale yellowish-white aspect. It is in this final stage of
degenerative atrophy that all electrical reactions are lost. In the
pseudo-hypertrophic state the interfibrillary and interfascicular
connective-tissue growth is much more active, and the wasting muscular
fibres are buried in masses of wavy and fatty connective tissue. In
this condition also electrical reactions may be wholly absent.
(_b_) Atrophy due to defective innervation sometimes affects the skin
and bones. In the former, after nerve-injuries more especially, we
observe loss of thickness, glossiness, and perverted circulation and
secretion; the hairs may fall out or grow abnormally; the nails are
slow of growth, thick, rugose, incurvated, and brittle. In other
cases, as in cerebral and spinal paralyses, the skin of the paralyzed
part is abnormally dry, rough, and furfuraceous, and it loses its
elasticity. In some varieties of so-called skin diseases the patches
of altered nutrition (eczema, bullæ, herpes, psoriasis, leucoderma,
scleroderma, etc.) are often, probably, dependent upon nervous
lesions.
In the very rare disease known as progressive facial atrophy the skin,
subcutaneous areolar tissue, and the bones undergo extreme atrophy.
The initial lesion is usually a patch of scleroderma with or without
neuralgic phenomena; the skin is thin, darker and smoother than
normal; it soon adheres to the subjacent bone (maxilla or zygoma),
which itself steadily diminishes in size. Almost the entire half of
the face (including the palate and tongue) may ultimately show the
atrophic changes. We are not yet prepared to state the causal
nerve-lesion in this disease.
The bones are abnormally fragile (fragilitas ossium) in some nervous
diseases, more especially in dementia paralytica and posterior spinal
sclerosis; but whether this condition is due directly to the nervous
disease or is the expression of more general malnutrition is now
undecided.