{35} insane), no longer correcting his sensations by the use of other
senses and by reasoning, firmly believes in their reality—_i.e._
externality. For example: in such patients visceral sensations give
rise to the belief that there is a foreign body or an animal inside
the patient, or that parts are misplaced or wrenched and beaten. Pains
are thought to be due to blows received or to the bites of animals or
projectiles thrown upon the patient. With perversions of muscular
sense an insane patient may believe that he is flying or floating in
the air.
In hypochondriasis many of the symptoms complained of are nothing but
paræsthesiæ exaggerated by a morbid state of the mind, and sometimes
created (projected) by expectant attention. The hallucinations of the
insane are in great measure phenomena of this group, the projections,
though special and common, never being so strong and definite as to
acquire apparent objectivity.
The auræ of epilepsy are paræsthesiæ. For example: a sensation in the
epigastrium preceding a fit indicates an irritation at the origin of
the vagus nerve and its projection as a subjective sensation at the
distribution of the nerve. An auditory or visual aura similarly
represents a discharge or projection from the acoustic and visual
cortical areas respectively.
In most cases of malingering, and in some cases of so-called railway
spine, the symptoms so loudly complained of belong to the two classes
of hyperæsthesiæ and paræsthesiæ; they are undemonstrable and
non-measurable; only the patient himself can vouch for their reality.
A diagnosis in such cases, without objective symptoms indicating
well-known lesions, should be very reserved.
ANÆSTHESIA, or loss of sensibility, may exist in every degree, from
one so slight as to be hardly demonstrable by delicate tests to the
most absolute loss of all feeling. It manifests itself in various
modes corresponding to the normal physiological varieties of
sensibility; in most cases the loss of feeling involves all of these,
but in others they are separately affected, and we observe the
following types, pure or combined:
(_a_) Tactile Anæsthesia. The capacity to perceive superficial and
gentle impressions upon the skin and mucous membrane, and the ability
to locate and separate such impressions, may be lost, while other
modes of sensibility remain normal.
(_b_) Analgesia is that condition in which painful impressions are not
perceived, though common, caloric, or muscular sensibility may be
normal or nearly so. Pricking, cutting, and bruising are unperceived.
This, the most common variety, is usually met with in hysterical
cases; it occurs at a certain stage of general artificial anæsthesia,
in chronic alcoholism, extreme emotional states, and in hypnotism.
Though a very striking symptom, it is not one of as serious meaning as
loss of tactile or thermic sensibility. Often the patient is unaware
of analgesia until tests reveal its existence.
(_c_) The sensibility of the skin to caloric is usually the last to
disappear in the progress of an organic lesion, so that in certain
cases (injury to nerves or spinal cord, myelitis, etc.) testing by ice
or by a burning object is a sort of last resort. Before deciding in a
given case that there is a complete break in the sensory tract, this
test should be used as well as the application of the most intense
induced electric current delivered upon the dry skin by a wire end.
{36} In some cases of partial anæsthesia (_e.g._ in posterior spinal
sclerosis) cold may be felt as heat and vice versâ, or pinching may be
felt as burning, and be quite persistent.
(_d_) The so-called muscular sense may be greatly impaired or lost
without ordinary anæsthesia. In such a case the subject is no longer
directly and spontaneously aware of the exact position of his limbs,
of passive motions done to them, and he executes voluntary movements
with uncertainty. He is also unable to judge correctly of differences
of weight in objects successively placed in his hand or hung from his
foot. He needs the aid of sight to guide the affected limb and to
judge of its position, etc. The awkwardness and uncertainty in
voluntary movements by impairment of muscular sense must not be
confounded, as is sometimes done, with ataxia, in which the attempted
volitional movement is jerky and oscillatory, owing to the
inharmonious action of antagonistic muscular groups.
(_e_) When a strong induced electrical current is passed through a
muscle by means of wet electrodes applied to the skin, so as to cause
a strong contraction, a special quasi-painful feeling, akin to that of
cramp, is experienced in the contracting muscle, and is clearly
distinguishable from the cutaneous sensation. This, the
electro-muscular sensibility, may be lost independently of other modes
of feeling and without loss of contractile power.
(_f_) Some observers claim that a special mode of sensibility exists
in the skin by which varying degrees of pressure are estimated,
independently of traction upon tendons and muscles (muscular sense),
and that this may be separately impaired or lost.
(_g_) Visceral anæsthesia shows itself in the ordinary way by loss of
that feeble degree of common sensibility which the internal organs
possess, and also by impairment of their special functions, giving
rise to anorexia, hydroadipsia, retention of feces and urine, loss of
sexual feeling (without progenital anæsthesia). Of course, these
symptoms may be due to other conditions, and each case must be
carefully studied. In the insane, visceral anæsthesia gives rise to
delusions of emptiness, destruction of organs, and even, if coinciding
with general cutaneous anæsthesia, to the notion that the body is dead
or absent.
A singular phenomenon often witnessed is retardation in the
transmission of an impression (usually a painful one). Thus, in
testing the sensibility of the skin of the legs in tabetic patients,
it is observed that instead of the normal, almost instantaneous,
appreciation of the impression made by a needle-point, there is a
lapse of two, five, ten, or even sixty seconds between the pricking
and the signal of sensation by the patient. It should always be
determined in such cases whether the retardation is peripheral and
actual, or central and due to psychic conditions (dementia, absorption
in a delusional state). Thus, in a case of profound melancholia we may
observe extreme slowness and dulness of sensory impressions or
complete anæsthesia; but the symptoms would have a very different
significance, diagnostic and prognostic, from the same noted in a
mentally clear patient.
An important result of impairment of sensibility is a reduction or
loss of reflex movements originating from the area or organ which is
anæsthetic. This is shown in anæsthesia of the distribution of the
trigeminus {37} when the reflex protecting movements of the eyelids no
longer take place, in atrophy of the optic nerve when the pupillary
reflex actions are lost. In posterior spinal sclerosis we see several
illustrations of this law: progressive degeneration of nerve-fibres in
the posterior root-zones of the spinal cord, causing loss of patellar
reflex, of vesical, rectal, and sexual reflexes, and in most cases of
cilio-spinal reflexes and of muscular tonus. In these and analogous
conditions one arc of the reflex mechanism is deranged, centripetal
conduction is interfered with, and the reflex motor discharge can no
longer be evoked.
That a similar pathological condition occurs in the cerebral
mechanism, and may serve to explain many psychic symptoms, is very
probable.
On the other hand, a destructive lesion may be so placed in the spinal
cord or brain as to allow centripetal impressions to reach healthy
spinal gray matter in the normal way, but preventing their passage
frontad (upward) to be recognized by consciousness. In such a case we
observe normal, or more commonly exaggerated, reflex action in parts
which are insensible in the ordinary sense of the term. Indeed, in
many cases the disconnected caudal portion of the spinal cord is in a
state of vastly exaggerated reflex activity, as shown by the tetanoid
and convulsive involuntary and reflex movements which take place in
completely paralyzed and anæsthetic limbs (paraplegia from transverse
myelitis). In general terms, it may be stated that when anæsthesia is
due to lesions of peripheral nervous endings, of nerve-trunks, and of
the posterior root system of the spinal cord, reflexes are diminished
or lost.
It is often stated that anæsthesia causes ataxia of movement. This,
from the results of experiments on animals and from clinical study, we
believe to be a gross error. In animals and in man loss of sensibility
gives rise to awkwardness or uncertainty in movement (increased if the
eyes be closed) which is properly to be classed as a special variety
of inco-ordination; but it is not from ataxia, in which irregular,
jerky, oscillating motions occur when a volitional act is attempted,
these movements resulting from want of harmony in the action of
antagonistic muscles which in the normal educated state automatically
act together to produce the desired result. Besides, we occasionally
observe cases of typical spinal ataxia in which no impairment of
sensibility can be observed.
THE TOPOGRAPHICAL DISTRIBUTION of alterations of sensibility requires
careful determination in practice, as from it we obtain most valuable
aid in diagnosis. The following are the principal types observed:
(_a_) Alterations of sensibility in one lateral (vertical) half of the
body and head. We thus have hemihyperæsthesia, hemiparæsthesia, or
hemianæsthesia, and the special senses on one side are frequently
involved. This clearly hemi-distribution indicates that the lesion or
functional disorder is in the cerebral hemisphere of the opposite
side, more especially in the caudal segment of the internal capsule or
in its areas of cortical distribution (occipital, temporal, and
parietal lobes). The distribution of hemianæsthesia, etc. from organic
disease in these parts is identical with that observed in some
functional (hysterical) cases; we can make the diagnosis only by the
help of other data.
If the sensory disorder does not affect the head, but is limited to
one {38} lateral half of the body, it is, if due to organic disease,
quite certainly of spinal origin.
(_b_) Two homonymous extremities or the two lateral halves of the body
may exhibit opposite states of sensibility—anæsthesia on one side and
hyperæsthesia on the other. This rare condition is witnessed in
hysteria and in some forms of injury to the spine (lesion of one
lateral half of the cord at a certain level). In the latter case
paralysis is usually present on the hyperæsthetic side: the symptoms
constituting, with some others, Brown-Séquard's spinal hemiplegia or
hemiparaplegia.
(_c_) Alterations of sensibility in one caudal (horizontal) half of
the body are said to have a paraplegic distribution, and are usually
due to lesions of the spinal cord. The upper level of the symptom may
be at any point between the neck and the toes; and the frontal (upper)
level indicates, due regard being had to the origin and oblique
distribution of the spinal nerves, the highest limit of disease in the
nervous centres. Very often, in organic disease especially, this is
also indicated by the presence of a cincture feeling (paræsthesia) at
the frontal (upper) limit of the anæsthesia, etc.
(_d_) Disorders of sensibility may be limited to one extremity. This
very rarely depends upon cerebral disease, and in such a case the
anæsthesia, etc. is evenly distributed throughout the member, being
most intense at its extremity, and being without sharp, distinct
limits near the trunk. When due to diseases of the spinal cord, the
cerebral (upper) limit of the symptom is usually clearly defined in
accordance with the distribution of sensory nerves from the other
(healthy) parts of the cord: a constriction band often marks the
limit. Sometimes the peripheral anæsthesia, etc. is more or less in
the territory of certain nerve-trunks. When we find the distribution
of the sensory symptoms to coincide exactly in the areas supplied by
the large nerves of the limb, without cincture feeling, it is certain
that the lesions affect one or more of these nerve-trunks or the
plexus above. In not a few cases the symptoms are due to hysterical or
dyscrasic conditions, and the seat of the lesions (dynamic or
molecular lesion) is uncertain. In judging of the distribution of
anæsthesia, etc. in a limb due regard must be paid to variations in
nerve-branching and to collateral nerve-supply.
(_e_) Alterations of sensibility occurring in well-defined areas of
the hand, trunk, or extremities, corresponding to the known
distribution of nerves, almost always indicates disease of the nerve
itself, much more rarely disease in the spinal cord at the origin of
the nerve. The reflexes are then diminished or lost. In judging such
cases Van der Kolk's law of the distribution of the motor and sensory
filaments of nerve-trunks should be remembered: it is, that of the two
sets of fibres in a mixed nerve, the sensory fibres are distributed to
parts which are moved by muscles which receive the motor fibres of the
same nerve. Thus, in nerve lesions the chief sensory symptoms are
always peripheral or distal from the chief motor symptoms.
(_f_) Disorders of sensibility sometimes appear in patches or
irregular areas whose nervous connections are indefinite. Such patches
of anæsthesia, hyperæsthesia, or paræsthesia sometimes indicate foci
of disease in the spinal cord (and brain?); as, for example, the
pains, etc. of posterior spinal sclerosis. These patches may also
occur in consequence of {39} interference with local circulation of
peripheral parts; and we meet with them in such conditions as
hysteria, neurasthenia, alcoholism, etc.
(_g_) Universal hyperæsthesia, paræsthesia, and anæsthesia may be
observed. The last condition, in the insane, is very apt to give rise
to delusions of non-identity and death of the body.
THE SENSORY DISTURBANCES OF THE SPECIAL SENSES are well worth separate
consideration.
(_a_) Optic Apparatus.—Hyperæsthesia of the retina shows itself
directly in photophobia, and indirectly (reflexly) by lachrymation and
involuntary closure of the eyelids. Paræsthesiæ of the optic nerve and
retina show themselves as flashes or projections of white or colored
light in the visual field. These may be irregularly or generally
distributed in the field, or appear as hemiopic (vide infra), or
sector-like forms. Phenomena of this order may be experimentally
produced by pressure on the eyeball or by the application of
electricity over or near the eye. Photopsiæ of most varied sorts, as
flashes, colored scotomata, or quasi forms may immediately precede
epileptic seizures or attacks of migraine, constituting an optic aura.
In some cases this assumes a definite picture form, when it partakes
of the character of an hallucination. Anæsthesia of the optic nerve
and retina varies infinitely in degree, from slight blurring or
veiling of vision (amblyopia) to complete blindness (amaurosis).
Another result is sluggishness or complete immobility of the iris
under the action of light. As regards distribution, optic anæsthesia
may affect the visual fields uniformly and generally, or it may assume
definite geometric forms, or may appear in irregular patches
(scotomata).
The definite geometric defects are classed under the general head of
hemianopsia, by which term is meant that one horizontal or vertical
half of the visual field is obscured. (1) Horizontal hemianopsia is
not bounded by a very sharp or straight boundary-line, and is almost
always due to intraocular disease (retinal lesions, embolism of one
large branch of the retinal artery, injuries, etc.). (2) Vertical
hemianopsia is usually marked by a sharply-defined vertical limit in
the visual field, passing through the point of fixation, or a little
to one side of it more usually, leaving central vision very acute.
(_α_) Temporal hemianopsia, in which the temporal halves of the visual
fields are dark, represents anæsthesia of the nasal halves of the
retinæ, and is usually caused by a lesion of the chiasm of the optic
nerve, so placed at its frontal or caudal edge as to injure the
fasciculi cruciati. This variety is usually bilateral, but a lesion
might be so situated as to affect only one fasciculus cruciatis.
(_β_) Nasal hemianopsia, in which the inner (nasal) halves of the
visual fields are dark, represents anæsthesia of the temporal halves
of the retinæ, and is caused by a lesion injuring one fasciculus
lateralis or both fasciculi. In the former case the nasal hemianopsia
would be unilateral; in the second case, bilateral or symmetrical,
(_γ_) Lateral or homonymous hemianopsia is that condition in which
physiologically similar halves of the visual field are darkened; for
example, the temporal half-field of the left eye and the nasal
half-field of the right. This represents anæsthesia of the nasal half
of the left retina and of the temporal half of the right. The patient
can only see, with one or both eyes, the right half of any object held
directly in front of him. In such cases the lesion is always caudad of
the chiasm, and may consist in interruption of the right optic tract,
{40} of disease of the primary optic centres (corpus geniculatum
laterale and lobus opticus) on the right side, of the caudo-lateral
part of the right thalamus, of the caudal extension of the internal
capsule or optic fasciculus within the right occipital lobe, of the
right superior parietal lobule or gyrus angularis penetrating deep
enough to interrupt the optic fasciculus; or, finally, the lesion may
injure the visual centre itself—viz. the cortex of the right cuneus
and fifth temporal gyrus (of Ecker). Hemianopsia of any type may be
incomplete or only sector-like—_i.e._ involving only a quadrant or
less of one visual field or of both fields. (Vide article on
Localization).
Perception of color may be reduced, confused, or abolished in the
retina, either a diffused general way, throughout the field of vision,
or following the laws of hemiopic distribution. In cases of hysteria,
achromatopsia is not rarely met with, affecting the eye corresponding
to the side on which the skin is analgesic or where paralysis exists.
Hysterical achromatopsia may be transferred from one eye to another by
the application of metals, by hypnotic manipulations, etc.
Hemianopsic phenomena may be functional and transient, as witnessed
just before attacks of migraine or sick headache.
Attempts recently made, from purely theoretical considerations, to
locate centres in the occipital cortex for perception of light, form,
and color separately, are wholly unjustified or at least premature.
Loss of reflex pupillary movements is a symptom of much importance. It
occurs chiefly under these conditions: (1) with paralysis of the iris
due to lesion of the third cerebral nerve; (2) with amaurosis or
anæsthesia of the retina; (3) with posterior spinal sclerosis. The
last condition is distinguished from the others by the fact that while
the reflex iritic movements are lost, the quasi-voluntary movement of
accommodation efforts is preserved. This condition is known as the
Argyll-Robertson pupil.
Diplopia, or double vision, is due to paresis or paralysis of one or
more of the ocular muscles, and as such is to be classed under motor
symptoms.
Megalopsia (apparent enlargement of objects) and micropsia (apparent
reduction in size of objects) are sometimes due to disorder of the
accommodation apparatus within the eye, and to local diseases causing
displacement of the rods and cones of the retina; but they are often,
no doubt, fanciful (in neurasthenia and hysteria). The same remarks
apply to monocular diplopia.
(_b_) Acoustic Apparatus.—We know less of the sensory disturbances in
the organs of hearing. Hyperæsia shows itself by undue (painful)
sensitiveness to sounds, and by the ability to perceive sounds which
are inaudible to normal persons. In meningitis, hydrophobia, the
hypnotic state, etc. this condition is observed. Paræsthesiæ are very
common, appearing as subjective noises or musical tones (tinnitus
aurium) of the most varied kinds (roaring, hissing, blowing, tinkling,
whistling, crashing, bell-sounds, etc.), which seem to the subject to
be in his ear or in his head. In the present state of our knowledge it
is impossible to positively distinguish tinnitus due to local
non-nervous ear disease from that which is strictly neural or cerebral
in origin. Certainly, intense tinnitus may coincide with complete
anæsthesia of the acoustic nerve and a {41} normal state of the middle
ear. Theoretically, we may admit tinnitus (corresponding to photopsia
in the optic apparatus) as due to an irritative lesion of various
parts of the acoustic terminal nervous organ, the acoustic nerve, or
the acoustic centre. An acoustic aura (subjective blowing, hissing,
etc.) may immediately precede an epileptic attack. Subjective noises
may be produced by excitation of the acoustic nerve and terminal
organs by the galvanic currents; these galvanic acoustic reactions are
regular in the normal condition, and are fully stated in works on
electro-therapeutics. Anæsthesia of the acoustic system by peripheral,
neural, or central (?) destructive lesions is frequent, and is
distinguished from other forms of deafness chiefly by the fact that a
sound transmitted through the bones of the cranium (as by a vibrating
tuning-fork held against the upper teeth or above the ear) is not
heard on one or both sides. Although in a few rare cases the attempt
has been made to define nervous deafness for certain sets of notes or
as limitations at either end of the musical scale, yet we are not
prepared to recognize in neurological practice a condition of partial
acoustic anæsthesia corresponding to hemianopsia or achromatopsia. We
believe that this progress will be made, however, thus enabling us to
locate disturbances in parts of the organ of Corti and in the cortical
centre for hearing.
(_c_) Olfactory Apparatus.—Hyperæsthesia of this sense is at present
considered more a personal peculiarity than as a symptom of disease.
Paræsthesiæ show themselves as subjective odors of various sorts, and
when transient may be an olfactory aura preceding epileptic attacks.
In conditions of organic disease subjective odors may coincide with
complete loss of smell. Anæsthesia of the olfactory nervous apparatus
may be due to (1) strictly local disease in the nose, catarrh, etc.;
(2) to anæsthesia of the trigeminus nerve and consequent local
lesions; (3) to a truly nervous lesion affecting the olfactory nerves,
the olfactory bulbs, the olfactory tracts, or, lastly, the cortical
centre for smell (at present unknown in man). The two last morbid
conditions are usually unilateral, and coexist with subjective odors.