THE PATHOGENY OF TIC
TIC AND SPASM
Our study of tic can be approached only after a preliminary
understanding as to the meaning of two words too frequently confounded
even in scientific literature--_tic_ and _spasm_. Let us explain, then,
once for all, exactly what we intend by the latter.
Etymologically ([Greek: spasmos, spaô, I draw) the word signifies a
twitch, but as it is unfortunately considered a synonym for convulsion,
the two expressions are used indifferently in medical parlance, though
the desirability of restricting the application of the former has more
than once been indicated. Littré's definition--"an involuntary
contraction of muscles, more particularly of those not under voluntary
control"--may appear somewhat idle, as the contraction of muscles not
under the influence of the will can scarcely be other than involuntary.
His intention was, no doubt, to reserve spasm for convulsive phenomena
in non-striped muscle fibres; but in this limited sense the term has not
met with acceptance, and it remains equivalent to "involuntary muscular
contraction," whatever that may mean. Thus interpreted, it is applicable
to any and every involuntary muscular movement, physiological and
pathological, to the inco-ordination of tabes, to chorea, athetosis,
tremor, etc.
Rather than imagine a new substantive to characterise certain of these
muscle contractions, we may retain the word in a somewhat wider though
equally precise sense, and follow the distinction drawn by Brissaud[9]
in 1893: "a spasm is the result of sudden transitory irritation of any
point in a reflex arc; ... it is a reflex act of purely spinal or
bulbo-spinal origin."
By definition, then, _a spasm is the motor reaction consequent on
stimulation of some point in a reflex spinal or bulbo-spinal arc_. To
differentiate between the reflex, which is physiological, and the spasm,
which is pathological, we may add as a corollary: _the irritation
provocative of the spasm is itself of pathological origin, and no spasm
can occur without it_. The anatomo-pathological substratum of a spasm
is, then, some focus of irritation on a spinal or bulbo-spinal reflex
arc, which may be situated in peripheral end organ, in centripetal path,
in medullary centre, or in centrifugal fibre. Whatever be its
localisation, it will determine a spasm in our sense of the word.
Cortical or subcortical excitation, however, as well as peripheral
stimuli, may provoke these bulbar and spinal centres to activity.
Irritation of a point on the rolandic cortex, or on the cortico-spinal
centripetal paths, is followed by a motor reaction exactly as with
afferent impulses; the sole change is in the route taken by the
centripetal stimulus; the reflex centre remains bulbo-spinal, and the
efferent limb of the arc is as before.
The application of the word spasm to these motor responses to cortical
or subcortical stimulation is quite justifiable. Developmentally the
grey matter of the cerebral convolutions is ectodermic, as is the skin,
and capable of functioning as a sensory surface; it may be considered
the end organ of an afferent path that conducts to medullary reflex
centres. According to our definition, then, provided the centre of the
reflex arc be bulbo-spinal and the irritation pathological, the
consequent motor phenomenon is a spasm.
A distinction most nevertheless be drawn between the two cases, inasmuch
as in the one the afferent path is peripheral, in the other it is
cortico-spinal, and there is a corresponding difference in the clinical
picture. Jacksonian convulsions, consecutive to cortical stimulation, do
not seem to bear much resemblance to spasmodic movements indicative of
peripheral--_i.e._ sensory nerve--irritation. As a matter of fact, it is
not always easy to differentiate the two, except by the aid of
concomitant phenomena. The characteristic evolution of the Jacksonian
convulsion is of course readily recognisable. We can similarly diagnose
an irritative lesion of the internal capsule not so much from the
objective features of the convulsive movements as from accompanying
indications. In short, there need never be any occasion for confusion.
Convulsive conditions attributable to irritation of cortico-spinal
centripetal paths have long been described and analysed: they constitute
well-recognised morbid entities, among which may be enumerated
Jacksonian epilepsy, hemichorea, hemiathetosis, pre-and post-hemiplegic
hemitremor, etc.
These clinical denominations for the affections under consideration it
is at present desirable to retain. We shall not call them spasms; above
all, we must not call them tics, else we shall end by confounding
conditions absolutely distinct. The case recorded by Lewin,[10] under
the title of "convulsive tic," of a three-year-old infant still unable
to walk, who has daily attacks in which "all the muscles" twitch for
about a minute at a time, is indeed a most singular tic. We were under
the impression that such an attack is usually known as an epileptiform
convulsion. Is the term "convulsive tic" quite a happy synonym?
Again, in the recent thesis of Cruchet the attempt has been made to base
the pathological physiology of tic on researches of von Monakow and
Muratow apropos of the occurrence of choreic, epileptoid, or athetotic
movements after certain lesions of the cerebro-spinal axis, and to find
an analogy in the action of various convulsion-producing substances
(Richet and Langlois). Cruchet's conclusion is that convulsive tic is as
often cortical or subcortical as spinal in origin; that it is, in short,
a mere symptom, common to many cerebro-spinal conditions.
The same regrettable confusion is discernible in various treatises on
neuropathology the work of German and other foreign authors.
As far as we are concerned, the outcome of the whole matter is simply
this: if tic is doomed to be used indifferently for convulsion, its
retention in scientific terminology is unjustifiable. Rather, then, than
widen its application, we prefer to restrict it; we shall employ the
term convulsion in its most general sense of "any anomaly due to excess
of muscular contraction," of whatever variety or origin; and we shall
limit the use of the word spasm to phenomena the result of irritation at
any point on afferent or efferent reflex paths, or in reflex
bulbo-spinal centres.
In thus indicating our position, we find ourselves once more in accord
with generally received opinion since the days of Charcot. These views
have been excellently expressed by Guinon:
Convulsive movements differ widely in kind. Some consist of
localised spasms in the domain of a motor or mixed nerve, most
frequently one of the cranial series--in especial the
seventh--consecutive to some anatomical lesion, central or
peripheral. The great majority of observers, French and foreign
alike, are in the habit of designating such movements "tics." ...
But they are only partial convulsions limited to the area of some
one nerve, not true convulsive tics, differing alike in essential
features and concomitant symptoms. From the anatomo-pathological
standpoint, moreover, lesions are as constantly present in the one
as absent in the other.
The opinion of Brissaud on the subject coincides with our own.
* * * * *
If we suppose now that the cortex ceases to act as a surface of
peripheral excitation, and becomes itself a reflex centre, we note at
once a complete change. The modification effected by the cortex on
afferent impressions is obvious in altered motor reactions, which appear
with the stamp of cortical intervention, herein differing from
bulbo-spinal phenomena. To this category belong the tics; we shall soon
see why and how.
Conformably, then, to convention sanctioned by usage, and especially by
the teaching of Charcot and Brissaud, we have given a precise definition
to the word spasm, and we can only solicit its general adoption.
To resume briefly the argument we have advanced in the foregoing
paragraphs, we maintain:
If in a given motor phenomenon there is no evidence of actual or
previous cortical intervention, it is not a tic.
If the motor reaction is consecutive to pathological irritation at any
point on a bulbo-spinal reflex arc, it is a spasm.
If the cortex is or has been involved in its production, it is not a
spasm.
Should it present, in addition to the fact of cortical participation,
certain distinctive pathological features, it is a tic.
It is precisely these distinguishing characteristics that we shall now
proceed to examine, preluding our study of them with one or two
physiological considerations.
TIC AND MOTOR REACTIONS; REFLEX, CO-ORDINATED, FUNCTIONAL, AUTOMATIC,
AND VOLUNTARY ACTS
The instantaneous muscular contraction that follows the application of a
drop of sulphuric acid to the limb of a decerebrate frog is an example
of a pure spinal reflex. With the persistence of the irritation
contraction of the other limb and of the whole body ensues; the simple
spinal reflex has become generalised. Observe the frog a little longer.
Soon the sound foot approaches the affected limb and attempts by rubbing
to remove the point of irritation. A movement of attack has succeeded
the simple movement of defence, and indicates a complete change in the
nature of the motor reaction. In the first case the limb is withdrawn
briskly from the painful stimulus; in the second the animal performs a
series of co-ordinated purposive movements. The first reflex is
automatic, and so no doubt is the second, since the frog is decerebrate.
But a co-ordinated movement is not of necessity automatic from the
outset; its automatism may be the sequel to voluntary education.
Co-ordination is often a manifestation of cortical activity.
Take, next, the case of the infant. His earliest muscular movements are
pure spinal reflexes. Pinch his leg, and he withdraws it; continue the
stimulus, and he moves the other leg, his arms, his whole body; he
starts to cry. The original reflex is becoming generalised, yet he makes
no attempt to remove the source of irritation. Should a particle get
into his eye, his lids will blink so long as the pain persists, but he
never rubs them to expel the foreign body. In Virchow's phrase, the
newborn infant is a spinal animal, endowed with spinal reflexes only;
his responses to stimuli are beyond voluntary control.
More complex motor phenomena, however, equally independent of cortical
influence, characterise the early days of the infant's life. The
contact of his lips with the breast at once elicits a reflex in the
shape of sucking movements. These are obviously co-ordinated and adapted
for a particular end; suction is a functional act. Yet the cortex plays
no part therein; the act is automatic from the beginning. Peripheral
excitation from tactile impression of nipple, teat, or finger is
sufficient to provoke this reflex response.
Similarly with the functions of respiration and nictitation--their
establishment follows the stimulation by air of the respiratory or
conjunctival mucosa. The appropriate movements constitute the
spontaneous reaction to afferent impulses; they are simple bulbar
reflexes. Co-ordinated and purposive though they be, they do not come
within the sphere of the will. The newborn child cannot voluntarily
accelerate or retard his respiratory rhythm.
But a day comes when the formation of cortico-bulbar or cortico-spinal
anastomoses renders possible the interaction of higher and lower
centres; respiration may be made quicker or slower; the eyelid may be
closed less rapidly, more often. In a word, cortical modification of
function becomes a reality.
A further step in advance is soon taken.
Under the "law of least effort" the inhibitory power of the will reduces
motor reaction for the attainment of a given object to a minimum. The
infant begins to make more complicated movements, attempting the removal
of a source of annoyance by direct attack, learning to scratch itself,
to spit instead of swallow, etc.
The essential difference between these acts--a thousand other examples
might be chosen--and the reflexes of the first group, is that the
precise and regular execution of the former demands more or less
prolonged education, repetition, and voluntary co-ordination.
It is true these co-ordinated acts are eventually performed with all the
spontaneity of the simplest reflexes; voluntary co-operation is no
longer indispensable; scratching, spitting, walking, can be effected
without any actual intervention of the will. But we must not forget such
muscular automatism entails a preliminary training in the shape of
frequent repetition of purposive movements--a training which varies in
duration with the individual and the nature of the particular movement.
It is only after several years of volitional effort that such acts as
locomotion or the expulsion from the throat of an irritant particle
become really automatic.
The fact that the newly hatched chick is capable of walking has been
advanced as an argument for the existence of congenital automatism. It
is true that the chick's movements are very imperfect--it stumbles and
falls, as does the infant, on the slightest provocation, and even
without any apparent cause; but the rapidity with which certain animals
acquire the faculty is so surprising that the latter almost appears to
have been innate.
In all phenomena characterised as instinctive we cannot deny the
existence of a certain congenital aptitude, the result possibly of
ancestral education, owing to which some individuals learn infinitely
more quickly than others, and in their case a period of preliminary
education may seemingly be awanting. Probably the truth is, however,
that this stage has been a very brief one. In man there is a gradual
transformation of voluntary into automatic acts. Though no teacher be
necessary, teaching is requisite. The infant learning to walk is really
independent of his parents, and might, for that matter, be entirely
self-taught; but the point remains, however automatic his walking
subsequently become, that he begins by voluntarily co-ordinating the
movements of his lower limbs and trunk towards a definite end.
Another advance is still to be made.
With increasing cortical development the individual is able, on
stimulation no longer peripheral but central in origin, spontaneously to
execute movements which frequent repetition has endowed with all the
features of functional acts. Of these ideomotor phenomena physical
exercises, games, manual trades, readily furnish instances. Swimming,
for an instance, requires the rhythmical co-ordination of arm and leg,
to attain which perseverance, retentiveness, and above all repetition
are essential. At length the time arrives when the swimmer is surprised
at the absence of any necessity for voluntary co-ordinating effort on
his part. In fact, to reintroduce volition into this acquired automatism
would be to court disaster. "What I do naturally," said Montaigne, "I
can no longer perform if I attempt it expressly."
From these physiological considerations we are led to make the following
classification of motor reactions:
1. Simple spinal reflexes, innocent of co-ordination or functional
systematisation, on whose production or inhibition the will has no
influence. To this division belong the movements known as spasms.
2. Functional motor acts. Among these we may distinguish:
_a._ Essential movements, _e.g._ respiration, suction, etc.,
appearing at birth, and co-ordinated in view of some definite
function.
_b._ Acts such as locomotion, mastication, etc., whose acquisition
is subsequent to a more or less prolonged period of education.
_c._ Non-essential ideomotor acts, acquired later in life, which
soon assume all the characters of functional acts.
The movements belonging to the first group in this latter category may
manifest themselves without any exertion on the part of the will, but
its activity is essential to the perfecting of the second, and the
originating of the third.
In this last division are placed the motor phenomena known as tics.
TIC AND CO-ORDINATION
We have thus come to see that a tic is a co-ordinated, systematised,
purposive act. The majority of observers are satisfied on this point,
although there exist various differences of opinion, more apparent than
real, the inevitable result of disagreement as to the interpretation of
certain expressions. It is imperative to obviate misunderstanding once
and for all.
In his first contribution to the study of the disease which bears his
name, Gilles de la Tourette gave the general description of _motor
inco-ordination_ to the convulsive movements of his patients. It has
been argued by Guinon, on the contrary, that they are really
systematised, and that they reproduce, in an involuntary manner, the
co-ordinated movements of everyday life. That this is sometimes the case
Tourette subsequently admitted, but he still professed their frequent
actual inco-ordination.
This divergence of opinion is entirely attributable to difference of
interpretation. Littré's definition of muscular inco-ordination is, "A
condition occurring in various diseases of the nervous system, in which
the patient cannot co-ordinate the necessary muscular movements for
walking, grasping an object, etc." In this sense the term is applicable
indiscriminately to the gesticulations of choreic, athetotic, or tic
patients; to the ataxia of tabetics and others; to the tremor of
disseminated sclerosis or paralysis agitans, etc. An expression so
general is not merely of no diagnostic value; it leads to positive
confusion.
It is precisely in the type of inco-ordination that the difference lies.
As rigorous a distinction must be drawn between the gestures of chorea
and the gesticulations of the sufferer from tic as between the tremor of
insular sclerosis and of Parkinson's disease.
In assigning an exact meaning to the term muscular inco-ordination, we
cannot do better than quote the remarks of Guinon:
The tabetic who throws his legs to right and left, who as he sits
at table cannot carry his spoon to his mouth, furnishes an instance
of true motor inco-ordination. On the other hand, the subject of
tic performs his voluntary actions with perfect assurance; though
his infirmity occasion all sorts of ridiculous involuntary arm
movements, he never brings his fork against his ear or his cheek,
nor does he spill a drop from his glass; his walk may be
interrupted by a sudden halt to bend his knees and kneel, or to
strike his foot violently on the ground, but he never trips one leg
over the other and never falls.
In his article in the _Dictionnaire Jaccoud_, Letulle distinguishes two
kinds of tics:
The _convulsive tic_ consists of a series of partial convulsions,
while the _co-ordinated tic_ is the expression of some complex act
by a sequence of muscular contractions for that purpose. In the
former case the resulting movement is irregular, abnormal, and
useless; it is a muscular "shock" evolved without reason and
continued without effect.... The normal individual usually
possesses _in potentia_ all the elements for the genesis of a
co-ordinated tic. Some little trick or mannerism, arising perhaps
from the necessity of gaining time for reflection, or from the
desire of concealing some innate timidity, or of dissimulating some
preoccupation, becomes sooner or later involuntary and automatic,
and though maintaining its regularity and co-ordination, passes
insensibly into the realm of pathology.
The distinction, however, is far from being absolute. Letulle himself
admits it is a question of degree rather than of kind; the co-ordinated
tic differs from the first variety only in its greater extent,
complexity, and duration. Now, the convulsive tic may be a local,
partial, irregular, abnormal convulsion, yet these characteristics are
not sufficient to differentiate it: biting the lips is classed by
Letulle as a co-ordinated tic, but it is surely a local, partial,
irregular, abnormal muscular act; and the explosive laryngeal "ahem!" he
would similarly place, yet it cannot be said to be a phenomenon
characterised by its extent, complexity, and duration.
According to Guinon, a further distinguishing feature of the convulsive
tic is its frequent though inopportune reproduction of some reflex or
automatic purposive movement of everyday life, whereas we have just seen
that one of the elements in Letulle's co-ordinated tic is its
purposiveness. In a word, these observers apply the same epithet to two
varieties of tic which they are endeavouring to separate.
The explanation of the apparent contradiction is simple. A gesture which
seems meaningless and useless to-day becomes intelligible and logical
to-morrow, when we learn the reason for it. In the course of an attack
of conjunctivitis a patient acquires the habit of winking his eye, and
though the inflammation subsides, the habit persists. If we are ignorant
of its cause, are we to call the tic convulsive since it appears to us
needless? And if we do know its origin; can we say it is co-ordinated
when one muscle only is involved in the contraction?
The distinction drawn by Letulle between the two groups may hold good in
some cases, but certainly not in all, and in our opinion it is
preferable to abstain entirely from the attempt to base a classification
on variation in muscular contraction. Noir remarks very justly that
intermediate forms occur which are difficult to place in one or other
category. In face of the confusion to which an illogical division
inevitably leads, we may safely leave this question aside. In our view,
the motor phenomena of the disease are always systematic, co-ordinated
movements, directed for the attainment of some definite object. We
exclude all simple bulbar or spinal reflexes, and all spasms, since the
cardinal feature in these conditions is the absence of any functional
systematisation.
THE GENESIS OF TIC
We have seen how various purposive, co-ordinated movements may, by dint
of education and voluntary repetition, become automatic and be
automatically repeated should occasion arise. Imagine some such act
recurring involuntarily without any apparent reason and for no apparent
object; what does such an anomaly signify?
Take, for instance, the case of a young girl who inclines her head on
her shoulder to relieve the pain of a dental abscess. The act is called
forth by a real exciting cause; the muscular response is voluntary,
deliberate, undeniably cortical in origin: the patient _wills_ to
appease the pain by pressing and warming her cheek. Should the abscess
persist, the movement will be repeated less and less voluntarily, more
and more automatically; but as the why and the wherefore still remain,
there is nothing pathological about it.
With the healing of the abscess, however, and the consequent relief of
the pain, the girl still inclines her head on her shoulder from time to
time, albeit cause and purpose have ceased to operate. Her primarily
volitional, co-ordinate, systematic, motor reaction is now automatic,
inopportune, and meaningless: it is a tic.
Charcot[11] has given us an excellent description of the process:
However complex and bizarre may appear the convulsive phenomena
known as tics, they are not always as irregular, inco-ordinate, and
contradictory as superficial examination might lead one to
believe. On the contrary, they are, as a general rule,
systematised; in a given case they recur always in an identical
manner, reproducing, and simultaneously exaggerating, complex,
automatic, purposive movements which are essentially physiological;
they are in a sense the caricatures of ordinary acts and gestures.
The tic is not in itself absurd; it appears so only because it
occurs inappositely, without obvious motive. Source of irritation
is absent, yet the patient scratches himself; he blinks, but no
foreign body is to be detected in his eye.
Mere repetition does not, cannot, evolve a tic in every case. Not all
who would may tic; psychical predisposition in the shape of volitional
enfeeblement is a _sine qua non_.
Of the rôle played by mental insufficiency in the genesis of tic we
shall have much to say later. The point we are desirous of emphasising
now is that the first manifestations of tic have their origin in, and
are dependent on, cortical activity, at least in a majority of cases.
Notwithstanding painstaking investigation, determination of the initial
cause may no doubt be difficult in some instances, owing to the
patient's ignorance or forgetfulness; for that matter, the observer may
not know how to set about his task. Prolonged interrogation, however,
and due consideration of the patient's environment, will generally
enable him to reconstruct the pathogeny of the condition.
It has been our practice for some years now to examine with especial
care into the mode of onset, and to scrutinise the reasons for the
particular localisation, of any given tic; and we have been able, in
practically every case, to rediscover the exciting cause, and
consequently to explain the form taken by the tic in its earliest
manifestations as a voluntary response to the stimulus. Time may have
distorted the original movement, but a little patient analysis will
facilitate its recognition even in the caricature made of it by the
tic.
A few concrete instances will help us better to understand the nature of
this psycho-physiological mechanism.
An individual is wearing a collar too small for him, and its frayed edge
chafes his skin; the neck is at once abruptly inclined away from the
irritating point--a simple spinal reflex movement of defence. Now that
he is warned by the sensation of pain, he wishes to avoid it, which he
does by bending his head to the opposite side. The act is similar to the
preceding, but of a totally different nature; it is voluntary, not
involuntary; cortical, not bulbo-spinal.
Next day the collar is replaced by another of ampler proportions. There
is no further irritation of the skin, and accordingly no occasion for
deviation of the head. Memory of the disagreeable sensation may perhaps
incite him to verify the disappearance of the irritation by a few
movements of the head, and in the normal individual the matter ends
there. Even should the idea of repeating the gesture, now become
meaningless, occur to him, he banishes it by an effort of the will.
With the candidate for tic things pass in quite a different fashion.
Uncalled for though it be, he performs the brusque movement of yesterday
perhaps with a view to satisfying himself that the pain is non-existent,
but he is not thus satisfied. He does not limit his experiments to one
or two attempts. He repeats it frequently and complacently. The original
source of irritation is gone; the movement intended at first to relieve
it persists. Soon the whole trouble is forgotten, but the reiterated
gesture becomes habitual and automatic; it may have been rational
yesterday, but to-day it is superfluous, if not actually prejudicial; it
is a tic. In its evolution the cortex has had a part, and the very
untimeliness of this cortical intervention indicates a certain disorder
of psychical function.
Or again: a speck gets under my eyelid, and I wink--a spasmodic act
independent of the cortex. The speck is removed, but the conjunctiva
remains a little tender, and I wink again--still only a spasm. All trace
of irritation vanishes, yet the blinking persists: it is degenerating
into a tic.
Wherein consists the rôle played by the cortex in the production of such
phenomena? It intervenes to order the repetition of the gesture provoked
involuntarily, in the first instance, by peripheral excitation; and
though one may not always be able later to discover evidence of this,
one must at the least recognise the fact that the mere inopportune
persistence of the movement bears witness to psychical imperfection.
It has been remarked by Guinon that patients suffering from tics of
blinking attribute them to the presence of foreign bodies; he declares,
however, that "if they bear a superficial resemblance to simple tic,
they differ widely in essential characters and from the point of view of
prognosis. They are really involuntary movements of reflex origin,
occasioned by abnormal sensations, usually of pain." He cites as a
typical instance the "tic douloureux" of the face.
The description is strictly accurate provided the pain continue; such
acts are not tics, they are spasms. On the other hand, the perpetuation
of the movement in the absence of all exciting cause and pain
constitutes it a tic. In this way a spasm may be the forerunner of a
tic, and in many cases no doubt a purely spasmodic motor reaction may
determine the form and localisation which the latter will adopt; but, as
we have said, its first manifestation is usually a voluntary act of
definite causation, and directed to the accomplishment of a definite
object.
The candidate for tic is mentally unstable. Indifferent perhaps to acute
suffering, he may become entirely preoccupied by some trifling sensation
of pain or by some source of petty annoyance, to rid himself of which he
will resort to all sorts of tricks and assume all sorts of odd
attitudes--tic germs quick to develop in suitable soil.
In many motor reactions of the class we are now considering the main
object is the _avoidance of some abnormal sensation_, suppression of
which, however, brings no relief to the patient's mind. He dreads its
reappearance; he must assure himself of its absence. He taxes his
ingenuity in the attempt to rediscover the sensation, and multiplies his
gestures and attitudes until once again he experiences it. The
satisfaction he felt originally in shunning the pain or the discomfort
is paralleled by the satisfaction he now knows in its rediscovery. In
each instance the motor phenomena are voluntary and co-ordinated, but
their excessive repetition betrays unstable mental equilibrium.
Instructive examples of this pathogenic process are furnished by the
history of O., and by the case of a young patient J., from which we
extract the following:
In 1896, during the holidays, a tic, secondary to some slight nasal
ulceration, made its appearance. The child learned the trick of
wrinkling its nose and of puckering its upper lip, sometimes
attempting by various facial grimaces to lessen the irritation due
to the little nasal sore, sometimes, on the contrary, finding
delight in deliberately seeking the unusual sensation. The sniffing
soon became involuntary, and for the next two months, long after
the ulceration was healed, this nasal tic continued.
Then another cause came into operation, occasioning a new gesture
and entailing a new tic. Cracking of the labial mucous membrane
during winter led to incessant licking and nibbling at the
roughened surface. With the first excoriation the patient proceeded
to moisten his lips with his tongue, whence fresh cracks, followed
by the renewal of nibbling and licking movements.
In March, 1899, after a severe attack of influenza accompanied by
fever and pains in the joints, he began to complain of stiffness
and a sort of cracking in the neck, disagreeable rather than
painful. To avoid this, or to reproduce it--as one sometimes amuses
oneself by "cracking one's joints"--he quickly learned to make all
sorts of bizarre head movements, and so a tic of the neck started
which lasted several months.
Noir has directed attention to a tic of frequent occurrence among
amaurotic idiots, consisting in rapid to-and-fro movements of the finger
before the eyes. The explanation seems to be that their blindness is not
absolute enough to prevent some faint appreciation of light by retinal
stimulation, and the effect of the luminous impression is enhanced by
the alternation of light and shade sensations produced by the waving of
the fingers in front of the eyes. The tic is neither more nor less than
a search after this effect.
Another case in point is reported by Dubois[12]:
The patient is a young woman twenty years old who has acquired the
habit of beating her right elbow against her chest fifteen or
twenty times a minute, until it happens to impinge with rather
greater violence on a whalebone in her corset; this is accompanied
by a slight guttural cry. It would appear the sole satisfaction in
her tic is in the attainment of this object, since it is succeeded
by temporary cessation of the movements. Their constant repetition
has caused an insignificant erosion of the skin over a limited area
on the elbow, and it is only when this particular spot is touched
that the ejaculation is uttered and the tic arrested. If the elbow
be at rest, the head is inclined from left to right several times a
minute.
Evidently, then, in the subjects of tic the _impulse to seek a
sensation_ is of very common occurrence, as is also the _impulse to
repeat to excess a functional act_. It is precisely this exaggerated and
inopportune multiplication of movement that is pathological.
The mother of one of Noir's patients was always tempted to repeat any
simple purposive movement that she had made a moment before, even
though the reason for the act no longer existed.
The imperiousness of these impulses, and the peculiar relief attendant
on submission to them, accentuate the closeness of the resemblance
between tic and obsession, to which reference will be made later; but it
is necessary at this early stage to indicate the bearing of these
psychical phenomena on the pathogeny and diagnosis of tic.
Many of the conditions with which we are dealing are characterised in
addition by an emotional element. Dupré[13] believes an emotional shook
is the exciting cause of tic, as it sometimes is of obsessions.
Apropos of this view, we may quote again from the history of the young
patient J.:
During his holidays he improved sufficiently to enable him to
resume his classes, but another attack of influenza in the
beginning of 1900 was the occasion of a relapse. He began to
complain of overpowering fatigue; became depressed and morbidly
anxious about his future; had attacks of hysterical sobbing;
suffered great mental anguish, accompanied by flushing and profuse
perspiration; in short, he fell into a veritable state of _mal
obsédant_.
At the same time, the slightest pain or annoyance was a pretext for
his tics to exhibit themselves with redoubled vigour. Even the mere
idea of his tics, the fear of them, incited him further in the same
direction. He seems then to have set himself to invent new
movements, and forgetting forthwith that he himself was their
creator, became alarmed at them as sure signs of the aggravation of
his disease.
Analogous details will be found in all cases which have been studied as
well from the mental as from the physical side. For our part, we
consider a tic cannot be a tic unless it be associated with a certain
degree of mental instability and imperfection, indubitable evidence of
which is furnished by a psychical abnormality of constant occurrence in
this malady--viz. anomalies of volition.
TIC AND WILL.
It might be imagined that a tic would cease to exist as such were a
voluntary element to enter into its constitution. The fact, however,
that tic is the sequel to frequent repetition of a primarily voluntary
act, and that it may be arrested, transformed, or aborted, is proof to
the contrary of which there is no gainsaying.
The truth is, once a tic is established, it has all the appearance of an
involuntary movement, but that nevertheless its manifestations may be
either modified or inhibited by an effort of the will is patent from
clinical observation. This is a fact of great importance.
Spasm knows no control (says Brissaud). Nothing will arrest the
bolus of food as it passes into the pharynx, unless by the
inversion of the whole function of deglutition.... As regards tic,
however, inhibition is possible because the phenomenon is cortical.
In almost every case, reinforcement of the will can momentarily at
least check it.
Consensus of opinion admits diminution of will power to be the cardinal
mental symptom of the tic patient. Inhibitory insufficiency, as Blocq
and Onanoff say, allows the persistence of fixed ideas of movement which
reveal themselves by involuntary acts. Noir has admirably supplemented
the researches of Ribot in this direction:
The infant's activity is purely reflex, and manifested by a
profusion of movements, to suppress or restrain the majority of
which is the task of education. It is highly probable that any
co-ordinated tic whose evolution can be traced at all has its
origin in the infant's spontaneous muscular play. From this point
of view the frequency of these movements in idiots is readily
explicable, since their intellectual development never gets beyond
the stage of childhood. The more confirmed the idiocy and the more
rudimentary their mind, the more prone are their tics to be complex
and inveterate.
These remarks are pertinent to the case not only of idiots, imbeciles,
or backward children, but of all the subjects of tic. In them some
degree of mental infantilism is of invariable occurrence. The tic
patient has the weak and capricious will of the child; young or old, he
does not know how to _will_; if his willing be sometimes excessive, it
is never resolute. Were it otherwise, he might control his meaningless
gestures, but his efforts are both feeble and ephemeral.
TIC AND HABIT
The view which regards tic as a "pathological muscular habit" provides
emphatic illustration of the sinister influence of volitional infirmity.
This aspect of the question is of deep significance. If we define a
habit, in the words of Littré, as a "disposition acquired by the
repetition of the same acts," we can easily conceive how intimate is the
relation between habit and automatism, and how constant rehearsal of the
same movement in the same manner will create a mode of motor reaction
independent of the function of the will. It has been made clear already
that the phenomena of tic, regarded from the motor standpoint, reveal an
identical process at work; but the fundamental difference between the
habits of normal individuals and those of tic subjects is that the
former can be checked or modified by voluntary effort, whereas the
latter gradually acquire the pathological features of tenacity and
irresistibility.
In a typical case of tic (says Dupré)[14] the establishment of a
reflex sensorimotor diastaltic arc, viâ the cortex, between
peripheral stimuli of whatever nature and corresponding muscular
reaction, is a sign that predisposition has changed the
physiological to the pathological, and transformed a habit into a
tic.
Guinon argues, however, that tic ought not to be cited in the catalogue
of diseases, since it is ultimately a deep-rooted "bad habit" only, not
a pathological fact.
We are not prepared to maintain, of course, that all motor "bad habits"
are tics, for a whole host of familiar gestures, tricks, and mannerisms
do not merit the name, superfluous and even detestable though they may
be. It is true they are the product of education, and become, since the
will has less and less to do with their appearing, at the last purely
automatic; they may thus developmentally bear a close resemblance to
tics. As Letulle says:
The infant who is constantly sucking its thumb, the individual who
never ceases picking his teeth, or rubbing his eyes, or lips, or
chin, or ear, who is for ever scratching his head or his beard--all
have no doubt, originally, been driven to the repetition of the
trick by some real necessity in the shape of dental caries, or
ciliary blepharitis, or pityriasis capitis; but removal of the
cause is not followed by cessation of the gesture. A man will learn
the habit of perpetually smoothing his hair, and will not desist
from his favourite trick though he become absolutely bald.
But such automatic habits and mannerisms are not genuine tics so long as
the movement executed conserves in form the characters of a normal
gesture. Be it never so inopportune or absurd, it is not a tic. It comes
rather under the heading of _stereotyped acts_, whose kinship with, and
difference from, the tics, have been well demonstrated by Séglas.
While the stereotyped act has all the appearance of a normal movement,
the tic, on the contrary, is a "corrupt" muscular contraction; its
subject is irresistibly impelled to its performance, and any attempt at
repression is painful, sometimes even agonising. Victory is perhaps not
entirely impossible, but any arrest is, as a rule, only temporary, and
entails suffering which well deserves to be considered pathological.
On the other hand, the thousand illogical and absurd mannerisms of which
we have been speaking betray no irresistible imperiousness in their
execution, and require no agonising struggle for their repression. They
are not tics. The crucial point in the differential diagnosis is the
presence or absence of mental suffering.
The distinction may be further elaborated. Concentration of the
attention may diminish the intensity or even inhibit the occurrence of a
tic; inversely, a simple bad habit is manifested preferably during this
very concentration. In the heat of physical or intellectual labour, we
have all our favourite and characteristic tricks: we curl our moustache,
we twist our beard, we scratch our forehead, we rub our chin, we nod our
head, we fidget with our fingers in reading, speaking, reciting--in any
mental or physical exercise requiring our attention we reveal
innumerable little oddities of movement; but let our thoughts be
directed for an instant to these gestures of distraction, and they
disappear forthwith, to reappear afresh when we are absorbed in our work
again. Charcot used to twist his hair round his index finger so
intricately that to disentangle the finger one day a lock of hair had
actually to be cut off. It was a trick of his, not a tic.
In the case of the latter, leisure of mind and body is the signal for
the apparition of the inopportune movements. Any form of effort
demanding the attention will, as a general rule, lessen their frequency
or abolish them altogether.
Trousseau quotes the case of a young girl afflicted with severe tic who
could play through any piece on the piano without the slightest
interruption. Guinon similarly has known cases, one of whom could juggle
accurately with knives, and another whose infirmity did not prevent her
from taking a successful part in operatic ballet. Young L. is
passionately fond of dancing, but he never tics in the ballroom. O. is
an excellent amateur billiard player and never handicapped by his tic
when playing, or, for that matter, when fishing or fencing; but if his
attention be not thus absorbed, it is only with the utmost difficulty
that he can master his tic.
We all have met the young man who cannot strike a ball at tennis without
protruding his tongue at the same moment; his partner bites his lips at
any difficult stroke. At other times neither betrays the slightest
grimace; neither is conscious of any effort in maintaining repose. The
occurrence of these movements during active concentration of the
attention, and the absence of either difficulty or distress in checking
them, justify their classification as stereotyped acts, in subjects
psychically normal.
Tic is a pathological habit, to use Brissaud's phrase, and its
description as a habit disease is in harmony with the facts. We must
expect, of course, to meet every intermediate variety between the bad
habit and the true tic, but this need not deter us from drawing the
above-noted distinction, the application of which will be found not
without value in the great majority of instances.
TIC AND IDEA
As we have already seen, a peripheral stimulus may originate a cortical
reflex whose expression is a motor reaction, or the reaction may take
place where the stimulus is entirely cortical; in other words, an idea
may be the starting-point of a movement which may in its turn degenerate
into a tic. All that has been already said of these phenomena is
applicable to this movement of ideational origin. It too will be
transformed into a tic when it is repeated without exciting cause and
for no definite end, when its reiteration becomes imperious and
irresistible, its suppression accompanied with malaise and its execution
with relief.
Tics of this sort are numerous enough. "To think an act," as Charcot
used to say, following Herbert Spencer and Bain, "is already to
accomplish it. When we think of the movement, say of extension of the
hand, we have already sketched it in our minds; and, should the idea be
too strong, we execute it."
In this connection Grasset most appropriately cites the fact that the
peoples of mid-France evince a peculiar aptitude for mimicking by
suitable gesture the various ideas which occur in the course of
conversation. "You will always succeed," he says, "with the following
little experiment. In a drawing-room ask ten individuals consecutively
to tell you what a rattle (_crécelle_) is. The answer will in every case
be accompanied by a gesture expressive of an object that turns. To think
an act is already to perform it; the thought and the gesture are
wellnigh inseparable."
The truth of this observation is not a question of geography. Examples
are met with on every hand. It is a law, abundant evidence for which is
furnished by all who tic. But however exuberant be accompanying
movements of explanation, they must present the additional features of
inappositeness and irresistibility to be denominated tics.
A case that has come under our own notice is worth mentioning because of
its peculiarity and instructiveness. The patient was an artistic,
well-educated, and well-travelled man, gifted to a remarkable degree
with the faculty of assimilation. Apart from genuine tics in the shape
of sudden jerks of face, arm, or leg, he had acquired the trick of
accompanying his conversation with a peculiar mimicry of its content.
Not satisfied with providing a gesture for nearly every word, he
divided the words themselves into syllables for each of which he had an
appropriate action, whence arose a series of mimicry puns of most
unexpected effect.
For instance, during the enunciation of the following sentence, "We were
on a paddle steamer, with captain, commissaire, and doctor," he first of
all imitated the movement of paddles; he then put his hand, with three
fingers apart, to his forehead (the captain's cap has three lace bands);
to mimic the word commissaire he shook hands with himself
(_commissaire_--_comme il serre_); to express the word doctor he
pretended to touch imaginary breasts on his body (_médecin_--_mes deux
seins_); and so on throughout all his conversation.
Voluntary execution of these puns had been succeeded by complete
automatism, yet they were not tics, because, however singular the
mimicry, it was appropriate; whereas his facial grimaces, the shrugging
of his shoulders, the tapping of his heels, repeated every minute for no
reason or purpose, were real tics.
If, when asked what a rattle is, we make a turning movement with our
hand, or if when asked to explain the word _brandebourg_ we indicate an
imaginary arrangement of braid on our coat--these two experiments always
succeed--we are attempting to express an idea by mimicry at the actual
moment of its arising in the mind; but the subject of a tic--which may
primarily have been the representation by mimicry of an idea--continues
the gesture long after the idea which provoked it has vanished.
A woman speaking with animation at a telephone will make with face or
hand a thousand useless gestures, useless since her friend cannot see
them, but they are not tics, even though they may be justly described as
functional, automatic, superfluous, and inopportune. If we are normally
constituted, we betray a pleasant idea by a smile, we express our
conviction by an appropriate gesture of affirmation; if we smile or
gesticulate with no motive for doing either, we have begun to tic. It is
not sufficient that the act be untimely at the moment of execution; we
must be persuaded that it no longer stands in any relation to the idea
which called it forth at the first, and that its repetition is
excessive, its inappositeness constant, its performance urgent, and its
inhibition transient, before we can say it is a tic.
Should the cortex be functioning harmoniously, afferent impulse and
efferent reaction stand in due proportion one to the other; but any
disturbance of psychical equilibrium--_e.g._ the fixity of some idea
combined with inhibitory weakness--will effect a corresponding
disturbance on the motor side. Charcot used to speak of tics of the mind
revealing themselves by tics of the body. Fear may elicit a movement of
defence, to persist as a tic after the exciting cause has vanished.
It is of course quite incorrect to say that each and every motor
reaction to a pathological idea is a tic. The psychasthenic who in his
fear of draughts shakes the door-knob a hundred times a day to make sure
the door is shut, is not a martyr to tic; in spite of the absurdity of
his action, it is logically connected with the idea that originated it,
and it is the idea which is absurd. To make an involuntary movement of
defence against some purely imaginary ill, on the other hand, and to
continue when all fear is past, is to tic.
In practice it may not always be a simple matter to uphold the
distinction, but some such demarcation of the tic's limits is called for
if we are to avoid its being applied to any act performed under the
compulsion of a pathological mental state.
In its mildest form the mental trouble may consist of an ordinary
psychomotor hallucination, but if it be not projected as an objective
phenomenon it does not deserve to be called a tic. One of Séglas's
patients met a choreic woman undergoing electrical treatment in the same
room as herself; on leaving she felt as though her own right arm were
the seat of spasmodic movements similar to those of the choreic patient,
but as they did not betray themselves by any external sign they cannot
be considered tics.
The exteriorisation of the hallucinatory phenomenon suffices at once to
bring it within the scope of our definition. Innumerable tics arise in
this way, provoked, mayhap, by some or other insignificant psychomotor
hallucination. The attitude adopted by certain patients, as remarked by
Séglas, is an index to the nature and seat of their hallucinations. Some
keep their tongue firmly bitten between the teeth; others cram their
mouth with pebbles, or compress their epigastrium tightly, under the
impression that it is the source of their voice. Should such gestures
persist while the hallucination does not, they may give rise to what we
are in the habit of calling "tonic tics," or "tics of attitude," but we
must repeat that the presence of a convulsive element is essential;
however out of place or absurd the contractions are, if otherwise they
are normal we are dealing with what Séglas designates stereotyped acts.
To this question we shall return later.
TIC AND CONSCIOUSNESS
According to Guinon, proof that "convulsive" tic is conscious is
furnished by the accurate description and rational explanation patients
supply of their affliction. Similarly Letulle's "co-ordinated" tic is a
conscious act, at least in its commencement; it is a "bad habit" which
finally passes beyond the limit of consciousness.
Now, while no doubt most subjects show a keen appreciation of their tic
when their attention is directed to it, they are none the less
unconscious of it at the moment of its manifestation. This is the ground
on which Letulle bases his statement that all tics, of whatsoever
variety, are habitually outside the domain of consciousness. To this
fact so much importance has been attached that the attempt has been
made, more especially by Blocq and Onanoff,[15] to differentiate the
conscious from the unconscious tic.
In our opinion, the distinction is ambiguous and tends needlessly to
complicate our ideas on the subject. The patient with "convulsive" tic
is conscious of it in the sense that he is well aware of its existence,
yet how can the gesture be a conscious one if it is synchronous with
mental preoccupation? On the other hand, the patient with "co-ordinated"
tic may bite his lips unconsciously, but he is by no means ignorant of
his little failing.
This divergence of opinion depends entirely on the possibility of
regarding the phenomena at different moments during their production.
The subject is in a position to appreciate his state both before and
after the tic, not during it. In a sense it may be said that tic is
alternately conscious and unconscious, in which respect it is comparable
to the obsession; the close analogy between the two conditions we shall
indicate more fully later. As a matter of fact, the same holds true for
every variety of spasm.
We are not disposed to introduce here a term sacred to the psychologist
and to speak of the tic as subconscious. Pierre Janet does not admit the
absolute unconsciousness of habit; even when the latter has degenerated
into a tic, it is not outwith the realm of consciousness. We prefer not
to venture, however, into the perilous region of the subconscious, in
spite of our appreciation of the happy results attributable to its
careful and discerning exploration by observers such as Janet himself.
According to Cruchet, certain so-called psychical tics are always
subliminal--for instance, the imitation tics common in children and in
idiots.
But if the consciousness of the normal adult be, as it admittedly is, a
most elusive conception to define, how infinitely more precarious is the
task in the case of idiots or infants! Cruchet says it is impossible to
be sure whether at any given moment a tic has been above the threshold
of consciousness or not; and we do not think the question will be
elucidated by the introduction of data so difficult to comprehend as the
consciousness, unconsciousness, or subconsciousness of the tic patient.
In any case, these conceptions are quite inadequate for the
establishment of useful distinctions. All that we can say is that the
participation of consciousness in the phenomena of tic varies in time
and degree. To hazard farther would be to invite disaster.
TIC AND POLYGON
The proposal has been made by Grasset to apply his attractive hypothesis
of the cortical polygon to the interpretation of the pathogenesis of
tic. It is desirable, first of all, to recall briefly the significance
of the word polygon in the sense adopted by that neurologist.[16]
At the central end of the physiological ladder is the superior or
cortical system of perception neurons whose cells form the grey
matter of the convolutions. Physiological and clinical research
necessitates the subdivision of this system into two groups--the
neurons of psychical automatism, and the neurons of superior
(_i.e._ voluntary or free) cerebration. The former function is not
of the same level as the ordinary reflex arc, since it is in
relation to co-ordinated, intelligent, and in a sense conscious
acts; at the same time it is to be distinguished assiduously from
the latter, in which we include our personality, moral
consciousness, free will, and responsibility.
Activity on the part of the inferior psychical neurons is seen:
1. In normal individuals--during sleep, dreams, and acts of
distraction.
2. In the nervous--in nightmares, oniric states, table turning,
thought reading, the use of the divining rod, automatic writing,
cumberlandism, spiritualism.
3. In the diseased--in somnambulism, catalepsy, hysteria, certain
phenomena of epilepsy, hypnotism, double personality; also in some
cases of aphasia, and in such conditions as astasia-abasia. Every
manifestation of this inferior psychism is characterised by
spontaneity, herein differing from mere reflex acts, but not by
freedom, which is the _propre_ of superior psychism.
The various neurons subserving the former or inferior function are
cortical, and form the cortical polygon. Situated at a higher
physiological level are those for the latter function, united in
what I designate the centre O.
Grasset's general conception of tic is accordingly as follows:
In contradistinction to a pure reflex, a tic is a complex or
associated act. There is, however, more than one centre for the
elaboration of these complex or associated acts, notably the
bulbo-medullary axis, and the cerebral polygon, as we call it. The
former serves as centre not merely for simple reflexes, but for
true associated acts also, such as conjugate deviation of the head
and eyes, walking movements in the decerebrate animal, etc.
We can conceive, then, a first group of non-mental tics
corresponding to and reproducing these movements of bulbo-medullary
origin.[17]
Let us turn now to our polygon formed by the various centres of
psychic automatism. Polygonal reactions, such as writing or
speaking, exceed both simple reflexes and bulbo-medullary
associated acts in complexity; they are to all appearance
spontaneous and in a certain measure intellectual, but they are
neither free nor conscious--attributes that distinguish the
functions of the centre O, the seat of the personal, conscious,
voluntary, responsible ego. The polygon consists of receptive
sensory centres for hearing, vision, and general sensibility, and
of transmitting motor centres for speaking, writing, and various
body movements. They all communicate with each other, with O, and
with the periphery, so rendering possible voluntary modification of
automatic action. In some cases, on the contrary, there may be a
sort of dissociation between O. and the polygon, when the activity
of the latter becomes supreme, as during sleep--we dream with our
polygon--or in distraction.
In states intermediate between the physiological and the
pathological, pure independent polygonal action may reveal itself
in the remarkable phenomena of nightmare, the divining rod, table
turning, automatic writing, etc., while certain aphasias and
agraphias, somnambulism, catalepsy, and various hysterical
conditions constitute the pathology of the polygon.
The fact that all mental attributes and functions are situate in O
definitely negatives, in my opinion, any classification in the
category of mental diseases of such conditions as hysteria, so many
of whose manifestations are polygonal alone.
Our second group of tics--polygonal tics, we may style them--are
correspondingly associated, co-ordinated, and psychical, but not
mental; they have nought to do with the superior psychism of O.
Finally, in direct and strict dependence on an actual idea is a
third group of tics, the psychical tics properly so called.
We have reproduced Grasset's theory in some detail since it is one of
the two most recent contributions to the study of the tic's
pathogenesis. The other is that of Brissaud.
An apparent lack of harmony between the rival hypotheses is, we shall
see, due rather to a difference in the interpretation of certain terms
than to a real opposition of ideas.
Brissaud's view that the tic is a co-ordinated automatic act and
consequently cortical is objected to by Grasset. Every automatic
co-ordinated act is not of necessity cortical. Conjugate deviation of
the head and eyes may be of bulbar origin; certain spinal movements even
may be no less co-ordinated and automatic. The decerebrate animal's walk
may be perfect in its co-ordination.
Careful analysis shows the divergence of opinion to arise merely from a
differing significance attached to the word origin. Brissaud is
considering the origin of the tic in time, at the moment of its
appearance; Grasset its origin in space, at the seat of its production.
Once the tic is constituted, its repetition each moment is a
manifestation of polygonal activity, but it is none the less true that
the movement which has degenerated into a tic had its source in
cortical, _i.e._ psychical, activity.
Any one who appreciates the import of Grasset's ideas will readily
understand his terminology; it is at the same time expedient that the
possibility of ambiguity in the use of words etymologically synonymous
should be avoided. Now, however judicious be the distinction he draws
between psychical and mental, it is to be feared it is not always
adequately grasped: we do not intend, therefore, to employ either mental
or psychical tic in our vocabulary, still less "psycho-mental" tic
(Cruchet). As for bulbo-medullary tic, it appears to us to be identical
with spasm as we have defined it, unless indeed it is to be taken as
signifying a tic begotten of a spasm, in which interpretation Grasset
and Brissaud both acquiesce.
TIC AND FUNCTION
We must now pass on to elaborate our conception of tic as a disordered
functional act.
The term function is employed to denote various biological phenomena
differing widely in manifestation and design. Vegetative functions such
as digestion, circulation, urination, etc., are regulated by a special
unstriped muscle system, the mechanism of which cannot be suspended by
cortical interposition; hence under no circumstances can its derangement
bring a tic into being.
Other functions, subserved by striped muscles, come within the range of
voluntary activity. Some--_e.g._ respiration--are essential to the
maintenance of life, and scarcely to be differentiated from those we
have called vegetative. Others, such as nictitation, mastication,
locomotion, are no whit less important, since their cessation, in the
absence of extraneous aid, would speedily have a detrimental effect on
the organism. They too are in a sense vital.
Others, again, such as expectoration, are useful, though not
indispensable. Some people labour under the disadvantage of being unable
to expectorate, but it is not a fatal defect. The function is not
universal.
Finally, let us take once more the case of the child.
As he grows up he passes by easy transitions from the voluntary to the
automatic stage. He is taught to swim, and swimming soon rivals walking
in the unconcern with which the movements are executed; he learns to
write, and no less rapidly does the act become one of unconscious
familiarity; his games, his exercises, the labour of his hands--be it
digging or typewriting--all reach the level of regular automatism; in
short, they are functional acts as truly as locomotion or even
respiration, with the qualification of being neither essential nor
general.
Such examples serve to illustrate the comprehensiveness of the term
functional, and embody all the intermediate forms between what is
inherently vital and what is purely acquired. When we have to deal in
practice with a case of functional disease, discrimination is obligatory
from the standpoint of prognosis. We are alarmed at our patient's
respiratory embarrassment, not at his impaired caligraphy.
A distinction has also been drawn between _functional_ and
_professional_ affections, profession being conceived as a function of
the individual in relation to society. But the latter term has the
drawback of being too exclusive. As a matter of fact, scriveners' palsy
is met with in people who, so far from being professional writers, do
not use the pen much at all. Nor is it necessary to be a professional
pianist to develop pianists' cramp. It would be more accurate to speak
of disturbances in "occupation acts," it being understood that these
have by dint of repetition acquired the automatic characters of true
functional acts.
* * * * *
Let us consider for a moment the salient features and component elements
in our conception of function.
First and foremost is repetition. It is an absolute law, this of the
periodicity of function, and strikingly exemplified in the case of the
circulation, digestion, urination, etc. Regularity of rhythm is no less
obvious in the muscular activity of mastication, locomotion, and
respiration, and its degree seems to be in direct proportion to the
duration and vital importance of the particular function.
The characters of this rhythm may be influenced by various extraneous
causes. A painful stimulus makes us blink or quickens our respiration.
The will may intervene, to accelerate or retard. The personal factor
accounts for individual differences, but for each individual a certain
rhythm and amplitude of movement, suited exactly to the end in view and
conforming to the natural law of least effort, may be regarded as
normal. It is only in pathological cases that this law admits of
exceptions, and these we shall now proceed to investigate.
Disobedience to the law in the shape of exaggeration or redundance of
purposive movement indicates functional excess. For instance, the object
of the function of nictitation is to moisten the conjunctiva. In its
evolution the child's unmethodical reaction gives place to the
rhythmical automatism of the adult. Perfection is the fruit of
education.
But the person whose impetuous and uninterrupted blinking far exceeds
the demand of the eye for lubrication is plainly troubled with excess,
with "hypertrophy" of function. Herein may consist a tic, and, in fact,
a large number of tics are nothing more than functional derangements of
this kind.
The execution of a functional act at an inopportune moment constitutes
another variety of functional disorder. A smile with no pleasant thought
to correspond; a cry, a word, that betoken no precise idea; a gesture to
relieve an irritation that does not exist; a chewing movement when the
mouth is empty--all are examples of untimely, inappropriate functional
acts, which merit the name of tics if in addition they are anomalous as
regards rhythm, amplitude, and intensity.
Again, the performance of function is accompanied by antecedent desire
and subsequent satisfaction. Authoritative proof of this law is
furnished by the case of micturition and of defæcation, although
momentary suspension of the function of nictitation or of respiration is
also a sufficiently convincing mode of demonstrating its truth. In the
case of locomotion and other motor functions a preliminary feeling of
need may not be so imperative, but it is none the less constant.
Now, it has been observed already that these are equally conspicuous
features in our conception of tic. In so far, then, as the latter is
preceded by irresistible impulsion and followed by inordinate content,
it may be considered a functional affection.
We cannot, however, dispose of each and every tic as an anomaly of some
normal universal function. We have already had occasion to notice a
large number of functional acts that are not of general distribution,
so-called professional movements, which of course are liable to
derangement. Such functional disturbances may be styled professional
cramps, spasms, or neuroses; but are they identical with tics?
To attach the majority of them to the tics is, in our opinion,
justifiable. They are the clinical expression of abnormalities
supervening in a function that has by repetition acquired the automatism
of genuine functional acts: they are germane to the tics. In certain
points, however, the analogy is not absolute.
Professional cramps are motor phenomena distinguished by arrest of
intended movement. Spasm signifies excess of motor reaction, cramp
denotes its inhibition. It cannot, then, be said that they present the
characteristic features of spasm as we have defined it: they are akin
rather to a form of tonic tic of which we shall give instances later.
With this premise, we can identify the professional cramp as a
functional anomaly recognisable by defective amplitude and force on the
part of the motor reaction. Its most special character is its appearance
exclusively during the exercise of the function of which it forms the
anomaly. Writers' cramp manifests itself in the act of writing, dancers'
cramp during dancing, and so on. We are ready to admit the close
affinity of professional cramp to tic, with which it has an additional
element in common in its occurrence among the psychically unstable. But,
regarded as a tic, it is unique in its dependence on the casual
exhibition of the professional act; as long as the telegraphist has no
occasion to transmit messages, his occupation cramp will not incommode
him in the least.
The great majority of genuine tics, on the other hand, are roused into
activity by anything or nothing, and this distinction is fundamental.
With all due recognition, therefore, of the marked resemblances between
the two, we shall be well advised in not confounding them under one
designation. For want of a better word, we shall use the phrase
professional cramp to specify functional disturbances taking place
solely during the discharge of professional acts.
One other class remains to be dealt with, consisting of functional acts
not merely superfluous but actually prejudicial to him who is at once
their creator and their slave. The idea that induced them and the object
they have in view are alike irrational.
An individual as he moves his arm one day becomes aware of a cracking
feeling in his shoulder-joint, and from the unwonted nature of the
sensation emanates the notion that he must have some form of arthritic
lesion. Renewal of the gesture is attended with reproduction of the
sound. The thought of a possible injury develops and extends until it is
an object of constant preoccupation and becomes a fixed idea. Under its
malign influence the movement is repeated a hundredfold and with growing
violence until it passes into the field of automatic action. It is
typically functional in its repetition, in the association of desire and
satisfaction; but it originates in an absurd idea, and is actuated by a
meaningless motive: its range is exaggerated, its performance
irresistible, and its reiteration pernicious. In fact, it is a tic.
We may thus regard tic as an obsolete, anomalous function--a _parasite
function_--engendered by some abnormal mental phenomenon, but obeying
the immutable law of action and reaction between organ and function, and
therefore just as prone to establish itself as any motor act of the
physiological order.