A system of practical medicine. By American authors. Vol. 5

by Unknown

The preceding argument will render it easy to comprehend the phenomena of night-terrors. These are commonly observed in young children of a highly nervous temperament before the conclusion of their second dentition. The subjects of the disorder are generally of neurotic descent. Insanity, hysteria, neurasthenia, epilepsy, chorea, and nervous dyspepsia are often discovered among their near relatives. Not infrequently they have been or will become themselves choreic.

The attack is often preceded by symptoms of indigestion, but it may result simply from the commotion of a brain wearied by the excitement and effort of the previous day. The little patient starts up out of an apparently sound sleep crying with alarm, calling for his mother, and staring wildly with every possible expression of terror. Sometimes he springs from his couch and runs headlong into a corner or seeks to hide under the bed, as if escaping from some frightful object. The eyes are open, tears flow, perspiration covers the skin, there is the greatest excitement, and the little one, convulsively clinging to its parent, will not be quieted. Only after fifteen or twenty minutes, as tranquillity gradually returns, does the child seem to recover the power of recognizing his friends. Presently, however, he lies down and falls quickly asleep, waking in the morning without the slightest recollection of the unpleasant event.

Such paroxysms occur during the early part of the night, one or two hours after the child has been put to bed, just at the time when, according to the previously-quoted experiments of Kohlschütter, sleep is passing from its maximum intensity to a lesser degree of depth. This, then, is the time when the controlling power of the sensory apparatus over other portions of the nervous system has already reached its minimum. The spinal centres and those intracranial ganglia which do not share in the full measure of this repose are therefore in a condition of relative exaltation. Disturbances of internal organs consequently produce inordinate excitement of these waking portions of the nervous apparatus. The morbid quality of this excitement is attested both by the history of the patient and by the fact that it does not arouse the whole brain. The distribution of motion in the cerebrum is impeded, so that certain portions of the organ remain asleep while other regions are thrown into a state of tumultuous uproar. Disconnection of these different organs of the nervous system, by withdrawing particular portions from the inhibitory influence of the remaining parts, gives opportunity for violent explosions of nervous force analogous to the convulsions of a headless fowl or to the course of an epileptic paroxysm. Now, in sleep, in somnambulism, in hypnotism, in delirium, in certain stages of intoxication with alcohol or with narcotics, such ungearing of the different nervous ganglia is more or less completely effected. In narcotic and anæsthetic sleep besides the disassociation of ganglia there is paresis of the nervous molecules; hence the phenomena soon merge into insensibility and coma. But in natural sleep, in somnambulism, or in hypnotism there is no toxic paresis; hence the dissociated portions of the brain and nervous system, if aroused, are in a physiological condition to dispense great stores of force. Hence the vividness of certain dreams and the astonishing vigor of particular nervous functions in somnambulism and hypnotism.

Somnambulism.

The phenomena of night-terrors constitute merely a special form of somnambulism, a condition of which the mechanism, so far as the present state of cerebral physiology will permit, has been already suggested. The affection should not be ranked by itself as a particular variety of disease, but should rather be considered a violent perturbation in the cerebral organs of a neurotic subject during the period of sleep. In ordinary dreaming the muscular apparatus usually remains passive, even though the dream be a nightmare or an incubus of the most terrifying character. But when the desires and the emotions are powerfully addressed by the dream, a certain amount of muscular movement may ensue, as when a dog barks in his sleep, or when a child laughs upon his nurse's lap, or when a weary soldier marches on though overpowered by sleep. One night, when parched with thirst during a voyage at sea,⁹ I saw in sleep a sparkling fountain, by the side of which appeared a young girl holding out a cup of cold water. Awakened by the excitement, I found myself sitting up in bed with my right arm extended in the direction of the tantalizing vision: my dream had merged itself in action. In like manner, the victim of night-terrors not only moves his body, but gives vocal expression of his feeling of apprehension and alarm. In like manner, projecting his dream into action, a sleep-walker may arise from his bed; he climbs out of the window and descends to the ground, executing all manner of complicated and dangerous movements; he walks long distances, and finally returns to his couch without waking. In the morning no recollection of the event of the night survives. Again, the movement may be less locomotive in its character. The intellectual faculties chiefly may be aroused, and then only such movements are executed as may be necessary to give expression to the mental process.

⁹ A proclivity to dreaming has often been remarked among the consequences of partial starvation.

Such, then, are the principal characteristics of somnambulism, a state in which dreams are supplemented by more or less complete and appropriate action, ordinarily without subsequent recollection of either dream or action.

The somnambulistic dream generally occurs during or soon after the period of deepest sleep, when the influences of the external world are largely suppressed. Released from the control of its sensory portion, the remainder of the brain awakes and becomes aroused to a condition of functional exaltation. No longer distracted by the recollection of the special senses, the attention is concentrated upon the hallucinations which constitute the dream. In the simpler forms of noctambulism only the automatic locomotive apparatus is awakened, and the sleeper moves in accordance with the impressions derived from habit aided by exaltation of the muscular sense. But in some of the more complicated cases a certain amount of special sensibility seems to exist. The patient is capable of exercising just that amount of sensation which is necessary to accomplish his purpose, though blind and deaf and insensible to every other impression. The more complete the waking of the organs of sense, the closer the resemblance to the condition of ecstasy in which cerebral exaltation is the prominent feature. Accordingly, it sometimes happens that the somnambulist can recall the events of his paroxysm.¹⁰ In such cases the power of recollection is due to the same conditions that control the recollection of our ordinary dreams. We remember very imperfectly, if at all, the dreams that occur during sound sleep, but the visions with which sleep sometimes commences (hypnagogic hallucinations) and those that occupy the period of morning slumber are very easily reviewed in memory, because they are associated with impressions directly derived from the partially-waking organs of sense. Such dreams are therefore chiefly recalled through their association with the train of our waking thoughts. But the dreams of somnambulism and the dreams of night-terrors, and all other visions during profound sleep, are as completely as possible cut off from all connection with the mental activities which arise directly from the action of the senses. By reason of such isolation the ordinary association of ideas affords no help to the memory, and the dream remains in the limbo of oblivion.

¹⁰ A. Bertrand, Traité du Somnambulisme, p. 80.

Alfred Maury expresses the opinion¹¹ that the principal cause of forgetfulness of the events of somnambulism consists in the exhaustion of the cerebral elements through the intensity of the excitement to which they are subjected during the paroxysm. Doubtless this in certain cases may contribute to the loss of memory, but it should be remembered that the excitement may be relative rather than absolute. Certain elements wake while others are asleep, and the waking cells may be aroused to a degree far in excess of what is usual during the sleep of the brain without attaining to the level of their diurnal activity. The mind, undisturbed by external impressions, gives its attention to the activity of these waking organs, and a dream with all its consequences, somnambulic or otherwise, is the result. In other words, the plane of consciousness, so to speak, is lowered during sleep to the level of these molecular vibrations. But when the whole brain is again awakened after sleep the residual vibrations of those elements which yielded the physical basis of the dream, and which, had they occurred during the waking state, might have persisted with energy sufficient to furnish a groundwork for recollection of the ideas which they had originally suggested, are no longer sufficiently energetic to be felt in consciousness. Recollection of mental states thus generated must necessarily be impossible so long as the mind is dependent upon the brain as its register of events. Sometimes, however, the somnambulist, who while awake had forgotten all the incidents of his somnambulic experience, can remember in a subsequent paroxysm all that occurred during the preceding attack. Facts of this kind have been observed in the waking life of certain hysterical persons,¹² but the apparent interruptions of their personality attach to the waking state, while in ordinary somnambulism it is only in sleep that the alternations of memory and forgetfulness occur. A similar recollection of previous visions is sometimes experienced in dreams, showing the close relation that subsists between the dreams of sleep and of somnambulism. The bond of association between these events thus isolated in time must be sought in a renewal of like conditions of the brain during the successive periods of somnambulic exaltation. We must suppose that the molecules which were in a state of functional excitement during the first paroxysm are again aroused in like manner after a period of waking quiescence. If, during sleep, their movements, though of an exalted character, have only just sufficed to arouse consciousness in the form of a dream, it would not be probable that during the phase of comparative inactivity which supervenes when the whole brain is awake their residual motion could disturb the sphere of consciousness. Hence the time occupied by their somnambulic vigor must remain a blank in memory during the waking state. But when the original state of exaltation has been reproduced by a second period of disorder, if the same molecular movements be in any way renewed, the conditions of memory are fulfilled; consciousness is once more aroused as before, and the patient remembers the dream or the events of the previous attack.