For convenience, the clinical manifestations of cerebral injury are usually described under the terms “concussion,” “cerebral irritation,” and “compression,” but no precise pathological significance attaches to these terms, they are essentially clinical. As the conditions so described do not occur as independent entities and may overlap or merge into one another their differentiation is more or less arbitrary, and cases are frequently met with that do not run the course characteristic of any of these groups.
Concussion of the Brain or Cerebral Shock.—The symptoms associated with concussion of the brain are to all intents and purposes those of surgical shock (Volume I., p. 250), the activity of the vital centres being disturbed by violence acting directly upon the brain tissue instead of by impulses transmitted to it by way of the afferent nerves. Various theories have been put forward to account for the depression of the vital functions in concussion. According to Duret, with whose views we agree, the wave of cerebro-spinal fluid set in motion by the impact of the blow on the skull, passes, both in the ventricles and in the sub-arachnoid space, towards the base, where it impinges upon the pons and medulla, stimulating the restiform bodies and so inducing a fall in the blood pressure and a profound anæmia of the brain. The disturbance of the cerebro-spinal fluid may at the same time produce the microscopic lesions in the brain tissues described on p. 341.
The symptoms of shock may be the only evidence of injury, or they may be superadded to those of fracture of the skull, or laceration of the brain.
The clinical features vary according to the severity of the violence. In the slightest cases the patient does not lose consciousness, but merely feels giddy, faint, and dazed for a few seconds. His mind is confused, but he rapidly recovers, and, perhaps after vomiting, feels quite well again, save for a slight shakiness in his limbs.
In more severe cases, immediately on receiving the blow the patient falls to the ground unconscious. Sometimes he suffers from a general tetanic seizure associated with arrest of respiration, which is usually of short duration and is frequently overlooked, but may prove fatal. The pulse is slow, small, and feeble, and is sometimes irregular in force and frequency. The respirations are short, shallow, slow, and frequently sighing in character. The temperature falls to 97° F., or even lower. The skin is cold and pallid and covered with clammy sweat, and the features are pinched and pale.
In uncomplicated cases the pupils are usually equal, moderately dilated, and react sluggishly to light. The patient can be partially roused by shouting or by other forms of external stimulation, but he soon subsides again into a lethargic condition. Although voluntary movement and the deep reflexes are abolished, there is no true muscular paralysis.
After a period, varying from a few minutes to several hours, he rallies, the first evidence often being vomiting, which is usually repeated. Sometimes reaction is ushered in by a mild epileptiform seizure. He then turns on his side, the face becomes flushed, and gradually the symptoms pass off and consciousness returns. The temperature rises to 99° or 100° F., and in some cases remains elevated for a few days. In most cases it falls again to 97° or 97.5°, and remains persistently subnormal for one or two weeks. During reaction the pulse becomes quick and bounding, but after a few hours it again becomes slow, and usually remains abnormally slow (40 to 60) for ten or fourteen days. There is sometimes a tendency to constipation, and for the bladder to become distended, although he has no difficulty in passing water. Very commonly the patient complains of pain in the head for some days after the return of consciousness. Children often sleep a great deal during the first few days, but sometimes they are very fretful.
In cases complicated by gross brain lesions the symptoms of concussion may imperceptibly merge into those of compression or there may be a “lucid interval” of some hours duration.
After-Effects of Concussion.—The majority of patients recover completely. A number complain for a time of headache, languor, muscular weakness, and incapacity for sustained effort—traumatic neurasthenia. Sometimes there is a condition of mental instability, the patient is easily excited, and is unduly affected by alcohol or other stimulants. Occasionally there is permanent mental impairment. It is not uncommon to find that the patient has entirely forgotten the circumstances of the injury and of the events which immediately preceded it. In some instances the memory is permanently impaired. On the other hand, it has occurred that a patient, after concussion, has recovered his memory of a foreign language long since forgotten.
As it is never possible to determine the precise extent of the damage to the brain, the immediate prognosis, even in the mildest cases of concussion, should always be guarded. If the patient has been actually unconscious, the condition should be looked upon as a serious one, and treated accordingly.