A rubber drainage-tube may be inserted in the manner depicted in the same [figure]. Except at the point of emergence of the tube, the dura mater is sewn up (with fine interrupted catgut sutures).
(B) Localized subdural hæmorrhage (subdural hæmatocele).
We are greatly indebted to Bowen[31] for our knowledge of subdural hæmatomata. That subdural hæmorrhage might take the form of a localized collection was a recognized fact, but the condition was but little understood, the typical clinical symptoms were not recognized, and surgeons hesitated to adopt surgical remedies. All these facts impeded advance in both diagnosis and treatment. Subdural hæmatoceles, even at this date, are often regarded as rarities, but, in the light of present knowledge, it would appear that wider recognition of the hæmorrhage in its clinical aspect will show that such ideas are erroneous.
In the preceding section it was shown that subdural extravasation resulting from sinus-injury tends to become diffused throughout the subdural space. With respect to localized hæmorrhages our data are by no means complete, but all available evidence tends to show that subdural hæmatoceles are dependent on laceration of the pia-arachnoid vessels—a condition practically synonymous with superficial laceration and contusion of the cortex. The blood, derived from small cerebral veins and minute cerebral arteries, exercises primarily but slight pressure effect. Its force is expended on compressing and emptying the subjacent and surrounding cerebral vessels, producing, in other words, a condition of local cerebral anæmia. This pressure is insufficient to lead to the development of general compression, but suffices to produce certain rather indefinite symptoms. We have, therefore, before us a very different picture to that depicted in cases of middle meningeal hæmorrhage. In such extra-dural hæmorrhages some definite period of time must elapse before the dura mater is sufficiently stripped from the bone to allow of the formation of a clot of size sufficing to exercise both local and general compression effects. Pressure effects then become very manifest.
On the other hand, in localized subdural extravasations there is an immediate effect, for the brain is contused or lacerated. On recovering from the immediate effects of the injury—concussion of a greater or lesser degree of intensity—the patient does not regain complete mental and bodily convalescence. He suffers from symptoms suggestive of brain irritation—headaches, photophobia, mental irritability, insomnia, loss of appetite, the pulse accelerated, and the temperature slightly raised. Later on, more definite symptoms arise, but, intervening between the day of the accident and the time at which these more definite localizing symptoms develop, there is an unmistakable latent period—a period to be sharply differentiated from the previously mentioned lucid interval (see [p. 139]).
This ‘latent’ period lasts for a variable period of time—seldom less than a week or more than three months. At the end of that time the picture changes, and the patient evidences symptoms obviously referable to local brain compression. From a clinical point of view it is fortunate that subdural hæmatoceles tend to involve the fronto-parietal region with the consequent development of motor symptoms, especially paresis or paralysis of the contra-lateral side. Hence the name sometimes applied to the condition—traumatic late apoplexy. The speech areas are implicated if the injury be situated on the left side. Paralysis limited to the lower extremity is exceedingly suggestive, such a palsy occurring only with the greatest rarity in extra-dural hæmorrhages (from the middle meningeal artery).
If the pressure be unrelieved by operation the patient passes from the excitatory to the paralytic stage of brain compression, gradually falling into a condition of coma, the pulse increasing in frequency and the respiration becoming more and more embarrassed.
In the study of this condition, the following are the points to which special attention should be paid:—
1. The comparative want of severity with respect to the injury received.
2. The absence of any ‘lucid’ interval, such as is present, for example, in middle meningeal hæmorrhage.