(b) Beneath the dura, between or into the membranes (subdural);
(c) Into the brain substance proper or the ventricles (subcortical or intraventricular).
The vessels whose injuries are most often under consideration are the meningeal arteries, the sinuses, the small vessels of the membranes, and the internal carotid. The arteries, like the sinus walls, may be ruptured either by substances forced in from without or by sheer laceration. The longitudinal sinus is most liable to injury from without. When this sinus is exposed, it may be dealt with either by suture if the wound be small, or by ligation, or by tamponing with prepared gauze. Hemorrhage from this source is ordinarily not difficult to check. Fatal air embolism has resulted through an opened sinus not properly plugged. The other sinuses are more rarely injured, as by gunshot wound, fracture of the base, etc. The sinuses have also been injured by compression of the skull during parturition. Bleeding from a sinus is usually indistinguishable from that from a meningeal artery, except that the former occurs more slowly.
Injuries to the Middle Meningeal Artery.
—Injuries to the middle meningeal artery naturally occur in the immediate neighborhood of this vessel, which is not infrequently ruptured by contre-coup. The artery runs sometimes in a groove of the bone, sometimes in the dura, and sometimes entirely in the bone. The more it lies within the bone the more likely it is to be ruptured when this part of the skull is fissured. Basal fractures often follow the groove for this artery. The anterior branch is more often injured than the posterior. Extravasations from this source are more common than from all others combined, the amount of blood varying within wide limits. 240 Gm. of blood clot have been known to collect and the dura to be separated down to the base of the skull. I have repeatedly taken away a small teacupful of blood clot in such cases ([Fig. 377] and [Plate XLIII]).
Fig. 377
Compression following hemorrhage from the middle meningeal artery. (Helferich.)
Symptoms.
—The symptoms of this hemorrhage are those of compression, while extravasation may be rapid and quickly fatal, delayed for some time, or may take place in two stages, the first but slight and producing no coma. New clots are always dark and disk-shaped, thick in the middle, with a definite margin. As the clots become older they become more adherent and difficult to remove. The symptoms of meningeal hemorrhage consist of an interval of consciousness or lucidity after injury, followed by epileptic or spastic symptoms, alterations in the pupils and pulse, unconsciousness passing into coma, and stertorous respiration. There may or may not be external evidence of head injury. The character of the paralysis (hemiplegia) may indicate that the clot is really upon the side opposite to that of the skull which shows evidence of injury. In this case arterial laceration is the result of contre-coup. According to the rapidity of the symptoms is the extent of the primary lesion. Meningeal hemorrhages involve immediately the motor area, which makes diagnosis all the easier.