The anterior branch overlies the pre-Rolandic motor area, whilst the posterior division is related to the temporo-sphenoidal and lower parietal regions--‘silent’ areas of the brain.
Middle meningeal hæmorrhage occurs most commonly in connexion with a fissured or comminuted fracture of the temporal region--the result of direct violence. A fracture, however, is not necessarily present, the hæmorrhage may take place on the side opposite to that at which the injury was received (laceration by contre-coup), and both vessels may be involved. Crisp English narrates three cases in which bilateral extravasation resulted. These more rare examples of middle meningeal hæmorrhage are more or less confined to patients suffering from marked arterial degeneration.
Middle meningeal hæmorrhage, uncomplicated by brain injury, is of infrequent occurrence, the associated injuries to bone and brain confusing the diagnosis. Moreover, the special pressure effects are dependent not only on the absence of serious brain lesion, but also on the non-existence of a safety-valve, such, for instance, as is afforded by a comminuted fracture of the bones entering into the formation of the temporal fossa, or of the roof of the middle and external ears. In the former case, blood will force its way into the temporal region, there forming a temporal hæmatoma--one that may pulsate--whilst, in the latter case, the blood escapes freely from the external auditory meatus. It should be noted, however, that pressure applied to the temporal hæmatoma may lead to the development of irritative or paralytic symptoms confined to the muscles of the opposite side of the body, whilst the restriction of aural bleeding, by means of plugs inserted into the ear, will lead to the early development of compression symptoms.
The amount of blood extravasated varies--according to the calibre of the vessel involved--from a drachm to several ounces. The largest coagulum that has come under my observation was 4¹⁄₂ inches in the long diameter and 1 inch in thickness. Krönlein narrates a case in which the clot weighed 9 ounces.
[Illustration: FIG. 50A. THE INNER ASPECT OF THE SKULL.]
[Illustration: FIG. 50B. THE INNER ASPECT OF THE SKULL SEEN ON TRANSILLUMINATION.]