59 lived and 29 died. Mortality, 37 per cent. =============================================
For the remote effects of skull fractures, see Chapter VI.
[17] _Brit. Med. Journ._, September 11, 1909, p. 645.
[18] Chassaignac, _Plans de la Tête_, 1842.
[19] _Milligan, Trans. of the Otolog. Soc._, vol. viii, p. 69.
[21] Delfau and Günther narrate a case in which death occurred from pressure on the tenth nerve. (_Deutsche Klinik_, Berlin, 1853.)
[23] _Surgical Experiences in South Africa._
[25] _Johns Hopkins Hospital Bulletin_, April, 1909.
INTRACRANIAL INJURIES: EXTRA- AND SUB-DURAL HÆMORRHAGES. INJURY TO THE BRAIN
Extra-dural hæmorrhage may be arterial or venous in origin. In the former case the blood is derived almost exclusively from the middle meningeal artery. When of venous origin the source is usually to be found in a laceration of one of the sinuses of the brain. When blood is poured out from a torn sinus it tends to occupy, and be widely diffused in, the subdural space. A venous extra-dural extravasation is relatively of infrequent occurrence, and the pressure exercised on the brain seldom suffices to permit of the development of local or general symptoms of cerebral compression. On these grounds extra-dural hæmorrhage may be regarded as almost necessarily of arterial origin, and as derived from a torn middle meningeal artery.
_General considerations._ The middle meningeal artery enters the middle fossa of the skull through the foramen spinosum, and divides, after a short intracranial course, into two main terminal divisions, anterior and posterior. The _anterior_ branch passes forwards towards the anterior inferior angle of the parietal bone, then changing direction and turning upwards and backwards towards the vertex of the skull. The _posterior_ branch passes horizontally backwards--grooving the squamous portion of the temporal bone--towards the posterior inferior angle of the parietal bone.
Throughout their intracranial course the main trunk and its terminal branches are embedded in the outer wall of the dura mater, except in the spheno-parietal region, where the anterior branch of the artery usually occupies a channel in the bone--one between ¹⁄₂ and 1 inch in extent.