222 THE HEAD AND NECK 



the onset of the disease. If it occurs after the closure of the 

 sagittal suture, the frontal and occipital regions are both affected, 

 but if the lambdoidal suture is also closed the bulging is confined 

 to the region of the forehead. 



Fracture of the Skull. In relation to cranial injuries 

 haemorrhage alone is of very little diagnostic value, but the 

 accompanying or subsequent discharge of cerebro-spinal or 

 subdural fluid is positive evidence of a fracture of the skull. 



Anterior Fossa. Fracture of the lamina cribrosa of the 

 ethmoid bone is usually accompanied by laceration of the mucous 

 membrane of the roof of the nose. This injury, therefore, 

 gives rise to epistaxis, accompanied or followed by a discharge 

 of cerebro-spinal fluid. In addition, there is frequently some 

 loss of smell due to laceration of the olfactory nerves as they 

 pass upwards from the nose. In fracture of the orbital part 

 (plate) of the frontal bone, sub-conjunctival ecchymosis is a 

 characteristic feature, and the haemorrhage within the orbit 

 may produce exophthalmos. When the frontal air sinus is 

 also injured, blood may pass down the infundibulum to the middle 

 meatus and be discharged from the nose. In these cases the 

 haemorrhage arises from the torn branches of the anterior 

 division of the middle meningeal artery or, more rarely, from 

 the ophthalmic vessels. Some of the blood may be swallowed, 

 giving rise subsequently to hsematemesis. 



Middle Fossa. This is the commonest site of fracture of the 

 skull, partly because of its position but also because it is weak- 

 ened by numerous canals and foramina. The tegmen tympani 

 (p. 212) is usually fractured, and the tympanic membrane is 

 torn. Blood and cerebro-spinal fluid are discharged from the 

 external acoustic meatus, and the facial and auditory (seventh 

 and eighth cerebral) nerves may be involved (p. 213). Some- 

 times the walls of the cavernous sinus are lacerated, and some 

 of the nerves (third, fourth, and sixth cerebral) which lie in its 

 lateral wall are paralysed (p. 225). 



Posterior Fossa. In this case the haemorrhage does not 

 become evident at once, unless the basilar part of the occipital 

 bone is fractured, with laceration of the mucous membrane of 

 the pharyngeal roof. Otherwise the blood is situated deeply 

 at the back of the neck, and the discoloration does not become 

 apparent for some days. It reaches the surface in the posterior 

 triangle or in the neighbourhood of the mastoid process. 



