178 THE HEAD AND NECK 



stylo-mastoid foramen and turns forwards, laterally and slightly 

 downwards. It at once enters the deep surface of the parotid 

 gland and gradually becomes more superficial. At the level 

 of the lobule of the ear, one finger's breadth below the zygomatic 

 arch, the facial nerve may be rolled against the neck of the 

 mandible, although it is here embedded in the parotid gland. 



Temporary facial paralysis may result from bruising of the 

 nerve by the application of forceps at birth, as the stylo-mastoid 

 foramen in the infant is placed on the infero-lateral aspect of 

 the skull and the mastoid process is not yet developed (p. 210). 



Immediately after it leaves the skull the facial nerve gives 

 off its posterior auricular and digastric branches ; the latter 

 supplies the stylo-hyoid in addition to the posterior belly of the 

 digastric. Within the parotid gland the nerve at once breaks 

 up into its main branches, which radiate away from one another 

 as they leave the gland (Fig. 52). They all terminate by sup- 

 plying muscles of facial expression. 



Incisions ascending from the neck behind the angle of the 

 mandible must be only skin-deep at the level of the lobule, other- 

 wise the main trunk of the facial nerve may be divided. 

 Similarly, incisions on the face should be made parallel to its 

 branches of distribution ; they should therefore radiate from 

 the middle of the anterior border of the lobule. In the child, 

 up to the age of two, the nerve may be divided by incisions 

 beneath the auricle, such as that employed in mastoiditis (p. 2 15). 



Division of the cervical branch of the facial nerve is referred 

 to on p. 108, 



Facio-Hypoglossal Anastomosis is performed for facial 

 paralysis produced by disease or injury of the nerve in its course 

 through the facial canal (aqueduct of Fallopius). 



The incision, which begins high up on the mastoid process 

 and runs downwards to the greater cornu of the hyoid bone, is 

 planned so as to give good exposure of both nerves. 



The deep fascia is incised immediately in front of the mastoid 

 process and the parotid gland is pushed forwards. An aneurism 

 needle is inserted deeply in the gap thus made, and hooked up 

 towards the surface. The facial nerve, which is caught by the 

 needle on a level with the middle point of the lobule of the ear, 

 is traced to the stylo-mastoid foramen and there divided. In 

 order to get a sufficiently long segment of the nerve the bone 

 may require to be chipped away, and the nerve may be traced 

 for a short distance into the parotid gland. 



