202 CLINICAL APPLIED ANATOMY. 



front teeth. There is a reaction of degeneration in the paralysed 

 muscles in the complete type of paralysis, since they are severed 

 from the facial nucleus. 



At the base of the brain the facial emerges close to the 

 auditory nerve, the latter lying external and the portio 

 intermedia between the two. The nerves appear at the lower 

 border of the pons, immediately above the restiform body, and 

 they pass together into the internal auditory meatus. As they 

 pass towards the meatus the facial lies in a groove on the upper 

 and fore part of the auditory trunk, whilst the pars intermedia 

 and the auditory artery lie between them. The close relation 

 of the nerves explains why gummatous and other new forma- 

 tions involving the dura at the base of the skull are so 

 likely to cause both facial and auditory paralysis. Lesions of 

 the facial trunk in this situation should not involve the fibres 

 which subserve taste, being above the level at which these 

 are generally supposed to pass into the great superficial 

 petrosal nerve on their way to the fifth trunk. 



A few cases of facial nerve paralysis are due to inflammation 

 or caries of the tympanum. The aqueduct of Fallopius 

 which transmits the facial trunk lies in the inner wall of 

 the tympanum, behind the foramen ovale, forming the inner 

 boundary of the isthmus of communication between the attic 

 and the antrum. The wall of the aqueduct is occasionally 

 incomplete, which accounts for the readiness with which the 

 nerve suffers in some cases of otitis, moreover the apertures which 

 transmit the chorda tympani, the nerve to the stapedius and the 

 stylomastoid artery may allow invasion of the aqueduct from the 

 middle ear. The nerve is liable to damage in this position from 

 operations on the mastoid, and the external semicircular canal, 

 which lies immediately behind and above the Fallopian aqueduct, 

 may be injured at the same time. Fractures of the base of the 

 skull may cause facial paralysis when they traverse the petrous 

 bone ; in fact the facial nerve is more often paralysed in fracture 

 of the base than any other cranial nerve. Impairment of taste 

 on the front part of the tongue indicates a lesion of the facial 



