THE FACIAL NERVE 87 



dition may be accompanied by some degree of alternate 

 hemi-anaesthesia (p. 62). 



Cases of nuclear lesions of the facial have been recorded in 

 which the orbicularis oculi and the orbicularis oris have 

 escaped paralysis, and they have led to the suggestion that 

 these muscles are innervated from the nuclei of the third and 

 twelfth nerves respectively. There is, however, no anatomical 

 evidence in support of this view, which is founded entirely 

 on clinical evidence. 



In lesions of the facial 7ierve situated between the surface of 

 the pans and the geniculate ganglion, the acoustic nerve, which 

 is so closely related to the facial in this part of its course, is 

 usually involved (Fig. 51). On this account the paralysis of 

 the stapedius cannot be determined. According to Ramsay 

 Hunt, the sense of taste is lost over the anterior two-thirds of 

 the tongue on the afTected side, since the lesion is almost 

 certain to involve the nervus intermedius. All the facial 

 muscles on the affected side are paralysed and, as the lesion 

 affects the lower neurone, the electrical reactions become 

 altered and the muscles atrophy. 



Lesions affecting the facial nerve between the geniculate gan- 

 glion and the origin of the chorda tympani usually result from 

 otitis media. The acoustic nerve is not afTected and the 

 condition of hyperacousis, due to paralysis of the stapedius 

 muscle, may sometimes be determined. The sense of taste is 

 lost over the anterior two-thirds of the tongue on the affected 

 side. The condition of the facial muscles is exactly the same 

 as in the lesion described in the preceding paragraph. 



In extra-cranial lesions (p. 82), only muscular paralysis is 

 present. The special senses are unaltered. 



The Acoustic or Eighth Cerebral Nerve is made up of 

 two parts, termed (a) the COCHLEAR and (b) the VESTIBULAR 

 nerve. The two meet at the bottom of the internal acoustic 

 meatus and run together, within a common sheath, to the 

 surface of the pons, where they separate, 



