724 



Paralysis of the Facial Nerves. 



of the lower jaw (figs. 103 and 104). Pricking the loaralj'zed 

 lower lip causes no contraction, but the animal moves its head 

 because it feels the prick. 



In the early stages the tongue frequently hangs out of the 

 mouth, but later assumes its normal position and is capable of 

 normal movements. Owing to paralysis of the cheeks, particles 

 of food remain between the cheeks and the molar teeth and the 

 mucous membrane is sometimes injured. During drinking the 

 head is sometimes held obliquely, the paralyzed side being the 

 lower. 



In cases of bilateral paralysis all the abnormalities are 

 present saving the lateral displacement of the lips. In the horse 

 there is great difficulty of respiration owing to narrowing of 

 both nostrils and if the animal be made to move fast this may 

 amount to sui¥ocation (Moller). In cases of bilateral paralysis 

 of the lips there is often difficulty in the prehension of food; 



horses bury their mouths deeply 

 in food or water and drink in a 

 manner resembling that seen in 

 pigs. When drinking out of shal- 

 low vessels they make lapping 

 movements with the tongue. In 

 cases of severe bilateral paralysis 

 a portion of the water taken in 

 escapes through the nose owing 

 to paralysis of the soft palate. 

 In mild cases the mechanical 

 ^ . , ^^^H^^K/ irritability of the nerve is either 



%^^\^^^^^^Kf^ normal or only slightly altered, 



whereas in severe cases it is soon 

 completely lost. 



Paralysis of the facial nerve 

 arising from disease of the brain 

 or its membranes may be associ- 

 ated with paralysis of other cra- 

 nial nerves and not rarely with hemiplegia of the opposite side 

 (hemiplegia alternans). Dupas observed h^^Deridrosis and hy- 

 perthermia of the same side of the head and the upper part of 

 the neck, and hyperesthesia of the larynx in a case of paralysis 

 caused by a subparotid abscess (see page 720). 



The symptoms rlescribed refer to paralysis due to lesions of the nerve trunk, 

 the root or the nucleus. Nothing definite is known reg^arding paralysis of the 

 facial nerve due to interruption of the central motor path leading to the nucleus 

 of the nerve (supra-nuclear paralysis). Such paralysis may occur in cases of 

 hemiplegia of supra-pontine origin and on the same side. The symptoms that 

 would be expected in such cases would be like those observed in the human subject; 

 persistence and even exaggeration of the reflex irritability, unaltered excitability 

 to mechanical stimuli, the absence of degeneration reaction, and finally, pronounced 

 abnormalities of the lower facial branches. 



Fig. 104. Parah-sis of the left facial 

 nerve in a dog associated with twist- 

 ing of the head owing to simultane- 

 ous internal ear disease. The left eye 

 cannot be closed and the left halves 

 of the lips hang down. 



Course. The cases of paralysis due to injury or cold, which, 

 as a rule, are unilateral and limited to the lower branch, recover 



