THE TRIGEMINAL NERVE 77 



In Fig. 41 the areas of distribution of the three great 

 divisions of the trigeminal have been indicated schematically. 

 It will be observed that the trigeminal is responsible for the 

 supply of the skin of the whole of the face with the exception 

 of a small area over the angle of the mandible, which is 

 supplied by the great auricular nerve (C. 2 -and 3). In 

 addition, it supplies the skin of the anterior part of the head, 

 the upper part of the external ear and the skin lining the 

 external acoustic meatus. 



The sensory branches of the fifth also supply a wide area of 

 mucous membrane, including the conjunctival sacs, the nose, 

 cheeks, lips, gums, palate, floor of the mouth and anterior 

 two-thirds of the tongue. 



PARALYSIS OF THE SENSORY PART OF THE 

 TRIGEMINAL NERVE 



Lesions of the sensory nucleus are usually associated with 

 the condition of alternate hemi-anaesthesia (p. 62). 



Complete unilateral anaesthesia in the region supplied by 

 the fifth nerve, unaccompanied by anaesthesia in other 

 regions, indicates a lesion of the large sensory root or the 

 semilunar (Gasserian) ganglion, usually caused by an intra- 

 cranial tumour in the cerebello-pontine angle. The cutaneous 

 anaesthesia reaches exactly to the median plane, as the two 

 trigeminal nerves do not overlap one another. As a result, 

 when the patient drinks from a vessel, it feels to him as if it 

 were broken, since the part in contact with the anaesthetic 

 halves of the lips cannot be appreciated. 



Trigeminal paralysis also produces marked effects on the 

 areas of mucous membrane which are rendered anaesthetic. 

 The mucous membranes of the nose, cheeks and tongue 

 become dry, and atrophic changes may occur. Ulceration of 

 the cornea is not uncommon. 



Trigeminal Neuralgia. Conditions which give rise to pain 

 in the areas supplied by the trigeminal may be immedi- 

 ately or only remotely connected with the nerve itself. 



