NUCLEI OF CRANIAL NERVES 



825 



geniculate body is thought to be wholly a crossed one. Further, some fibres are described as 

 terminating in the superior quadrigeminate body of both the same and the opposite side. These, 

 forming the stratum lemnisci of this body, are especially suggestive of associating auditory 

 impulses with 63^6 movements. 



All the fibres arising in the superior olivary nucleus do not enter the corpus trapezoideum 

 and the lateral lemniscus. A small bundle, the peduncle of the superior olive, arises in each 

 nucleus and courses dorsally to the region of the nucleus of the abducens. Here certain of its 

 fibres terminate about the cells of the nucleus of the abducens, while others enter the medial 

 longitudinal fasciculus and pass to the nuclei of the trochlear and oculomotor nerves, thus 

 further establishing connections between auditory impulses and eye movements. 



The facial nerve is commonly described as consisting of the "facial proper" and its so-called 

 sensory root or pars intermedia, the two together being designated as the seventh cranial nerve. 

 However, the pars intermedia neither serves as a sensory root for the facial nor is it purely 

 sensory. Many years ago Sapolini considered it a separate nerve and later it was called the 

 intermediate nerve of Wrisberg. More recent investigations of its development and distribution, 

 especially those of Streeter and Sheldon, further indicate that it merits a separate description 



Fig. 651. — Transverse Section through Inferior Border of Pons and Portion of 

 CK'ERLYiNG Cerebellum. (From Villiger.) 



Nucleus of roof 

 Nucleus globosus 



Nucleus emboliformis 



Dentate nucleus 



Brachium 

 conjunctivum 



Superior nucleus 

 of vestibular 

 (Bechterew) 

 Lateral nucleus of 

 vestibular 

 (DeitersM 

 Spinal tract of 

 trigeminus 



^^Restiform body 



Brachium pontis 



Nucleus of facial 



Superior olive 



Thalamo-olivaris tract 



Vestibular nerve 



Pons 



and a separate name, and, indicative of its distribution, it is here described as the glosso-palatine 

 nerve. The facial, the glosso-palatine and the abducens all have their nuclei within the level 

 of the pons though the roots of all appear from under its inferior border. 



The facial [nervus facialis] has its nucleus (of origin) in the ventro-lateral region of the 

 reticular formation, superior to and in line with the nucleus ambiguus. The axones given off 

 by the cell-bodies of the nucleus collect into a bundle which, instead of passing ventrally and 

 directly to the exterior of the pons, courses at first dorso-mesially to the mesial side of the nucleus 

 of the abducens (ascending root of the facial) ; then it turns and courses superiorly for a few milli- 

 metres, parallel with the nucleus of the abducens and immediately beneath the floor of the fourth 

 ventricle {genu internum); then it turns abruptly and pursues a ventro-lateral and inferior 

 direction to its point of exit at the inferior border of the pons, just lateral to the olive and 

 mesial to the entrance of the vestibular nerve. Its exit usually involves a few pons fibres. 

 In transverse sections through the middle of the nucleus of the abducens the genu of the facial 

 appears as a compact transversely cut bundle at the dorso-medial side of this nucleus. 



The nucleus of the facial is described as consisting of two chief groups of cells, an anterior 

 and a posterior group which give rise respectively to the axones of the superior and inferior 

 branches of the facial nerve. It receives cortical impulses from the lower portion of the anterior 

 central gyrus of the cerebral cortex, from the root fibres of the trigeminus of the same side, which 

 serves as its sensory root, and (chiefly) fibres arising from the nuclei of termination of the 

 trigeminus. The nuclei of termination of the optic and the auditory nerves of the same and 

 opposite sides give rise to fibres which terminate about its cells. The fibres from the cerebral 

 cortex descend in the pyramidal fasciculi and cross by way of the raphe and arcuate fibres to 

 terminate in the nucleus of the opposite side. The anterior group of the cells of the facial 

 nucleus must receive cortical fibres not only from the cerebral hemisphere of the opposite but 

 also from that of the same side, evidenced by the fact that the superior branch of the nerve is 

 but little affected in facial paralysis resulting from a lesion in the cerebral cortex of one side. 

 A lesion destroying the root of the nerve or its nucleus of origin will of course give total facial 

 paralysis in the side of the lesion. 



