Page 388 - Clinical Anatomy

ECA6 7/18/06 6:54 PM Page 373

The cranial nerves 373

trigeminal nerve in having a motor as well as parasympathetic, sympa-
thetic and sensory components. It lies immediately below the foramen
ovale as a close medial relationship to the mandibular nerve.
Its parasympathetic fibres reach the ganglion by the lesser superficial pet-
rosal branch of the glossopharyngeal nerve; these relay in the ganglion and
pass via the auriculotemporal nerve to the parotid gland, and are its secre-
tomotor supply. The sympathetic fibres are derived from the superior cervi-
cal ganglion along the plexus which surrounds the middle meningeal
artery, while the sensory fibres arrive from the auriculotemporal nerve; they
are, respectively, vasoconstrictor and sensory to the parotid gland.
Motor fibres pass through the ganglion from the nerve to the medial
pterygoid (a branch of the mandibular nerve) and supply the tensor
tympani and tensor palati muscles.

The submandibular ganglion

This is suspended from the lower aspect of the lingual nerve. Its parasympa-
thetic supply is derived from the chorda tympani branch of the facial nerve
(see Fig. 263) by which it is conveyed to the lingual nerve; it carries
the secretomotor supply to the submandibular and sublingual salivary
glands.
Sympathetic fibres are transmitted from the superior cervical ganglion
via the plexus on the facial artery and supply vasoconstrictor fibres to these
same two salivary glands. The sensory component is contributed by the
lingual nerve itself, which provides sensory fibres to these salivary glands
and also to the mucous membrane of the floor of the mouth.

The central connections of the trigeminal nerve
The central processes of the trigeminal ganglion cells enter the lateral
aspect of the pons and divide into ascending and descending branches
which terminate in one or other component of the sensory nucleus of V
(Figs 243, 260). This nucleus consists of three parts, each of which appears
to subserve different sensory modalities: a chief sensory nucleus in the
pontine tegmentum concerned with touch; a descending, or spinal, nucleus
subserving pain and temperature; and a mesencephalic nucleus receiving
proprioceptive afferents. The motor root of the trigeminal nerve lies just
medial to the sensory nucleus in the upper part of the pons; its efferents
pass out with the sensory fibres and are distributed by way of the mandibu-
lar division of the nerve.

Clinical features

1◊◊Section of the whole trigeminal nerve results in unilateral anaesthesia of
the face and anterior part of the scalp, the auricle and the mucous mem-
branes of the nose, mouth and anterior two-thirds of the tongue, together
with paralysis and wasting of the muscles of mastication on the affected