IV pair, the nerve block (n. Trochlearis), starts from the nuclei located in front of the aqueduct (sylvieva), at the level of the lower tubercles of the quadruple. Leaves on the surface of the brain in the region of the upper cerebral sail, performs here a complete cross-over of the fibers, rounds the stalk of the brain and through the upper orbital fissure enters the orbit. Innervates the upper oblique muscle of the eye. When the lesion of the nerve block is marked by diplopia - the doubling of objects when looking down, a small strabismus.
Fig. 2. Topography of the trigeminal nerve:
1 - the mandibular nerve;
2 - node of the trigeminal nerve;
3 - the orbital nerve;
4 - maxillary nerve.
V pair, trigeminal nerve (n. Trigeminus), leaves two roots on the surface of the brain between the bridge and the middle leg of the cerebellum . A large spine, sensitive, consists of axons of the trigeminal nerve node, located on the front surface of the pyramid of the temporal bone. Entering the brain, the fibers that conduct tactile sensitivity end in the core lying in the tire of the bridge (variolyev), and the fibers that conduct pain and temperature sensitivity are in the nucleus of the spinal tract. From the cells of the sensitive nuclei, the second neuron begins, going in the loop of the trigeminal nerve to the visual tubercle. Further, the sensitive path of the trigeminal nerve goes to the cortex of the posterior central gyrus, where it ends. Dendrites of cells of the node of the trigeminal nerve form three peripheral branches: the orbital, maxillary and mandibular nerves, innervating the skin of the forehead and face, teeth, mucous membrane of the nasal cavity and mouth (Fig. 2). A small spine, motor, is formed by fibers emerging from the nuclei lying in the tire of the bridge. Exiting the bridge, it is located on top and inside of the sensitive pathway, it forms part of the mandibular nerve and innervates all the chewing muscles.
When the sensitive part of the trigeminal nerve is affected, brief attacks of very sharp pains (neuralgic pains) occur in the corresponding areas of the face, accompanied by reddening of the face, lacrimation (see Neuralgia). Damage to the motor part of the trigeminal nerve makes it impossible to shift the lower jaw to the healthy side due to the weakening of the masticatory and temporal muscles.
The sixth pair, the abducent nerve (n. Abducens), consists of fibers that extend from the cells of the nucleus of this nerve, which lies in the bridge cover. Hence, the fibers of the outgoing nerve pass through the thickness of the bridge and extend to the base of the brain between the pyramid of the medulla oblongata and the bridge. Then they penetrate into the orbit and innervate the outer rectus muscle of the eye. With defeat of the outflowing nerve, the outward movement of the eyeball is violated, which leads to a converging strabismus, there may be double vision in the eyes.