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Oculomotor Nerve
02-09-2009
This nerve is mainly motor, but it also contains parasympathetic fibers to the smooth muscles of the eyeball, sympathetic fibers and a small number of sensitive fibers. Conglomerate nuclei III couples located in the central gray matter of the midbrain (at the bottom of the IV ventricle, at the level quadrigemina). Provision is large-(somatic) and small cell (parasympathetic) nucleus. By somatic are paired zadnelateralnye and anteromedial nucleus (nn. dogsolategalis et ventgomedialis), as well as unpaired central nucleus (n. caudatis centgalis) kernel Perlea, lying between the lateral
eye nuclei.
Paired (side) the nucleus innervate external muscles of the eyeball, and the nucleus Perlea innervates the ciliary muscle eye (ie ciliagis). Tsilliarnaya muscle regulates the configuration of the lens, thus the process of accommodation, ie set eyes on near vision, convergence of visual axes when installing the eye at close distances.
In accordance with the scheme Berngeymera, in the lateral nuclei emit 5 parts (front to back):
1) the core muscles for lifting the upper eyelid (m.levatog palpebge supegiog);
2) kernel for the upper rectus muscle (ie gectus supegiog);
3) kernel for the medial rectus muscle (Sh gectus shedialis);
4) core for the lower oblique muscles (S. obliquus infegiog);
5) core for the lower rectus muscle (Sh gectus infegiog).
The first two nuclei are connected with the muscles of his hand, the last three with the muscles of the opposite side, and for the inner line and the lower oblique decussation is incomplete, for the lower rectus muscle complete. Thus, when unilateral nuclear
Mr. lesion paralyzed muscles are 4 one eye on the same side and 1 arm of the other eye. With the defeat of most branches of the oculomotor nerve violations had only one eye muscle.
Small cell (parasympathetic) nucleus (n. oculo shotogius accessogius) is located in front and medial motor nucleus \ glazodvigatelnogo nerve. It consists of several clusters of nerve cells, which are united in front and rear groups. Front group (pair) lies near the midline of the brain near the water. Going on backward, left and right boundaries are combined in unpaired tyazhyadroanegpessi. Rear Unit (Jakubowicz nucleus Edinger-Westphal) adjoins to the anterior segment of the motor nucleus and innervates the inner smooth muscle of the eyeball, shoulder pupil (sphincter of the pupil), providing the reaction of the pupil to light and convergence, ie convergence of visual axes of eyes during the installation of view on close objects.
The nuclei of the oculomotor nerve fibers through the posterior longitudinal bundle (fasc.longitudinalis postegiog) associated with the nuclei of the block and abducens vestibular system and auditory nuclei, nucleus of the facial nerve nuclei and the front of the spinal cord. Because of those neural connections between the nuclei of the oculomotor nerve unit is coordinated activity of facial muscles, eyeball, and also provided Co-reflex reactions of the eyeballs, head and torso on the vestibular, auditory, visual, and possibly other signals.
The fibers of the oculomotor nerve, cross the red nucleus (n. I'ubeg) and appear on the base of the brain immediately before the bridge in the sulcus negvi osuloshotogi at the medial region of the brain stem in the fossa integpedunculagis and go to the base of the brain in sinus cavegnosus. At this stage in the oculomotor nerve is composed of sympathetic fibers of the cavernous nerve plexus surrounding the internal carotid artery in the sinus cavity,
and sensory fibers of the optic nerve (n. orhthalshisus 1 branch of the trigeminal nerve).
Then the nerve through fissuga ogbitalis supegiog enters the cavity of the orbit, and penetrating into the muscular funnel, is divided into two branches: the upper and lower (top to Sh.levatog palpebge supegiog and S. gectus supegiog, nizhnyayadlya three other muscles).
In the initial part of the orbit gives the parasympathetic oculomotor nerve to ciliary root node, which are short ciliary nerves to the ciliary muscle and
sphincter of the pupil. The number of fibers in the oculomotor nerve of about 15000 (for Cgause).
Symptoms defeat
Peripheral neuropathy of the oculomotor nerve are observed in the localization of the lesions in the aqueduct of Sylvius and the top of the optic fissure (tumor, Ha
rusheniya cerebral blood flow, inflammation, etc.). Inflammatory processes affect nerve usually at the base of the brain, between the legs of the brain. Fibers, reaching to the upper eyelid, is located externally, they suffer in the first place. Therefore, meningitis, when the inflammatory process involved and the shell of the oculomotor nerve, in the first place there ptosis.
When the oculomotor nerve is affected in the brain stem, in the pathological process involved, and the pyramidal path that leads to the development of alternating Bebert syndrome: paralysis of the oculomotor nerve on the side of the hearth and hemiplegia on the opposite.
When complete paralysis of the oculomotor nerve is noted: ptosis (eyes closed), exotropia (ekzotropiya).
Eye movements upwards, inwards impossible downwards bounded by.
Pupil expanded, there is no direct reaction of the pupil to light.
Disorders are identified convergence and accommodation.
Incomplete paralysis may be a slight ptosis, ekzotropiya, limitation of movement upwards, inwards, downwards. It may mark the defeat and certain branches of the oculomotor nerve (for example, only ptosis, a small vertical strabismus due to lesions of the upper rectus muscle).
However, please know that the ptosis is not always a sign of the defeat of the oculomotor nerve. Ptosis syndrome occurs in tumors of the century, when reactive edema, with zapadenii eyeball (decrease retrobulbarno cellulose), etc.
Any damage to the nucleus occurs Perlea paresis or paralysis akkomodatsiibolnoy starts badly to see objects up close. Convergence is usually weakened.
The weakening of convergence is often observed in exotropia (explicit or hidden) with any refraction, with myopia without strabismus, and sometimes
normal eye refraction (emmetropia) without strabismus.
Accommodation in such cases is preserved, the internal recti are working in full. Nevertheless meets diagnosis: paralysis (paresis) convergence, rather a violation of the relationship between accommodation and convergence. This state
susceptible of correction by special exercises. In the diagnosis indicated: the lack of convergence.
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