Unit 32 FAL

Trochlear Nerve Palsy

Creates intorsion (bring the top of the eye toward the nose) of the eye. When it contracts, it will rotate the eye inward and when you use your trochlear nerve Cranial nerve IV (trochlear nerve) innervates the superior oblique muscle which is responsible for depression (bringing the eye downward) and intorsion of the eye(many times worse with downgaze). Patients will have a hypertropia ( condition of misalignment of the eyes) of one eye relative to the other and may adopt a compensatory head tilt Oculomotor nerve brings the eye upward so since oculomotor nerve isn't affected, the eye is moving upward but instead of the trochlear motor nerve (superior oblique muscle) to move downard it's not

Uncal herniation

occurs when rising intracranial pressure causes portions of the brain to flow from one intracranial compartment to another The uncus can squeeze the oculomotor nerve (a.k.a. CN III), which may affect the parasympathetic input to the eye on the side of the affected nerve, causing the pupil of the affected eye to dilate and fail to constrict in response to light as it should.

Oculomotor nerve palsy

Oculomotor nerve palsy is an eye condition resulting from damage to the third cranial nerve or a branch thereof. As the name suggests, the oculomotor nerve supplies the majority of the muscles controlling eye movements. Thus, damage to this nerve will result in the affected individual being unable to move their eye normally. In addition, the nerve also supplies the upper eyelid muscle (levator palpebrae superioris) and the muscles responsible for pupil constriction (sphincter pupillae) . The limitations of eye movements resulting from the condition are generally so severe that the affected individual is unable to maintain normal alignment of their eyes when looking straight ahead, leading to strabismus ( more commonly known as cross-eyed or wall-eyed, is a vision condition in which a person can not align both eyes simultaneously under normal conditions. One or both of the eyes may turn in, out, up or down.) and, as a consequence, double vision (diplopia complete oculomotor nerve palsy will result in a characteristic down and out position in the affected eye. The eye will be displaced outward "exotropia" and displaced downward "hypotropia"; outward because the lateral rectus (innervated by the sixth cranial nerve) maintains muscle tone in comparison to the paralyzed medial rectus. Lacteral rectus moves to the side The eye will be displaced downward, because the superior oblique (brings the nerve downwarD) (innervated by the fourth cranial or trochlear nerve), is unantagonized (not hostile) by the paralyzed superior rectus , inferior rectus and inferior oblique. The affected individual will also have a ptosis, or drooping of the eyelid, and mydriasis (pupil dilation). Oculomotor nerve brings the eye upward so since trochlear nerve isn't affected, the eye is moving downward (supeiror oblique muscle)

Abducens nerve palsy

Sixth nerve palsy occurs when the sixth cranial nerve is damaged or doesn't work right. It's also known as the abducens nerve. This condition causes problems with eye movement. The sixth cranial nerve sends signals to your lateral rectus muscle. This is a small muscle that attaches to the outer side of your eye. When this muscle contracts, your eye moves away from your nose. Each eye has its own lateral rectus muscle served by its own cranial nerve. Damage at any point along its path can cause the nerve to work poorly or not at all. Because the lateral rectus muscle can no longer contract properly, your eye turns inward toward your nose instead of away laterally Symptons: Hearing loss Facial weakness Decreased facial sensation Droopy eyelid

Cavernous sinus thrombosis

is the formation of a blood clot within the cavernous sinus (a cavity at the base of the brain which drains deoxygenated blood from the brain back to the heart) This is a rare disorder