A similar mechanism is also accurate for diabetes. As the somatic fibers are located in the inner part of the nerve, these fibres are affected more in the setting of ischemia. Ischemic stroke affects the vasoneurium, which starts to supply the nerve from outside to inside. Ischemic stroke selectively affects somatic fibers over parasympathetic fibers, while traumatic stroke affects both types more equally. The "surgical" type of oculomotor nerve palsy is caused by external structures compressing on the nerve or trauma, which affects the entire nerve, thus affecting pupillary reflex. Thus pathologies affecting the nerve's core without affecting the superficial part of the nerve (thus sparing the pupillary reflex) are known as "medical" oculomotor nerve palsy. The nerve's core contains the main trunk of the oculomotor nerve, supplied by vasa vasorum. The parasympathetic aspect of the nerve (which constricts pupils and thicken the lens) is located on the nerve surface, supplied by pial blood vessels. Post-operatively as a complication of neurosurgeryĪs the pair of oculomotor nerves arises from different subnuclei in the midbrain, courses through different structures in the brain and branches into superior and inferior divisions after exiting the cavernous sinuses, any lesions along its path will produce different pathological features of the third nerve palsy.Autoimmune disorders such as myasthenia gravis.Demyelinating disease ( multiple sclerosis).Space occupying lesions or tumours, both malignant and non-malignant.Vascular disorders such as diabetes, heart disease, atherosclerosis and aneurysm, particularly of the posterior communicating artery.It can also occur as a consequence of severe birth trauma. The condition can also result from aplasia or hypoplasia of one or more of the muscles supplied by the oculomotor nerve. There is some evidence of a familial tendency to the condition, particularly to a partial palsy involving the superior division of the nerve with an autosomal recessive inheritance. The origins of the vast majority of congenital oculomotor palsies are idiopathic. Non traumatic pupil-sparing oculomotor nerve palsies are often referred to as a "medical third", with those affecting the pupil being known as a "surgical third". Oculomotor palsy can arise as a result of a number of different conditions. The affected individual will also have a ptosis, or drooping of the eyelid, and mydriasis (pupil dilation). The downward displacement occurs because the superior oblique muscle (innervated by the fourth cranial or trochlear nerve) is unantagonized by the paralyzed superior rectus, inferior rectus and inferior oblique. The outward displacement occurs because the lateral rectus muscle (innervated by the sixth cranial nerve) maintains muscle tone in comparison to the paralyzed medial rectus. The limitations of eye movement resulting from the condition are generally so severe that patients are often unable to maintain normal eye alignment when gazing straight ahead, leading to strabismus and, as a consequence, double vision ( diplopia).Ī complete oculomotor nerve palsy will result in a characteristic displacement outward ( exotropia) and downward (hypotropia). The nerve also supplies the upper eyelid muscle ( levator palpebrae superioris) and is accompanied by parasympathetic fibers innervating the muscles responsible for pupil constriction ( sphincter pupillae). Damage to this nerve will result in an inability to move the eye normally. As the name suggests, the oculomotor nerve supplies the majority of the muscles controlling eye movements (four of the six extraocular muscles, excluding only the lateral rectus and superior oblique). Oculomotor nerve palsy or oculomotor neuropathy is an eye condition resulting from damage to the third cranial nerve or a branch thereof.
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