The cause of involvement of each of the eye motors is usually quite common until a quarter are idiopathic and more than half recover spontaneously.

The most frequent causes are trauma, especially in the fourth pair and diabetic or hypertensive microangiopathy; there are others less frequent but more serious such as aneurysms.

Other rarer may be meningeal or nearby infections such as sphenoid sinuses, sarcoidosis. 

 Third Cranial Nerve

 It can be divided into internal ophthalmoplegia (กล้ามเนื้อตาอ่อนแรง which is the term in Thai) if the involvement is exclusively pupillary, external if it is exclusive of ocular motility and complete if it affects both.

 Etiology 20% is idiopathic. It is important to differentiate ischemic from aneurysmal causes, especially if they are accompanied by pain.

It is an ominous prognostic data, for example, in alterations in the level of consciousness, since it implies temporal uncus herniation against the tentatory, regardless of the etiology of intracranial hypertension. Sometimes the paresis of the third pair is contralateral to the herniation because what happens is a displacement of the trunk towards the contralateral edge of the tentatory

 Clinical

 If the lesion occurs in the territory of the trunk, it can have other accompanying symptoms and gives rise to certain syndromes clinical.

 Complete paralysis causes ptosis, difficulty in looking up and down, loss of accommodation, dilated pupil that does not react to light either directly or by consensus or near vision. There may be no diplopia if the ptosis is marked, and if it exists, it is usually oblique due to the involvement of different muscles.

 Incomplete lesions, present variations of symptoms; in general, the ischemic, respect the pupil, nuclear, and nerve trunk lesions in their mesencephalic path are usually complete. The isolated pupillary involvement is exceptional.

 Nuclear injuries can be of very particular phenomenology. Due to the contralateral innervation of the upper rectum, there may be a weakness in the contralateral elevation. The lesion of the central caudal nucleus can generate bilateral ptosis with or without the involvement of the ipsilateral oculomotor III and also vice versa palpebral respect with impaired motility.

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