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Defeats of the abductor (VI) nerve (n. Abducens)
Last reviewed: 23.04.2024
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Topical diagnosis of injuries of the abduction (VI-th) nerve is possible on the following three levels:
- I. Level of the nerve nucleus.
- II. Level of the nerve root.
- III. The level (trunk) of the nerve.
I. Damage of the VI nerve at the level of its nucleus in the brainstem
| The defeat of the nucleus of the VI nerve | Paralysis of the eye in the direction of the lesion. |
| Damage to the dorso-lateral section of the parolysis bridge | Ipsilateral paralysis of the gaze, peripheral paresis of facial muscles, dysmetry, sometimes with contralateral hemiparesis (Foville syndrome) |
II. Damage at the level of the root of the VI nerve
| Lesion of the root of the sixth nerve | Isolated paralysis of the muscle turning the eyeball outwards. |
| Defeat of anterior paramedian bridge sections | Ipsilateral paralysis of muscles innervated by VI and VII nerves, plus contralateral hemiparesis (Millard-Gubler syndrome). |
| Defeat in the area of the preprint tank | Paralysis of the muscle that removes the eye from the outside, with (or without) contralateral hemiparesis (if the corticospinal tract is involved) |
III. Damage to the trunk of the abducent nerve.
| Defeat in the apex of the pyramid (Dorello channel - Dorello) | Paralysis of the eye muscle of the muscles (VI nerve); hearing loss on the same side, facial (especially retroorbital) pain (Gradenigo syndrome) |
| Cavernous sinus | Isolated involvement of the VI nerve; or involvement of the VI nerve plus Horner's syndrome; III, IV nerves and I branch of the trigeminal nerve can also be affected. Exophthalmos, chemosis. |
| Syndrome of the upper orbital gap | The defeat of the sixth nerve with variable involvement of the III, IV nerves and I of the V branch of the nerve. Possible exophthalmos. |
| Orbit | Symptoms of the defeat of the VI nerve (and other oculomotor nerves), decreased visual acuity (II nerve); variable exophthalmos, chemosis. |
Possible causes of isolated defeat of the VI (outflowing) nerve: diabetes mellitus, arterial hypertension (in these forms, the paralysis of the sixth nerve has a benign course and usually undergoes reverse development within 3 months), aneurysms, strokes, metastasis, pituitary adenomas, sarcoidosis, giant cell arteritis, multiple sclerosis, syphilis, meningioma, glioma, craniocerebral trauma and other lesions. In addition, the lesion at the level of the nucleus of the VI nerve is observed in congenital Mobius syndrome (Mobius): paralysis of the horizontal gaze with diplegia of facial muscles; The Duane retraction syndrome with paralysis of the eye, retraction of the eyeball, narrowing of the eye gap and bringing the eyeball.
The defeat of the sixth nerve should be differentiated from the syndromes of "pseudoabdusense": distyroidoid orbitopathy, bilateral convergence spasm, myasthenia gravis, congenital Du'an syndrome, friendly strabismus and other causes.
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