The VIth cranial nerve runs in the carotid sinus body adjacent to the internal carotid artery and oculo-sympathetic fibers responsible for pupil control, thus, lesions at this site might be associated with pupillary dysfunctions.
The VIth nerve’s course is short in the orbit and lesions in the orbit rarely give rise to isolated VIth nerve palsies.
Typically 6th nerve, abducens, palsies involve one or more of the other extraocular muscle groups.
Onset usually is sudden, with symptoms of horizontal diplopia.
Limitations of eye movements are confined to abduction of the affected eye or eyes.
Abduction limitations may mimic sixth nerve palsy may result from surgery, trauma, myasthenia gravis or thyroid eye disease.
Fresnel prisms are slim flexible plastic prisms that can be attached to the patient’s glasses, or to plano glasses, and serve to compensate for the inward misalignment of the affected eye.
Other management options include the use of botulinum toxin, which is injected into the ipsilateral medial rectus.
When the deviation is too large for prismatic correction to be effective, occlusion may an option for those unfit or unwilling to have surgery.
The surgical procedure performed will depend upon the degree of function that remains in the affected lateral rectus.
With complete paralysis, the pref2242ed surgical managementb is to perform vertical muscle transposition procedures, with the aim of using the functioning inferior and superior recti to gain some degree of abduction.
An alternative surgical approach is to operate on both the lateral and medial rectii of the affected eye, with the aim of stabilising it at the midline.
Causes of bilateral sixth cranial nerve palsy include:
Diabetes mellitus type 2
Superior orbital fissure syndrome
Cavernous sinus thrombosis