Final answer:
In the presence of sixth cranial nerve (abducens nerve) impairment, neurological examination findings would show normal eyelids and pupil reactions, but the position of the affected eyeball may be medially deviated, and there would be impaired lateral movement (abduction) of the eye leading to horizontal diplopia.
Step-by-step explanation:
The abducens nerve, also known as the sixth cranial nerve, is responsible for contracting the lateral rectus muscle, which is one of the extraocular muscles that controls the movement of the eye.
When there is an impairment of the abducens nerve, the findings of a neurological examination would typically include the following:
- A. Eyelids: Normal; the abducens nerve does not innervate the muscles controlling the eyelids.
- B. Pupils: Normal size and shape; the abducens nerve does not affect the pupils directly.
- C. Reaction of pupils to light: Normal; the abducens nerve does not control the pupillary light reflex.
- D. Position of eyeballs: Affected eye may show a medial deviation at rest due to unopposed action of the medial rectus muscle.
- E. Eyeball movements: Impaired abduction (lateral movement) of the affected eye. When attempting to look laterally, the affected eye will not move outward as it should.
- This can lead to horizontal diplopia (double vision) when looking towards the side of the affected eye.
The extraocular muscles are innervated by the oculomotor, trochlear, and abducens nerves with coordinated movement regulated by the brain stem.
An impairment in conjugate gaze, particularly in horizontal gaze movements, is indicative of abducens nerve dysfunction.