If an examiner finds a patient has a missing or decreased corneal reflex in one eye, which cranial nerve could be affected, indicating an acoustic neuroma?

The presence of a missing or decreased corneal reflex in one eye suggests an issue related to the sensory and motor pathways involved in that reflex arc. The corneal reflex is primarily mediated by the trigeminal nerve, which is responsible for sensory input from the cornea, and the facial nerve, which controls the motor output causing the blink response.

When considering an acoustic neuroma—typically a benign tumor that occurs on the vestibulocochlear nerve (cranial nerve VIII)—it can also influence nearby cranial nerves, particularly the trigeminal nerve (cranial nerve V) and sometimes the facial nerve (cranial nerve VII). Damage or compression of the trigeminal nerve can lead to a diminished or absent corneal reflex, as it disrupts the sensory limb of this reflex arc.

The optic nerve (cranial nerve II) is primarily responsible for vision and does not play a role in the corneal reflex. The oculomotor nerve (cranial nerve III) is involved in eye movements and autonomic functions like pupil constriction, and the abducens nerve (cranial nerve VI) primarily controls lateral eye movement. None of these nerves are directly involved in mediating the corneal reflex, making them less relevant in