Professional and Linguistic Assessments Board (PLAB) Practice Exam

What is an expected finding in a patient with 6th nerve palsy?

1. Inability to adduct the eye

2. Unable to abduct ipsilateral eye

3. Double vision

4. Ptosis

The correct answer is: Unable to abduct ipsilateral eye

In a patient with 6th nerve palsy, the primary expected finding is the inability to abduct the affected eye. The sixth cranial nerve, also known as the abducens nerve, is responsible for the lateral movement of the eye. When this nerve is damaged or impaired, the eye on the affected side cannot move laterally toward the ear. This results in noticeable difficulties when attempting to visually track objects to the side. Patients often experience symptoms associated with this condition, including double vision (diplopia), as the eyes are not properly aligned due to the inability to abduct one eye. However, while double vision might be reported by the patient, the hallmark sign of 6th nerve palsy is specifically the inability to abduct, making it a pivotal finding in the diagnosis. Items such as inability to adduct the eye, double vision, and ptosis may involve other cranial nerves or conditions but do not specifically highlight the essential dysfunction caused by 6th nerve palsy. The inability to adduct the eye relates more to impairment of the medial rectus muscle, which is innervated by the third cranial nerve, while ptosis indicates issues with eyelid elevation, typically linked to involvement of the same third nerve.