Question

The earliest feature of 3rd cranial nerve involvement in diabetes mellitus patient is :

• A. Normal light reflex
• B. Abnormal light reflex
• C. Normal light and accommodation reflex
• D. Abnormal light and accommodation reflex

Answer 1

The Correct Option is A

Patients with diabetes mellitus are at risk for cranial nerve palsies, including the 3rd cranial nerve or oculomotor nerve. The oculomotor nerve controls most of the eye's movements and its parasympathetic fibers regulate pupil constriction and accommodation (focus change).

In diabetes, the involvement of the oculomotor nerve often spares the parasympathetic fibers, which are responsible for the pupillary light reflex. This is because these fibers are located on the periphery of the nerve and have a different metabolic support system, making them less susceptible to ischemic damage caused by diabetes.

As a result, the earliest feature of 3rd cranial nerve involvement in a diabetes mellitus patient is typically a "pupil-sparing" oculomotor palsy. This means the light reflex remains normal despite other functions being impaired, leading to the correct answer: Normal light reflex.