**Question:** III nerve palsy causes all of the following except:

A. Horizontal gaze palsy
B. Inability to close the eye on the affected side
C. Inability to elevate the eyebrow on the affected side
D. Inability to abduct the eye on the affected side

**Core Concept:** III nerve palsy, also known as the oculomotor nerve palsy, is a condition caused by damage to the oculomotor nerve (CN III) which controls the muscles responsible for eye movement. The oculomotor nerve contains three components: the trochlear nerve (CN IV), the superior rectus muscle, and the inferior rectus muscle. The trochlear nerve controls the movement of the superior oblique muscle, while the superior rectus and inferior rectus muscles control the movements of the eyes.

**Why the Correct Answer is Right:** Option A (Horizontal gaze palsy) is incorrect because III nerve palsy primarily affects the superior rectus and inferior rectus muscles, not the trochlear nerve responsible for horizontal gaze.

Option B (Inability to close the eye on the affected side) is incorrect because the III nerve palsy primarily affects the eye movement rather than the eyelid closure, which is controlled by the sympathetic nervous system and the Renshaw cell reflex.

Option C (Inability to elevate the eyebrow on the affected side) is incorrect because the III nerve palsy primarily affects the eye muscles, and the eyebrow elevation is controlled by the facial nerve (CN VII) and its branches, not the III nerve.

Option D (Inability to abduct the eye on the affected side) is incorrect as it relates to the trochlear nerve (CN IV), which is a part of the III nerve and controls the superior oblique muscle, not the III nerve itself.

**Why Each Wrong Option is Incorrect:**

Option A (Inability to elevate the eyebrow on the affected side) is incorrect because the eyebrow elevation is controlled by the facial nerve (CN VII) and its branches, not the III nerve. The III nerve primarily affects the eye muscles, and the eyebrow elevation is unrelated to it.

Option B (Inability to close the eye on the affected side) is incorrect because the III nerve palsy primarily affects the eye movement, and the eyelid closure is controlled by the sympathetic nervous system and the Renshaw cell reflex, which are not directly related to the III nerve.

Option C (Inability to elevate the eyebrow on the affected side) is incorrect because the eyebrow elevation is controlled by the facial nerve (CN VII) and its branches, not the III nerve. The III nerve primarily affects the eye muscles, and the eyebrow elevation is unrelated to it.

Option D (Inability to abduct the eye on the affected side) is incorrect because the abduction of the eye is controlled by the trochlear nerve (CN IV), which is a part of the III nerve, and not the III nerve itself. The III nerve primarily affects the eye muscles, and abduction is controlled by the trochlear (CN IV), not the III nerve.

**Clinical Pearl:**

The