Earliest ocular finding in acoustic neuroma:
**Core Concept**
Acoustic neuroma, also known as vestibular schwannoma, is a benign tumor arising from the Schwann cells of the vestibulocochlear nerve (cranial nerve VIII). The earliest ocular finding in acoustic neuroma is related to the compression of the adjacent structures, particularly the oculomotor nerve (cranial nerve III).
**Why the Correct Answer is Right**
The earliest ocular finding in acoustic neuroma is often an ipsilateral ptosis (drooping of the eyelid), which is caused by the compression of the levator palpebrae superioris muscle by the tumor. This muscle is innervated by the oculomotor nerve, which is located close to the vestibulocochlear nerve. As the tumor grows, it can compress the oculomotor nerve, leading to weakness or paralysis of the levator palpebrae superioris muscle, resulting in ptosis.
**Why Each Wrong Option is Incorrect**
* **Option A:** While hearing loss is a common symptom of acoustic neuroma, it is not the earliest ocular finding.
* **Option B:** Diplopia (double vision) can occur in acoustic neuroma, but it is not the earliest ocular finding.
* **Option C:** Optic neuritis (inflammation of the optic nerve) is not a direct consequence of acoustic neuroma.
**Clinical Pearl / High-Yield Fact**
In acoustic neuromas, the oculomotor nerve is often compressed before the optic nerve, leading to ptosis as the earliest ocular finding. This is an important clinical correlation to remember when evaluating patients with suspected acoustic neuroma.
**Correct Answer:** C.