## **Core Concept**
Unilateral sensorineural hearing loss refers to a condition where there is damage to the inner ear or the auditory nerve pathways on one side, leading to hearing loss. This type of hearing loss can result from various causes, including infections, trauma, tumors, or vascular events affecting the auditory system.

## **Why the Correct Answer is Right**
The correct answer, **C. Acoustic neuroma**, is right because acoustic neuroma, also known as vestibular schwannoma, is a benign tumor that grows on the vestibular nerve, which is responsible for balance. As the tumor grows, it can compress the adjacent cochlear nerve, leading to unilateral sensorineural hearing loss. This condition is a classic cause of unilateral sensorineural hearing loss and tinnitus.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because while otosclerosis can cause hearing loss, it typically causes conductive hearing loss due to abnormal bone growth in the middle ear that affects the stapes bone's movement. However, in rare cases, otosclerosis can cause mixed hearing loss or, very rarely, sensorineural hearing loss, but it's not the most direct cause of unilateral sensorineural hearing loss.
- **Option B:** This option is incorrect because Meniere's disease usually causes episodic vertigo, tinnitus, and hearing loss, but the hearing loss is typically fluctuating and affects low-frequency ranges initially. It can become bilateral but usually starts unilaterally.
- **Option D:** This option is incorrect because while ototoxicity can cause sensorineural hearing loss, it more commonly causes bilateral hearing loss due to the systemic distribution of the ototoxic substance.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that unilateral sensorineural hearing loss, especially when sudden in onset, necessitates an MRI to rule out a retrocochlear lesion like an **acoustic neuroma**. Early detection of such tumors can prevent complications like facial paralysis and ensure better outcomes.

## **Correct Answer:** C. Acoustic neuroma