**Core Concept**
The patient's symptoms of tinnitus, vertigo, and fullness in the ear are indicative of a disorder affecting the vestibulocochlear nerve or the structures within the inner ear. This is a classic presentation of a condition that requires prompt diagnosis and treatment to prevent further complications.

**Why the Correct Answer is Right**
The patient's symptoms are most likely due to Meniere's disease, a disorder of the inner ear characterized by the abnormal production of endolymph in the membranous labyrinth. This leads to an accumulation of fluid in the inner ear, causing damage to the vestibulocochlear nerve and resulting in the characteristic symptoms of tinnitus, vertigo, and fullness in the ear. The pathophysiology involves an overproduction of potassium ions in the endolymph, which disrupts the normal ionic balance and leads to the symptoms.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because while acoustic neuroma can cause tinnitus and vertigo, it typically presents with unilateral hearing loss and is not associated with fullness in the ear.
* **Option B:** This is incorrect because otosclerosis is a condition that affects the middle ear and is characterized by abnormal bone growth in the ossicles, leading to hearing loss, but it does not typically present with vertigo and tinnitus.
* **Option C:** This is incorrect because labyrinthitis is an inflammation of the inner ear and can cause vertigo and hearing loss, but it is typically associated with fever and other systemic symptoms, and not with fullness in the ear.

**Clinical Pearl / High-Yield Fact**
Meniere's disease is often divided into four stages, with the first stage being characterized by fluctuating hearing loss and fullness in the ear, while the second stage is marked by persistent hearing loss and tinnitus. The third and fourth stages are characterized by significant hearing loss and vertigo.

**Correct Answer: C. Labyrinthitis**