Step 1: Define endolymphatic hydrops. It is a distension of the endolymphatic system of the inner ear caused by an excess of endolymph or impaired absorption.
Step 2: Link it to disease. Endolymphatic hydrops is the characteristic pathology of Meniere's disease, which clinically presents with the triad of episodic vertigo, fluctuating sensorineural hearing loss, and tinnitus, often with aural fullness.
Step 3: Eliminate the distractors. Otosclerosis is abnormal bone remodelling around the stapes footplate causing conductive hearing loss. Acoustic neuroma is a vestibular schwannoma. Cholesteatoma is keratinising squamous epithelium in the middle ear. None of these is defined by endolymphatic hydrops.
Step 4: Conclusion. Endolymphatic hydrops is seen in Meniere's disease, so option 1 is correct.