A 55-year-old woman is admitted to the emergency department with ear pain, ringing in her ear (tinnitus), dizziness, and vertigo. Radiographic examination reveals indications of Meniere's disease. Which of the following structures is most likely affected by the edema that is associated with Meniere's disease?

Hydrops (edema) results from accumulation of excessive fluid in the endolymphatic sac. Labyrinthine hydrops or endolymphatic hydrops is known as Meniere disease. This disease can result in hearing loss, roaring noises in the ear, and episodic dizziness (vertigo) associated with nausea and vomiting. About 10% of patients require surgical intervention for persistent, incapacitating vertigo; others are treated with diuretics, low salt intake, and reduction of stimulants like caffeine to lower the volume of body fluids and alleviate the symptoms of Meniere disease.