||Since the diagnosis of Meniere's disease can be established only on the basis of the patient's history and audiovestibular findings, it is important that before the diagnosis is made all other known causes of episodic vertigo and hearing loss are ruled out. These conditions include acoustic neuroma, syphilis, cochlear otosclerosis, and perilymphatic fistula among others.
In animal experiments, destruction of the endolymphatic sac is usually followed sooner or later by endolymphatic hydrops. In Meniere's disease, a malfunction in the resorptive capacity of the endolymphatic duct appears to be the primary cause of the increase in the amount of endolymph. Normally, endolymph flows from the cochlea, through the ductus reuniens into the saccule, and out through the endolymphatic duct (which acts primarily to absorb the endolymph) and into the endolymphatic sac (which is mainly phagocytic and acts as a local immunodefense organ for the inner ear).
The specific location of the abnormality responsible for the decreased resorption of endolymph within the endolymphatic sac appears to be the richly rugose portion (pars rugosa). There are fewer and smaller blood vessels in the rugose and the cranial orifice portions of the endolymphatic sacs of patients with Meniere's disease.