Delayed endolymphatic hydrops as a clinical entity.

Delayed endolymphatic hydrops (DEH) is a clinical entity that can be differentiated from Ménière's disease and is typically observed in patients who have been suffering from longstanding unilateral profound inner-ear hearing loss. DEH probably is caused by delayed atrophy or fibrous obliteration of the endolymphatic resorptive system of the membranous labyrinth. The time that elapses between the occurrence of hearing loss and the onset of DEH can range from 1 to 74 years. The most common cause of hearing loss preceding DEH is juvenile-onset unilateral profound deafness (early childhood unilateral profound sensorineural hearing loss of unknown etiology), followed by labyrinthitis from various causes and physical and acoustic traumas to the inner ear. Two types of DEH exist: the ipsilateral type, in which the ear with profound hearing loss suffers progressive endolymphatic hydrops, and the contralateral type, in which the formation of progressive endolymphatic hydrops takes place in the ear opposite to the previously deafened ear. The incidence of the ipsilateral type is higher than that of the contralateral type, and the contralateral type is more common in older patients. When recurrent episodic vertigo cannot be remedied through conservative treatment, labyrinthectomy and vestibular neurectomy on the deaf ear are curative for ipsilateral DEH. However, no such surgical treatment is available for the contralateral type.