Short Scientific Communication A New Theory for Me´nie`re’s Disease: Detached Saccular Otoconia Otolaryngology– Head and Neck Surgery 1–3 Ó American Academy of Otolaryngology—Head and Neck Surgery Foundation 2016 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0194599816675843 http://otojournal.org Jeremy Hornibrook, FRACS 1,2,3 and Philip Bird, FRACS 1,2,3 No sponsorships or competing interests have been disclosed for this article. Abstract Me´nie`re’s disease is an inner ear disorder characterized by ver- tigo attacks, fluctuating and progressive hearing loss, tinnitus, and aural fullness in the affected ear. The pathophysiology of Me´nie`re’s disease remains elusive. Theories so far are anatomi- cal variation in the size or position of the endolymphatic sac and duct, viral inflammation or autoimmune involvement of the sac, or a genetically determined abnormality of endolymph control. Animal studies on blocking the ductus reuniens and endolymphatic duct have produced hydrops in the cochlea, saccule, and utricle. Cone beam computed tomography images show a similar pattern with apparent obstruction of the ductus reuniens, saccular duct, and endolymphatic sinus. New studies documenting the age of onset of Me´nie`re’s disease show a pat- tern similar to benign paroxysmal positional vertigo, raising the possibility that the fundamental cause of Me´nie`re’s disease might be detached saccular otoconia. Keywords Me´nie`re’s disease, BPPV, otoconia, saccule Received July 7, 2016; revised September 8, 2016; accepted October 4, 2016. T he inner ear remains one of the most difficult organs in the body to investigate and to internally image. The common causes of vertigo involve inner ear structures or its connections to the brainstem. A major advance has been the elucidation of the cause of benign paroxysmal positional vertigo (BPPV) as being due to detached utricular otoconia entering the semicircular canals. This cause was postulated from temporal bone histology 1 but not proven as otoconia are degraded in the decalcification preparation. However, the theory has been supported by the results of ‘‘cupulolithiasis’’ and ‘‘canalithiasis’’ repositioning treatments and surgical confirma- tion of otoconia in a posterior canal. 2 With the exception of trauma, most cases are idiopathic with spontaneous release of utricular otoconia, particularly in individuals older than 50 years. In contrast, the pathophysiology of Me´nie`re’s disease remains unproven and controversial. Based on temporal bone histology (and now magnetic resonance imaging of the inner ear), the fundamental pathophysiological feature of Me´nie`re’s disease is endolymphatic hydrops. Postulated causes include anatomical variation and size of the endolymphatic sac and duct, viral infection or autoimmune involvement of the sac, or a genetically determined abnormality of endolymph control. While the effects of detached urtricular otoconia are gen- erally accepted as the cause of BBPV, it is seldom asked, what is the fate of saccular otoconia? Histological and Imaging Studies In a study by Kimura et al, 3 the ductus reuniens was surgically blocked, with the majority of animals showing histological cochlear hydrops, saccule collapse, and an abnormal utricle. In some whose endolymphatic duct was later obstructed, the hydrops was in the cochlea, saccule, and utricle, leading to their conclusion that ‘‘a blocked ductus reuniens might also explain the pathophysiological basis of the auditory form of Meniere’s disease.’’ Gussen and Adkins 4 studied the temporal bones of a 25-year-old woman who died of metastatic malig- nant melanoma who was assumed to have Me´nie`re’s disease in her right ear. In the right ear, the entrance to the ductus reuniens appeared blocked by otoconia with ‘‘slight bowing’’ of Reissner’s membrane (early hydrops) in the basal turn. Calzada et al 5 studied the endolymphatic system in patients undergoing labyrinthectomy for vestibular drop attacks, delayed endolymphatic hydrops, and symptomatic Me´nie`re’s disease, with patients having surgery for acoustic neuroma removal as controls. All patients with vestibular drop attacks had disrupted utricular otolithic membranes, whereas approxi- mately 50% of patients with delayed endolymphatic hydrops and Me´nie`re’s disease had that feature. Although their con- clusion was that ‘‘the underlying pathophysiology in vestibu- lar drop attacks results from injury to the otolithic membrane of the saccule and utricle, resulting from free-floating otoliths 1 Department of Otolaryngology–Head and Neck Surgery, Christchurch Hospital, Christchurch, New Zealand 2 University of Otago, Christchurch, New Zealand 3 University of Canterbury, Christchurch, New Zealand Corresponding Author: Jeremy Hornibrook, FRACS, Department of Otolaryngology–Head and Neck Surgery, Christchurch Hospital, 2 Riccarton Avenue, Christchurch, 8011, New Zealand. Email: jeremy@jhornibrook.com by guest on November 9, 2016 oto.sagepub.com Downloaded from