Ménière's disease: Is it time to approach it from another point of view?

Abstract

Since it was fi rst described in the 19th century, M é ni è re ’ s disease (MD) has presented with a series of fundamental aspects the basis of which still remain unclear. It is commonly accepted that an endolymphatic hydrops occurs; the modalities and mostly the causes of this alteration are still under debate despite numerous attempts at an explanation over the decades. A review of the suggested aetiopathogenetic explanations (1) reveals that these range from genetic abnormalities to viral infections, autoimmune alterations, Eustachian tube dysfunction, disorders of the transport and regulation of water, dietary factors, hormonal changes and psychological triggers. As a consequence of the uncertainties concerning MD, various medical and surgical therapeutic strategies have been proposed but none has proved universally acceptable to date. Although a number of supposed causes of MD involve systemic alterations, there is a tendency to focus attention on local treatment, thus scarcely considering the link between the homeostasis of the inner ear and the systemic changes. As all the surgical proposals are clearly aimed at fi nding a ‘ local ’ solution, the medical therapies tend toward producing an effect that only involves the inner ear; however, even in this case the match between the labyrinthine circulation and fl uids, on one hand, and the systemic plasmatic volume, on the other, is often poorly emphasized. In our opinion, however, the key to a better understanding of the behaviour of the inner ear is to consider it as a very sensitive terminal that works in accordance with the changes occurring in the whole organism and infl uencing circulation. A very recent explanation that has been advanced by our group, stresses the possible role of the inner ear proton pumps working under ischaemia in the genesis of the fl uid imbalance, leading to a series of unexplained inner ear alterations including hydrops (1). The possible infl uence of a more or less transient ischaemia, that can even be due to functional and transitory causes (2), is not negligible when considering the terminal type of the labyrinthine blood supply, its interaction with inner ear fl uid pressure (3), and the occurrence of mild auditory fl uctuations even under physiological hormonal changes such as those occurring in the ovarian cycle (4). Moreover, the presence of cochlear sympathetic efferent fi bres, that are reported to infl uence susceptibility to noise (5), further supports the importance of vasomotor changes in the inner ear. Briefl y, a haemodynamic imbalance that can be represented by an abrupt lowering of blood pressure values followed by an exaggerated peripheral vasoconstriction could have adverse effects of different kinds on the labyrinth (1); this could reliably explain various labyrinthine disorders of unexplained origin and, as stated above, be extended to MD. This orientation is given important support when considering the role of a specialized central nervous system structure, the subfornical organ, that due to the lack of the blood-brain barrier receives direct information on the changes of signalling molecules in circulation, and subsequently transmits this information to the autonomic hypothalamic control centres (6). The existence of such a controlling system, able to yield integrated and contemporary information about the homeostasis of the whole organism, can be considered of crucial importance for the perfusion of peripheral organs, and could help explain the hormonal changes observed during MD crises (7). Audiological Medicine, 2012; 10: 151–152