Etiology (cause) of Menieres Syndrome
Timothy C. Hain, MD . Please read our disclaimer.
|Figure 1a: Normal membranous labyrinth||1b. Dilated membranous labyrinth in Meniere's disease (Hydrops)|
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Content last updated: 2/03
Most authors feel that Menieres syndrome, and specifically endolymphatic hydrops (see figure 1a-b), has several causes (etiologies). Reasonable possibilities are obstruction of endolymphatic outflow at the endolymphatic duct level, increased production of endolymph, or reduced absorption of endolymph caused by a dysfunctional endolymphatic sac. Recently, the most generally accepted idea that Meniere's disease and endolymphatic hydrops are always associated has been questioned. Hydrops is not found in all persons with Meniere's disease, and hydrops is also commonly found (6%) on autopsy studies of persons who had no Meniere's type symptoms (Honrubia, 1999; Rauch et al, 2001). Because Meniere's disease occurs in roughly 0.2/100 persons, and Hydrops is found in 6/100 temporal bones, the there are 30 times more people with hydrops than Meniere's disease. Thus logically, there must be something more than simply hydrops involved in the origin of Meniere's disease
Explanations for Meniere's that depend on unilateral injury to an ear, such as a blockage of a "drainage pipe" in the ear, also seem hard to sustain in view of the known long-term studies that show that Meniere's becomes bilateral in roughly 50% of all people, after 15 years (Stahle et al, 1991). Although ruptures of membranes are found at post-mortem, there is no evidence of when they occurred. For ruptures to be the cause of the periodic auditory and vestibular symptoms of Meniere's disease, one would have to accept the idea that there are multiple ruptures of thin membranes that are repaired over and over. This seems very implausible. It is also questionable that even if a rupture were to occur, that the mixture of endolymph and perilymph would be sufficient to create the symptoms of Meniere's disease.(Honrubia, 1999)
Recently attention has been mainly focussed on the immunologic function of the endolymphatic sac -- immune disease may contribute to a substantial percentage of Meniere's disease. There also is some thought that Meniere's and Migraine are two faces of the same indistinguishable condition. This may be indeed the case in a few people.
A synthesis of present thought is that Menieres syndrome appears to be the final common pathway that the inner ear responds to nearly any injury, and that Menieres syndrome has many separate causes, some of which reflect injury, and others which reflect more generalized metabolic or genetic processes that injure both ears fairly symmetrically.
-- Herpes virus (HSV) antibodies are found more commonly in Meniere's patients (Arnold and Niedermeyer, 1997). On the other hand, others have not found viral DNA from herpes simplex, CMV or varicella zoster in the vestibular ganglion (Welling et al, 1997). HSV antigen and HSV DNA are also found in the endolymphatic sac and epithelium of healthy people. There is some recent pathologic data supporting a viral cause (Gacek and Gacek, 2001). Linthicum has also recently reported that herpes simplex DNA is found in the endolymphatic sacs of 12 of 16 Meniere's cases, vs. 2 of 26 controls (Linthicum, 2001). Our take on this is that these finding are interesting, and need more investigation.
Otosyphilis can produce a clinical picture identical to Meniere's. Pulec indicated that syphilis is the cause of Meniere's disease in 6% of all cases (1997). This is much higher than the author's experience in whom certainly less than 1% of all patients have a positive FTA for syphilis.
-- About one in three patients with Menieres disease have a first-degree relative with Menieres disease. In theory, hereditary predisposition might be related to differences in anatomy of fluid channels within the ear or differences in immune response.
-- about 60% of patients with Meniere's disease have serum antibodies for inner ear proteins. About 10% of Meniere's patients have well documented autoimmune disorders (but the general population also has a high prevalence of these disorders). Some Meniere's patients show evidence for a change in their immunity around the time of their attacks (Mamikoglu et al, 2002).
With respect to allergy, Derebury has suggested that 30% of patients with Meniere's disease have food allergy, and suggested that allergy may play a role in three ways that allergy may contribute:
All of these hypotheses involve the endolymphatic sac, but some authors feel that the sac is not necessarily the culprit. There is evidence for cytokines in the cochlea including interleukin-1A, TNF-alpha, NFkB P65 and P50, and IkBa (Adams, 2002). Drugs that block TNF such as etanercept seem to be potentially effective in autoimmune inner ear disease (AIED) which resembles some forms of Meniere's disease (Rahmen et al, 2001).
Currently the best guess is that the immunological pathway for Meniere's disease involves the sac which is the immune organ, or "lymph node" of the ear. Immune stimulation of the sac may disturb its fluid regulatory function, or may cause hydrops via independent mechanisms such as production of inflammatory mediators. Click here for more detail about autoimmune disease.
-- there are clearly cases of post-traumatic Meniere's syndrome. These cases are attributed to hydrodynamic changes caused by scarring from bleeding into the inner ear.