Abstract
We report the case of a man affected by a unilateral Ménière’s disease who, after being free from vertigo spells and tinnitus for more than ten years, manifested an exacerbation of symptoms just before the diagnosis of a choroidal melanoma. Melanoma is an aggressive form of cancer derived from neuroectodermal melanocytes. Melanocytes are present in the inner ear where they contribute to the production of endolymphatic potentials and to the maintenance of normal volumes of the inner ear fluids. A possible autoimmune connection between the exacerbation of audiovestibular symptoms and melanoma is discussed.
1
Introduction
Ménière’s disease (MD) is an inner ear disorder characterized by recurrent episodes of rotational vertigo, fluctuating progressive hearing loss, aural fullness and tinnitus. The etiology of the disease is still not well understood, however endolymphatic hydrops is considered the pathological basis. Endolymphatic hydrops implies a fluid imbalance within the inner ear.
Melanocytes are present in the inner ear, both in the intermediate layer of the stria vascularis of the cochlea and in the dark cells of the vestibular organs . They contribute to the production of endolymphatic potentials and to the maintenance of normal volumes of the inner ear fluids .
As far as we know, no previous report has suggested a possible link between melanocyte disorders and MD or, more generically, audiovestibular dysfunctions. In this report we present the history of a patient affected by MD who manifested an exacerbation of symptoms some months before the diagnosis of a choroidal melanoma, and we discuss possible pathophysiologic mechanisms.
1.1
Case presentation
A 49-year-old man presented with a history of MD that had been diagnosed fifteen years before. He had suffered from repeated episodes of vertigo lasting 20 minutes or longer with audiometrically documented right ear sensorineural hearing loss, tinnitus and aural fullness, thus fulfilling all the criteria for definite MD . His response to medical treatment was good, symptoms progressively reduced and for twelve years he had had no further episodes of vertigo or tinnitus. Then, suddenly, a tinnitus associated with hearing loss had returned in the right ear and during the three months prior to examination the patient had suffered from frequent spells of vertigo. The audiogram showed a moderate sensorineural hearing loss, which was predominant at low-middle frequencies in the right ear. In the contralateral ear, the hearing threshold proved to be normal and transient evoked otoacoustic emissions were present. Auditory brainstem responses were bilaterally normal, thus excluding a retrocochlear impairment. Spontaneous vestibular signs were absent; routine and immunological blood tests proved to be negative: in particular, specific tests for lupus-like anti-coagulants, anti-nuclear, anti-mitochondria, anti-thyroid, anticardiolipin auto-antibodies and rheumatoid factor gave negative results. The high resolution computerized tomography (CT) scan was normal. Medical therapy, salt restriction and increased water intake did not stop the vertigo attacks, which had become daily during the 4-month follow-up, and did not significantly change the audiometric thresholds of the right ear. The left ear threshold showed normal hearing in repeated audiometric tests.
Four months after the first examination, a choroidal melanoma in the right eye was diagnosed. Gadolinium magnetic resonance imaging (MRI) of the brain resulted normal. The ocular melanoma was treated with plaque radiotherapy, after which the patient stopped having vertigo attacks and tinnitus. A mild low-frequency hearing loss persisted but for the whole of the one-year follow-up he had no further attacks of vertigo and tinnitus.
2
Discussion
The natural history of MD is often characterized by quiescent phases, during which the auditory and vestibular symptoms are absent, and periods of exacerbation of the disease. In the case reported above, the patient had experienced a long symptom-free period, then the disease exacerbated but without an evident involvement of the contralateral ear. A few months after the exacerbation of the disease an ocular melanoma was diagnosed.
A melanoma is an aggressive form of cancer derived from neuroectodermal melanocytes. Melanocytes are present in the inner ear where they are believed to play an important role in the maintenance of normal volumes and ion concentration of the inner ear fluids .
Some audiological abnormalities have been associated with melanocyte disorders. A defect in the development of melanocytes is associated with the Waardenburg syndrome, a varying combination of sensorineural hearing loss, heterochromia iridis and patchy abnormal depigmentation of the hair and skin . An autoimmune mechanism affecting the cochlear and visual pigment has been proposed for the Vogt-Kayanagi-Harada syndrome (uveitis, vitiligo and dysacusis) . Abnormalities of hearing and auditory brainstem responses have been reported also in patients affected by vitiligo .
To the best of our knowledge, a possible role of melanocytes in MD has not yet been proposed. Seaman BJ and coworkers reported a suspected autoimmune attack on the inner ear melanocytes causing hearing loss and vestibular dysfunction after adoptive cell immunotherapy targeting pigment-pathway cell proteins in patients with metastatic melanoma . This led us to hypothesize that an autoimmune genesis could be advocated also for the exacerbation of audiovestibular symptoms in our patient. A melanoma is an immunogenic tumor, frequently associated with spontaneous autoimmune manifestations such as spontaneous regression, vitiligo-like reactions or auto-immune retinopathy, which seem to be linked with a better prognosis . Melanoma-associated antigens are also expressed in the normal melanocytes in the skin, eye and ear. It is likely that the immune system may produce antibodies that cross-react with both the melanoma and the labyrinth cells, as well as in melanoma-associated retinopathy the cross-reaction targets retinal cells . A dysfunction of the labyrinth melanocytes may lead to a disruption of the endocochlear potentials thereby resulting in vestibular symptoms and hearing loss.
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