Unilateral endolymphatic hydrops: what about the contralateral ear?

INTRODUCTION: The early recognition of incipient Meniere's disease (MD) in the asymptomatic ear of a patient with known unilateral disease has profound implications for patient management and follow-up, but the criteria for a right and precocious diagnosis is still controversial. MATERIALS AND METHODS: We evaluated forty-nine patients with MD, selected according to Committee on Hearing and Equilibrium guidelines. All patients underwent laminar tonal audiometry, stapedial reflex study, Glycerol dehydration test, Auditory Brainstem Response (ABR) vestibular examination. MRI was performed in 14 patients. RESULTS: A raised hearing threshold in the contralateral ear was found in 27 patients, but only 7 (14.3%) fulfilled the requirements to be considered affected by bilateral MD. The average delay of occurrence in the contralateral ear was 7 years (from 5 to 12 years). The glycerol test was positive only in 4 patients with unilateral MD and moderate hearing loss. It was not positive in any case of bilateral MD. The membranous endolymphatic duct and sac is not well visualised with MRI on the affected side in the majority of patients. CONCLUSION: A MRI study must be included in the diagnostic protocol for MD and with improvements in this imaging modality will possibly allow detection of variations in the size of inner ear structures. Glycerol dehydration test was useful only in selected cases. A full assessment of incipient disease in the asymptomatic ear in unilateral Meniere's disease should be undertaken. A conservative approach in surgical treatment of unilateral MD is recommended because of the possibility of evolution of a bilateral form, which can occur even 10 years after the onset of the disease.