Late Diagnosis of Enlarged Endolymphatic Duct and Sac Syndrome in a Case of Unilateral Sudden Hearing Loss with Retrocochlear Pattern. Case Report

Keywords: enlarged endolymphatic duct and sac syndrome; sudden hearing loss; retrocochlear pattern Abstract: Enlarged Vestibular Aqueduct (EVA) is one inner ear malformation found in 35% of children with unilateral sensorineural hearing loss.(1) Case reports of late diagnosis of enlarged vestibular aqueduct in young adulthood are extremely rare. The authors present a case of unilateral sensorineural hearing loss with sudden onset and retrocochlear pattern in an 18-year-old patient. MRI examination showed an enlargement of the left endolymphatic sac, without any other anomalies of the inner ear. The controlateral ear had normal hearing and no imaging abnormalities were found. This is a very rare case of unilateral enlarged endolymphatic duct and sac syndrome (EEDSS) discovered on MRI (Magnetic Resonance Imaging) assessment in a case of sudden hearing loss in early adulthood. INTRODUCTION Large vestibular aqueduct (LVA) or enlarged vestibular aqueduct (EVA) is a congenital anatomical defect, in which the mid vestibular aqueduct is larger than 1 mm in diameter.(2) Hearing loss or balance symptoms associated with an EVA can occur when the endolymphatic duct and sac expand to fill the larger space. When EVA is associated with such symptoms, it is referred to as enlarged vestibular aqueduct syndrome (EVAS). The anomaly can be diagnosed by imaging, such as high resolution CT which accurately measures the diameter of the aqueduct and / or by MRI which highlights the dilated endolymphatic duct and sac.(3) It is often associated with other congenital inner ear anomalies, the most common being an abnormally large vestibule, an enlarged semicircular canals, or a hypoplastic cochlea. EVAS is the only radiographically detectable inner ear anomaly associated with sensorineural hearing loss.(4) Enlarged vestibular aqueduct is usually diagnosed in early childhood, 12% of these patients being under the age of 4.(5) The exact mechanism which causes hearing loss in EVAS is not well defined, especially the cases of sudden hearing loss where a possible haemorrhage is the cause.(6) Patients with EVAS have residual hearing and most of them experience sudden hearing deterioration, particularly following minor trauma or infection. The rupture of Reissner's membrane(7), the vulnerability of dysmorphic cochlea to pressure changes and the reflux of hyperosmolar content into the endolymphatic sac