Most patients with acute sensorineural hearing loss experience both emotional and social challenges. Idiopathic sudden sensorineural hearing loss (SSNHL) is among those diseases specified by the Japanese government as ‘intractable diseases’ and entailing a considerably high risk of disability. Although much work has been done to identify the cause of idiopathic SSNHL and establish effective treatments, no consensus has yet been reached.
Utilizing large cohort data is an efficient strategy to solve such ambiguous questions. In Japan, nationwide epidemiological surveys of various hearing disorders, including idiopathic SSNHL, have been conducted by the Research Group of the Ministry of Health and Welfare for Intractable Diseases from 2014 to 2016. In connection with this epidemiologic survey, a multicentre database was constructed, with data for more than 3000 idiopathic SSNHL patients, and several hundreds of other hearing disorders registered to date. This is the biggest collection of clinical data concerning idiopathic SSNHL and other hearing disorders in the world.
Various etiologies are known to be involved in acute sensorineural hearing loss.
In this supplement, we present our findings regarding various forms of acute sensorineural hearing loss, including idiopathic SSNHL, acute low-tone sensorineural hearing loss (ALHL), perilymphatic fistula, mumps, acoustic trauma, and acute noise-induced hearing loss.
With regard to idiopathic SSNHL, based on an analysis of the epidemiologic survey database, significant correlations were observed between the severity of hearing loss and diabetes mellitus, kidney disease, past history of brain infarction, heart disease, age, and symptoms of vertigo. In addition, the present epidemiological study showed that patients with idiopathic SSNHL showed significantly higher proportions of current smokers as well as those with a history of diabetes mellitus than did healthy controls. From genetic view points, gene polymorphisms in the GSR and NOS3 genes were related to prognosis in patients with SSNHL. It is thus speculated that oxidative stress and its resistance pathways are important in patients with idiopathic SSNHL. These data suggested that at least some cases of idiopathic SSNHL are closely related to microvascular disorders.
This supplement also discusses other related diseases, including ALHL, perilymphatic fistula, mumps, and noise-induced hearing loss, using large cohort data collected from across Japan. I believe this supplement represents an excellent collection of etiological and epidemiological data related to these forms of acute sensorineural hearing loss, and provides an overview of current knowledge on these disorders.
Finally, I would like to dedicate this supplement to my mother Eiko Usami, who turns 88 this year. She experienced idiopathic SSNHL in September 2014. She was first treated with systemic steroid treatment, but her hearing loss did not recover. She subsequently received an intra-tympanic injection of steroids, but again her hearing did not respond. She underwent heart valve replacement surgery in April 2014. I could not accept these two events as being purely coincidental, regarding them instead as associated in some manner. This case is just one of the many, but the data collected for more than 3000 cases has enabled us to make some hypotheses regarding idiopathic SSNHL, some forms of which are likely to be closely related to microvascular events.