Establishing the causes of sudden deafness

A Deafness Research UK grant to researchers at the Wythenshaw Hospital in Manchester has enabled a study aimed at establishing the causes of sudden deafness.

[Project grant: 2005-2008]

The inner ear consists of two functionally separate parts: the cochlea for sound reception and the vestibular apparatus which senses gravity and movement for the maintenance of balance. Sensorineural hearing loss occurs when there is damage to either the cochlea or the nerves that transmit sound from the cochlea to the brain. It can occur suddenly or can be gradually progressive.

Sudden deafness is a devastating condition that affects around 5,000 people in the UK each year. Although deafness may occur due to a number of recognised causes, most cases remain undiagnosed and the term idiopathic (of unknown cause) sudden sensorineural hearing loss has been adopted. Although up to 60% of these patients undergo spontaneous full or partial recovery, significant proportions are left with permanent deafness.

The blood supply to the inner ear comes solely from the labyrinthine artery and so its blockage would lead to damage to the inner ear, resulting in sudden sensorineural hearing loss. Given the rapid speed of onset and the predominantly one-sided nature of this condition, such a cause seems likely.

Mr Simon Freeman and his research team at the hospital have been testing patients who have experienced sudden deafness. The aim is to establish if there is a link between blood clots and sudden deafness.

Recruitment of volunteers to the study has proved difficult; however the last patients and controls have now been tested and their data are currently being analysed.

The potential impact of this research is wide-reaching, not just on our ability to develop treatments for the condition but also our ability to identify people at risk of sudden deafness.