In current trials of a hearing aid that is directly and permanently anchored to the skull behind the ear, doctors at Hong Kong's Prince of Wales Hospital, the teaching hospital of The Chinese University of Hong Kong, report significant hearing improvements in patients with hearing loss caused by complications arising from radiation therapy for nasopharyngeal carcinoma (NPC). The device also shows to increase patient satisfaction, set to improve quality of life and bring socioeconomic benefits, researchers say.

　　The device, the bone anchored hearing aid (BAHA), has been successfully used since 1996, to assist patients with hearing disabilities arising from other causes at the Prince of Wales Hospital. This is the first time that the BAHA has been used to offer improved results to patients with this particular cancer, which is well-known for its high prevalence in southern China.

　　The BAHA is anchored to the skull by a tiny titanium screw. Instead of sounds entering the outer ear canal and impinging on the eardrum as in normal hearing, the sounds amplified by the device are conducted through the screw and the bones of the skull to the cochlea, the snail-shaped inner ear structure responsible for converting sounds into electrical signals carried to the brain by the auditory nerve.

　　Dr Gordon Soo, Honorary Clinical Assistant Professor, Division of Otorhinolaryngology of the Department of Surgery, CUHK, who is directing the clinical research team involved said, "Radiation therapy has proved highly successful in curing this particular cancer but among its frequent side effects are damage to the delicate structures of the ear and different types of hearing loss."

　　"Patients cured of this cancer," he continued, "may often have an ear discharge, ear canal ulceration or other complications arising from the therapy. This can make the wearing of a conventional hearing aid problematic or even impossible. So far in our studies we have been delighted with the levels of satisfaction being reported by patients fitted with a BAHA."

　　NPC is found worldwide, but its particularly high prevalence in Hong Kong and southern China generally - around 32 new cases yearly per 100,000 of the population - has led to its being called the "Cantonese cancer".

　　Its consequences extend far beyond the devastating effect on the patients themselves to involve their families, friends and colleagues. In particular, because most people contract NPC at an age when their earning powers are at their highest, it is vital both economically and for their self-esteem that they return to productive work. This is a very challenging proposition for the newly hearing-impaired, particularly those who cannot successfully use conventional hearing aids.

　　Over and above the observed improvements in hearing and the expected upturn in quality of life that the BAHA brings, the pioneering use of the device should thus, the researchers consider, have a marked socioeconomic impact on the affected families, where there were 1,120 new cases in 2000 in Hong Kong alone. More and beyond Hong Kong, NPC afflicts an estimated 13,220 new cases in Guangdong each year. Regional countries such as Singapore, Malaysia and Thailand have an estimated 900, 6,000 and 7,800 new cases annually. Indeed the BAHA could everywhere bring benefits as NPC has a worldwide distribution. For a disease with which such a wide reach, the impact could indeed be global.

How does the BAHA work?

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