on My Life at Bangkok Post June 10, 2010
For centuries, it has been believed that only a miracle can cure deafness. It was not until forty years ago that scientists first attempted to restore normal hearing to the deaf by electrical stimulation of the auditory nerve.
Hearing impairment can be found in newborns. There are several risk factors that can cause such a disability. Some occur during pregnancy, while many others or others may occur at birth or after birth. Therefore, it is advisable for women to be coutious during pregnancy, especially during the first three months.
Dr. Suchitra Prasansuk, Director of Hearing, Speech, Tinnitus & Balance Center at Bangkok Hospital, confirmed that 2 out of 1,000 babies are born with hearing impairment without any recognizable reason and the figure is as higher as 20 in 100 in higher risk groups. This may occur as a result of an abnormal pregnancy, complications during pregnancy, infection during pregnancy, congenital diseases, Rubella (German measles), intrapartum asphyxia or impairment of the delivery of oxygen to the brain.
“In adults, hearing loss may happen due to serious infections which may affect the inner ear and the nerves of hearing in the inner ear. This may be caused by meningitis, head injury, listening to very loud music, especially through ear buds, and repeated exposure to loud sound, such as machinery” Dr. Suchitra explained.
“As technology advances, severe hearing loss that occurs at birth or later in life can be remedied when hearing aids cannot help with the help of ‘Cochlear Implants’,.” Dr. Suchitra said.
How hearing works
The ear comprises three different sections: the outer ear, the middle ear, and the inner ear. The inner ear is the most important as it conveys the messages to the brain via the hearing nerve. These parts work together so you can hear and process sounds. The outer ear picks up sound waves. The middle ear transfers the vibrations through the eardrum into the inner ear where the cochlear, a sensory hearing organ, awaits to send message to the brain. The brain process the sounds into meaningful message.
The cochlear is filled with liquid and is lined with thousands of hair cells. These hair cells send the sound information to the hearing nerve which then sends it to the brain, allowing you to hear and understand sound and achieve language.
Testing hearing ability in newborns
“Screening of newborns’ hearing before they leave the hospital is conducted at most prestigious hospitals in Bangkok. However, parents should be attentive to their babies’ hearing and check their response to sound in both ears. Normally, babies will slowly turn their heads or move their eyes to the direction of the sound. It is important that a child’s hearing loss is diagnosed before three months of age. If hearing loss is present at birth, it should be treated before the age of six months, which is the time when they start to recognise sounds and learn to develop speech. Children who receive early treatment can function normally by the time they enter school. The longer you wait, the higher the risk that your child will become deaf and unable to speak,” Dr. Suchitra advised.
Cochlear implant – a bionic ear
In most cases, the tests will detect any hearing loss present as well as the nature of that hearing loss. Based on the hearing test, physicians or otologists rather can determine whether patients need to use a hearing aids or receive further more sophisticated treatment.
“Hearing can often be restored if the hearing-impaired person receives the right type of treatment or the correct hearing aid. However, in severe cases when hearing loss occurs in the cochlear area of the inner ear, a cochlear Implantation is recommended,” said Dr.Suchitra.
The doctor stressed that both babies and adults can benefit from such implants provided that they have intact hearing nerves, normal ear passage and no brain pathology. Prior to implantation the cochlea, the nerve and the intact central auditory pathway must be evaluated.
Dr. Suchitra and her team started Cochlear Implantation at Siriraj Hospital in 2000. The implants have proven successful for people with severe neural hearing loss and where conventional treatments, including medications and hearing aids, have not worked. People of all ages, from one year onwards, can receive the implant. The operation usually takes between 2 and 3 hours.
“Cochlear Implantation is a one-time operation in babies because we are born with fully-developed hearing organs and can be done in one or both ears,” said Dr. Suchitra.
Often referred to as a ‘bionic ear’, a cochlear implant is a surgically implanted electronic device that provides a sense of sound or sound perception through direct electrical stimulation of the hearing nerve, bypassing the inner ear. Unlike hearing aids, the cochlear implant does not amplify sound, but works by directly stimulating any functioning auditory nerves inside the cochlea with electrical impulses.
The device comprises two parts – an internal device and an external device. The internal device is surgically implanted under the skin and is comprised of a receiver, a magnet, a decoder and an electrode array. The external device, worn over a magnet on top of the implanted internal device near the ear, includes a microphone, speech processor and transmitter that allows the patient to adjust the sound quality and amplification.
How do implants work?
The microphone picks up incoming sounds. The sounds then travel to the sound processor which analyses the sounds and converts them into patterns of electrical current. The current is carried along the cable and delivered across the skin by radio wave transmission to a receiver implanted under skin. The receiver carries the current to a decoder before the sound is transmitted into electrode array which has been implanted into the cochlea. The current stimulates the hair cells and results in hearing.
Benefits of cochlear implant
With the experience and skill of a professional team, most implant users are able to understand spoken speech. They are able to enjoy music and/or hold conversations on the phone. However, the users will hear electrical sounds rather than natural sounds. It takes time before the brain adapts to the new "sound" from the implant. Speech signals and environmental sounds from the implant steadily begin to sound more natural.
Be supportive and committed
Dr. Suchitra also advised that cochlear implantation involves a lifetime commitment of the individuals concerned, including patients, family and care givers. After implantation, patients must return to the clinic approximately every two months for a series of follow-ups to receive advice, get medical check-ups, and have the speech processor reprogrammed, including ‘mapping’ to set parameters of electrode stimulation that give patients the best hearing. Regular speech and language therapy, especially for children, is part of the programme.
“Hearing and listening to new sounds will be fun,” Dr. Suchitra encouraged.
Should you or someone that you know is hearing impairment, please contact our Ear Nose and Throat (Otolaryngology, Head and Neck Surgery), call 1719 (24 hours), or to set up a doctor’s appointment.
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