Thursday, February 11, 2010

Deaf boy hears after brain implant

Deaf boy hears after brain implant

CHENNAI: Eleven months ago, when doctors switched on the equipment on his ear lobe, two-year-old Koushik Gandhi cried out in fear. Tears of joy trickled down his mother’s cheeks as she realised that Gandhi, who was born deaf, was hearing sound for the first time.

Koushik was born with a rare congenital disorder, where his inner ear comprising vital auditory parts like cochlea and auditory nerve were missing. Doctors at the Madras ENT Research Foundation ruled out a cochlear implant as it would be useless without the nerve which takes electrical impulses to the brain.

Instead, they along with doctors at VHS and experts from Germany conducted in January 2009 a complex surgery called the auditory brainstem implantation, bypassing the outer and the middle ear to implant a chip on the brainstem. Three months later, when they switched on the device, the boy began to hear. Doctors at the hospital, where the surgery was done for the second time, claim that Koushik is the world’s youngest patient to have undergone such a surgery. He turns three on Friday.

The implant consists of a small electrode applied to the brainstem, a microphone on the outer ear, and a speech processor. The electrode stimulates vital acoustic nerves by means of electrical signals and the processor digitally transmits the sounds to a decoding chip placed under the skin. A wire connects the chip to the implanted electrode attached to the brainstem. Depending on the sounds, the electrode delivers different stimuli to the brainstem making deaf people hear sounds.

"Though his outer and inner ear are functioning normally, we will not be using them. He will be using the external device and the implant for the sensation," said Dr Mohan Kameswaran who heads the Madras ENT Research Foundation. "Initially, the sound of speech would be bizarre because it could seem like a cartoon talking. But soon the brain tunes itself to the sound," he added.

The last time, a 16-year-old patient who had lost hearing after a disease
found it difficult for the first few days. "She told me I sounded like Mickey Mouse. But within a few days, she heard me speak normally. There was no change in my voice or the equipment. The only change was that her brain learned to tune to the waves. For this boy, things will be easier because he had never before heard sound," he said.
Koushik would be in school by the time he turns six and on Friday, as people sing for his third birthday, he may hear and, may be, smile.

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