Researchers at the University of California, San Francisco, said Monday that they have developed an improved type of ear implant that is giving deaf people the ability to hear and recognize at least some human speech.
Earlier success with the four-channel cochlear implant led the UCSF team to begin working with an even more sophisticated eight-channel model, Dr. Robert Schindler, clinical director of the UCSF Cochlear Implant Project, told the neuroprostheses section of the Materials Research Society meeting in Boston. The cochlea is the spiral-shaped part of the inner ear that contains the auditory nerve endings.
The new device may give deaf patients improved ability to recognize speech and may broaden the opportunity for success in patients who received only minimal benefit from the four-channel implant, Schindler said.
He said 16 patients have been implanted with the four-channel device, and all but three can now understand some speech. Seven of the patients scored 50% or better on standard tests of speech recognition without lip reading.
"These high percentages of speech recognition appear to be unique among the various cochlear implant research groups," Schindler said. "These patients can clearly distinguish human speech, rather than just hearing sound, as is the case with some implants."
UCSF plans to begin clinical trial of the new eight-channel implant next year.
Like the four-channel device, the new eight-channel implant consists of a receiver and electrodes that are surgically implanted beneath the skin behind the ear, and an external speech processor worn in a pocket or on a belt. The processor converts speech and sound into electrical signals, which are transmitted to the auditory nerve via the implant.
The new device consists of 16 electrodes that can operate singly, in eight pairs, or in any combination of individual or paired electrodes to stimulate the auditory nerve.
"This flexibility in stimulation is the key because it makes it possible for the patient to hear more of the tone or pitch qualities that are present in normal speech," Schindler said. "If an implant provides only single channel stimulation, the patient may hear some environmental and a few speech sounds, but complete speech recognition is highly unlikely."