Optical Neuro-Imaging of Deaf Children with Cognitive Delays after Cochlear Implantation
John S Oghalai, M.D.
Baylor College of Medicine, Houston, TX
David Mahoney Neuroimaging Program
December 2007, for 3 years
Imaging May Guide Cochlear Implant Programming to Maximize Speech and Language Perception
To develop an objective measure of auditory perception, researchers will use conventional near-infrared spectroscopy (NIRS) imaging in deaf children that are learning to hear through a cochlear implant. This technique has the promise of guiding cochlear implant programming to optimize speech and language understanding.
The most common treatment for congenital deafness, which impedes a child’s ability to learn speech and language, is the surgical placement of an electronic device that receives incoming sounds and electronically stimulates the auditory nerve. This process by-passes the malfunctioning inner ear. To date, placement and programming of the electronic stimulator relies on the child’s subjective behavioral responses used to define their hearing threshold. This situation is even more complex in children with cognitive delays, which often accompany congenital deafness, since these children initially have no behavioral responses to speech. The investigators hypothesize that NIRS can provide an accurate and immediate measure of speech perception in deaf children who hear through a cochlear implant.
A total of 160 children will be offered enrollment in the study. Investigators will test the hypothesis by first assessing the accuracy of NIRS imaging. They will compare behavioral and NIRS imaging responses in children who have used a cochlear implant for more than two years and whose behavioral responses have already been shown to be accurate. Next, they will test the immediacy of the NIRS imaging measure, by comparing behavioral responses with NIRS imaging responses in children with newly implanted cochlear implants. After they assess NIRS imaging’s accuracy and immediacy by comparing it to children’s behavioral responses, they will study its utility in children with cochlear implants who are cognitively delayed and have no behavioral responses to speech, and see whether responses in the brain’s cortex can be measured using NIRS. If so, NIRS may be effectively used in this population as well.
Significance: If NIRS imaging provides an accurate and immediate measure of speech perception in congenitally deaf children who hear through cochlear implants, NIRS can be used to maximize the children’s speech and language perception, ultimately improving their ability to learn.
Optical Neuro-Imaging of Deaf Children with Cognitive Delays After Cochlear Implantation
Congenital deafness inhibits a child’s ability to learn speech and language. The most common treatment for deafness is the surgical placement of a cochlear implant, an electronic device that receives incoming sounds and electrically stimulates the auditory nerve, thereby bypassing the malfunctioning inner ear. Achieving optimal results with a cochlear implant requires programming it so that it appropriately stimulates the auditory nerve. To date, this process completely depends upon the measurement of subjective behavioral responses to define the threshold of hearing. However, congenitally-deaf children have no concept of what sound is, and thus have highly variable behavioral responses. These issues are even more complex in children with cognitive delays, a condition that often co-exists with congenital deafness, because they often have no behavioral responses.
We propose to use near-infrared spectroscopy (NIRS) in deaf children who hear with a cochlear implant to optically image activity within the auditory cortex in response to speech stimuli. Our overall goal is to develop an objective measure of auditory perception that could be used to guide cochlear implant programming, even if behavioral responses are absent. We hypothesize that NIRS can provide an accurate and immediate measure of speech perception in deaf children hearing through a cochlear implant.
We have three specific aims:
First, we will correlate behavioral responses with NIRS responses from children who have used a cochlear implant for >2 years. This aim will test the hypothesis that NIRS thresholds accurately predict behavioral thresholds using patients with reliable behavioral thresholds.
Second, we will compare behavioral responses with NIRS responses from children at initial cochlear implant activation. This aim will test the hypothesis that NIRS thresholds immediately predict behavioral thresholds.
Third, we will determine whether cortical responses can be measured using NIRS from implanted children with cognitive delays. Because of their lack of behavioral responses, this patient population has a significant need for such technology and could benefit immediately from its use. This proposal is innovative because this technology has never before been applied to hearing-impaired patients. This research is translational and could have an immediate, significant positive impact on patient health because NIRS may prove to be a valuable clinical tool. It has the potential to guide cochlear implant programming in any patient with unreliable behavioral responses.
John S Oghalai, M.D.
John Oghalai grew up in Madison, Wisconsin, and received his undergraduate degree in electrical engineering and his medical degree at the University of Wisconsin, Madison. During this time, he began studying auditory neurophysiology in the laboratories of William Rhode and Dan Geisler. He moved to Houston in 1994 to begin residency training in otolaryngology-head and neck surgery at Baylor College of Medicine. During this time, he spent two additional years in the basic science research lab of William Brownell studying hair cell physiology. From 2001-2003, he trained at the University of California, San Francisco in otology, neurotology, and skull base surgery with Robert Jackler, Anil Lalwani, and Steve Cheung. He moved back to Baylor College of Medicine in 2003 to join the faculty of the Bobby R. Alford Department of Otolaryngology – Head and Neck Surgery as an Assistant Professor.
Dr. Oghalai is a clinician-scientist, dividing his time between clinical and research activities. His clinical duties are dedicated to treating adult and pediatric patients with hearing loss, middle ear disorders, and tumors involving the cranial base. He is the Clinic Chief of The Hearing Center at Texas Children’s Hospital, which includes directing the cochlear implant program for deaf children. Dr. Oghalai’s research lab is working to understand mechanisms behind hearing loss, to clarify the implications of hearing loss on childhood development, and to translate this knowledge towards the development novel treatment strategies for hearing loss.