Cochlear Implants Restore Auditory Synapses in Deaf Cats
Scientists supported by the National Institute on Deafness and Other Communication Disorders (NIDCD) of the National Institutes of Health have demonstrated that cochlear implants can restore the structure of synapses along the auditory nerve in deaf cats. This finding may explain why cochlear implants work best in young children before irreversible abnormalities occur.
The investigators designed their experiments to compare the synapses of deaf cats whose auditory nerves are electrically stimulated by a cochlear implant to the synapses of deaf cats with no implants and cats with normal hearing. The researchers found that following stimulation, the synapses of deaf cats with cochlear implants closely resembled the synapses of cats with normal hearing, as opposed to the abnormal synapses found in deaf cats with no cochlear implant. As with the cats, synaptic changes in young children who are deaf are believed to occur after cochlear implantation.
This research appeared in the Dec. 2, 2005 issue of Science and was conducted at the Department of Otolaryngology-Head and Neck Surgery and Department of Neuroscience at the Johns Hopkins University Center for Hearing and Balance.
Chemotherapy and Hearing Loss
A new study published in the Journal of Clinical Oncology found that the frequency and severity of ototoxicity have long been underreported.
The research states that a well-known classification system doctors use for reporting toxicities in patients-the National Cancer Institute's Common Terminology Criteria for Adverse Events, or CTCAE-doesn't consider high-frequency hearing loss. This allows the miscalculation of ototoxicity in children treated with platinum agents.
Researchers at Oregon Health and Science University, Portland, examined the incidence of and time to hearing loss in 67 patients aged 8 months to 23 years who received chemotherapy.
Forty-one of the patients (61%) experienced a decrease in hearing sensitivity after chemotherapy. Hearing loss was more severe among children who received chemotherapy for medulloblastoma (a type of brain tumor), osteosarcoma (a type of bone cancer), and neuroblastoma (cancer of developing nerve cells in the fetus), and males had higher-grade hearing loss than females.
After an average follow-up of 20.7 months, none of the patients experienced an improvement in hearing.