Single-sided deafness (SSD), while caused by factors ranging from viral infections to brain tumors, is incurable and rather difficult to treat. Now, it has been discovered that it is closely related to issues involving plasticity in the brain, particularly a misalignment of brain hemispheres.
These new findings from researchers at the University of California, San Francisco could pave the way for a cure for SSD, which remains elusive partially because of the current lack of biomarkers to signify the disease.
The condition currently affects about 60,000 every year in the United States and has symptoms that include hearing impairment and difficulty gauging sound direction.
The team of Dr. Srikantan Nagarajan and Dr. Steven Cheung harnessed recent developments on brain plasticity, or the organ’s ability to alter its structure and function based on bodily changes.
They recruited 26 individuals, with 13 diagnosed with SSD and 13 maintaining normal hearing. Exposing them to a series of sounds at varying frequencies and then using methods such as MRI scans, they saw differences in how the left and right auditory cortices of the two groups functioned.
Neurons in the cortices are lined up in a tonotopic map in a way that those activated by a certain frequency of sound are found near others activated by a similar frequency. This is how the balance in hearing works, according to the researchers.
It appeared that subjects with normal hearing had symmetrical neuron stimulation, unlike subjects with SSD that had extended neuron activation in one hemisphere of the brain but a reduced one in the other.
The results suggested that a certain type of brain stimulation may help restore normal relationship between the two cortices, therefore potentially restoring normal auditory processing.
“Hearing optimization in the only hearing ear may require remediation of both spatial and temporal central auditory changes in SSD,” the authors wrote in the study, which was published in the journal Laryngoscope.
In March, a separate study concluded that taking nutritional supplements every day may help slow down the progression of genetic loss of hearing among children.
Photo: Nick Kenrick | Flickr
