Hearing loss affects an estimated 50 million people in the United States. Now researchers have found that hearing loss may be affecting the long-term brain structure of those who suffer from it.
Beckman Institute faculty member Fatima Husain led the research, which employed two different imaging modalities in studies of people with hearing loss, normal hearing, and those with hearing loss and tinnitus (ringing in the ears). They found that those in the hearing loss group showed structural changes in their brains.
“This suggests that functional changes due to sensory deprivation may result in long-term structural changes,” Husain said. “However, in the case of tinnitus, surprisingly, there were few changes to brain structure despite changes to function, suggesting that when sensory deprivation is accompanied by self-generated noise, it may be better at preserving neural tissue.”
Husain and her collaborators on the study measured neuroanatomical changes in gray and white matter in the brains of participants with only bilateral hearing loss (HL), participants who had hearing HL and tinnitus (TIN), and a control group with normal hearing (NH) without tinnitus. Their study, reported on in a paper titled Neuroanatomical changes due to hearing loss and chronic tinnitus: A combined VBM and DTI, looked at neuroanatomical alterations associated with hearing loss and tinnitus.
The researchers used structural magnetic resonance imaging (MRI) scans and voxel-based morphometry (VBM) to examine changes in gray matter, and diffusion tensor imaging (DTI), to identify changes in white matter tract orientation. The researchers noted that while tinnitus is often accompanied by hearing loss, not everyone with hearing loss experiences tinnitus. Their goal in the study was to investigate structural gray and white matter changes related to tinnitus and hearing loss and try to dissociate them from changes due only to hearing loss.
“We observed that the HL group had the most profound changes in both white and gray matter relative to the other groups,” Husain said. “The gray matter decreases seen in the HL group relative to the NH group were in the anterior cingulate, putamen and middle frontal gyrus.
Husain added that two of these regions, the anterior cingulate and frontal cortex, were “also implicated in our companion study that studied functional response of the brain in the same group of subjects and points to involvement of the attention processing network.”
The researchers concluded that by dissociating the effect of tinnitus from hearing loss, they observed that “hearing loss rather than tinnitus had the greatest influence on gray and white matter alterations.”