Imaging of the brain stem can pinpoint assess brain stem function in patients with hearing loss.
PET/CT imaging could be used to predict how well a cochlear implant will improve hearing for people who have lost hearing in one or both ears.
In a small study from the University of Freiburg Medical Center in Germany, published in the March issue of the Journal of Nuclear Medicine, investigators, using 18F-FDG PET/CT imaging, determined that individuals with hearing loss in only one ear (asymmetric hearing loss) also have reduced glucose metabolism in parts of their brain stem and primary auditory cortex (PAC) – the area of the brain responsible for hearing tones and pitch. A healthy glucose metabolism in the brain ensures neurons are functioning properly.
It’s possible the PAC could be influenced by cortical reorganization – changing the cortical map due to outside stimuli. Understanding why and how this occurs could help providers determine how well a cochlear implant might work for individual patients, said lead study author Iva Speck, M.D., resident of otorhinolaryngology. And, fully digital clinical PET/CT systems provide the enhanced imaging and quantitative assessment of small brain stem nuclei necessary to answer these questions.
To determine the impact, researchers imaged 13 patients with asymmetric hearing loss, examining glucose metabolism in the inferior colliculus (IC) – the part of the brain that acts as the body’s main auditory pathway – and in the PAC. They performed an analysis to determine how the length of hearing impairment impacts glucose metabolism, and to compare glucose metabolism between the IC and PAC.
According to their results, patients had significantly reduced regional glucose metabolism of both the IC and PAC in the ears that had better hearing when compared to the impaired ears. Researchers discovered the longer a patient had hearing impairment, the higher their metabolism in the PAC on the unimpaired ear side. However, the duration of hearing impairment didn’t predict regional glucose metabolism for the impaired ear’s PAC or the IC with either ear.
“Previous studies suggest that the association between longer duration of hearing impairment and higher glucose metabolism indicates cortical reorganization. In bilateral deaf patients, this has been shown to lessen the benefits of cochlear implants,” Speck said.
Augmented imaging with a fully digital PET/CT could help predict successful cochlear implant outcomes, she said, because significant aspects of the auditory system, including small brain nuclei, such as the IC, can be evaluated for pre-operative patient characterization.
Alongside these results and potential applications with cochlear implants, she said, the findings could also be on interest to other neurological research fields, including neurodegenerative diseases, that affect the brain stem early in the course of the disease.