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Background: Bone anchored earing devices have developed over the years and today more than 250 000 persons in the world benefit from these devices. A review of the development will be given. Recent studies show a greater impact on hearing, learning and in social life than earlier recognized when suffering from single sided ear canal atresia especially during development. Persons with single sided conductive hearing loss have earlier not been habilitated. Objective: Central hearing pathways in humans and in an animal model with single sided conductive hearing loss due to ear canal closure has been studied. Material and Methods: Children and adults with single sided conductive loss due to ear canal atresia have been tested using functional Magnetic Resonance Imaging and Diffusion Weighted Imaging. An experimental model has been established in Sprague Dawley rats where one ear canal was sutured and closed at birth to mirror the human congenital malformation of ear canal atresia. MRI testing were performed at 1,3,6 and 12 months of age. Results: White tissue in the human brain is statistically shown to be thinner on the affected side. Software developed for human data could be transformed and used on images of rats. The developed method handles formatting issues, artefact corrections, diffusion metrics calculations and statistical group comparisons of magnetic resonance diffusion weighted images. Three month old rat brains have been investigated and found to have special patterns and connection between the central hearing nuclei. Conclusion: Investigation with MRI has made it possible to map regions of interest in humans and to find connectivity between different hearing nuclei in the brain in a rat model with single sided ear canal closure. [ABSTRACT FROM AUTHOR]