Diffusion Kurtosis Imaging Detects Microstructural Changes in the Rat Brain with Sensorineural Hearing Loss

To examine the reliability of Magnetic resonance diffusion kurtosis imaging (DKI) on detecting microscopic structural changes in brain auditory cortex caused by deafness in live animals. In this study, DKI scans were performed on 20 deafness model rats using a 7T magnetic resonance imager. Ten normal rats from each age group served as controls. Changes in DKI quantitative indexes of temporal lobe cortex and auditory radiation in newborn rats after establishment of hearing impairment were measured. Electron microscopy were used to observe the ultrastructural and immunohistochemistry was used to investigate the growth-associated protein-43 (GAP-43) expression in the auditory cortex between the model and age-matched normal rats. Compared with the normal control group, DKI showed lower fractional anisotropy (FA) values in the temporal lobe and auditory radiation in 8-week-old rats, and 12-week-old deafness model rats showed decreased FA values and mean kurtosis (MK). No significant difference of DKI parameters between them in 2-week-old rats. In the deafness model rats, Electron microscopy showed abnormal ultrastructure changes of auditory cortex cells. At 12 weeks postpartum, GAP-43 expression in the auditory cortex was statistically substantially higher than in the normal control rats. DKI can reveal the effects of sound deprivation on cerebral cortex development. The findings of DKI, Electron microscopy, expression of GAP-43 in the auditory cortex after afferent auditory injury in rats, might provide imaging laboratory evidence for the need for early cochlear implantation to promote neuro-development.