Diffuse brain injury does not affect chronic sleep patterns in the mouse

Primary objective: To test if the current model of diffuse brain injury produces chronic sleep disturbances similar to those reported by TBI patients. Methods and procedures: Adult male C57BL/6 mice were subjected to moderate midline fluid percussion injury (n=7; 1.4atm; 6-10 minutes righting reflex time) or sham injury (n=5). Sleep-wake activity was measured post-injury using a non-invasive, piezoelectric cage system. Chronic sleep patterns were analysed weekly for increases or decreases in percentage sleep (hypersomnia or insomnia) and changes in bout length (fragmentation). Main outcomes and results: During the first week after diffuse TBI, brain-injured mice exhibited increased mean percentage sleep and mean bout length compared to sham-injured mice. Further analysis indicated the increase in mean percentage sleep occurred during the dark cycle. Injury-induced changes in sleep, however, did not extend beyond the first week post-injury and were not present in weeks 2-5 post-injury. Conclusions: Previously, it has been shown that the midline fluid percussion model used in this study immediately increased post-Traumatic sleep. The current study extended the timeline of investigation to show that sleep disturbances extended into the first week post-injury, but did not develop into chronic sleep disturbances. However, the clinical prevalence of TBI-related sleep-wake disturbances warrants further experimental investigation.