Traumatic brain injury (TBI) is a leading cause of death and disability in children. One of the leading causes of severe TBI in infants is abusive head trauma (AHT). Shaken baby syndrome (SBS) is a subset of AHT in which brain injury is present without obvious signs of head impact, thus the head injury is thought to be caused by shaking. SBS is one of the most difficult forms of TBI to study as the injuries are complex and the histories surrounding the child’s injuries are questionable, or unknown. In this thesis, we investigate potential mechanisms of brain and eye injury from AHT and SBS. In Chapter 2, we investigate the potential coupling effect of the physiological response to crying (i.e. increased intracranial pressure (ICP) and increased cerebral blood volume (CBV)) with repetitive head trauma. Increased ICP and CBV prior to and during head trauma did increase the amount of injury and there was some macroscopic findings unique to that group; however, levels of injury were not as severe as reported clinically in SBS.
In Chapters 3 and 4, we investigated two potential mechanisms of retinal hemorrhage (RH), a common ocular injury reported in AHT. The first study investigated whether repetitive occlusion of the optic nerve (ON) could lead to RH. Occluding the ON for 1-10 minutes and then releasing resulted in large RH that spanned the posterior pole and periphery of the retina. Cyclic, repetitive occlusion of the ON, however, resulted in no hemorrhage. In the second study, rapid increases in intraocular pressure (IOP) were evaluated as a possible mechanism of RH from AHT. A device mechanically indented the eyes of 3-5-day-old piglets at different rates and depths to produce large changes in IOP. No hemorrhages were caused from the rapid changes in IOP, and it was concluded that rapid changes in IOP by itself does not cause RH. This work identified two mechanisms which can influence or cause injury from abuse, and another mechanism was shown to likely not be a factor in abuse.
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