Defining an Analytic Framework to Evaluate Quantitative MRI Markers of Traumatic Axonal Injury: Preliminary Results in a Mouse Closed Head Injury Model.

Diffuse axonal injury (DAI) is a hallmark of traumatic brain injury (TBI) pathology. Recently, the Closed Head Injury Model of Engineered Rotational Acceleration (CHIMERA) was developed to generate an experimental model of DAI in a mouse. The characterization of DAI using diffusion tensor magnetic resonance imaging (MRI; diffusion tensor imaging, DTI) may provide a useful set of outcome measures for preclinical and clinical studies. The objective of this study was to identify the complex neurobiological underpinnings of DTI features following DAI using a comprehensive and quantitative evaluation of DTI and histopathology in the CHIMERA mouse model. A consistent neuroanatomical pattern of pathology in specific white matter tracts was identified across ex vivo DTI maps and photomicrographs of histology. These observations were confirmed by voxelwise and regional analysis of DTI maps, demonstrating reduced fractional anisotropy (FA) in distinct regions such as the optic tract. Similar regions were identified by quantitative histology and exhibited axonal damage as well as robust gliosis. Additional analysis using a machine-learning algorithm was performed to identify regions and metrics important for injury classification in a manner free from potential user bias. This analysis found that diffusion metrics were able to identify injured brains almost with the same degree of accuracy as the histology metrics. Good agreement between regions detected as abnormal by histology and MRI was also found. The findings of this work elucidate the complexity of cellular changes that give rise to imaging abnormalities and provide a comprehensive and quantitative evaluation of the relative importance of DTI and histological measures to detect brain injury.

Oral health and hospitalization in Western Australian children.

Over the past 20 years, the prevalence of dental disease in Western Australian children has diminished. The causes of this significant improvement in health are associated with better care models, water fluoridation and changes in lifestyle. In this study, the authors examine the reasons for hospitalization for oral health conditions in Western Australia for the calendar year 1995 using the Health Department of WA database. A total of 3,754 episodes of care (4,395 bed days) was recorded for dental conditions. Dental caries resulted in the fifth and sixth highest number of episodes of hospitalization in preschool (1-4 years) and primary-school age (5-12 years) children respectively. Abnormal tooth eruption resulted in the highest number of episodes of hospitalization in high-school age (13-17 years) children. From the age-stratified rates of hospitalization (per 1000), non-Aboriginal children were more than twice as likely to enter hospital for dental related conditions. The primary cause of this is the 15 times higher rate of hospitalization for high-school age non-Aboriginal children which clearly reflects the greater use of services for impacted third molars by the metropolitan non-Aboriginal community. Examination of the distribution by health service region revealed the hospitalization rate was significantly less than the state average for the Kimberley, Pilbara, Northern Goldfields and Wanneroo regions. These data reflect the paucity of oral health care available to residents of these regions, particularly the northwest, and does not reflect a diminished burden of disease. Similarly, the rate of hospitalization for Aboriginal children reflects population and service delivery differences particularly in regional and remote WA. These data highlight the need to develop new strategies in oral health care to target 'at risk' groups in the community, particularly new parents of young children. The preventive measures associated with good oral health in children are clearly aligned with those for good general health and can be integrated into existing health messages.