The prevalence of accessory sutures and wormian bones in a contemporary cohort of Dutch children. Gisela de Heus, 11414901 MSc in Forensic Science, University of Amsterdam Supervisors: Prof. Dr. R.R. van Rijn Amsterdam University Medical Centres UMC, Department of Radiology K.L. Colman Amsterdam University Medical Centres UMC, Department of Anatomy, Embryology and Physiology H.H. de Boer Amsterdam University Medical Centres UMC, Department of Pathology, NFI Department of Medical Forensic Research Examiner: 36 European Credits Prof. Dr. R.J. Oostra Amsterdam University Medical April 2018 – October 2018 Centres UMC, Department of Medical Biology Date of submission: 19-10-2018 Abstract Child abuse is a widely prevalent problem in the Western world. It is estimated that 118.000 to 180.000 children are abused in the Netherlands annually, of which physical abuse constitutes almost 18% of all abusive cases, with Abusive Head Trauma (AHT) being categorised as a severe form. In child abuse cases, skull fractures are a strong indication of AHT. However, the presence of accessory sutures and Wormian bones, sometimes lead to erroneous conclusions. This is because accessory sutures sometimes present similar morphologically characteristics on radiographs as fractures. Knowledge on the prevalence of accessory sutures and Wormian bones would help in preventing erroneous conclusions, however all current knowledge is based on dry skull collections mostly on adult skulls. Accessory sutures may not persist into adulthood together with the fact that modern population experienced secular changes makes these collections not representative for the modern Dutch children population. The aim of this study was to determine the prevalence of accessory sutures and Wormian bones in a contemporary cohort of Dutch children below the age of 6. For this research, 532 cranial CT scans of children below the age of 6 were selected from a PACS system (AGFA Impax 6.6.1. 4024, Agfa Healthcare, Mortsel, Belgium. Volume Rendering Technique (VRT) of the program Syngo.via was used to create 3D reconstructions of the CT scans. The scans were retrospectively reviewed by two observers, one of which an experienced paediatric radiologist. The presence of various accessory sutures and Wormian bones were scored and evaluated using 3D reconstructions of CT scans. The mean age of the cases was 28.47 months (range 0.033 to 72 months) for males and 22.57 (rang 0.066-72 months) for females. The results from this study showed that accessory sutures were present in 34.3% of the cases. Of these accessory sutures, the metopic and mendosal suture were seen most frequently with 29.9% and 23.9% respectively. Other accessory sutures that were found including the intraparietal horizontal suture, intraparietal vertical suture, obelion suture and an occipital unossified midline were seen less frequently with 7.2%, 3.8%, 2.2% and 0.9% respectively. None of the accessory sutures showed sexual preference. Most accessory sutures were found in the lower age groups and particularly the prevalence of the metopic and mendosal suture showed a decrease with age. Wormian bones were found in 78% of the cases, with the most frequent location being the lambdoid suture with 64.2%. Only the parietal notch showed a significant difference between female and male (p=0.024). Knowledge about the existence, prevalence and topographical location of various accessory sutures and wormian bones will aid in the ability to make correct diagnosis and thereby increase the evidential value of the diagnosis in cases of abuse. However, because of several limitations of this study the results have to be interpreted and used with care. Keywords: Accessory cranial sutures, Skull fractures, Child abuse, Wormian bones, 3D CT reconstruction Page 2 of 34 Table of Contents Abstract .................................................................................................................................................... 2 1. Introduction .......................................................................................................................................... 4 1.1 Normal development of the skull ................................................................................................... 4 1.2 Accessory sutures ......................................................................................................................... 5 1.3 Wormian bones ............................................................................................................................. 6 1.4 Aim of the study ............................................................................................................................. 7 2. Methods ............................................................................................................................................... 8 2.1 Study population ............................................................................................................................ 8 2.2 Data collection ............................................................................................................................... 8 2.3 Data analysis ................................................................................................................................. 9 2.4 Ethical aspects .............................................................................................................................. 9 3. Results ............................................................................................................................................... 10 3.1 Intra- and inter-observer variability .............................................................................................. 10 3.2 Prevalence ................................................................................................................................... 10 3.2.1 Metopic suture ...................................................................................................................... 10 3.2.2 Intraparietal horizontal suture ............................................................................................... 11 3.2.3 Intraparietal vertical suture ................................................................................................... 12 3.2.4 Obelion suture ...................................................................................................................... 13 3.2.5 Occipital unossified midline membrane ................................................................................ 13 3.2.6 Mendosal suture ................................................................................................................... 14 3.2.7 Wormian bones .................................................................................................................... 14 3.2.8 Craniosynostosis .................................................................................................................. 17 4. Discussion ......................................................................................................................................... 18 4.1 Intra- and inter- variability ............................................................................................................ 18 4.2 Accessory sutures ....................................................................................................................... 18 4.3 Wormian bones ........................................................................................................................... 19 4.4 Craniosynostosis ......................................................................................................................... 20 4.5 Limitations.................................................................................................................................... 20 4.6 Practical implications ................................................................................................................... 21 4.7 Future research ........................................................................................................................... 21 5. Conclusion ......................................................................................................................................... 23 Acknowledgements ............................................................................................................................... 24 References ............................................................................................................................................ 25 Appendix A Glossary ............................................................................................................................. 28 Appendix B Case Report Form (CRF) ................................................................................................... 29 Appendix C Reference figures Case Report Form ................................................................................ 33 Page 3 of 34 1. Introduction Child abuse is a worldwide problem and the prevalence in the Netherlands is approximately between 118.000 and 180.000 cases a year 1–3. However, abuse is often not detected because of lack of symptoms or is not reported by the physician. Therefore the actual prevalence is expected to be even higher1. Physical abuse constitutes almost 18% of all abusive cases of which Abusive Head Trauma (AHT) is a severe form often characterized by cranial fractures 2–4. However, a