Quantification of Isolated Craniosynostosis: Introducing and Implementing UCSQ as a New Skull Shape Quantification Method

The aim of this thesis was to develop a new, objective and reproducible quantification method for (isolated) craniosynostosis. Additionally, this new method was used for the subgroups, trigonocephaly, scaphocephaly and brachycephaly to quantify the severity of each subtype. UCSQ (Utrecht Cranial Shape Quantificator) is an objective and outline-based classification method, developed in order to capture the skull shape using external landmarks (porion and exocanthion). A base plane and a plane at 4 cm height from base plane are created, outlines are segmented, and sinusoidal curves are plotted. The following distinctive features of the sinusoidal curve per diagnosis of craniosynostosis were found: scaphocephaly has a high forehead peak and low troughs, in contrast to brachycephaly. Anterior plagiocephaly has asymmetry and shifting of the forehead peak. Trigonocephaly has a high and narrow frontal peak. Control patients have a symmetrical skull shape with low troughs and a high and broader frontal peak. Characteristics per diagnosis are extracted and calculated from the curves. Based on these characteristics a diagnostic flowchart is developed. For clinical and research purposes it is important to quantify severity of different subgroups of isolated craniosynostosis. Additionally, UCSQ was compared to existing methods of quantification for each subgroup. Quantification of severity of scaphocephaly and the link between the severity of the deformity and its intracranial volume (ICV) was discussed. UCSQ uses the following distinctive variables for scaphocephaly: width of skull and maximum occiput and forehead.We found that UCSQ is preferable for research, however in daily clinical practice CI is preferable since it is easy to use and minimally invasive. Negligible correlation was found between ICV and UCSQ. Quantification of severity of trigonocephaly using the following distinctive variables for trigonocephaly: forehead width and relative skull elongation, was discussed. Additionally, forehead (a)symmetry is assessed. UCSQ has the strongest correlation with clinical judgment and is suited for severity quantification.Trigonocephaly is known as symmetrical, however unexpectedly we found a larger triangle area right than left, indicating forehead asymmetry, possibly caused by accompanying positional plagiocephaly. Quantification of severity of anterior brachycephaly using the following distinctive variables for brachycephaly: width of frontal peak ratio, difference forehead peak and occiput peak, and width between sides of the head, was discussed. UCSQ can quantify anterior brachycephaly according to severity using characteristics and it outperforms traditional quantification methods. Furthermore, ICV in trigonocephaly was calculated and correlated to severity of trigonocephaly and to the presence of increased intracranial pressure (ICP). ICV was found to be within normal ranges for trigonocephaly patients, due to compensating skull growth from patent sutures, in both mild and severe cases. No correlation was found between severity of trigonocephaly and ICV and ICP. Additionally, UCSQ was implemented on 3D photogrammetry in craniosynostosis patients. Every included patient was correctly diagnosed based on the objective variables. Therefore, by using the diagnostic flowchart, based on specific characteristics for each subgroup of isolated craniosynostosis, diagnosis can be established while using 3D photogrammetry