Three-dimensional CT evaluation of oculoauriculovertebral spectrum patients use of Katsumata’s asymmetry index

Objectives To evaluate patients with oculoauriculovertebral spectrum (OAVS) malformations based on Katsumata’s asymmetry index and to assess the usefulness of the scores thus obtained in identifying degrees and sites of asymmetry. Methods Multislice spiral computed tomography (MSCT) datasets of 8 female and 12 male OAVS patients aged 5.7–23.9 years were retrospectively analyzed. After three-dimensional reconstruction, central and bilateral anatomical landmarks were identified within a coordinate system defined by the sella, nasion, and dens axis. MSCT datasets of 20 clinically symmetrical patients were used to define the cutoff values for asymmetry. Based on the mean asymmetry scores and their standard deviations, the severities and sites of asymmetry were evaluated and processed for visual presentation in charts. Results Both interrater (ICC 0.7070–0.9984) and intrarater (FVU 0.0014–0.2930) reliability was very high. The calculated asymmetry scores added up to mean values and standard deviations that were higher by factors of around 1.5–2.5 than reported by Katsumata et al. More anatomical landmarks were rated as asymmetric in OAVS patients showing unilateral agenesis of an external acoustic pore than in OAVS patients without such agenesis: in the former patients, statistically significant asymmetries compared to the control group were present at the L1M (coronal pulp cavity of the lower first molar), CoP (coronoid process), and Co (condylion superius) landmarks, whereas the latter group showed such significant asymmetries at the CoP and Co landmarks. Likewise, more patients with unilateral agenesis showed asymmetries at the level of the maxilla. Highly variable severities of asymmetry were found in both subgroups of OAVS patients. Conclusion Katsumata’s asymmetry index can yield well-structured and illustrative views of landmark distribution, thus, suitably allowing for qualitative asymmetry evaluation of OAVS cases and identification of the skeletal regions involved.