Figure 1: Illustration of radiological cephalometric landmarks (left) and synopsis of measurement results in FPNF group (right).
The measurement points are marked on a schematic representation of the skull surface. In this position, the cranial border of the condylar process is not visible with the bare eye and therefore is shown in dashed outline. The individual lines CoR-M, CoL-M, AgR-M and AgL-M are defined by their perpendicular intersection with the median-sagittal axis. The total distance CoR-CoL is defined in transversal diameter and is calculated from a line connecting the highest point of left and right condyle (Intercondylar distance). The line AgR-AgL connects the highest points of the indentation of the mandibular base close to the angle. On the right side, a schematic representation illustrates the position changes of the measurement points in patients with facial plexiform neurofibromas. In patients with FPNF, the condyle is positioned more laterally and caudally on the affected side compared with the unaffected opposite side. Patients who have developed PNF only in the third trigeminal branch deviate from this pattern. The position of the condyle in this group (NV3), which is closer to the M plane, differs significantly from that of other FPNF groups. This finding is illustrated by the medially directed dashed arrow below the measurement point. This deviation is in the same direction as the more medial position of the antegonion in this group (NV3-FPNF, see below). In patients with FPNF, the antegonion measurement point is shifted cranially and laterally. This effect is particularly evident in patients with hemifacial FPNF. The position of the antegonion on the tumor-affected side deviates from this scheme in patients with PNF manifesting only in the third trigeminal branch. In this case, the measurement point of the tumor side deviates towards the median sagittal. The different position of Ag on the affected side in patients with FPNF restricted to the mandibular nerve (NV3-FPNF) is indicated by the dashed arrow below the measuring point AgR (right side is the FPNF side in this illustration). The findings are discussed in more detail in the text.