Three-dimensional facial analysis in subjects with Moebius Syndrome using stereophotogrammetry

OBJECTIVES Moebius Syndrome (MS) is a rare disorder defined by bilateral con­ genital paralysis of the abducens and facial nerves in combination with various odontological, cra­ nio-facial, ophthalmological and orthopaedic conditions. Despite the broad spectrum of clinical manifestations, the main feature of patients with MS is due to the involvement of the VII cranial nerve and consists in the absence of movement of the facial mimic muscles with important aesthetic and functional consequences. The aim of this study is to quantify the surface facial asymmetry in two subjects affected by MS, us­ ing a novel stereophotogrammet­ ric method. MATERIALS AND METHODS A male patient (case 1, age 17.3 years) and a female patient (case 2, age 7.7 years), both affected by MS, were imaged with a ste­ reophotogrammetric facial scan­ ner. A three-dimensional (3D) elaboration was performed throughout the software View box (dHAL Software, Kiflissia, Greece) and each original image was du­ plicated in a mirror version. The root mean square error (RMSE) of the distances between the corre­ sponding points of each original photograph and its mirror copy was calculated for the whole face and for each trigeminal third, as defined by the innervation of tri­ geminal branches. Deviations between the original and mirror facial images were al­ so presented graphically as color maps and quantitatively on histo­ grams. RESULTS Case 1 presented incomplete bi­ lateral denervation of the facial nerve and had a RMSE value of 4.028, which quantified the global asymmetry; such a value progres­ sively increased from the upper third (RMSE = 2.277), through the middle third (RMSE = 3.675) and to the lower third of face (RMSE = 5.031). By contrast, case 2 had bilateral agenesis of facial nerve (missing facial nerves) and showed a minor global asymme­ try of the face (RMSE = 2.427) with a similar distribution of asym­ metry in all trigeminal thirds, whose RMSE values were respec­ tively 2.244 in the upper third, 2.023 in the middle third and 2.674 in the lower third. The evaluation of color maps confirms the data regarding the different degree and localization of the asymmetry in the two sub­ jects examined: in case 1 the asymmetry involves the region of the lateral and alar cartilages of the nose and the nasolabial fold, extending to the cheeks, man­ dibular angles and lateral areas of the chin; case 2 shows asym­ metrical areas mainly in corre­ spondence with the lateral sides of the nose, from the root to­ wards the apex, with a reduced involvement of the peri-labial and para-symphyseal surfaces. CONCLUSIONS The reported 3D technique provid­ ed an accurate topographic analy­ sis of the facial asymmetry and it is recommended for the quantitative and qualitative evaluation of rare cranio-facial conditions such as MS, showing a wide range of phe­ notypic presentations. CLINICAL SIGNIFICANCE The study of the facial morphology using methods based on stereo­ photogrammetry may improve both cranio-facial research and clinical practice, providing addi­ tional information for diagnosis, treatment planning and follow-up.