Soft tissue facial asymmetry in subjects with Moebius syndrome : bilateral vs. unilateral palsy

Aim. Moebius syndrome is a congenital, mono- or bilateral palsy of the facial and abducens nerves. We investigated soft tissue facial asymmetry in a group of patients with Moebius syndrome, comparing patients with monolateral palsy with patients with bilateral palsy, and using a set of asymmetry indices that could be employed by clinicians in their daily practice. Methods. The three-dimensional characteristics of the facial soft tissues of 16 male and 11 female patients aged 2 to 46 years were obtained by stereophotogrammetry; 18 paired (right and left) facial distances were calculated (ex-ch; n-ex; t-ex; t-sn; go-me; t-go; n-ch; sn-ch; sto-ch), and asymmetry indices computed. Data obtained in 10 patients with a monolateral palsy were compared to those obtained in 17 patients with a bilateral palsy. Results. In patient with a bilateral facial palsy, all mean asymmetry indices were smaller than 10%. In contrast, the patients with a monolateral palsy had two mean asymmetry indices that were larger than 15%. The nasion-exocanthion (monolateral: 7.53%, SD 4.55; bilateral: 4.13%, SD 2.44) and subnasale-cheilion (monolateral: 15.97%, SD 23.53; bilateral: 3.87%, SD 2.69) asymmetry indices were significantly larger in patients with monolateral than with bilateral palsy (Student’s t, P<0.05). A large intragroup variability was found. Conclusion. Patients with monolateral Moebius syndrome are more asymmetrical than patients with a bilateral syndrome, but not systematically. Patients with a bilateral palsy may possess an asymmetrical facial alteration.