Summary of Treacher-Collins Syndrome: Surgical Management

## Introduction Treacher–Collins syndrome (also called mandibulofacial dysostosis) is a congenital condition that primarily affects the bones and soft tissues of the midface and lower face. It commonly involves the orbits, zygomaticomaxillary complex, mandible, eyelids, ears, and sometimes the palate and pharynx. Intelligence is usually normal. Management is multidisciplinary and staged over childhood. > **Definition:** Treacher–Collins syndrome is an autosomal-dominant disorder with variable penetrance that causes bilateral malformations of structures derived from the first and second branchial arches. ## Key anatomical and clinical features Break complex features into clear parts to understand how the syndrome presents and why functional problems occur. ### Face and skull - **Malar (cheek) region:** hypoplastic or absent zygomatic bone and zygomatic arch; leads to flattened midface contour. - **Orbit:** lateral and inferior orbital walls often deficient, altering orbital shape and eyelid support. - **Maxilla:** narrow, underprojected, with a high and narrow palate. - **Mandible:** hypoplastic with shortened ascending ramus and body; long, retruded chin and often an exaggerated antegonial notch. ### Eyes and eyelids - **Palpebral fissures:** antimongoloid (inferior) obliquity and shortening. - **Lower eyelid colobomas:** partial defects of the lower eyelids. - **Lateral canthal dystopia** and **notching of upper eyelids/eyebrows**; eyelashes may be reduced or absent. ### Ears and hearing - **Microtia** or other external ear deformities. - **Absence or atresia of the external auditory canal** and middle ear anomalies leading to conductive hearing loss. ### Oral and airway - **Macrostomia** (large mouth) and possible velopharyngeal insufficiency. - **Narrow pharynx and micrognathia** can cause obstructive sleep apnea; airway compromise is a major early concern. > **Definition:** Coloboma — a notch or defect in an anatomical structure, often describing a lower eyelid defect in Treacher–Collins syndrome. ## Genetics and etiology - Inheritance: autosomal-dominant with variable penetrance and expressivity. - About 40% of cases have a family history; approximately 60% are sporadic (de novo) mutations. - Phenotypic severity can increase in successive generations (anticipation in expressivity reported). - Advanced paternal age is a risk factor for new mutations. - Pathogenesis: abnormal development of structures derived from the first and second pharyngeal (branchial) arches. ## Diagnosis and imaging - Clinical diagnosis is based on the characteristic craniofacial features summarized above. - Radiographic signs: - Waters and posterior–anterior views show malar hypoplasia and partial/complete absence of zygomatic arches. - Frontal tomograms and 3D CT reveal deficiencies of the lateral orbital rim and malar bone. - Lateral cephalogram: normal anterior face height with reduced posterior face height, vertical occlusal plane, shortened choanae, mandibular retrognathism. > **Definition:** Waters view — a radiographic projection useful for visualizing the maxillary sinuses and zygomatic arches. ## Clinical problems and functional impact - **Airway obstruction:** Narrow pharynx and short mandible risk obstructive sleep apnea and neonatal respiratory compromise. - **Feeding difficulties:** Neonates with severe micrognathia may have problems feeding. - **Hearing impairment:** Conductive hearing loss due to external and middle ear anomalies; early audiologic assessment is important. - **Ocular exposure/irritation:** Lower eyelid colobomas can cause exposure keratopathy if severe. - **Dental/occlusal issues:** Class III malocclusion with anterior open bite, vertical occlusal plane changes. ## Multidisciplinary evaluation and typical care pathway 1. Neonatal period - Prioritize airway assessment and management. Early mandibular growth support may be necessary. - Feeding support and audiology screening. 2. Early childhood