Hemifacial microsomia

Last revised by Joshua Yap on 9 Oct 2022

Hemifacial microsomia (HFM) is the second most common congenital facial anomaly after cleft lip/palate. The condition may vary from mild to severe. Goldenhar syndrome has been described as a variant of hemifacial microsomia, in which vertebral anomalies and epibulbar dermoids are present.

Hemifacial microsomia is also known as craniofacial microsomiafirst and second branchial arch syndrome, otomandibular dysostosis, and lateral facial dysplasia

As many as 55% of patients with hemifacial microsomia also have extracranial anomalies, which may include central nervous system (CNS), skeletal, cardiac, lung, gastrointestinal, and kidney defects 3,4.

Hemifacial microsomia results from the abnormal development of the first and second branchial arches, hence it primarily affects the ear (aural), mouth (oral cavity), and jaw (mandible).

 A classification that grades mandibular deficiency was developed by Pruzansky in 1969 5:

  • grade I: minimal hypoplasia of the mandible

  • grade II: functioning but deformed temporomandibular joint with anteriorly and medially displaced condyle

  • grade III: absence of the ramus and glenoid fossa

CT is the usual imaging modality of choice to assess the extent of microsomia. There are a number of features:

  • ear: hypoplasia, aplasia, or malformation of the external ear and middle ear; there may be a hypoplastic mastoid process with partial or complete lack of pneumatization of the mastoid air cells

  • mandible: hypoplastic mandibular condyle, reduced height of the mandibular ramus with the chin deviated towards the affected side

    • the temporomandibular joint deformity can range from mild hypoplasia of the condyle with normal joint anatomy to a grossly disorganized joint anatomy and pseudo-articulation of the condyle at the cranial base

  • maxilla: may be normal or reduced in height with delayed eruption of the mandibular and maxillary molars

  • zygoma: may be hypoplastic with short or absent zygomatic arch

  • orbit: may be reduced in dimensions and the frontal bone can be flattened

  • soft tissues: facial musculature, facial nerve supply, and other adjacent soft tissues may be hypoplastic

The CT dataset may also be used to produce 3D models using advanced printing techniques popular for pre-surgical planning.

  • Pierre Robin syndrome: micrognathia, glossoptosis, and cleft palate

  • Treacher Collins syndrome: hypoplasia of facial bones, especially malar and mandibular bones, malformation of the external, middle, and internal ear, macrostomia, and high palatal arch

  • Parry-Romberg syndrome (facial hemiatrophy): progressive wasting of subcutaneous fat, sometimes accompanied by atrophy of skin, cartilage, bone and muscle

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