Department of Oral & Maxillofacial Surgery/Dental & Maxillofacial Surgery, Faculty of Dental Sciences, College of Health Sciences, Usmanu Danfodiyo University/Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria.
Hemifacial microsomia (HFM) is the 2nd most common craniofacial birth defect after cleft lip and palate. It is said to arise from the 1st & 2nd intrauterine branchial arches. HFM is believed by many experts to be congenital but not inherited as most patients afflicted have no previous family history. It also known as craniofacial microstomia with cranial involvement. The real cause is unknown but largely blamed on hemorrhage of the stapaedial artery. The phenotypic expression is variable from mild to severe involving many structures such as bone, nerve, muscular tissues and soft tissue. Facial structures commonly affected include the ears, the mouth and the mandible. Mostly unilateral but bilateral have been reported. However, not much is known about this condition in sub-Saharan Africa. Multidisciplinary team management is the general consensus for optimal care. Awareness in sub-Saharan Africa of this disorder is still evolving This review identifies various classifications, diagnoses, investigations, treatment and timelines for management of HFM. The aim of the current review was to discuss the diverse controversies, classification, diagnosis and treatment of HFM so as to increase the understanding of this condition.
Keywords: Congenital malformation, Syndrome, Hemifacial microsomia, Hypoplasia, Classification, Distraction osteogenesis, Orthognathic surgery
Hemifacial microsomia (HFM) is among over 250 congenital syndromes that cause asymmetrical anomalies of derivatives of the first and second brachial arches.1,2,3 In 1881, Carl Ferdinand Von Arlt a German physician was the first to describe this malformation.4 It has attracted sizeable attention in the literature over several decades resulting in conflicting names such as brachial arch syndrome, lateral facial dysplasia, oto-mandibular dystosis and first and second brachial arch syndrome.4,5,6 Many authors used to consider Goldenhar syndrome as a different entity from HFM until current evidence proved that it is actually a variant of HFM.1, 3,4,6 Goldenhar syndrome which Gorlin and associates formerly referred to as oculo-auriculo-vertebra dysplasia/spectrum is also associated with cardiac and renal defects in addition to vertebral malformation and epibulbar dermoids.1,7,8 ‘Craniofacial microsomia’ as coined by Converse and associates involves the presence of cranial defects with other characteristic features of HFM.5
According to several studies across the globe, HFM is the second most common congenital craniofacial birth defect after cleft of the lip and palate.1,5,6 Cohen et al (1989) put the incidence of this anomaly as 1 in every 5600 newborn.1 However, recent finding of a higher figure of 1 in 3000 have been reported.7,8 Predilection for males with a male-female ratio of 3:2 has been demonstrated by many investigators.1,2,6 HFM occurs sporadically with most people affected possessing no positive family history of this deformity; hence, there is strong consensus that it is genetic but not hereditary.6,7,8
The genetic basis of HFM is just gradually being unraveled.7,9 A recent study in 2018 by Chen and associates found mutation in large host of genes such as OTX2, PLCD3 and MYT1 in people with HFM.10 Coincidentally, HFM is associated with about 7% to 15% of both typical cleft lip/palate and Tessier;s atypical facial cleft.6,8 Similar environmental factors and teratogens like maternal diabetes and thalidomide, retinoic acid, triazene, vasoactive medications have been blamed for the occurrence of HFM. 3,4,10 Nevertheless, the controversies persistently engulf the aetiopathogenesis of HFM with three models proposed.4,9,10,11,12 Experimenting in animals, Poswillo declared that following administration of 10mg/kg of thalidomide to female pregnant mice; resultant hemorrhage from rupture of stapaedial artery led to complete damage or partial disruption of the development of the first and second brachial arches and localized necrosis of their derivatives.11,12 The others are the abnormal development of the cranial neural crest cells and Merkel’s cartilage due to damage or destruction by teratogens.10,11,12 Although, Chen and colleagues advocated that the first theory is the most plausible of the lot.10 However, they insisted that these three mechanisms might have acted in concert during the first 9-8 weeks of gestation to cause the derangements that produce the numerous related features of HFM.13
Phenotypic expressions of HFM depend on the extent of this haemorrhage and its effect on these two arches.11,12,13 Therefore, there is a wide spectrum of presentation of this malformation varying from the mild to the severe spanning the skeletal, neural, muscular tissues and soft tissue. It affects the development of the lower half of the face, most commonly the ears, the mouth and the mandible.6,8,9,13 There is an assortment of degrees and combinations of underdevelopment and malformations of this region.6 Several reports observed usual occurrence on one side of the face, but involvement of both sides have been shown.6,11,13 However, there is paucity of research and knowledge about this complex malformation in Nigeria and the sub-Saharan Africa.
The purpose of this current article is to review the literature and summarize pertinent information about the aetiopathogenesis, classification, clinical presentation, radiological investigations, differential diagnosis and surgical treatment of hemifacial microsomia.
MATERIALS AND METHODS
An electronic search of the literature was performed in PUBMED and google scholar without time restriction for appropriate English papers on hemifacial microsomia based on a series of keywords in different combinations: “craniofacial microsomia”, “oto-mandibular dystosis”, “auriculo-oculo-vertebra spectrum”, “Goldenhar syndrome”, “lateral facial dysplasia”, “first and second brachial arch syndrome”, “OMEN”, “distraction osteogenesis”, “maxilla”, “mandible”, “treatment”, “Kaban and Pruzansky”, and “classification”. Prospective, retrospective studies, randomized/nonrandomized clinical trials, meta analysis, cohort studies, case–control studies, and case reports were considered. The reference lists of original and review articles were also sought. In addition, a manual exploration of major oral and maxillofacial surgery textbook was undertaken. Letters to the Editor, historical reviews, and unpublished articles were excluded.