Hemifacial Microsomia

Mar 13, 2021 6 min read
Hemifacial Microsomia

Hemifacial microsomia is the commonest craniofacial abnormality with significant phenotypic variability. Genetics, signs and treatment options are detailed.

In this Article

5 Key Points

The aetiology, genetics, clinical picture, and management options of Hemifacial Microsomia can be summarised in 5 key points:

  1. Hemifacial microsomia is the commonest craniofacial defect, which often occurs sporadically without genetic inheritance.
  2. There is a spectrum of phenotypic variability – as a result hemifacial microsomia has a broad clinical picture from minor skin tags to severe mandibular hypoplasia with facial nerve dysfunction.
  3. Hemifacial microsomia clinically correlates with Tessier Craniofacial Cleft 7.
  4. There are several classification systems for hemifacial microsomia, which include: OMENS, Pruzansky and Meurman.
  5. Management of hemifacial microsomia is centred on a disciplinary team to correct ocular, mandibular, ear, facial nerve and soft tissue issues over a prolonged period of staged treatments..

Definition of Hemifacial Microsomia

Congenital condition with variable phenotype, characterised by underdevelopment of one side of the face. It correlates with Tessier Craniofacial Cleft 7.

It also referred to as First and Second Brachial Arch Syndrome, Otomandibular Dysostosis, Craniofacial Microsomia, or oculoauriculovertebral spectrum.


Genetics of Hemifacial Microsomia

  • 1 in 4000-6000 live births (commonest craniofacial abnormality)​3​
  • Majority is sporadic mutations with seldom autosomal dominant inheritenace​4​.

Theories regarding the aetiology have been proposed:

  • Mesodermal Insufficiency​5​
  • May arise due to haemorrhage from an abnormal stapedial artery​6​

Clinical Features of Hemifacial Microsomia

Hemifacial microsomia is a clinical diagnosis. There is a variable phenotype and clinical features are part of a spectrum of severity. It is usually unilateral but can be bilateral (but still asymmetric) in about 10%.

Patient with hemifacial microsomia and their CT 3D reconstruction
Patient with hemifacial microsomia and their CT 3D reconstruction 

Classic Clinical Picture

  • External and middle ear underdevelopment (microtia, anotia, atresia)
  • Hypoplasia of the bone (mandible, zygoma, maxilla, temporal bone)
  • Underdevelopment of the muscles (mastication, palatal, tongue)

Associated pathologies

  • Cleft Palate – 35% incidence in hemifacial microsomia​7​
  • Facial Nerve Dysfunction – 22% incidence in hemifacial microsomia​8​ and can be associated with an absent parotid gland.
  • Macrostomia – 23% incidence in hemifacial microsomia​9​
Bilateral Macrostomia
Bilateral Macrostomia

Goldenhar Syndrome is a variant of hemifacial microsomia (features of hemifacial microsomia + Tessier Cleft 8). Hemifacial microsomia is not to be confused with Treacher Collins Syndrome.


Classification Systems for Hemifacial Microsomia

Due to the heterogeneity of clinical appearances, multiple classifications systems for hemifacial microsomia have been published.

OMENS Classification for Hemifacial Microsomia

This classifies deformities based on Orbits, Mandible, Ear, Nerve (Facial) and Soft Tissue​10​.

OMENS Classification for Hemifacial Microsomia
OMENS Classification for Hemifacial Microsomia

Pruzansky Classification of the Mandible

This classification system focuses on the mandible in hemifacial microsomia. Most commonly, there is an asymmetric mandible with only unilateral involvement.

  • Type 1: Mild ramus hypoplasia, the body is minimally affected.
  • Type IIa: Ramus and condyle hypoplasia, but the glenoid-condyle relationship is maintained
  • Type IIb: Same as type IIa but with a non-articulating TMJ
  • Type III: ramus is very thing or absent with no evidence of a TMJ
Pruzansky Classification of the Mandible for Hemifacial Microsomia
Pruzansky Classification of the Mandible for Hemifacial Microsomia

In severe micrognathia, patients can suffer from Pierre Robin Sequence.

Meurman Classification of the Ear

  • Grade I: Small, malformed auricle, all components are present
  • Grade II: vertical remnant of cartilage and skin, atresia of the external meatus
  • Grade III: Total or near-total absence of muscle.
Meurman Classification of the Ear for Hemifacial Microsomia
Meurman Classification of the Ear for Hemifacial Microsomia

Treatment of Hemifacial Microsomia

There is no standardised treatment algorithm for hemifacial microsomia. Due to the phenotypic variation of patients, current evidence-based medicine provides a guide that should be individualised for each patient.

Skin Tags

This is the milder spectrum of the condition. Remove skin tags at an appropriate age. Caution of the facial nerve because the cartilage remnants can be closely associated.

Microtia

If microtia is present, ear reconstruction with autologous material should be delayed until the patient is age appropriate, between 7 and 10 years, depending on the technique used​11,12​. Hearing aids should be fitted from an early age to ensure no speech delay.

Mandibular Hypoplasia

There is no standardised algorithm for timing of surgical management of mandibular hypoplasia. Traditionally, surgeons have waited until skeletal maturity to correct malocculusion with orthognathic procedures​13,14​.

In severe cases, early intervention followed by mandibular distraction should be considered​15​This allows for appropriate bone stock so that subsequent traditional orthognathic can be attempted.

Facial Paralysis

Management of these patients should be at centres that specialise in facial reanimation surgery. Ocular protection from corneal desiccation and ulceration is priority.


References

  1. 1. Keogh IJ, Troulis MJ, Monroy AA, Eavey RD, Kaban LB. Isolated Microtia as a Marker for Unsuspected Hemifacial Microsomia. Arch Otolaryngol Head Neck Surg. October 2007:997. doi:10.1001/archotol.133.10.997
  2. 2. Fawzy HAAR, Ghareeb F, Farghaly A-S, Al Barah A, El Sheikh Y. Patterns and management of congenital nasal clefts. Menoufia Med J. 2015:99. doi:10.4103/1110-2098.155960
  3. 3. Grabb W. The first and second branchial arch syndrome. Plast Reconstr Surg. 1965;36(5):485-508. doi:10.1097/00006534-196511000-00001
  4. 4. Burck U. Genetic aspects of hemifacial microsomia. Hum Genet. 1983;64(3):291-296. doi:10.1007/bf00279415
  5. 5. STARK R, SAUNDERS D. The first branchial syndrome. The oral-mandibular-auricular syndrome. Plast Reconstr Surg Transplant Bull. 1962;29:229-239. doi:10.1097/00006534-196203000-00001
  6. 6. Poswillo D. The pathogenesis of the first and second branchial arch syndrome. Oral Surg Oral Med Oral Pathol. 1973;35(3):302-328. doi:10.1016/0030-4220(73)90070-4
  7. 7. Sokol AB. Velopharyngeal insufficiency in hemifacial microsomia. Journal of Pediatric Surgery. June 1978:344. doi:10.1016/s0022-3468(78)80416-3
  8. 8. Carvalho G, Song C, Vargervik K, Lalwani A. Auditory and facial nerve dysfunction in patients with hemifacial microsomia. Arch Otolaryngol Head Neck Surg. 1999;125(2):209-212. doi:10.1001/archotol.125.2.209
  9. 9. Fan W, Mulliken J, Padwa B. An association between hemifacial microsomia and facial clefting. J Oral Maxillofac Surg. 2005;63(3):330-334. doi:10.1016/j.joms.2004.10.006
  10. 10. Vento A, LaBrie R, Mulliken J. The O.M.E.N.S. classification of hemifacial microsomia. Cleft Palate Craniofac J. 1991;28(1):68-76; discussion 77. doi:10.1597/1545-1569_1991_028_0068_tomens_2.3.co_2
  11. 11. Brent B. Auricular repair with autogenous rib cartilage grafts: two decades of experience with 600 cases. Plast Reconstr Surg. 1992;90(3):355-374; discussion 375-6. https://www.ncbi.nlm.nih.gov/pubmed/1513882.
  12. 12. Nagata S. Modification of the stages in total reconstruction of the auricle: Part IV. Ear elevation for the constructed auricle. Plast Reconstr Surg. 1994;93(2):254-266; discussion 267-8. https://www.ncbi.nlm.nih.gov/pubmed/8310017.
  13. 13. Meazzini M, Mazzoleni F, Bozzetti A, Brusati R. Comparison of mandibular vertical growth in hemifacial microsomia patients treated with early distraction or not treated: follow up till the completion of growth. J Craniomaxillofac Surg. 2012;40(2):105-111. doi:10.1016/j.jcms.2011.03.004
  14. 14. Schreuder W, Jansma J, Bierman M, Vissink A. Distraction osteogenesis versus bilateral sagittal split osteotomy for advancement of the retrognathic mandible: a review of the literature. Int J Oral Maxillofac Surg. 2007;36(2):103-110. doi:10.1016/j.ijom.2006.12.002
  15. 15. Wan D, Taub P, Allam K, et al. Distraction osteogenesis of costocartilaginous rib grafts and treatment algorithm for severely hypoplastic mandibles. Plast Reconstr Surg. 2011;127(5):2005-2013. doi:10.1097/PRS.0b013e31820cf4d6
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