Hemifacial microsomia (otomandibular dysostosis) is due to asymmetric abnormal development of the first and second branchial arches. It primarily affects the ear, mandible, maxilla, muscles of mastication and soft tissues of the lower face of the affected side. It may also involve the eye, other parts of the skull, as well as nerves and soft tissue. | Dr Mostafa Mahmoud El-Feky
Contents
Introduction
Hemifacial microsomia (HFM) or first & second brachial arch syndrome is an asymmetric craniofacial malformation which results in hypoplasia of the components of the first and second branchial arches: maxilla, mandible, external and middle ear, facial and trigeminal nerves, muscles of mastication, and overlying soft tissue.
2nd M/C birth defect of the face (after cleft lip and cleft palate)
Usually unilateral, but sometimes bilateral (20% cases) but always asymmetrical
Classification
Figueroa and Pruzanksky classification:
Type I: Mild hypoplasia of the ramus, and the body of the mandible is slightly affected.
Type II: The condyle and ramus are small, the head of the condyle is flattened, the glenoid fossa is absent, the condyle is hinged on a flat, often convex, infratemporal surface, the coronoid may be absent.
Type III: The ramus is reduced to a thin lamina of bone or is completely absent. There is no evidence of a TMJ.
Clinical features
This 6-year-old girl demonstrates the typical characteristics of hemifacial microsomia. Frontal (A) and lateral (B) views demonstrate facial asymmetry and severe microtia with aural atresia. The chin point is deviated toward the right, with an upward cant of the ipsilateral commissure and nasal alar base. The facial soft tissue is less prominent on the right side. | Keogh, I. J., Troulis, M. J., Monroy, A. A., Eavey, R. D., & Kaban, L. B. (2007). Isolated Microtia as a Marker for Unsuspected Hemifacial Microsomia. Archives of Otolaryngology–Head & Neck Surgery, 133(10), 997–1001. https://doi.org/10.1001/archotol.133.10.997
OMENS classification
O.M.E.N.S. indicates one of the 5 major manifestations of HFM:
O: Orbital distortion
M: Mandibular hypoplasia
E: Ear anomaly
N: Nerve involvement
S: Soft tissue deficiency
OMENS Classification System | Keogh, I. J., Troulis, M. J., Monroy, A. A., Eavey, R. D., & Kaban, L. B. (2007). Isolated Microtia as a Marker for Unsuspected Hemifacial Microsomia. Archives of Otolaryngology–Head & Neck Surgery, 133(10), 997–1001. https://doi.org/10.1001/archotol.133.10.997
Case study:
Diagnosis
Clinical diagnosis
Frontal view of the patient biting on a tongue depressor. A, This photograph demonstrates the upward occlusal cant on the right side that is a result of the short mandibular ramus and secondary vertical growth inhibition of the maxilla. B, Anteroposterior cephalogram demonstrates the asymmetry of the mandible, with a short right ramus, antegonial notching, and a flat contour. The piriform aperture is elevated on the right, also indicative of deficient vertical midface growth on that side. | Keogh, I. J., Troulis, M. J., Monroy, A. A., Eavey, R. D., & Kaban, L. B. (2007). Isolated Microtia as a Marker for Unsuspected Hemifacial Microsomia. Archives of Otolaryngology–Head & Neck Surgery, 133(10), 997–1001. https://doi.org/10.1001/archotol.133.10.997
OMENS classification:
Global Assessment of the modified pictorial OMENS-Plus classification system | Gougoutas AJ, Singh DJ, Low DW, Bartlett SP. Hemifacial microsomia: Clinical features and pictographic representations of the OMENS classification system. Plast Reconstr Surg. 2007;120:112e–120e.
Imaging
Orthopantomogram (OPG):
Orthopantomogram demonstrates a grade 2A mandible of abnormal shape and size. | Keogh, I. J., Troulis, M. J., Monroy, A. A., Eavey, R. D., & Kaban, L. B. (2007). Isolated Microtia as a Marker for Unsuspected Hemifacial Microsomia. Archives of Otolaryngology–Head & Neck Surgery, 133(10), 997–1001. https://doi.org/10.1001/archotol.133.10.997
Panoramic radiograph showing missing right mandibular premolars and molars; right hypoplastic mandibular ramus and small condylar head, reduced height of body of mandible, high level of external oblique ridge | Chhabra, N., & Chhabra, A. (2017). Hemifacial Microsomia : Clinicoradiological Insight and Report of a Case. Ethiopian Journal of Health Sciences, 27(1), 91–94. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/28458495
X-ray skull:
Postero-anterior skull projection showing absence of upper part of ramus, condyle and coronoid on left side, both orbits not at the same level, mandibular midline shift towards the left side | Mishra, L., Misra, S. R., Kumar, M., & Tripathy, R. (2013). Hemifacial microsomia: a series of three case reports. Journal of Clinical and Diagnostic Research : JCDR, 7(10), 2383–2386. https://doi.org/10.7860/JCDR/2013/5773.3532
Left lateral oblique view of the mandible showing absence of upper part of ramus, condyle and coronoid on left side | Mishra, L., Misra, S. R., Kumar, M., & Tripathy, R. (2013). Hemifacial microsomia: a series of three case reports. Journal of Clinical and Diagnostic Research : JCDR, 7(10), 2383–2386. https://doi.org/10.7860/JCDR/2013/5773.3532
3D CT scan:
3D CT scan showing facial asymmetry and a small hypoplastic ramus on the right side | Mishra, L., Misra, S. R., Kumar, M., & Tripathy, R. (2013). Hemifacial microsomia: a series of three case reports. Journal of Clinical and Diagnostic Research : JCDR, 7(10), 2383–2386. https://doi.org/10.7860/JCDR/2013/5773.3532
Management
Treatment scheme: (Left, upper and lower) Preoperative frontal cephalogram and face. White and gray arrows mark protruded zygoma and mandibular angle, respectively. The lower facial midline is deviated to the affected side. The dotted red line shows the mirror image of the jaw line. (Middle, upper and lower) Postoperative frontal cephalogram and face, status after 1st stage of correction. White and gray arrows show reduction of zygoma and mandibular angle, respectively. The bone gap between the mandibular segments is maintained to augment the jaw line of the left affected side. Red arrows indicate the movement of each segment. The asymmetric deformity along the affected jawline can be accentuated after OGS (black arrows). (Right) The final result after the 2nd stage of treatment. Fat injection could address the deficient area after OGS to obtain symmetry. Abbreviations: BFPR, buccal fat pad removal; MAR, mandibular angle resection; MR, masseter muscle reduction; Type, Pruzansky-Kaban classification; OGS, orthognathic surgery; ZR, zygoma reduction. | Yamaguchi, K., Lonic, D., Ko, E. W.-C., & Lo, L.-J. (2017). An integrated surgical protocol for adult patients with hemifacial microsomia: Methods and outcome. PLOS ONE, 12(8), e0177223. Retrieved from https://doi.org/10.1371/journal.pone.0177223
Evaluation of facial surface area discrepancy index (FDI) (FDI = affected side area / non-affected side area. Digitized facial landmarks: n, nasion; sn, subnasale; ls, labiale superius; me, menton.) | Yamaguchi, K., Lonic, D., Ko, E. W.-C., & Lo, L.-J. (2017). An integrated surgical protocol for adult patients with hemifacial microsomia: Methods and outcome. PLOS ONE, 12(8), e0177223. Retrieved from https://doi.org/10.1371/journal.pone.0177223
Performing the visual analogue scale (VAS) on one of the patient photographs: The scale is from 0 (complete symmetry) to 10 (complete asymmetry). | Yamaguchi, K., Lonic, D., Ko, E. W.-C., & Lo, L.-J. (2017). An integrated surgical protocol for adult patients with hemifacial microsomia: Methods and outcome. PLOS ONE, 12(8), e0177223. Retrieved from https://doi.org/10.1371/journal.pone.0177223
The 24-year-old female patient (case 4) was diagnosed with HFM (type I): Her natural head position was inclined to the right to compensate for her chin deviation. She was treated using Le Fort I, bilateral sagittal split osteotomy, genioplasty, and mandibular angle reduction, without a second stage of fat injection. Her natural head position adjusted spontaneously after surgery. | Yamaguchi, K., Lonic, D., Ko, E. W.-C., & Lo, L.-J. (2017). An integrated surgical protocol for adult patients with hemifacial microsomia: Methods and outcome. PLOS ONE, 12(8), e0177223. Retrieved from https://doi.org/10.1371/journal.pone.0177223
