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Oral Medicine

Authors: Dr. Suraj Agarwal, Dr. Achint Garg

ABSTRACT

Hemifacial microsomia (HFM) is the second most common congenital facial anomaly after cleft lip/palate, characterized by deficiency in the amount of hard and soft tissues on one side of the face. It is primarily a syndrome of first and second branchial arches involving underdevelopment of theTemporomandibular joint, mandibular ramus, masticatory muscles, ears and occasionally defects inFacial nerve and muscles. Here, we report two cases of hemifacial microsomia diagnosed based on clinical and radiographic findings.

INTRODUCTION

Hemifacial microsomia is a facial birth defect derived from the first and second branchial arches. The phenotype is highly variable and in addition to craniofacial involvement, vertebral, cardiac and central nervous system defects can exist.1The high variability and wide range of anomalies has led to a number of names for this condition. (Table 1)
 
  • Oculo-auriculo-vertebral spectrum
  • Goldenhar syndrome
  • Oculo-auriculovertebral dysplasia
  • Facio-auriculovertebral sequence
  • Temporo-auromandibular dysplasia
  •  First arch syndrome
  • First and second branchial arch syndrome
  • Goldenhar–gorlin syndrome
  • Lateral facial dysplasia
  • Unilateral craniofacial microsomia
  • Otomandibulardysostosis
  • Unilateral intrauterine facial necrosis
  • Auriculo-branchiogenic dysplasia
  • Facio-auriculo-vertebral dysplasia
  • Facio-auriculo-vertebralmalformation complex
  • Craniofacial microsomia
  • (Hennekam et al,2010)2

HFM was first described by German physician Carl Ferdinand Von Arlt in 1881 3.The term hemifacial microsomia (HFM) was first used by Gorlin to refer to patients with unilateral microtia, macrostomia, and failure of formation of the mandibular ramus and condyle. It is the second most common craniofacial malformation after cleft lip and palate,whereas Goldenhar syndrome was described as a variant, with vertebral anomalies and epibulbar dermoids.4
INCIDENCE

Poswillo6 suggested a frequency of HFM was 1 per 3500 births, although there was no data to support this claim. Grabb7estimated an incidence of at least 1 per 5600 births. The male-to-female ratio is 3:2, and thereis also a 3:2 ratio of right-side versus left-side involvement.8,9,10

ETIOLOGY

The most commonly accepted is a teratogen theory of a vascular insult. Haemorrhage and hematoma formation in the developing first and second branchial arches and subsequent mal-development of the latter. The stapedial artery is a temporary embryonic collateral of the hyoid artery, which forms connections with the pharyngeal artery, only to be replaced by the
external carotid artery. Defects of this temporary vessel may result in haemorrhage, accounting for injury to the developing first and second branchial arches.5 Reports indicate that several teratogenic agents, such as retinoic acid, primidone, and thalidomide, have produced HFM in infants born to pregnant women exposed to those agents.Poswillo produced facial anomalies in laboratory animals by maternal intake of 10 mg/kg thalidomide or 60 mg/kg triazene. He believed that either total or incomplete development of stapedial artery caused by an expanding hematoma could trigger a localized necrosis in the derivatives of the first and second branchial arches which would cause HFM11,12.Granström also induced microtia and other craniofacial defects in rats by injecting excessive dose of retinoic acid or etretinate to pregnant rats.13,14

Dysregulation of BAPX1was found in several patients. BAPX1 plays an important role in craniofacial growth. Epigenetic dysregulation of BAPX1 likely plays a role in HFM and can explain many of the genetic and phenotypic peculiarities (fischer et al., 2006).15

Most cases of HFM are sporadic, but familial instance has been reported,16 but successive generations of affected persons17,18,19,20 and affected siblings with normal parents have also been reported. Autosomal dominant and autosomal recessive inheritance have both been hypothesized to explain various familial occurrences.21,22,23,24

 
 
Type I. Mild hypoplasia of the ramus, and the body of the mandible is minimally or slightly affected. Type IIA: The ramus and condyle demonstrate abnormal morphology but the glenoid fossa has maintained a position in the temporal bone similar to that of the contralateral side.
 
Type IIB: The ramus/condyle is hypoplastic, malformed, and displaced outside the plane of that of the contralateral side. Type III: The ramus is essentially absent without any evidence of temporomandibular joint.


CLINICAL FEATURES

JAWS
The most obvious deformity is the mandible, especially the ascending ramus, which can be absent or reduced in the vertical dimension. The size of the condyle usually reflects the degree of hypoplasia of the ramus. Involvement of the temporomandibular joint (TMJ) can range from mild hypoplasia to only a pseudoarticulation at the cranial base. In addition to being short, the ramus is usually displaced toward the midline.
Because of the hypoplastic ramus, the mandibular plane angle is increased and the body of the affected mandible can show an increased horizontal dimension. The chin is deviated toward the affected side and there is a corresponding cant of the mandibular occlusal plane, which is paralleled in the corresponding planes of the floors of the maxillary sinuses and the pyriform apertures. Similarly, the maxillary and mandibular dentoalveolar complexes are also reduced in the vertical dimension on the affected side. In addition to crowding, there is often delayed eruption of the deciduous andpermanent teeth; the molars can also be absent.5
 
 
 
Extra Oral Examination reveals , asymmetry on right side of faceasymmetry (pt. does not give any history of trauma for his facial asymmetry) with right preuricular tag (malformed ear), loss of hearing(8th nerve paralysis),
 
On Extra Oral Examination, Depressed area on the right side of middle 1/3rd of face, Drooping of corners of mouth, Receding hair line, Absence of wrinkling of forehead on rt. Side, unable to close the right side, accumulation of food on rt. Side ( 7th nerve paralysis),


MUSCLES OF MASTICATION

The syndrome is not restricted to the skeleton; the associatedmuscles of mastication are hypoplastic. The deficiencyis not always proportional to the skeletal deficiency. A threedimensionalcomputed tomography (CT) scan study comparedthe volume of the mandibular deformity to that of theadjacent muscles of mastication and noted that there wasnot always a 1:1 relationship in the degree of pathologicinvolvement.Muscle function is impaired, as is especially evident with lateralpterygoid muscle function on the affected side.
The lateralpterygoid muscle is responsible for movement of the mandibleand chin point to the contralateral side. Consequently, in patients with unilateral craniofacial microsomia who attempt aprotrusive chin movement, the chin deviates to the affected sideduring opening and during forceful protrusion. The hypoplasticlateral pterygoid muscle on the affected side is overpoweredby its unaffected counterpart. Moreover, mouth opening is alsoadversely affected by the hypoplastic ramus and malpositionedtemporomandibular joint.5
 
Radiological Investigations of OPG, PA Ceph, Lat. Ceph, Submentovertex revealed accentuated antegonial notch on right side with decreased ramus height and agenesis of right condylar process with facial asymmetry on right side.


ORAL MANIFESTATIONS

Intraoral deformity include hyperplastic or aplastic teeth and enamel. Common oral manifestations ofHFM include a significant delay of tooth development on the affected side, frequent absence of mandibularthird molar on the affected side, and increased frequencyof missing teeth on the affected side. The incidenceof delayed tooth development with HFM is proportionalto the extent of mandibular deformity.26,27Hypodontia is found particularly in the mandibular secondpremolars involving the affected side. Chalkyopacifications of enamel are occasionally found on themaxillary central and lateral incisors of the underdevelopedside as a marker of development for HFM.28

EARS

Involvement of the auricle occurs in most patients. Meurmannproposed a classification of the external ear deformities:Grade I, distinctly smaller malformed auricle but allcomponents are present; Grade II, only a vertical remnantof cartilage and skin with complete atresia of the externalauditory canal; Grade III, almost complete absence of the auricleexcept for a small remnant, usually a soft tissue lobule.5
 
FACIAL ASYMMETRY ONLEFT SIDE. PREAURICULAR TAG ON LEFT SIDE INTRAORAL EXAMINATION REVEALS POOR ORAL HYGIENE, FLUOROSIS WITH DEEP BITE ON LEFT SIDE
NERVOUS SYSTEM

Cerebral abnormalities, although rare, can occur and includehypoplasia of the cerebrum and corpus callosum, as well as hydrocephalusof the communicating and obstructive types. Thebrainstem can be involved secondarily because of anomalies ofthe cervical vertebrae, resulting in disturbances such as impressionof the brainstem.
The most common cranial anomaly is a facial palsy ofvarying degrees, attributed to the following (alone or in combination):absence of the intracranial portion of the facialnerve and nucleus in the brainstem, aberrant pathway of thenerve in the temporal bone, or agenesis of the facial muscles.Absence of facial nerve function in the distribution ofthe marginal mandibular branch is seen in approximately25% of patients, with weakness of other components, suchas the buccal and zygomatic branches, occurring in a smallerpercentage.5

SOFT TISSUE

On the affected side, preauricular skin tags are common, andthe skin and subcutaneous tissue of the cheek region show varyingdegrees of hypoplasia. The musclesof mastication are also involved, and hypoplasia or aplasiaof the parotid gland has been documented. The soft-tissue deficiency is multidimensional and may result in a marked reductionin the distance between the oral commissure and therudimentary ear on the affected side.Lateral facial clefts (macrostomia) are common associatedfindings and also contribute to the overall cheek hypoplasia.Overt clefts of the soft palate are said to occur in 25% ofpatients, and the soft palate may deviate to the affected side onvoluntary function.5

CLASSIFICATION SYSTEM29,30,31,32

PREOPERATIVE ASSESSMENT

A panoramic radiograph provides an excellent overview of the osseous structures of the mandible and maxillofacialComplex. Since a cleft palate is often associated withHFM, an occlusal radiograph is needed. The relationship of the mandible and maxilla to the cranial base can be established initially with a lateral cephalometric radiograph.A frontal skull radiograph (posterior-anterior view) can be used to depict the degree of osseous asymmetry of the face.Computed tomography (CT) can provide both a threedimensional rendition of the soft tissue of the face and an image of the underlying bone.
Information on comparative Muscle development can be assessed through CT orMagnetic resonance imaging on a case-by-case basis.Hearing evaluation, phonics tests, laryngoscopicinspection vocalization analysis help establish each patient’sAnatomical, neurological and functional status 3.
 
OPG REVEALS ACCENTUATED LEFT SIDE ANTI-GONIAL NOTCH WITH DECREASE RAMUS HEIGHT ON LEFT SIDE AND INCREASE VERTICAL HEIGHT ON RIGHT SIDE. PA CEPH REVEALS ASYMMETRY WITH DEVIATION OF MANDIBLE ON LEFT SIDE
DIFFERENTIAL DIAGNOSIS

The differential diagnosis of this condition includesPierre Robin syndrome, Moebius syndrome and TreacherCollins syndrome. Unlike HFM, Pierre Robin syndromealways consists of cleft palate, micrognathia and glossoptosis.Moebius syndrome is a nonfamilial deficientdevelopment of cranial muscles consisting of facial diplegiawith bilateral paralysis of the ocular muscles, particularlythose supplied by abducens. HFM usually does not leadto ocular muscle paralysis and nerve involvement occursunilaterally. Most of the features of Treacher Collinssyndrome mimic HFM; however, the latter occursunilaterally and it is sporadic in a vast majority of cases.33

TREATMENT

In designing the course of treatment, the dental occlusion must be considered in conjunction with the underlyingskeletal condition. Typically, a combined surgicalorthodonticapproach is taken. In the past, growth-directingdevices such as functional appliances were used toencourage growth and to minimize the extent of Orthognathic surgery needed once the child has finished growing.Osteotomies followed by acute orthopedic movement andosseous fixation were used in the past. Unfortunately, theinherent risk of relapse caused by the inability of musclesto be acutely stretched often compromised the results.When autogenous costochondral grafting was used inmore severe deformities, infection, pain and donor sitemorbidity posed important postoperative concerns.34 Use of an alternative procedure called distractionosteogenesis is now widely accepted. It is a process in whichnew bone is formed between the surfaces of bone segmentsthat are gradually separated by incremental traction. Thisis a gradual method of creating bone after a surgicalcorticotomy sectioning of the cortical plates. Prosthetic earreconstruction can also be done for deformed ears.34

CASE 1

Pt. reported to the Department of Oral Medicine &Radiology with a chief complaint of decayed teeth in upper & lower jaw region since 3-4 months. Pt. gives history of pain & swelling in Right lower back tooth region which aggravated on taking food & relieves on medication.past medical history: nothing relevant reported. Past dental history reveals undergone multiple extraction, last extraction 1yr back. Pt. had a habit of bidi smoking 1 bundleperday since 20yrs. On extra oral examination, Facial asymmetry (pt. does not give any history of trauma for his facial asymmetry), Deviation of face on right side, Depressed area on the right side of middle 1/3rd of face, Malformed ear, loss of hearing(8th nerve paralysis), Drooping of corners of mouth, Receding hair line, Absence of wrinkling of forehead on rt.
Side, unable to close the right side, accumulation of food on rt. Side ( 7th nerve paralysis), On TMJ examination no clicking , crepitus & tenderness felt , deviation of mouth on left side on mouth opening.OPG reveals accentuated antegonial notch on right side with decreased ramus height and agenesis of right condylar process. PA ceph reveals facial asymmetry on right side. Patient was diagnose with HEMIFACIAL MICROSOMIA of right side and was advise further radiographic investigations.

CASE 2

Pt. complains of pain in right lower back tooth region since 10-15 days. On history of present illness reveals that patient was apparently asymptomatic 10-15 days back when he started experiencing dull , intermittent , remittent pain which aggravates on taking food & relieves on medication. On Medical & dental history, nothing relevant was reported. On extra oral examination Facial asymmetry, Depressed area on the left side of middle 1/3rd of face, Deviation of mandible on left side , Malformed ear , absence of hearing on left side, On TMJ Examination no clicking , no tenderness, no crepitus felt, Reduced mouth opening.
Radiological Inestigations revealed, accentuated left side anti-gonial notch with decrease ramus height on left side and increase vertical height on right side. PACeph reveals asymmetry with deviation of mandible on left side. Patient was Diagnose with Hemifacial Microsomia of left side and was advise further radiological investigations.

REFRENCES
 
  1. Edwin Ongkosuwito ; Aspects of Hemifacial Microsomia
  2. Hennekam RC, Krantz ID, Allanson JE (2010). Oculo-auriculo-vertebral spectrum (hemifacial microsomia, Goldenhar syndrome). In: Gorlin’s syndromes of the head and neck. New York: Oxford university press, pp. 879-886.
  3. Manu Dhillon et al; Hemifacial microsomia: a clinicoradiological report of three cases; J Oral Sci 52, 319-324, 2010).
  4. Russell R. Wang; Hemifacial microsomia and treatment options for auricular replacement:A review of the literature;J prosthetic dentistry 82 (2)
  5. Joseph G. Mccarthy; Craniofacial Microsomia;GrabbAnd Smith's Plastic Surgery, sixth edition by Charles H. Thorne.
  6. Poswillo D. The pathogenesis of the first and second branchial arch syndrome. Oral Surg Oral Med Oral Pathol 1973;35:302-28.
  7. Grabb WC. The first and second arch syndrome. PlastReconstrSurg 1965;36:485-508.
  8. Smith DW. Recognizable patterns of human malformation. 3rd ed.Philadelphia: WB Saunders; 1982. p. 497-500.
  9. GN. Craniofacial defects in the Goldenhar syndrome. Am J Med Genet 1983;14:435-43.
  10. Rollnick BR, Kaye CI, Nagatoshi K, Hauck W, Martin AO. Oculoauriculovbertebral dysplasia and variants: phenotypic characteristics of 294 patients. Am J Med Genet 1987;26:361-75.