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True hemifacial microsomia and hemimandibularhypoplasia with condylar-coronoid collapse:

Diagnostic and prognostic differences

Maria C. Meazzini,a Roberto Brusati,b Alberto Caprioglio,c Patrik Diner,d Giovanna Garattini,e Ennio Giann,f

Faustina Lalatta,g Carlo Poggio,h Enrico Sesenna,i Alessandro Silvestri,j and Catherine Tomatk

Milan, Varese, Parma, and Rome, Italy, and Paris, France

Introduction: Long-term results after orthopedic or surgical treatment of hemifacial microsomia (HFM) have

shown a tendency toward recurrence of the facial asymmetry. However, the literature contains a number of suc-

cessful case reports that show surprising changes in the morphology of the condyles. In addition, patients with

similar mandibular asymmetries, treated early with surgery, have excellent long-term follow-ups, especially

those who have little or no soft-tissue involvement, but only severe mandibular ramal deformities. The

phenotypes of these cases are unexpectedly similar, with a consistent collapse of the condyle against the

coronoid and a deep sigmoid notch. The objectives of this article were to help distinguish true HFM from this

peculiar type of hemimandibular asymmetry morphologically and to quantify their differences before

treatement and in the long term. Methods: Panoramic radiographs taken at pretreatment and the long-term

follow-up of 9 patients with hemimandibular hypoplasia, characterized by the collapse of the condyle against

the coronoid, were compared with those of 8 patients with severe type I and type II HFM; these records were

collected before and at least 10 years after distraction osteogenesis. Results: Ratios and angular measure-

ments before and after treatment differed significantly between the 2 groups. Conclusions: Perhaps these

patients were misdiagnosed and actually had secondary injuries of the condyle, which have a normal functional

matrix. Therefore, with growth and functional stimulation, they would tend to grow toward the original symmetry.

To make a differential diagnosis between true HFM and this peculiar type of hemimandibular hypoplasia, the

collaboration between not only orthodontists and surgeons, but also geneticists and dysmorphologists, is of

great importance because of the different prognoses. (Am J Orthod Dentofacial Orthop 2011;139:e435-e447)

Etiologic diagnosis is possibly the most difficult,

but also the most important, step in orthodontictreatment. Facial asymmetries are certainly a chal-

lenging chapter for both the orthodontist and the max-illofacial surgeon. Hemifacial microsomia (HFM), the

best known of the branchial arch syndromes, is a rela-tively common craniofacial anomaly with a birth preva-

lence of at least 1 in 5600, characterized by asymmetric

underdevelopment of the structures originating fromthe first and second branchial arches. Deformities caninvolve the ear, the mandible, the maxilla, the zygo-matic arch, the temporal bone, the fifth and eighth cra-nial nerves, the cervical spine, and the facial muscles.

The degree of ear involvement is markedly variable.Ear tags and pits might be present.1 The condition isetiologically heterogeneous. Many chromosome abnor-malities have been recorded, but also environmentalcauses including thalidomide, primidione, and retinoicacid administered during the organogenesis. A recentmodel, based on a mutation of a locus on chromosome

aAdjunct professor, Department of Maxillofacial Surgery, and orthodontic con-

sultant, Cleft Lip and Palate Center, University of Milano, Milan, Italy.bProfessor and head, Department of Maxillofacial Surgery, Cleft Lip and Palate

Center, University of Milano, Milan, Italy.cAssociate professor and head, Department of Orthodontics, University of Insub-

ria, Varese, Italy.dAssociateprofessor,Department of Plastic Surgery,TrousseauHospital, Paris, France.eAssociate professor, Department of Orthodontics, University of Milano, Milan, Italy.fProfessor, Department of Orthodontics, University of Milano, Milan, Italy.gDirector, Department of Medical Genetics and Diagnosis of Rare Anomalies, Mangi-

agalli Hospital, University of Milano, Milan, Italy.h

Clinical professor, Department of Orthodontics, Instituto Stomatologico, Universityof Milano, Milan, Italy.iProfessor and head, Department of ENT-Dental-Ophthalmologic and Cervico-Facial

Sciences, Maxillofacial Surgery Unit, University of Parma, Parma, Italy.jAssociateprofessor,Department of OrthodonticsIII, University of La Sapienza, Rome,

Italy.kOrthodontic consultant, Department of Plastic Surgery, Trousseau Hospital, Paris,

France.

The authors report no commercial, proprietary, or financial interest in the prod-

ucts or companies described in this article.

Reprint requests to: Maria C. Meazzini, Via Appiani n.7, 20121 Milano, Italy;

e-mail, [email protected].

Submitted, June 2009; revised, December 2009; accepted, January 2010.

0889-5406/$36.00

Copyright 2011 by the American Association of Orthodontists.

doi:10.1016/j.ajodo.2010.01.034

e435

ONLINE ONLY
mailto:[email protected]:[email protected]:[email protected]


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10, appears to support the hypothesis that HFM anom-

alies have partly a genetic cause.2,3 Most cases are

sporadic, but rare familial instances with autosomaldominant inheritance have also been observed.4,5

HFM is 1 of 4 conditions defined as otofacial

malformations, which are neurocristopathies, sharinga major involvement of neural crest cells, together

with DiGeorge syndrome, retinoic acid syndrome, and

Table I. Differential diagnosis between true HFM and hemimandibular hypoplasia with CCC

HFM CCC

History Generally diagnosed at birth Usually not diagnosed at birth

Seldom history of trauma

Clinical examination Soft-tissue defects (may be very mild) No soft-tissue defects Ea r defects, preauricular tags Normal ears , no preaur icular tags

Facial nerve asymmetries No nerve deficit

Masseter muscle hypoplasia Well-developed masseter

Deviation of the chin on the affected side, associated

with flatness on the affected cheek

Deviation of the chin on the affected side, associated

with fullness on the affected cheek

Mild deviation to the affected side during opening Significant deviation to the affected side during

opening

Panoramic x-ray (or computed

tomograph)

Hypoplasia of the ramus and condyle and coronoid

processes up to absence of the condyle and temporal

fossa

Hypoplasia of the ramus and condyle and coronoid

processes, which are typically collapsed one on the

other; the temporal fossa is always present

Fig 1. A-C, Type II Pruzansky HFM ramal deformity (note the associated ear deformity); D-F, misdiag-

nosed ramal deformity.

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Treacher Collins syndrome.6,7 A condition analogous to HFM has been induced in mice by causing a local

hemorrhage from the embryonic stapedial artery between the 30th and 40th days of fetal develop-ment, a critical period of neural crest cell migration.8

Neural crest cells are a migratory cell population. Just

before the neural fold fuses to form the neural tube,neuroectodermal cells adjacent to the neural plate mi-grate into the facial region, where they form the skeletaland connective tissues of the face: bone cartilage, fi-

brous connective tissue, and all dental tissues exceptenamel. Thus, facial mesenchyme is of neural crest ori-

gin; this in turn guides the formation of vascular endo-thelium and skeletal muscles, which are of mesodermalorigin.9 Thus, a craniofacial malformation can be theconsequence of a disruption in the migration or prolif-eration of neural crest cells, but the primary defectmight have a genetic origin.

What is more important than the etiology, in view ofthe aim of this article, is that the neural crest cells that

migrate into the first branchial arch carry the patternof information needed for proper morphogenesis of me-sodermal derivates such as cranial muscles.10,11

Extirpation of the mandibular neural crest stream leads

to severe alterations of mandibular-muscle patterning.Whereas Meckels, palatoquadrate, suprarostral, and in-frarostral cartilages can be severely malformed or miss-ing, all muscles of the levator mandibulae group willalso be similarly affected.12 Therefore, although HFMcan be variable in terms of phenotype, mandibular de-

formity is always proportionate to the associated muscu-lar deformity.

As stated before, under the diagnosis of HFM,there is much variability; thus, treatment varies.13

Patients with HFM with minor mandibular and soft-tissue involvement can be treated by using

Fig 2. Male patient mislabeled with HFM and treated with unilateral mandibular osteotomy: A and B,

before surgery, tomograph shows the affected side; C and D, immediately after surgery; E and F, 29

years postsurgery.

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a conservative approach, obtaining good dentoalveo-lar correction and some mild improvement in the

skeletal asymmetry.14 Orthodontic functional appli-ance therapy during growth has been suggested

even in moderate to severe cases, but there is no con-sensus about the value and the true effect of suchtreatment.15

At present, the timing of treatment and the optimal

treatment protocol are still controversial. Therapy in-cludes orthodontic and surgical measures for the cor-rection of the skeletal asymmetry. Preoperative andpostoperative treatment with functional applianceshas been recommended to improve muscle functionand to stimulate growth of the soft and hard tissues.16

Vargervik et al14 demonstrated that functional appli-

ances improved the short-term results after costochon-dral grafting, but, nevertheless, in most cases, theasymmetry returned during subsequent growth. Like-

wise, it was recently shown that functional therapyassociated with distraction osteogenesis only slows

down the return to the original asymmetry of HFM.17

In contrast, the literature includes many case reports

describing successful orthopedic treatment in patientsdiagnosed with severe forms of HFM.1821

Asymmetrical mandibular growth is also seen inpatients who have suffered postnatal trauma orinfection in the condylar region. This deformitydiffers from HFM in that it is limited to the jaw,

without affecting the ear, soft tissues, or otherorgans.22 Therefore, mandibular asymmetry can bepart of many conditions with different causes. Accord-ing to the time of their onset, they might be related to(1) abnormality of early embryonic development (lackof neural crest cell migration) such as HFM or micro-

gnathia (In these conditions, some alteration of growthpatterns is observed as a consequence of the develop-mental abnormality. Usually orthopedic treatment haslittle probability of changing the pattern.) or (2)

abnormality of late fetal or postnatal growth, whereit is presumed that the abnormal process becomes

Fig 3. Male patient misdiagnosed with HFM and treated with unilateral mandibular DO: A and B,

before DO, the ear, although normal in structure, is abnormally positioned due to the skeletal

deformity; it is lateral and more prominent on the affected side; C and D, immediately after DO;E and F, 8 years after DO.

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causative after the embryonic period. This group in-cludes abnormalities due to trauma, infection, or surgi-

cal iatrogenic deformities. Often these patients haveinvolvement of only the bony structures of the mandi-

ble, but usually the soft tissues or the neuromuscularpattern is not affected. Therefore, these conditionsare more likely to show good responses to functionalstimulation.

The aim of this article was to describe a peculiar typeof mandibular asymmetry, frequently misdiagnosed as

HFM. The patients shown share 2 main characteristicsthat distinguish them from more traditional HFM pa-tients (Table I, Fig 1). (1) There is no soft-tissue involve-ment, the external ear is present and well-formed, and

the musculature seems to be well developed. Althoughthe chin point deviates to the affected side, there isnot the typical flatness of the gonial area seen in HFMpatients ( Fig 1, A-C). On the contrary, there is more

fullness on the affected side than on the unaffectedside (Fig 1, D-F). (2) The shape of the hypoplastic ramus

is peculiar and extremely similar in all patients. The con-dyle is short and collapsed against the coronoid process(Fig 1, D-F). Figures 2 through 5 show 4 patients who

were treated surgically with excellent long-term results;Figures 6 through 10 show 5 patients who were treatedorthodontically, with a similar remarkable ramal

deformity correction. All had been erroneouslydiagnosed as having HFM by a surgeon or an

orthodontist. Other patients with almost identicalphenotypes misdiagnosed a s having HFM can be

found in the literature,18-21,23 and others alreadyidentified as without HFM can be also found.2426

All of these, whether treated surgically or orthopedi-cally, had successful long-term follow-ups. In contrast,

we also followed for over 10 years (range, 10-13 years)a sample of patients affected by HFM and treated withunilateral mandibular distraction osteogenesis (DO) dur-ing early childhood (Figs 11 and 12). The 5-year follow

up of these patients was previously reported.27 The ob-jective of this study was to clearly define, not only in

Fig 4. Male patient misdiagnosed with HFM and treated with unilateral mandibular DO: A and B,

before DO, the ear, although normal in structure, is abnormally positioned due to the skeletal

deformity; it is lateral and more prominent on the affected side; C and D, immediately after DO;E and F, 6 years after DO.

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Fig 5. Female patient misdiagnosed with HFM and treated with unilateral mandibular DO: A and B,

before DO; C and D, immediately after DO; E and F, 10 years after DO.

Fig 6. Male patient misdiagnosed with HFM and treated with an Andreasen modified appliance:

A and B, pretreatment; C and D, 11-year follow-up. Note the normal ear and the fullness of

the soft tissues on the affected side, even fuller than the contralateral side.

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terms of morphology, but also quantitatively in terms ofinitial differences and posttreatment long-term follow-ups, the differences between patients with HFM and

those with hemimandibular asymmetries with a peculiarramal morphology consisting of the collapse of the con-dyle against the coronoid process (CCC).

Fig 7. Femalepatient misdiagnosed with HFMand treated with a Class II bionator: A and B, at pretreat-

ment, the ear, although normal in structure, is abnormally positioned due to the skeletal deformity; it is

lateral and more prominent on the affected side; C and D, at the 12-year follow up, note the typical pre-

treatment shape of the condyle-coronoid relationship, similar in all of these patients. Note the integrity

of theears andthe fullness of thesoft tissues on theside of themandibulardeviation (in true HFM, there

is usually flatness of the gonial area).

Fig 8. Male patient misdiagnosed with HFM and treated with an asymmetrical functional activator:

A and B, at pretreatment, the ear, although normal in structure, is abnormally positioned due to theskel-

etal deformity; it is lateral and more prominent on the affected side; C and D, at the 9-year follow up,

note the fullness of the soft tissues on the affected side before treatment and the excessive fullness

after treatment. In the posttreatment panoramic x-ray, there is an evident tendency toward overgrowth

on the affected side (pattern similar to a hemimandibular hypertrophy). Overgrowth is an uncommon,

but reported, effect of trauma.25

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MATERIAL AND METHODS

One sample consisted of panoramic radiographs of 9patients with unilateral mandibular hypoplasia with CCC,

who had all been previously misdiagnosed as having HFM, at pretreatment (Tpre) and long-term follow-up(Tlt) (range, 8-29 years) after DO (Figs 2-5) and after

functional treatment ( Figs 6-10). These patients wereselected from several centers based on the similarity oftheir pretreatment condylar-coronoid morphology. The

other sample included panoramic radiographs of 8consecutively treated patients affected by HFM from 2centers (confirmed by a dysmorphologist) at Tpre and Tlt

Fig 9. Male patient misdiagnosed with HFM and treated with a morpho-correcting functional appli-

ance: A and B, pretreatment; C and D, 12-year follow-up.

Fig 10. Female patient misdiagnosed with HFM and treated with an asymmetric functional activator23:

A and B, pretreatment; C and D, 10-year follow-up.

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(10-13 years) (Figs 11 and 12). Measurements considered

on the panoramic x-rays are described in Figure 13.The use of panoramic x-rays in the diagnosis of man-

dibular deformities, in particular for gonial angle mea-surements and vertical ratios, has been previouslydemonstrated to be reliable.28,29

An unpaired Student ttest was used to check for sig-

nificant differences in the HFM sample at Tpre and Tltand between the HFM and the pseudo-HFM sample ateach time point.

RESULTS

The results of the comparisons at Tpre and Tlt in the

true HFM patients and the CCC patients are listed inTable II.

The gonial angle was significantly smaller on the af-fected side in the CCC patients at Tpre, whereas at Tltthere was no difference between the affected and

unaffected sides. The angle increased an average of

24.7 from Tpre to Tlt (P\0.01). In the HFM patients, both affected and unaffected gonial angles were

reduced, but not significantly.The condylar-coronoid process angle was negative at

Tpre in the CCC patients and increased an average of 31

at Tlt, justifying the stunning morphologic change of the

ramus (P\0.01). In the HFM patients, both sidesincreased, but not significantly.

The ratio between the affected and unaffected ramiincreased significantly by 27% from Tpre to Tlt in theCCC patients. On the contrary, the true HFM patients re-turned to the same ratio from the Tpre to the Tlt records

(Figs 11 and 12).The ratio between the affected and unaffected sig-

moid notch depths decreased significantly from Tpreto Tlt in the CCC patients. Conversely, the true HFM pa-

tients had no significant difference from the Tpre to theTlt records.

Fig 11. Male patient affected by left HFM (type II mandibular deformity), treated with unilateral mandib-

ular DO: A and B, before DO; C and D, immediately after DO; E and F, 13 years after DO.

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DISCUSSION

In 2005, the American Association of OrthodontistsCouncil on Scientific Affairs concluded that there is

no evidence that functional appliances significantly in-crease mandibular growth when evaluated in the long

term.15

Functional appliances certainly induce major den-toalveolar changes, but the actual mandibular bonychanges are 1 to 2 mm according to the literature.

This is e ven more true for vertical lengthening of theramus.30

This aspect must be carefully considered when treat-ing any mandibular asymmetry, but even more so whentreating syndromic patients. Although minor soft-tissueand skeletal asymmetries in HFM patients can be treated

with satisfactory results with functional treatment andgood dentoalveolar compensations are obtained withsome mild skeletal improvement, it is still controversial

whether it is appropriate to subject children affected

by more severe forms of HFM to long functionalorthopedic treatments.

Unilateral surgical lengthening of the ramus in

growing patients through distraction osteogenesis issuccessful in the short term but has been disappointingin the long term.31 Asymmetry recurs with time, to-gether with a consistent tendency toward a return tothe original phenotype and facial proportion.27,3234

The 8 HFM patients evaluated and measured over 10 years postdistraction showed returns to the original

ratio between the affected and unaffected ramus

heights (Table II, Figs 11 and 12). The reappearanceof the asymmetry is linked to the involvement notonly of the bony segments, but especially of the

neuromuscular pattern, which slowly returns the bonyproportions to the original architecture. The 4 CCC

patients who were surgically treated, on the contrary,have gained and maintained symmetry in the longterm (Table II, Figs 2-10). The similarity of thephenotype of these patients and the entity of the

response to functional stimulation are certainly ofgreat interest. The long-term changes of the gonial an-gle, the angle formed by the condylar and coronoid

Fig 12. Female patient affected by left HFM (severe type I mandibular deformity) and treated with uni-

lateral mandibular distraction DO: A and B, before DO; C and D, immediately after DO; E and F, 13

years after DO.

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processes, and the ratio of ramal height between the af-fected and unaffected sides in these patients compared

with true HFM patients are not only visually evident, but also quantitatively and statistically significant

(Table II).Getting back to the results of functional treatment,

Harkness and Thorburn24 questioned Kaplans orthope-dic results suggesting that the shape of the mandibularhypoplastic side could be related to a mandibularfracture instead of HFM. Several long-term studies on

mandibular condylar fractures show the ability toself-correct35 or successful correction with orthope-dics.36 These authors suggested that all the patientsdescribed might have had undiagnosed early traumas.These patients had a bony defect, but a normal neuro-muscular pattern, which can remodel the damaged

bony structure into a new condyle-coronoid complex, with the help of functional stimulation or early man-dibular surgery. However, early trauma does not alwayscause a condylar-coronoid deformity such as the one

described and measured here, nor does it have thesame prognosis. In some instances, even with a positive

history of trauma, the prognosis is not as good becauseof secondary scarring that can severely disturb thefunctional matrix. These patients often show some hy-pomobility of the affected side, and the ramal mor-

phology is not as disrupted as in the CCC patientsshown. Other types of acquired mandibular hypoplasia,

such as rheumatoid arthritis and Parry-Romberg syn-drome, have a different clinical history and aspect, es-pecially radiologically, and should not be as difficult todifferentiate.

Long-term results of both functional and surgicaltreatment of hemimandibular hypoplasia with CCCare successful, compared with those of true HFM,

which are poor in the long term, as shown in thisstudy.

Because of the great heterogeneity of the HFM phe-

notype and the little genetic knowledge on the syn-drome, the differences between these 2 types ofhemimandibular hypoplasia are not always obvious.

We have attempted to summarize the most importantclinical and radiologic differences qualitatively andquantitatively (Tables I and II, Fig 1) to aid in differential

diagnosis.We believe that it is crucial to correctly recognize

patients often misdiagnosed as having HFM, whomight have a great benefit from functional stimula-

tion. True HFM patients, on the other hand, be-cause of the early onset of the pathology, aremore likely to have bony and neuromuscular defi-

cits, which orthopedics might improve, but certainlynot correct.

CONCLUSIONS

Cooperation between not only surgeons and ortho-

dontists, but also geneticists and dysmorphologists, iscrucial in the treatment of craniofacial anomalies. It

is embryologically unlikely that a congenital diseasesuch as HFM, which occurs between the 30th and40th days in utero, could cause no deficit in theneuromuscular pattern and the soft tissues. The neuro-

muscular pattern drives craniofacial growth,16

and, al-though orthopedic treatment has been proposed,37

orthodontists might not have the proper tools at thistime.15

However, some patients with a recognizable condy-lar deformity, such as those we have described, might

benefit from functional stimulation. It is important toidentify patients eligible for this approach and distin-guish them from true HFM patients, in order not to im-pose ineffective orthopedic therapy or surgical

treatment with a poor prognosis on those with a clearembryologic deficit.

Fig 13. Tracing of a panoramic radiograph of a patient

with CCC before treatment. Co (condylion), uppermost

point of the condyle; Cor (coronoid), uppermost pointof the coronoid process; Syg, deepest point of the sig-

moid notch; Go (gonion), most inferior and posteriorpoint of the mandibular ramus where it intersects the

tangent to the lower border of the mandible. A tangent

to the proximal segment of the coronoid process is

traced. A tangent to the posterior border of the ramus

is also traced. The angle formed by these 2 lines defines

the condylar-coronoid angle. The angle formed by the

tangent to the posterior border of the ramus and the tan-

gent to the lower border of the mandible defines the go-

nial angle. The height of the ramus is defined by the

distance Go-Co. The depth of the sigmoid notch is de-fined by the perpendicular distance of Syg to the line

connecting Coand Cor.

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Table II. Measurements on panoramic radiographs of patients with HFM and with hemimandibular hypoplasiacharacterized CCC

CCCDifference

HFMDifference

T1 T2 T1 T2 RHa/RHna 0.716 0.05 0.98 6 0.07 0.27* 0.67 6 0.09 0.66 6 0.01 0.01

CC angle () a 21.2 6 6.8 10.1 6 4.6 31.3y 4.7 6 4.1 6.9 6 3.8 2.2

na 13.7 6 3.2 15.2 6 5.1 1.5 12.3 6 4.0 14.8 6 4.8 2.5

Gonial angle () a 102 6 10.6 126.7 6 8.2 24.7* 144 6 10.5 149 6 8 5

na 128.8 6 6.4 124 6 5.6 4.8 131.5 6 5.1 124 6 4.9 7

SigNa/SigNna 2.1 6 0.4 1.1 6 0.3 1.0y 0.65 6 0.2 0.64 6 0.2 0.01

RHa/RHna, Ratio of the height of the affected ramus and unaffected ramus; CC angle, angle formed by the tangent to the posterior border of the

mandible and the tangent to the coronoid process; Gonial angle, formed by the tangent to the posterior border of the mandible and the tangent to

the inferior border; SigNa/SigNna, ratio of the depth of the sigmoid notch on the affected and unaffected sides; a, affected; na, unaffected.

*P\0.05; yP\0.001.

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