|Year : 2015 | Volume
| Issue : 1 | Page : 41-45
Nonsyndromic hemimandibular hypoplasia: A case report with a short review of the literature
Sourav Bhattacharya1, Dibyendu Mazumder1, Debarati Ray1, Sumit Ray2
1 Department of Dentistry, Medical College, Kolkata, West Bengal, India
2 Department of Pathology, Medical College, Kolkata, West Bengal, India
|Date of Web Publication||20-May-2015|
Dr. Sourav Bhattacharya
Flat No. A2-203, Sugam Park, Narendrapur, 195 NS Road, Kolkata - 700 103, West Bengal
Source of Support: None, Conflict of Interest: None
Mandibular hypoplasia (MH) is a condition, which characterizes deviation in the mandibular growth patterns causing functional and esthetic alterations. MHs encountered in the craniofacial region may be of three types: Congenital, developmental and acquired. Majority of the MHs are associated with syndromes with very little emphasis on the "nonsyndromic" category. Furthermore, the hypoplasias generally have a bilateral manifestation on the mandible. We focus on the nonsyndromic category and report a case of isolated unilateral MH in a 17-year-old boy with obvious facial disfigurement but with no association to any syndrome. The objective of this presentation is to highlight the rarity, possible manifestations and diagnostic approach of the nonsyndromic group.
Keywords: Hemimandibular, hypoplasia, nonsyndromic
|How to cite this article:|
Bhattacharya S, Mazumder D, Ray D, Ray S. Nonsyndromic hemimandibular hypoplasia: A case report with a short review of the literature. J Orofac Sci 2015;7:41-5
|How to cite this URL:|
Bhattacharya S, Mazumder D, Ray D, Ray S. Nonsyndromic hemimandibular hypoplasia: A case report with a short review of the literature. J Orofac Sci [serial online] 2015 [cited 2019 Dec 8];7:41-5. Available from: http://www.jofs.in/text.asp?2015/7/1/41/157382
| Introduction|| |
Mandibular hypoplasia (MH) is a common craniofacial anomaly, which is of three types: Congenital, developmental and acquired. The most frequently presented congenital type is usually associated with syndromes. Distinct from this group are the patients with nonsyndromic malformations of the mandible.  Earlier literatures show reporting of aplasia of the mandibular condyle without any other facial malformations by Prowler and Glassman in 1954 and Krogstad in 1997.  To the best of our knowledge, no case has been reported on isolated nonsyndromic MH showing its manifestation unilaterally on the entire half of the bone. This has further attracted us, to summarize, the case with comparative evaluation of the "syndromic" group versus the "nonsyndromic" group.
| Case Report|| |
A 17-year-old male reported to us with complain of difficulty in mouth opening along with progressive deviation of the face on the right side. No history of forceps delivery, trauma, any severe infection or parafunctional habits were present.
Extraorally, he had deviation of the lower third of the face and chin on the right side along with decreased fullness of the face [Figure 1]. On palpation, the temporomandibular joints (TMJs) were within normal limits. A thorough screening for any other craniofacial anomaly was found negative. Exploratory radiographs of the skull, chest, spine, extremities and routine hemogram were also within normal range.
Intraoral examination revealed absence of 46, which was extracted 8 years ago due to carious exposure. No midline shift of the occlusion was noted, but mouth opening was limited with extreme deviation on the right side [Figure 2].
|Figure 2: Photograph showing extraoral view of the patient on mouth opening|
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The orthopantomograph revealed hypoplasia of the mandibular bone on the right side, which was in sharp contrast to the left side showing features like a small body, obtuse gonial angle, and a short ramal height. The deformed condylar head was short, flattened, slightly posteriorly located in the joint cavity, and the affected coronoid process was sharp and rudimentary [Figure 3].
|Figure 3: Orthopantomogram X-ray of the jaws showing unilateral mandibular hypoplasia of the right side|
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The three-dimensional view of the computer tomography scan showed no significant abnormality of the visualized parts of the brain parenchyma, orbits, maxilla, paranasal air sinuses nasal cavities and temporal bones. The bone window revealed erosion of the right mandibular condyle with deviated and deformed right TMJ. Section wise close observation showed the articular surfaces of the right TMJ were irregular with uneven joint spaces, having features of secondary osteoarthritic changes. Flattening of the convexity of the condylar head was also observed [Figure 4].
|Figure 4: Computer tomography scan showing condylar hypoplasia and irregular right temporomandibular joints with secondary osteoarthritic changes|
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The soft tissue profile showed relative atrophy of the right side facial muscles with respect to that of the left side.
After reviewing the details, the case was provisionally diagnosed as an isolated hemimandibular hypoplasia. The differential diagnosis incorporates all the associated syndromes that involves the craniofacial region and affects the mandibular growth pattern to any degree like those of the oculo-auriculo-vertebral (OAV) spectrum or Treacher Collins' syndrome (TCS). Close scrutiny of relevant anatomical structures and multimodal diagnostic procedures helped us to exclude this case from the syndromic category. Important features aiding us to conclude this to be a case of nonsyndromic hemimandibular hypoplasia in comparison to the syndromic category is further delineated in detail in the following discussion.
| Discussion|| |
Mandibular development begins in the 4 th week of gestation with migration of the neural crest cells in the future head and neck region. The first branchial arch develops into the mandible, the maxilla, zygoma, and the squamous portion of the temporal bone. Among the three types of MHs, the congenital type results from insufficient migration of the neural crest cells into the first branchial arch resulting in the bilateral deformity. Developmental hypoplasias are of unknown etiology with characteristic class II malocclusion. Acquired hypoplasias include oncologic defects, radiation damage, trauma and hemifacial atrophy. 
According to Gorlin, the most frequently encountered congenital type is associated with more than 60 syndromes as one of their components. Among them, the OAV spectrum followed by the mandibulofacial dysostosis (MFD) group or TCS comprises the most common types and hence requires a short discussion. 
The oculo-auriculo-vertebral spectrum
The OAV includes a broad spectrum of anomalies ranging from isolated microtia to Goldenher syndrome. Hemifacial microsomia (HFM) of this spectrum is the most common craniofacial malformation after cleft lip and cleft palate. It is characterized by an asymmetric facial defect in which the mandible and overlying structures fail to develop normally. ,
An extensive investigation on this group of patients has led to the evolution of different classification systems, which incorporate the mandibular deformity as one of the central elements. This include pioneer works carried out by Pruzansky in 1969, David et al. in 1987 (SAT Classification), Vento et al. in 1991 (OMENS Classification), Kaban et al., 1998, Prahl-Andersen et al. 2001 (Mandibular Deformity Score and Cranial Deformity Score) and Madrid et al., 2010. 
The mandibulofacial dysostosis group
The next most common is the MFD group where after Teacher Collins (1900) subsequent writers, de Lima and Montiero (1923), Isakowitz (1927), Lockhart (1929), Waardenburg (1932), Herman (1936), Van Linnt and Hennebert (1936), McEnery and Brennemann (1937), Debusmann (1940) and Mann (1943), added to its characteristic features.  It shows birdlike facial morphology with hypoplasia of zygoma, maxilla, mandible, malformed external ears, antimongoloid obliquity and variable effects on the TMJs and muscles of mastication (Madhan and Nayar 2006). , Study of MFD fetus (15 weeks) even showed a bilateral failure of growth of rami, bodies and condyle resulting in severe retrusion of lower face. 
Apart from these numerous publications have been made regarding patients with syndromic congenital MH (Lauritzen et al. 1985; Monahan et al. 2001, Poon et al. 2003).  It is beyond the scope of this paper to comprehend and summarize all the syndromes associated with MH in a single attempt.
The nonsyndromic group
The rare group of patients with nonsyndromic malformations of the mandible had very little investigations done on it. Noteworthy among them was an interesting work carried out at the Children's Hospital of Philadelphia for a period of 27 years between 1975 and 2003. There, in a retrospective analysis of 266 patients with congenital MH, only 18 turned out to be nonsyndromic with only one having unilateral growth disturbance. 
In 2008, Kaneyama et al. classified congenital deformities of the mandibular condyle into three major groups as hypoplasia, hyperplasia and bifidity that involves both "syndromic" and "nonsyndromic" category. 
Singh and Bartlett classification
The most promising discussion was however made by Singh and Bartlett in 2005, where they illustrated an algorithm to classify MH [Graph 1].  According to this classification, congenital hypoplasias can be either deformational or malformational on the basis of whether extrinsic forces or an intrinsic growth disturbance causes the resultant deformity. These patients can be further classified as having syndromic or nonsyndromic MHs.
The subset of patients who are with nonsyndromic, malformational MH included four subgroups: Patients with TMJ ankylosis, those with aglossia/microglossia, those with rare craniofacial clefts (RCFC), and those with isolated MH. 
It is interesting to note that our case matched properly in the last subgroup and specified as nonsyndromic, malformational isolated MH. Absence of any history of premature birth, prenatal or postnatal trauma rules out the possibility of TMJ ankylosis congenitally or due to trauma. Normal tongue size and absence of any craniofacial cleft also justifies the exclusion from the aglossia/microglossia and RCFC subgroups.
Hemifacial microsomia versus isolated mandibular hypoplasia
Numerous reports have been published on this category of patients. In a retrospective analysis of 40 HFM patients, carried out by Rahbar et al., showed MHs (97%) and auricular abnormalities (95%) as the most common clinical manifestations. Prevalent functional deficits like facial nerve weakness and hearing loss prompted them to suggest combined study of temporal bone abnormalities and any type of MH.  Investigations carried out by Keogh et al. on 100 patients with isolated microtia for unsuspected HFM, showed 37 to have mandibular asymmetry.  Our patient had no malformation of the external ear, hearing deficit, facial nerve weakness or aberrations of the temporal bone.
Pierre Robin syndrome and mandibulofacial dysostosis versus isolated mandibular hypoplasia
Pierre Robin syndrome and MFD syndromes are both defects of the branchial arches. The former condition is characterized by failure of development of the mandible in the utero with relatively enlarged tongue resulting in the upper airway obstruction and may require airway management. , It may be associated with cleft palate in over 50% of the cases.  In the later syndrome, the most usual features are the lack of mandible, zygoma and ear development, characteristic depressed malar arches and antimongoloid slant of the eye.  In our patient absence of any clefting, malformed ears or orbital abnormality helps to exclude the case from this category.
Mandibular hypoplasia with microtia and other skeletal anomalies
High number of dentofacial anomalies with various spinal diseases has been reported. In a statistical study on 297 patients with microtia, a positive association between MH and cervical spine fusion or other skeletal anomalies has been reported. They also illustrated that 73% of the patients with unilateral microtia exhibited MH.  Atresias of the external auditory meatus, MH, hypoplasia of internal auditory canals, absence of TMJs along with other cardinal features were also noted in patients with Goldenher syndrome by Engiz et al., 2007.  Our patient had normal morphology of the ears and radiographs of the chest and spine showed no obvious anomaly. It can be explained that as the external ear, middle ear, mandible, and cervical spine, all are derived from the first and the second branchial arches, teratogenesis of these structures is naturally related.
Parry-Rhomberg syndrome versus isolated mandibular hypoplasia
Parry-Rhomberg syndrome (Parry 1852, Rhomberg, 1846) has drawn special attention as its features closely simulate our case. It was later named as "progressive hemifacial atrophy" (Eulenberg, 1871) and consists of slowly progressive atrophy of the soft tissues of essentially half the face, atrophy of half the tongue, short body and ramus of the mandible and delayed tooth eruption of the affected side.  Though the right side facial muscles were relatively atrophic in our case, normal tooth eruption pattern and adequate tongue mass rules out the possibility of this syndrome.
A possible hypothesis
Mandible behaves as long bones with endochondral growth mechanism at each end and intramembranous growth between. In specific areas, muscle function and tooth eruption controls the growth than by intrinsic cartilaginous or osteogenic factors. The muscle attached areas of the ramus plays an important role in extensive localized remodeling to produce the outline of adult mandible. The gonial regions and the coronoid processes become fully differentiated only in response to the development and functioning of the muscles that insert there. Experiments proved that these regions do not develop well if the muscles are removed early or if the nerves and vessels serving them are severed. Interestingly, during the vital stages of development of face at about 7 weeks of intrauterine life, shifting of blood supply from internal to external carotid artery via the stapedial artery takes place. If for any reason this shift is delayed, the effect on the developing tissues will be noted undoubtedly. 
In the light of this hypothesis, the present case could be explained by the relative atrophy of the facial muscles on the right side resulting in underdevelopment of half of the bone with short ramus, rudimentary coronoid process and obtuse gonial angle. The growth of the alveolar process remains unaltered as it is controlled by tooth eruption, which is unhindered, in this case.
| Conclusion|| |
Mandibular hypoplasias may fall within a wide spectrum of different syndromes that commonly affect the craniofacial region. It is customary to search for other clinical findings to make a clear differentiation between the syndromic and the nonsyndromic categories as the subsequent diagnostic procedures, treatment modalities, and prognosis vary accordingly.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]