Journal of Orofacial Sciences

: 2020  |  Volume : 12  |  Issue : 1  |  Page : 61--63

Cone Beam CT Evaluation of Bilateral Maxillary Sinus Hypoplasia with Unilateral Mandibular Hypertrophy

Mohammed Bindakhil1, Mel Mupparapu2,  
1 Department of Oral Medicine, Penn Dental Medicine, Philadelphia, USA
2 Professor of Radiology, Penn Dental Medicine, Philadelphia, PA, USA

Correspondence Address:
Mel Mupparapu
Penn Dental Medicine, 240 S 40th Street, Philadelphia, PA 19104


Maxillary sinus hypoplasia (MSH) is a rare condition characterized by underdevelopment or decrease in the volume of the maxillary sinus. It is thought that MSH may be embryological in origin but acquired etiologies have also been discussed in the literature. MSH is usually detected upon radiographic examination of the maxillofacial area. Three types have been described based on variations in sinus anatomy. A case of bilateral maxillary sinus hypoplasia with concurrent hemimandibular hypertrophy is presented, and pertinent clinical and cone beam computed tomography findings are reported.

How to cite this article:
Bindakhil M, Mupparapu M. Cone Beam CT Evaluation of Bilateral Maxillary Sinus Hypoplasia with Unilateral Mandibular Hypertrophy.J Orofac Sci 2020;12:61-63

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Bindakhil M, Mupparapu M. Cone Beam CT Evaluation of Bilateral Maxillary Sinus Hypoplasia with Unilateral Mandibular Hypertrophy. J Orofac Sci [serial online] 2020 [cited 2020 Nov 23 ];12:61-63
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Maxillary sinus hypoplasia (MSH) is present in only 1.73% to 10.4% of patients who have symptoms related to the maxillary sinus.[1] It is thought to occur because of embryological underdevelopment of the maxillary sinus or because of trauma or infection.[1] MSH is classified into three different types on the basis of its severity and the involvement of the uncinate process.[2] Most patients with MSH are asymptomatic and unaware of their condition.[3],[4] The most common symptoms are postnasal drip and nasal obstruction, but some patients may present with headache, facial pain, or vocal change.[3],[4],[5] Because these symptoms can mimic the symptoms of other sinus diseases, like chronic sinusitis, MSH is often misdiagnosed.[4],[5] In asymptomatic patients, it is detected incidentally through unrelated imaging studies.[2] We report a case of a patient who initially presented with complaints of trismus and facial asymmetry. Cone-beam computed tomography (CBCT) revealed radiographic findings consistent with type I MSH. This study discusses the clinical and radiographic features of a rare and frequently misdiagnosed condition of which clinicians should be aware.

 Case History

A 42-year-old female with facial asymmetry and malocclusion presented to the department of Orthodontics at the University of Pennsylvania School of Dental Medicine for a consultation. She reported that her uneven smile had been present since childhood. Her medical history was noncontributory, and she was not taking any medications or nutritional supplements. Clinical examination revealed a moderately asymmetric facial skeleton, as well as imbrication of the mandibular anterior teeth. It was noted that several teeth were missing in the maxilla and mandible, including maxillary central incisors. Results of examinations of the cranial nerves and temporomandibular joints were within normal ranges. A panoramic radiograph showed right mandibular hypertrophy, and the maxillary sinuses were not clearly visualized. A plan for orthodontic treatment of the malocclusion was agreed upon, and the patient was referred for CBCT in order to check for bone pathology and contraindications to orthodontic treatment if any. The CBCT volume revealed moderate dysmorphia of the maxilla and mandible, with bilateral atresia of the maxillary sinuses. The inferior conchae were within normal limits bilaterally. Middle nasal conchae were pneumatized, and it was observed that the concha bullosa was more prominent on the right side. The maxillary sinuses were hypoplastic, but the uncinate process was intact bilaterally. Bilateral Haller cells were incidentally noted, along the infraorbital margin [Figure 1],[Figure 2][Figure 3][Figure 4]. The radiological findings were consistent with type I MSH. It was recommended that the patient follow up with an Otorhinolaryngologist if she develops sinus symptoms. Since the patient had no contraindications for orthodontic treatment, no further recommendations were made, except that the MSH and unilateral mandibular hypertrophy be disclosed to the patient. A surgical consultation was recommended for possible surgical management of facial asymmetry in addition to the orthodontic treatment. In this case, facial asymmetry was deemed to have been caused by non-syndromic unilateral mandibular hypertrophy. Conditions that lead to facial asymmetry due to mandibular hypoplasia, such as hemifacial microsomia, were therefore not considered.{Figure 1}{Figure 2}{Figure 3}{Figure 4}


During the first trimester of prenatal life, mucosal evagination of the middle meatus of the nasal cavity, along with resorption of the maxillary bone, leads to the formation of maxillary sinuses.[1] The volume of the maxillary sinus continues to grow until puberty, attaining an approximate average volume of 25 × 33 × 34 mm.[4] The functions of the maxillary sinuses include warming and humidification of inhaled air, contributions to the sensation of smell and the resonance of the voice, lightening of cranial weight, and insulation of the orbits.[4] Although many studies have reported the incidence of MSH to be between 1.5% and 10%, some studies have reported an incidence that is even lower.[4] Several acquired factors, including trauma, infection, and surgical procedures, can lead to the arrest of maxillary sinus pneumatization and therefore to hypoplasia.[4] Other acquired conditions involve irradiation, thalassemia, eosinophilia with polyangiitis, and neoplasms.[4] Congenital conditions have also been implicated in the etiology of maxillary sinus hypoplasia.[1] Among these are Treacher Collins syndrome (TCS), Craniosynostosis, and Down syndrome.[1],[4],[6] TCS is an autosomal malformation that affects the craniofacial structures. Patients with this syndrome almost always present with malar flattening, hypoplasia of zygomatic complex, or downward-slanting palpebral fissures. Mandibular micrognathia is seen in about 80% of patients with TCS.[6] Because the patient discussed in this report did not manifest any of these common symptoms of TCS, this diagnosis was ruled out. Craniosynostosis and Down syndrome may have significant facial deformities, and individually have characteristic clinical and radiographic features that are distinct.[1],[4],[6] In the absence of any other clinical features, known genetic abnormalities, or pathognomonic skeletal malformation in this patient, these conditions were ruled out.

Bolger et al.[2] classified MSH into three types:Type I is characterized by a normal uncinate process, minor sinus hypoplasia with a normally developed uncinate process, and a well-defined infundibular passage.Type II is characterized by the absence or hypoplasia of the uncinate process, an ill-defined infundibular passage, and significant sinus hypoplasia.Type III is characterized by profound sinus hypoplasia (manifested in a cleft-like sinus) and the absence of the uncinate process.

Type I is the most common, according to one study accounting for 52.5% of all MSH cases;[3] 33.7% of MSH patients also have frontal sinus hypoplasia.[3] Mucosal thickening of the hypoplastic sinus may be present to variable degrees in cases of type I, whereas complete opacification of the involved sinus may be present in cases of type II MSH.[3]

Conventional radiographic findings of MSH may overlap with the findings of other conditions, such as mucosal thickening in infectious disease or maxillary sinus neoplasms.[4] CT, CBCT, or endoscopic examination is essential to establishing a diagnosis of MSH.[4] CBCT is superior to MDCT for diagnosis of MSH, since it provides the same level of detail as multiple detector computed tomography (MDCT) when evaluating the maxillofacial region but requires a much lower radiation dose.[4],[7] Radiographic evaluation using MDCT or CBCT is essential in differentiating between MSH and inflammatory, infectious, or neoplastic conditions.[4] The appropriate radiographic imaging is critical if a surgical option is being considered in order to avoid procedural complications and orbital surgical trauma.[4]

The inflammatory symptoms of MSH respond poorly to medical therapy that can effectively treat more common inflammatory sinus diseases of chronic sinusitis and acute sinusitis.[5] Although there are currently no generally agreed upon guidelines for management of MSH, several medical and surgical treatments have been used.[5] Endoscopic sinus surgery is a standard surgical intervention for the condition.[6] The main limitation of this procedure is the risk of intraoperative injury to the infraorbital area in cases of a hypoplastic or absent uncinate process.[5] Medical treatment involves the use of low-dose antibiotics with a known anti-inflammatory effect, like Clarithromycin. But this therapy results in only minimal benefit.[5]

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