Zygomaticotemporal Suture Synostosis Causes Progressive Facial Deformity and Asymmetry

Sir: Premature fusion of a facial suture is exceedingly rare. We recently reported the first case of progressive facial asymmetry caused by unilateral zygomaticotemporal suture synostosis.1 Serial photographs demonstrated that the condition worsened with facial growth. The effects of the sutural fusion were not isolated to the zygoma: the patient also had severe maxillary retrusion, nasal deviation, and sagittal shortening of the ipsilateral cranium. However, the orbits and the occlusal plane were level. The widespread effects of this isolated fusion were enigmatic. We hypothesized that the zygomaticotemporal synostosis stress-shielded normal mechanical strain across patent co-planar sutures, resulting in undergrowth of otherwise normal adjacent bony elements (“co-planar suture theory”).2,3 In this article, we report another patient with this unusual fusion. A healthy 7-year-old boy was referred to our center for progressive right frontofacial flattening. According to his mother, he was first noted to have minor facial asymmetry at age 1 year, which worsened with growth. No formal work-up was initiated. Physical examination revealed moderate right midfacial and frontal retrusion. His nose and chin-point were deviated toward the side of the fusion, and his occlusal plane was minimally tilted. His orbits were level, and there was no enophthalmos or orbital dystopia. Computed tomography scanning was recommended but was never obtained. Genetic testing revealed normal karyotype studies and a neutral amino acid substitution in TWIST exon 1 that was also present in his phenotypically normal mother. This polymorphism has not been previously reported and the clinical significance is unclear. Two years later, he returned to our unit and exhibited more severe facial and cranial asymmetry. Computed tomography demonstrated patent calvarial sutures and isolated fusion of the right zygomaticotemporal suture (Fig. 1). There was severe retrusion of the right maxilla with moderate flattening of the right frontal bone (Fig. 2). The ipsilateral zygomatic arch, greater sphenoid wing, and temporal and frontal bones were all shorter in the sagittal dimension than on the contralateral side. Midfacial width and vertical maxillary height were similar on both sides. The anterior cranial base was angulated nearly 10 degrees toward the side of the fusion.Fig. 1.: Axial computed tomographic image demonstrating right zygomaticotemporal suture fusion (black circle) with shortened and bowed zygomatic process of the temporal bone. The left zygomaticotemporal suture (white circle) is patent.Fig. 2.: Submental vertex view demonstrating severe retrusion of the right maxilla and moderate flattening of the right frontal bone.On the basis of our previous experience, we anticipated that the hemifacial undergrowth would worsen during adolescence. In an attempt to halt the progressive asymmetry, we performed a segmental right zygomaticotemporal suturectomy through an upper buccal sulcus incision. We hypothesized that removing the fusion should allow more normal growth. The effectiveness of this procedure will not be known for several years. Zygomaticotemporal suture synostosis should be considered in patients with otherwise inexplicable, progressive facial asymmetry. Because this suture is small and irregular, three-dimensional reconstructions are unreliable. The diagnosis is best made using high-resolution computed tomography with thin axial cuts (1 to 2 mm). Stephen R. Sullivan, M.D. Arin K. Greene, M.D., M.M.Sc. John B. Mulliken, M.D. Gary F. Rogers, M.D., M.B.A., M.P.H. Department of Plastic Surgery and the Craniofacial Center Children’s Hospital Boston and Harvard Medical School Boston, Mass. DISCLOSURE There are no commercial associations, supporting funds, or financial disclosures for any of the authors that might pose or create a conflict of interest with information presented in this article.