Unilateral fusion of the coronal suture is the most. Isolated frontosphenoidal synostosis: a rare cause of synostotic frontal plagiocephaly

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1 J Neurosurg Pediatrics 13: , 2014 AANS, 2014 Isolated frontosphenoidal synostosis: a rare cause of synostotic frontal plagiocephaly Clinical aicle Tina M. Sauerhammer, M.D., Albe K. Oh, M.D., Michael Boyajian, M.D., Suresh N. Magge, M.D., John S. Myseros, M.D., Robe F. Keating, M.D., and Gary F. Rogers, M.D., J.D., M.B.A., M.P.H. Division of Plastic and Reconstructive Surgery, Children s National Medical Center, Washington, DC Object. Unilateral fusion of the frontoparietal suture is the most common cause of synostotic frontal plagiocephaly. Localized fusion of the frontosphenoidal suture is rare but can lead to a similar, but subtly distinct, phenotype. Methods. A retrospective cha review of the authors craniofacial database was performed. Patients with isolated frontosphenoidal synostosis on CT imaging were included. Demographic data, as well as the clinical and radiographic findings, were recorded. Resus. Three patients were identified. All patients were female and none had an identifiable syndrome. Head circumference was normal in each patient. The mean age at presentation was 4.8 months (range months); 2 fusions were on the right side. Frontal flattening and recession of the supraorbital rim on the fused side were consistent physical findings. No patient had appreciable facial angulation or orbital dystopia, and 2 patients had anterior displacement of the eral ear. All 3 patients were initially misdiagnosed with unilateral coronal synostosis, and CT imaging at a mean age of 5.4 months (range months) was required to secure the correct diagnosis. Computed tomography findings included patency of the frontoparietal suture, minor to no anterior cranial base angulation, and veical flattening of the orbit without sphenoid wing elevation on the fused side. One patient underwent CT scanning at 2.1 months of age, which demonstrated a narrow, but patent, frontosphenoidal suture. The patient s condition was assumed to be a deformational process, and she underwent 6 months of unsuccessful helmet therapy. A repeat CT scan obtained at 10.7 months of age demonstrated the synostosis. All 3 patients underwent fronto-orbital correction at mean age of 12.1 months (range months). The mean duration of postoperative follow-up was 11.7 months (range months). Conclusions. Isolated frontosphenoidal synostosis should be considered in the differential diagnosis of atypical frontal plagiocephaly. ( Key Words frontosphenoidal craniosynostosis frontal plagiocephaly synostotic plagiocephaly craniofacial Unilateral fusion of the coronal suture is the most common cause of synostotic frontal plagiocephaly, occurring at an estimated frequency of 1:10,000 live bihs. 16 Unilateral coronal synostosis (UCS) has become synonymous with premature closure of the frontoparietal suture, but this is overly simplistic. The fronto-parietal fusion in UCS expands in an age-dependent fashion to involve another suture in the coronal ring, that is, the lateral aspect of the frontosphenoidal suture. 1,12 Synostotic extension into the skull base in patients Abbreviations used in this paper: DP = deformational plagiocephaly; IFS = isolated frontosphenoidal synostosis; UCS = unilateral coronal synostosis. with UCS was first repoed by Seeger and Gabrielsen using plain radiographs 15 and later by others using CT scanning. 5,12 Moreover, the fusion appears to limit growth of other anterior cranial and facial sutures that lie on the same plane as the frontoparietal suture (for example, the fronto-ethmoidal, sphenozygomatic, sphenotemporal, and zygomaticotemporal sutures), ahough these sutures do not appear to fuse. These findings have led some authors to recommend expanding the classic definition of the coronal ring (frontoparietal, frontosphenoidal, and frontoethmoidal sutures) to include the sphenotemporal suture. 14 This aicle contains some figures that are displayed in color on line but in black-and-white in the print edition. 553

2 T. M. Sauerhammer et al. Thus, UCS cannot be considered a single suture fusion. It is more correctly classified as a complex craniosynostosis involving both the frontoparietal and frontosphenoidal sutures. Frontal plagiocephaly has been attributed to isolated involvement of other coronal ring components and adjacent sutures. Currarino described 2 patients presenting with eral frontal flattening with contralateral bossing secondary to fusion of the frontozygomatic suture.3 Neveheless, the accuracy of this diagnosis must be questioned since it was made using plain radiographs and has not been repoed since. Smat and coworkers observed frontal asymmetry in patients with squamosal synostosis.17 Isolated frontosphenoidal synostosis (IFS) was first described by Francel and coworkers in 1995,6 and, while rare, it has until now only been repoed in 16 patients. This study adds another 3 patients to the small clinical pool and reinforces the unique challenges faced in correctly diagnosing and treating these patients. Methods Following institutional review board approval, a retrospective review of the craniofacial database at Children s National Medical Center was performed. All patients treated for craniosynostosis between 1989 and 2010 were identified. Patients with IFS confirmed by high-resolution CT imaging were included in the study. Recorded variables included demographic information, clinical presentation, physical findings, surgical treatment, and outcomes. Preoperative CT images with 3D reconstruction were analyzed for suture patency and calvarial morphology. Photographs, when obtained, were evaluated for phenotypic appearance. Resus Three patients demonstrated frontal plagiocephaly secondary to IFS. All patients were female and none had an identifiable syndrome. The mean age at presentation was 4.8 months (range months). Two patients had fusion of the right side. All patients exhibited a normal percentile head circumference and growth. In addition, consistent physical findings included frontal flattening and recession of the supraorbital rim on the fused side and minor to no facial angulation or orbital dystopia. The nasal root was slightly deviated to the unfused side, and the chin point did not appear deviated. Two patients had anterior displacement of the eral ear (Figs. 1 3). All 3 patients were initially misdiagnosed with UCS, and CT imaging performed at a mean age of 5.4 months (range months) was required to secure the correct diagnosis. Computed tomography findings included patency of the frontoparietal suture, little or no anterior cranial base angulation, and veical flattening of the orbit without sphenoid wing elevation on the fused side. One patient was diagnosed as having UCS sholy after bih, but a CT scan obtained at 2.1 months of age demonstrated a widely open frontoparietal suture and a narrowed, but patent, frontosphenoidal suture. The infant also demonstrated posterior cranial flattening and other signs con554 Fig. 1. Preoperative frontal (A) and submental (B) veex photographs obtained in a 2-month-old girl with right frontosphenoidal synostosis. Three-dimensional CT reconstruction showing frontal (C) and veex (D) views at 3 months of age, a fused frontosphenoidal suture (E), and a patent frontoparietal suture (F). sistent with deformational plagiocephaly (DP). The flattening was assumed to be the resu of deformation, and the patient underwent 6 months of helmet therapy that improved the posterior shape but did nothing for the frontal asymmetry. Repeat CT scanning at 10.7 months of age clearly demonstrated synostosis of the frontosphenoidal suture. All 3 patients underwent fronto-orbital correction at mean age of 12.1 months (range months). Gross examination confirmed fusion of the frontosphenoidal suture in all cases. All patients were managed with fronto-orbital advancement at a mean age of 12 months. Notwithstanding the contrasting clinical features of UCS and IFS, the surgical treatment is the same. Our operative technique

3 Isolated frontosphenoidal synostosis Fig. 2. Preoperative frontal (A) and submental (B) veex photographs obtained in a 16-month-old girl with left frontosphenoidal synostosis. Three-dimensional CT reconstruction showing frontal (C) and submental (D) veex views at 10 months of age, left frontosphenoidal fusion (E), and right frontosphenoidal suture patency (F). Axial image revealing deviation of the cranial base (G). involved a standard open coronal approach. The frontal bone elements and supraorbital bandeau were contoured with radial cuts and osteotomies, respectively, to give an average advancement of 15 mm on the side of the synos- tosis. The contalateral side was either left at its normal anatomical position or advanced slightly to create symmetry. The bandeau on the eral side is adjusted higher (since it is depressed) in contrast to UCS, where Fig. 3. Preoperative frontal (A) and submental (B) views obtained in a 12-month-old girl with right frontosphenoidal synostosis. Three-dimensional CT reconstruction showing frontal (C) and veex (D) views at 2 months of age with bilateral patent frontosphenoidal sutures (E and F). Repeat imaging at 10 months reveals right frontosphenoidal fusion (G). 555

4 T. M. Sauerhammer et al. it is lowered. A combination of small wires and absorbable plates were used for fixation of the bony segments. Endocoical cancellous bone graft was used to fill in any bony defects. The mean postoperative follow-up was 11.7 months (range months). All 3 patients demonstrated stable symmetry of the frontal and orbital bones. At 2 years of follow-up, 1 patient exhibited a significant decrease in head circumference; CT imaging to rule out postoperative muisuture closure is pending. Discussion Isolated frontosphenoidal synostosis is rare; fewer than 20 cases are described in the literature. Francel and colleagues described the first documented case of IFS in The patient demonstrated eral flattening and contralateral bossing of the forehead, eral superior orbital rim elevation and recession, contralateral nasal root deviation, symmetric chin and ear position, and mild anterior cranial base angulation. The authors repoed a harlequin sign on 3D CT imaging. Subsequent descriptions have varied from this initial description. Rogers and coworkers repoed a series of 3 patients with IFS. 13 While the forehead, nasal, and facial findings were consistent, the eral superior orbital rim was depressed (not raised), the eral maxilla was retruded, and there was no harlequin deformity. These physical findings are consistent with other cases. 4,7,8,11 Dundulis et al. repoed a case of IFS with the above-noted findings but with chin point deviation to the affected side 5 (Table 1). The clinical diagnosis of IFS can be challenging since this entity has physical findings of both DP and the more common hemicoronal ring fusion, UCS. Neveheless, there are clear phenotypic differences that can help secure the diagnosis (Table 2). All 3 entities present with forehead asymmetry in the sagittal plane, but only the synostoses have a negative sagittal orbital-globe relationship. The concept of the sagittal orbital-globe relationship, promulgated by Mulliken and coworkers in 1996, defines the sagittal distance between the superior orbital rim (orbitale superior) and the anterior cornea and is one of the most powerful clinical tools to identify (or rule out) fusions in the coronal ring. 9,10 Because the coronal ring sutures are responsible for anterior growth of the forehead and bandeau, synostosis of any of these elements will restrict sagittal growth and produce a negative relationship (that is, the superior orbital rim lies posterior to the anterior cornea). A negative superior orbital rim anterior cornea relationship is ubiquitous in patients with UCS and was observed in all of our patients with IFS. This finding is not present in DP. Clinical distinction between IFS and UCS rests on the presence of notable orbital dystopia and facial asymmetry in the latter, but not the former, diagnosis. Both entities have forehead flattening, even though the frontoparietal suture in IFS is patent. This finding has been attributed to the observation that fusion along any of the coronal ring sutures can resu in growth impairment of the other collinear patent sutures in the ring. 2,13,15 Orbital asymmetry in UCS is well described; the affected orbit is horizontally narrow and veically taller than that on the contralateral side. These changes are presumably a consequence of greater and lesser sphenoid wing elevation in the posterior orbit. We previously proposed an explanation for elevation of the greater sphenoid wing; early fusion of the frontoparietal suture impairs growth of patent TABLE 1: Case repos and series of IFS* Authors & Year No. of Patients Age at Diagnosis (mos) Side of Synostosis Nasal Tip Deviation Orbit Misdiagnosis Francel et al., recessed, harlequin Rogers & Mulliken, normal Dundulis et al., de Ribaupierre et al., normal hypoplastic hypoplastic Marucci et al., Mathijssen et al., normal recessed 14 9 normal recessed Plooij et al., depressed DP current series * Computed tomography scanning was performed in all patients in the studies. 556 recessed DP UCS UCS UCS DP

5 Isolated frontosphenoidal synostosis TABLE 2: Comparison of physical and radiographic findings among UCS, IFS, and DP Finding UCS IFS DP physical finding eral forehead flattened flattened flattened contralateral forehead bossed bossed bossed eral superior orbital rim elevated; recessed depressed or elevated; recessed depressed; recessed eral maxilla protruded symmetric or retruded retruded nasal root erally deviated midline or contralaterally deviated midline chin contralaterally deviated midline erally deviated eral ear anterior symmetric, anterior, posterior posterior radiographic finding frontoparietal suture fused open open frontosphenoidal suture open or fused fused open anterior cranial base erally deviated contralaterally deviated midline coplanar sutures along the sphenoid (that is, frontosphenoidal, sphenoparietal, sphenotemporal, and sphenozygomatic sutures) and resus in the impaired sagittal growth and inferior displacement of the greater sphenoid wing. 12 In contrast, fusion of the frontosphenoidal suture may occur later in embryogenesis 8 and, because of its position, can only affect growth in the frontoparietal (thereby creating forehead and brow retrusion) and sphenozygomatic sutures. Thus, the impact on sphenoid position and size is negligible, and a harlequin sign is rarely present. 4 Facial asymmetry and nasal deviation in UCS is caused by angulation of the anterior cranial base toward the side of the fusion with severe shoening of the eral cranium. In contrast, anterior cranial base angulation is minor in IFS and is typically toward the contralateral side. 4,13 Consequently, facial and nasal asymmetries are quite mild. When present, nasal root deviation in IFS is to the contralateral side as opposed to the eral side in UCS. In spite of these clinical differences, all of our patients were initially misdiagnosed: 2 with UCS and 1 with DP. Given the rarity of IFS and the fact that it shares features of both UCS and DP, this is not surprising. Of the 19 repoed cases of IFS in the literature, at least 3 cases (including one in the present series) have been incorrectly diagnosed as DP and 2 have been inadveently treated with molding helmets. The one patient from this series who was misdiagnosed with DP underwent CT at an early age after the frontal flattening failed to improve. Unfounately, the CT scan appeared to confirm the absence of craniosynostosis. In retrospect, there were several findings on the initial CT that were suspicious for IFS. First, the sagittal position of the bandeau was clinically and radiographically posterior to the anterior cornea (that is, a negative superior orbital rim anterior cornea relationship). This does not occur in DP. Second, there was mild anterior cranial base deflection on CT. Lastly, ahough the suture appears open on the 3D reconstructions, careful review of the axial images revealed that the frontosphenoidal suture appeared very narrow and nearly obliterated over most of its course. Given our experience, any child with severe frontal flattening that does not improve with observation and/or helmet therapy should undergo high resolution CT (1 mm orbital and superior orbital cuts) to rule out IFS. While our follow-up is limited, all 3 patients in our series demonstrated a stable fronto-orbital contour. Longer follow-up of these patients is required to fuher assess the effectiveness of our repair over time. Conclusions Isolated frontosphenoidal synostosis is a rare and often misdiagnosed cause of frontal plagiocephaly. Careful clinical consideration can help to distinguish this entity from other forms of frontal asymmetry, and CT scanning is recommended to confirm the diagnosis. Disclosure The authors repo no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper. Author contributions to the study and manuscript preparation include the following. Conception and design: Rogers. Acquisition of data: all authors. Analysis and interpretation of data: Sauerhammer, Rogers. Drafting the aicle: Sauerhammer, Rogers. Critically revising the aicle: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Sauerhammer. Statistical analysis: Sauerhammer. Administrative/technical/material suppo: Rogers. Study supervision: Rogers. References 1. Beelsen TI: The premature synostosis of the cranial sutures. Acta Ophthalmol Suppl 36 (Suppl 51):1 176, Burdi AR, Kusnetz AB, Venes JL, Gebarski SS: The natural history and pathogenesis of the cranial coronal ring aiculations: implications in understanding the pathogenesis of the Crouzon craniostenotic defects. Cleft Palate J 23:28 39, Currarino G: Premature closure of the frontozygomatic suture: unusual frontoorbital dysplasia mimicking unilateral coronal synostosis. 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6 T. M. Sauerhammer et al. onal ring involvement in patients treated for unilateral coronal craniosynostosis. Plast Reconstr Surg 114: , Francel PC, Park TS, Marsh JL, Kaufman BA: Frontal plagiocephaly secondary to synostosis of the frontosphenoidal suture. Case repo. J Neurosurg 83: , Marucci DD, Jones BM, Dunaway DJ, Hayward RD: Unilateral isolated frontosphenoidal craniosynostosis causing frontal plagiocephaly. J Plast Reconstr Aesthet Surg 62:e255 e258, Mathijssen IM, van der Meulen JJ, van Adrichem LN, Vaandrager JM, van der Hulst RR, Lequin MH, et al: The frontosphenoidal suture: fetal development and phenotype of its synostosis. Pediatr Radiol 38: , Mulliken JB, Godwin SL, Pracharktam N, Aobelli DE: The concept of the sagittal orbital-globe relationship in craniofacial surgery. Plast Reconstr Surg 97: , Pai L, Kohout MP, Mulliken JB: Prospective anthropometric analysis of sagittal orbital-globe relationship following fronto-orbital advancement in childhood. Plast Reconstr Surg 103: , Plooij JM, Verhamme Y, Bergé SJ, van Linde EJ, Borstlap- Engels VMF, Borstlap WA: Unilateral craniosynostosis of the frontosphenoidal suture: a case repo and a review of literature. J Craniomaxillofac Surg 37: , Rogers GF, Mulliken JB: Involvement of the basilar coronal ring in unilateral coronal synostosis. Plast Reconstr Surg 115: , Rogers GF, Proctor MR, Mulliken JB: Unilateral fusion of the frontosphenoidal suture: a rare cause of synostotic frontal plagiocephaly. Plast Reconstr Surg 110: , Sakamoto Y, Nakajima H, Tamada I, Miyamoto J, Kishi K: Involvement of the sphenosquamosal suture for unilateral coronal synostosis. J Craniofac Surg 23: , Seeger JF, Gabrielsen TO: Premature closure of the frontosphenoidal suture in synostosis of the coronal suture. Radiology 101: , Shillito J Jr, Matson DD: Craniosynostosis: a review of 519 surgical patients. Pediatrics 41: , Smat JM Jr, Singh DJ, Reid RR, Hellinger JC, Hsu VM, Balett SP: Squamosal suture synostosis: a cause of atypical skull asymmetry. Plast Reconstr Surg 130: , 2012 Manuscript submitted February 25, Accepted January 21, Please include this information when citing this paper: published online March 7, 2014; DOI: / PEDS1378. Address correspondence to: Tina M. Sauerhammer, M.D., Division of Plastic and Reconstructive Surgery, Children s National Medical Center, 111 Michigan Ave., NW, West Wing, 4th Floor, Ste. 100, Washington, DC tsauerha@cnmc.org. 558