Preoperative anthropometric dysmorphology in metopic synostosis

Abstract

Anthropometric identification of dysmorphology in craniofacial anomalies, including the craniosynostoses, provides invaluable assistance in clinical diagnosis as well as offering a technique for interpreting possible deformities in skeletal remains. Premature closure of the metopic suture is a rare form of craniosynostosis, representing about 4% of clinically diagnosed synostoses. Accompanying this closure are defects of the head and face, particularly the upper face and orbits. To identify quantitatively the craniofacial dysmorphology associated with metopic synostosis, 50 patients with a diagnosis of primary (nonsyndromal) metopic synostosis were examined using a battery of 24 anthropometric measurements from which 11 proportion indices were calculated. The data were compared to sex- and age-matched normal students and converted to standard (Z) scores before being analyzed using Student's t-test. The data indicate a complex pattern of dysmorphology arising from the synostosis which affects the upper face and orbits as well as the cranial vault. The entire fronto-orbito-zygomatic complex is narrowed, and vertex is reduced. There is compensatory sagittal and transverse growth of the posterior neurocranium and compensatory vertical and sagittal growth of the upper face. There are statistically significant differences in the pattern of dysmorphology between patients presenting prior to 6 months of age and those older but not significant differences between sexes.

Metopic synostosis

“…Vertical growth restriction as expressed in reduced auricular head height is one of the most significant components of the midline growth anomalies. The cephalic index (maximal skull width/maximal skull length) remains within normal limits, even though there is bitemporal shortening and biparietal widening [6, 8, 15, 28, 30, 53, 57, 75, 81, 91, 109]. Since the growth restriction results in a reduced intracranial volume, surgery is indicated to restore the scull volume as well as its appearance.

Fig 2 a CT scan of metopic synostosis ( top view ).

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The Changing Epidemiologic Spectrum of Single-Suture Synostoses

“…3 This translates into a prevalence of between one in 10,000 and one in 100,000 live births. 4 More recent literature conveys a high variability in the relative frequency of this form of craniosynostosis: between 5 and 50 percent 5-8 of all cases (Table 1). We suspect that there has been an increase in the number of trigonocephaly patients who have presented to the Facial Reconstruction Center at The Children's Hospital of Philadelphia over recent years.…”

Objective Assessment of the Interfrontal Angle for Severity Grading and Operative Decision-Making in Metopic Synostosis

“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Because metopic synostosis, like all craniosynostosis, is a skeletal problem, craniofacial surgeons have scrutinized radiographs for different features that might be useful for diagnosis and classification. Whitaker et al insightfully argued for differentiation of synostosis from normal fusion based on the "omega sign," a distinctive feature of the pathologic suture in cross-section.…”