Q: Which is the first skull suture to close?
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A: The metopic suture is the first skull suture to close; it is the only calvarial suture that usually closes during infancy. Fusion of the metopic suture is a progressive process initiated at the nasion and completed at the anterior fontanelle. This suture starts to close at three months, and the complete fusion occurs by six and nine months.
Q: What is a metopic ridge?
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A: A metopic ridge is a palpable midline ridge over the forehead that usually occurs with the physiological closure of the metopic suture and consists of a normal variant. Patients with metopic craniosynostosis may also present similar ectocranial ridging. Therefore it is essential to differentiate between the two groups of patients because metopic ridge, due to physiological closure, needs no treatment or surgery, and metopic craniosynostosis with trigonocephaly may require surgical correction, depending on the severity of the deformity.
Q: What is the definition of metopic craniosynostosis?
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A: Metopic craniosynostosis occurs due to the premature fusion of the metopic suture. Metopic synostosis ranges from isolated metopic ridge to severe trigonocephaly, usually associated with a frontal narrowing deformity characterized by a triangular forehead shape, biparietal widening, and hypotelorism.
Q: How is made the diagnosis of the metopic ridge?
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A: The diagnosis is on clinical features, including a palpable and visible frontal ridge. There may be confusion in differentiating between the metopic crest due to physiological closure or craniosynostosis with mild trigonocephaly. Patients with metopic craniosynostosis usually present earlier than those with metopic ridge due to physiological closure. CT scan can help differentiate between the two conditions. MRI can be a valuable tool in patients with craniosynostosis; however, the accuracy in defining bony abnormalities of MRI is inferior compared to CT.
Q: What are the metopic ridge's radiographic signs due to the metopic suture's physiological closure?
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A: The radiographic signs of a metopic ridge due to physiological closure of the metopic suture are a deformity with ectocranial midline ridging of the forehead, usually associated with an endocranial bony spur. The other signs of metopic craniosynostosis are not present.
Q: What are the radiographic signs of metopic craniosynostosis with trigonocephaly?
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A: The radiographic signs of metopic craniosynostosis with trigonocephaly include a closed metopic suture, a ridge over the metopic suture, pulled anterior fontanelle, a straight lateral frontal bone, a posteriorly displaced lateral frontal bone, frontal bone tangent to mid-orbit, lateral orbital hypoplasia, a triangular anterior vault deformity with a narrow forehead, biparietal widening, Interorbital narrowing with hypotelorism and the intercanthal distance less than 15 mm in infants less than one-year-old, narrowing of the upper orbital width, hypoplastic ethmoid sinuses, and an invagination at the suture, known as the omega sign.
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