IS Case 25: Trigonocephaly
Imaging Sciences URMC 2008
Publication Date: 2009-05-18
Trigonocephaly is a triangular, forward pointing skull due to premature closure of the metopic fissure. The metopic suture normally closes between 1 and 2 years of age and is completely fused by 3 years. In trigonocephaly, the premature fusion is completed prior to birth.
Trigonocephaly is seen in 10-20 % of all craniosynostosis patients. The incidence is 1 in 2,500 with 3 to1 male predominance. The highest incidence of premature metopic suture closure has been described in Japanese.
In 1862, Hermann Welcker, prosector, professor, and later director of the Anatomical Institute at the University of Halle an der Salle, was first to use the term “trigonocephaly” to describe the shape of the skull in a patient with metopic suture synostosis The deformity is most commonly an isolated finding without a known cause. Familial cases are seen in 2 to 5%. In 10 to 20% it is associated with Opitz C, Say-Meyer, or Frydman syndromes. In addition, other syndromes, such as Carpenter, Baller-Gerold, and Seathe-Chotzen may cause premature metopic suture closure. Multiple chromosomal defects without named syndromes have association with this deformity as well.
The facial features of trigonocephaly include keel-shaped forehead, absence of frontal eminences, retruded lateral orbital rims, epicanthus, and hypotelorism. Decreased interpterional width and reduced frontal height cause anterior displacement of coronal suture, which leads to reduced capacity of the anterior fossa. The increased interparietal width is thought to be compensatory. In some cases cerebral midline defects and cognitive deficiency are seen.
The general consensus is that a minor form of trigonocephaly consisting of prominent metopic ridge without other abnormalities does not need an operation. Management of other cases is controversial. Intracranial pressure is reported to be elevated in 8% cases. In addition, some researchers speculate that small anterior fossa restricts brain growth leading to mental retardation. However, this relationship is not clearly established. Most authors agree that the main reason for surgical repair is aesthetics. Although the surgery can be performed at any age before 24 months, some studies suggest that repair within the first 6 months (3-9 months range) may prevent frequently seen development of astigmatism and strabismus. Recontouring of the fronto-orbital bar is most commonly preformed. Overall, trigonocephaly has the best postoperative results compared to other craniosynostosis.
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