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Neuroradiology Case of the Week

Case 283

Edward Lin, MD

Clinical Presentation: Patient is a four-month-old male with deformity of the forehead.

Imaging Findings: Axial computed tomography section (Fig. 1) and 3-dimensional reconstruction (Fig. 2) reveal fused and ridged metopic suture.

Diagnosis: Trigonocephaly

Discussion: Trigonocephaly results from premature in utero closure of the metopic suture, resulting in a pointed forehead and ridged midline deformity. Trigonocephaly is one of several types of skull deformities related to premature suture closure called craniosynostosis. Craniosynostosis may be either primary, which refers to a developmental error, or secondary, which refers to other causes of premature suture closure, such as intrauterine compression of the skull, teratogens or deficient brain growth.
     The majority of craniosynostosis are non-syndromic (85%). Of these, scaphocephaly, which results from premature closure of the sagittal suture, is the most common, accounting for approximately 60% of cases. Unilateral or bilateral premature closure of the coronal suture is the second most common, accounting for approximately 25%. Trigonocephaly accounts for approximately 15 to 18% of simple (single suture) non-syndromic sutural synostosis. Associated syndromes are rare and include Optiz trigonocephaly syndrome, which consists of trigonocephaly, orofacial deformities (metopic prominence, upward slanting of the palpebral fissures, epicanthal folds, hypoplastic nose, malformed ears, abnormal palate), renal, pulmonary, genital and cardiovascular anomalies.
     The metopic suture normally closes at birth. Deformities secondary to premature closure of the metopic suture may range from mild and asymptomatic cases that do not require intervention to more severe cases that result in severe constriction of the forehead and symmetric expansion of the skull posterior to the coronal sutures. The more severe cases require surgical intervention. Severe deformities may be associated with underlying brain malformations such as arrhinecephaly and holoprosencephaly, which result in mental retardation. Other midline deformities associated with trigonocephaly include cleft lip, coloboma and hypotelorism, which occur if the frontonasal suture is also involved.
     Trigonocephaly is typically diagnosed by physical examination and can be confirmed by radiographic imaging. Computed tomography with three-dimensional reconstructions of the calvarium is often used for pre-operative planning. Aside from confirming closure and ridging of the metopic suture, CT can screen for associated brain anomalies. Therapy depends on the severity of trigonocephaly. Patients with severe deformity commonly undergo a bilateral cranial vault remodeling procedure.

References:

1. Ridgeway EB, Weiner HL. Skull deformities. Pediatr Clin N Am 2004; 51:359-387.
2. Kanev PM. Congenital malformations of the skull and meninges. Otolaryngol Clin North Am. 2007 Feb;40(1):9-26. [Medline]
3. Barkovich JA. Non-syndromic craniosynostosis in: Pediatric Neuroimaging. Lippincott Williams and Wilkins, Philadelphia. 2005; 410-413.