Overview
In metopic suture craniosynostosis, or trigonocephaly, the forehead will have a triangular shape and the eyes may appear closer together.
The metopic suture begins at the nose and continues superiorly to meet the sagittal suture dividing the frontal bone into two halves. The incidence of trigonocephaly is somewhere between one in every 2,500 – 15,000 live births with a male to female ratio of 3:1.
Causes
The metopic suture is usually open at birth and fusion normally occurs in the first 12 months of life. Premature fusion of the metopic suture compromises the transverse growth of the forehead which causes a triangular shaped forehead that is associated with orbital hypotelorism (abnormal closeness of the eyes).
This deformity has no genetic basis or any familial history, and usually does not occur in association with other craniofacial syndromes.
Symptoms
The deformity can vary from mild to severe. There is usually a prominent mid-frontal ridge (pointed forehead) down the forehead that can be seen or felt and the eyebrows may appear “pinched” on either side. The eyes are usually spaced closer to each other than normal, causing a definite recognizable deformity of the forehead and eyes. When viewed from above the forehead has a triangular shape.
Diagnosis
On physical examination of the skull the triangular shape of the forehead is seen and the ridging metopic suture can be palplated. Bone growth is apparently reduced along all margins of the frontal bones adjacent to the stenotic suture. Hypotelorism, and other characteristic features of the trigonocephalic skull are well recognizable. Skull radiography is performed to confirm the diagnosis of a prematurely closed metopic suture.
Treatment
Many children can have a ridge running down the center of their forehead suggesting that the metopic suture has closed early. However, in most cases this fusion occurs late enough in life that it does not produce trigonocephaly. Only those children who have overt trigonocephaly need treatment.
The traditional procedure is done through a bicoronal scalp incision (from ear to ear) and treatment involves releasing the suture and expanding and rounding out the upper face, forehead and skull. The entire bony supraorbital bar may sometimes require being removed and reshaped with orbital advancement to restore the normal brow contour.
Prognosis
In general, a single operation is all that is necessary to treat this condition and the cosmetic and clinical outcomes are usually excellent especially for otherwise healthy, nonsyndromic infants. As an isolated abnormality there is no associated neurological deficit, but occasionally the hypotelorism may be associated with holoprosencephaly or other congenital abnormalities of the ear, mandible and skin, short ribs and a pelvic dysplasia, forming a trigonocephaly syndrome.
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