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A congenital anomaly of the skull
characterized by premature fusion of one or more cranial sutures.
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Estimated to be approximately 1:200,000 live births.
Sagittal and lambdoid craniosynostosis (the most common type) are
approximately four times more common in males than in females, whereas
unicoronal craniosynostosis is more common in females. For the other forms,
the distribution is about equal between the two genders.
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A positive family history is present in up to
40% of cases, with genetic syndromes accounting for at least 50% of
those cases. The most common syndromes include Apert Syndrome and
Crouzon Syndrome. Both autosomal dominant and autosomal recessive
inheritance have been described, but sporadic occurrence also is common.
Genetic mutations that may be responsible for craniosynostosis include
mutations in the fibroblast growth factor receptors (FGFR1, FGFR2, FGFR3),
the TWIST, and MSX2 genes.
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The etiology is unknown but may involve abnormal
cranial suture development resulting in failure of growth perpendicular to
the affected suture and overgrowth of skull parallel to the affected suture.
Environmental factors etiologically linked to craniosynostoses include
rickets and hyperthyroidism. Drugs that may be involved in craniosynostosis
include phenytoin, retinoids, valproic acid, aminopterin/methotrexate,
fluconazole, and cyclophosphamide. In some cases, local intrauterine factors
related to constraint of the fetus (e.g., abnormal positioning in utero,
multiple pregnancy, oligohydramnios) have been linked to craniosynostosis.
The developing brain is the driving power behind skull growth and forces the
skull to compensatory growth in directions perpendicular to the fused suture
along adjacent open sutures.
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The diagnosis may be suspected clinically if special
attention is paid to the head circumference (percentiles), shape and
presence of any deformities, size of the fontanelles, palpable ridges over
affected sutures with absent movement of the bone on either side of the
suture on palpation, neurologic behavior and development of the infant, the
pupils and their reaction to light, and funduscopic evaluation for
papilledema. Radiologic examinations (e.g., computed tomography scanning
and/or magnetic resonance imaging) confirm the diagnosis. True
craniosynostosis must be differentiated from birth molding (present at birth
and resolving within days or weeks) and positional plagiocephaly without
synostosis (a frequent finding resulting from local pressure on a specific
area of the skull (same position), typically the occipital region leading to
occipital or lambdoid plagiocephaly.
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It must be differentiated between syndromic and
nonsyndromic craniosynostosis. Nonsyndromic cases account for approximately
50% of all craniosynostoses and are commonly limited ...