Introduction to craniosynostosis

Craniosynostosis is the premature closure of one or more cranial vault or cranial base sutures. The prematurely closed suture imposes restrictions to the growth of underlying brain, resulting in compensatory growth and expansion of less restricted areas.

Syndromic

• Defined inheritance and associated anomalies
• Usually involves coronal sutures but may involve any and all sutures
• Often called craniofacial dysostosis

Nonsyndromic

• Based on morphology and suture involvement
• Single suture synostosis or multiple suture synostosis
• The nonsyndromic craniosynostosis can be further subdivided into symmetrical (bilateral involvement) and asymmetrical (unilateral involvement) craniosynostosis.

Craniosynostosis has been estimated to occur in 1:2000 to 1:2500 births. The distribution between the different synostosis are as follows:

• Sagittal synostosis 40 – 55 %
• Coronal synostosis 20 – 25 %
• Metopic synostosis 5 - 15 %
• Lambdoid synostosis 0 – 5 %
• Multiple suture synostosis 5 – 15 %, mainly as a part of a syndrome.

Factors associated with nonsyndromic premature fusion of cranial sutures are as follows:

• Environmental factors
• Multiple gestation (eg. twins, triplets)
• Large infant size
• Abnormal infant position
• Uterine abnormalities
• Head constraint
• Drugs (eg. Nitrofurantoin, Warfarin,
• Endocrine abnormalities

During the first year of life the brain will triple in size, followed by slower growth until it reaches its full size in the teen age years. Restrictions of this growth may have functional consequences. The most typical ones are listed below.

• Elevated intracranial pressure (>15-17mm Hg) occurs in approximately 47% of patients with multiple, and in 14% of patients with single suture fusion
• Blindness: optic nerve atrophy, corneal exposure
• Hydrocephalus (mainly for Syndromic patients)
• Developmental delay
• Abnormalities of speech and hearing
• Abnormalities of the ocular axis and adnexa
• Abnormalities of the airway
• Malocclusion (Angle class III)
• The x-ray on the left show the appearance of the "Beaten Copper Cranium" pattern found in a patient with elevated intracranial pressure