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Background and Management Principles
Craniosynostosis, defined as the untimely and premature closure of a calvarial suture in an infant, leads to well-defined and described phenotypic deformational changes of the neocranium, endocranium, or both. The first recorded description in modern times is ascribed to Otto in 1830. Twenty-one years later, Rudolf Virchow, a German pathologist, developed a classification system for the phenotypes of deformities associated with craniosynostosis. The underlying principle in his theory is that bone growth takes place perpendicular to the suture, and premature closure leads to defined skull shapes based on compensatory brain growth in other areas of the skull. Dr. Odilon Marc Lannelongue, a French surgeon, was the first to report a surgical correction for craniosynostosis in 1890. His procedure consisted of two parallel strip craniectomies lateral to the midline, leaving a strip of bone over the sagittal sinus. Lannelongue performed this operation on 59 patients and reported only one death. This work was quickly adopted by other surgeons, including Dr. L.C. Lane of San Francisco in 1892. Since the introduction of the original surgery in 1890, a multitude of surgeries and procedures have been developed and instituted throughout the world. In 1967, French surgeon Paul Tessier performed the first “craniofacial” operation and thus instituted and pioneered the discipline of craniofacial surgery. Subsequently, craniofacial techniques championed by Tessier were used for the treatment of craniosynostosis. Many different types of extensive reconstruction procedures are now classified under the term “calvarial vault remodeling” (CVR) and have become the standard of care for managing this condition.
Epidemiology and Other General Facts
It has been generally estimated that craniosynostosis develops in about 1 in 2500 births worldwide. The incidence varies according to the affected suture. Prevalence is approximately 3.1 to 6.4 in 10,000 live births and reportedly rising. A 2016 study in the Netherlands found a prevalence of 7.2 per 10,000 live births. This study also showed an annual increase prevalence for total craniosynostosis of 12.5%, sagittal (+11.7%), and metopic (+20.5%) from 1997 to 2013. Another study in Australia indicated the prevalence there to be 3.1 per 10,000 live births and an overall increase in incidence on nonsyndromic craniosynostosis of 2.5% per year. Metopic synostosis was found to have increased by 7.1% over a 25-year period. It has been our experience over the last 25 years that there has indeed been an increase in the overall incidence of metopic synostosis, with this suture accounting for the second highest number of cases after sagittal synostosis. It is also estimated that up to 20% of the cases are caused by specific single gene mutations or chromosomal abnormalities. The most commonly mutated genes include FGFR2, FGFR3, TWIST 1, and EFNB1. Most genetically determined craniosynostosis is characterized with an autosomal dominant inheritance pattern, with half of the cases being new mutations and most commonly present in syndromic patients. Craniosynostosis has been described in more than 150 syndromes but most frequently, it has been associated with Apert, Crouzon, Pfeiffer and Saethre-Chotzen syndromes. ,
In a 10-year prospective study, a genetic diagnosis was achieved in 21% of cases, with 86% being single gene disorders and 15% being chromosome abnormalities. FGFR2 accounted for 32% of all genetic cases, FGFR3 for 25%, TWIST for 19%, and EFNB1 for 7%. Other associations found included the following genes with the corresponding syndromes: FGFR1 (Pfeiffer syndrome), POR (Antley-Bixler syndrome), RAB23 (Carpenter syndrome), ESC02 (Roberts syndrome), GL13 (Greig syndrome), JAG1 (Alagille syndrome), KRAS (Noonan syndrome), FGFR2 (Apert syndrome), and FRFR3 (Muenke and Crouzon syndromes).
A persistent debate in the literature has been whether single suture craniosynostosis causes decreased intracranial volume and elevations in intracranial pressure (ICP). Several studies have found little difference in the intracranial volume among the different types of craniosynostosis , ; as such, craniosynostosis has not been found to be associated with low or lower intracranial volumes. This is most likely due to compensatory brain growth in other areas secondary to other patent sutures. Likewise, hydrocephalus has not been found to have a higher incidence in patients with craniosynostosis, with an estimated incidence of 0.28% in infants with nonsyndromic synostosis. This is the same incidence of hydrocephalus and shunting seen in the general population. However, even though craniosynostosis has not been shown to be associated with decreases in intracranial volumes, multiple studies have shown a positive correlation with increased intracranial pressure. A study which defined elevated ICP as greater than 15 mmHg, found an incidence of intracranial hypertension of 20%, with a large number being found in syndromic cases. Another study found an incidence of intracranial hypertension in 30% of the affected children and included a 14% incidence in infants with single suture synostosis. Thompson also found an incidence of increased ICP in 15% of single suture synostosis and 24% in nonsyndromic craniosynostosis. These findings raise the question of the need for early rather than delayed surgery in these patients. It has been our experience with the use of minimally invasive early surgery to find that most of our parents consistently report improvement in the child’s behavior and development soon after surgery. Anecdotally, we are told that the baby is no longer irritable and fuzzy, that the child sleeps and eats better. Motor function has also repeatedly been found to improve. We have also found this to be the case on many postoperative follow-up clinic visits. We did (unpublished) a prospective study looking at irritability and fuzziness of our endoscopically treated patients, assessing frequency and severity on a scale from 0 to 5. Parents were asked to rate their children before and at 1 and 2 months after surgery. Our results indicated a significant decrease in both parameters as related to frequency and severity ( P < .001). These findings seem to indicate that the cause of the patient’s irritability immediately subsided after surgery. That would not be as evident with the much more invasive and traumatic CVR surgery.
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