Craniosynostosis

Craniosynostosis is a birth condition where the bones in a baby’s skull join together too early, before the brain finishes growing. This happens when the flexible seams between skull bones, called sutures, close prematurely. The condition affects about 1 in every 2,000 to 2,500 babies and can change the shape of the head as the brain continues to grow.

Table of contents

• What is craniosynostosis
• Types of craniosynostosis
• Symptoms and signs
• Causes and risk factors
• How doctors diagnose craniosynostosis
• Treatment options
• Outlook and prognosis

What is craniosynostosis

A newborn baby’s skull is not one solid piece of bone. Instead, it consists of several separate bones that fit together like a puzzle^[1]. The spaces where these bones meet are called sutures — flexible seams made of fibrous tissue that hold the skull bones together^[2].

These sutures serve an important purpose. They allow the baby’s head to squeeze and flex during birth as it passes through the mother’s pelvis. More importantly, they let the skull expand as the baby’s brain grows rapidly during the first years of life^[3]. You may have noticed the “soft spots” on a baby’s head — these are areas called fontanels, where several sutures meet^[7].

Normally, cranial sutures remain flexible and open during infancy and early childhood. They typically close and turn into solid bone around age 2 to 3, once the brain has had enough room to grow^[5]. Some sutures naturally remain open until someone is in their twenties^[7].

In craniosynostosis, one or more of these sutures close too early — either before birth or within the first few months after birth^[1]. When a suture fuses prematurely, the skull cannot grow in that area. The brain underneath continues to get bigger, so the skull compensates by growing in different directions where sutures are still open^[3]. This causes the baby’s head to develop an unusual shape.

Most cases involve only one suture closing early and are classified as non-syndromic, meaning the condition occurs by itself^[4]. However, sometimes craniosynostosis happens as part of a genetic syndrome that affects multiple body systems^[4].

Types of craniosynostosis

The type of craniosynostosis depends on which suture or sutures close too early. Each type causes a different head shape^[3].

Sagittal craniosynostosis is the most common type. The sagittal suture runs along the top of the head from front to back. When this suture closes too early, the baby’s head grows long and narrow, with a boat-like shape called scaphocephaly^[3]. There may be bulging at the forehead or the back of the head^[6].

Coronal craniosynostosis is the second most common type. The right and left coronal sutures run from each ear to the top of the head. When one coronal suture closes early, it causes flattening of the forehead on that side, with the eye socket possibly raised up and the nose pulled toward the affected side. This is called anterior plagiocephaly^[3]. When both coronal sutures close early (bicoronal synostosis), the baby’s head becomes short and wide, a shape called brachycephaly^[3].

Metopic craniosynostosis affects the metopic suture that runs from the baby’s nose to the top of the forehead. Early closure creates a triangular shape to the forehead when viewed from above, called trigonocephaly^[3]. The eyes may appear abnormally close together^[6].

Lambdoid craniosynostosis is the least common type. The lambdoid suture runs along the back of the head. When it closes too early, the back of the baby’s head becomes flattened, a condition called posterior plagiocephaly^[3].

When more than one suture closes early, it is called multiple-suture craniosynostosis^[9]. This is more serious because the brain has less room to grow.

Symptoms and signs

The main symptom of craniosynostosis is an unusually shaped head^[2]. The specific shape depends on which suture has closed. Parents or doctors may not notice the abnormal shape right away, as it’s normal for a baby’s head to look a bit misshapen in the first few weeks after birth^[7].

Additional signs that may be noticed include a missing or very small soft spot on the baby’s head, a small hard ridge of bone that can be felt along the fused suture, facial features that look uneven or asymmetrical, and a head size that is smaller than expected for the baby’s age^[5].

In many children with craniosynostosis, the unusual head shape may be the only symptom^[2]. However, some children develop increased pressure inside the skull as the brain continues to grow with limited space. This condition, called increased intracranial pressure, can cause additional symptoms such as headaches, being very sleepy or less active than usual, persistent crying or fussiness, feeding problems, and pauses in breathing during sleep^[7].

If left untreated, increased intracranial pressure can lead to more serious complications including seizures, developmental delays, vision problems or blindness, and brain damage^[3]. Children with multiple sutures fused have a higher risk of developing increased brain pressure^[2].

Some babies with craniosynostosis as part of a genetic syndrome may have additional symptoms such as fused fingers or toes, heart problems, or other facial differences^[7].

Causes and risk factors

In most cases, doctors don’t know exactly what causes craniosynostosis^[5]. Single-suture craniosynostosis usually happens by chance for unknown reasons^[7].

About 20% of all craniosynostosis cases have a genetic basis^[4]. Sometimes a random gene change occurs that causes the condition. In other families, the gene change can be inherited, though this is less common^[5]. Most genetic forms are inherited in an autosomal dominant pattern^[4].

Roughly 86% of genetic cases involve a single-gene mutation, while 15% are linked to chromosomal abnormalities^[4]. The most commonly affected genes are in the fibroblast growth factor receptor (FGFR) pathway^[4]. Different FGFR genes are associated with different syndromes: FGFR-1 with Pfeiffer syndrome, FGFR-2 with Apert, Crouzon, and type 1 Pfeiffer syndromes, and FGFR-3 with Muenke syndrome^[4].

Researchers have also found that the following may contribute to craniosynostosis: external pressure on the fetus’s head before birth, growth abnormalities of the membranes around the skull and at the base of the skull, and certain underlying genetic conditions^[5].

When craniosynostosis happens along with other birth differences, or when more than one suture fuses too soon, doctors may suspect a syndrome and recommend genetic testing^[7].

How doctors diagnose craniosynostosis

Sometimes craniosynostosis is seen on ultrasound scans before a baby is born^[7]. More often, it is noticed when the baby is born or during the first few weeks of life^[1].

If a healthcare provider suspects craniosynostosis, diagnosis typically involves several steps. A physical examination is performed where the doctor carefully feels the baby’s head for ridges along the suture lines and looks for changes in head shape and facial features^[10].

Imaging studies provide detailed pictures of the skull and help confirm the diagnosis. A computerized tomography (CT) scan or magnetic resonance imaging (MRI) can show whether sutures have fused^[10]. When sutures close, they can no longer be seen on imaging, so not seeing sutures means they have closed^[10]. X-rays or cranial ultrasound imaging may also be used^[10].

The imaging results, along with measurements from laser scans and photographs, provide precise information about skull shape. These measurements help doctors plan the best treatment approach^[10].

If doctors suspect that craniosynostosis is part of a genetic syndrome, they may recommend genetic testing to identify the specific syndrome^[10]. Additional evaluations may include a dilated eye exam to check for vision problems, a developmental exam to look for signs of other conditions affecting the nervous system, and a neuropsychological exam to check brain and nervous system function^[17].

Specialists in pediatric neurosurgery or plastic and reconstructive surgery typically make the diagnosis and work together with other specialists to confirm craniosynostosis and develop a treatment plan^[10].

Treatment options

For most babies with craniosynostosis, surgery is the main treatment^[10]. The type of surgery and when it’s performed depends on the type of craniosynostosis, the baby’s age, and the individual needs of each patient. In mild cases, treatment may not require surgery^[10].

Surgery aims to correct the shape of the skull and ensure the brain has enough room to grow properly. Early diagnosis and treatment are important for the best outcomes^[1]. After surgery, most children develop normally and have a more typical head and face shape^[1].

There are several surgical approaches available. Minimally invasive endoscopic surgery is used for single-suture craniosynostosis in very young babies, typically less than 3 to 4 months old^[17]. The surgeon uses a fiber-optic tool and makes tiny incisions to operate on the skull^[17]. After this surgery, babies usually wear a special helmet for up to 12 months to help shape the head properly^[17].

For babies 6 to 12 months old, cranial vault remodeling is commonly used. This is a traditional open surgery where the surgeon removes the affected suture and rebuilds the skull to allow brain growth^[17]. Most children do not need a helmet after this type of surgery^[17].

Some centers also use cranial spring surgery for sagittal synostosis in babies younger than 5 months. This involves placing stainless steel springs after removing the fused suture to help increase room for brain growth and improve skull shape^[11].

For children with multiple sutures affected, cranial vault distraction osteogenesis may be recommended. In this traditional open surgery, doctors carefully separate skull bones and place devices that slowly stretch the bone and skin to allow brain growth^[17].

Depending on the type of surgery, babies typically spend one to three nights in the hospital^[17]. The care team makes sure the child is comfortable and behaving normally before going home.

Helmet therapy (cranial orthotics) is used to help shape the skull after some types of surgery. After endoscopic surgery, children need a series of helmets to continue shaping their skull as it grows^[17].

The care of children with craniosynostosis involves a team of specialists working together. The team may include pediatric neurosurgeons, plastic surgeons, geneticists, ophthalmologists, psychologists, and other specialists depending on the child’s needs^[10].

Outlook and prognosis

With early diagnosis and proper treatment, most children with craniosynostosis do very well. After surgery, most children develop as expected and have a more average shape to the face and head^[1].

Most children with craniosynostosis are otherwise healthy and have normal intelligence^[8]. Single-suture craniosynostosis typically does not have significant effects on a child’s cognitive development when treated appropriately^[20].

In most cases, children do not need follow-up surgery^[17]. However, ongoing care is important. Children typically have annual checkups for six years or longer, based on individual needs^[17]. Specialists monitor brain and nervous system development, vision, hearing, and overall development to ensure the child is progressing well.

Children with syndromic craniosynostosis or multiple sutures involved may need additional surgeries and more intensive long-term care. They have a higher risk of complications such as increased brain pressure, developmental delays, and other health issues related to their specific syndrome^[2].

Without treatment, craniosynostosis can lead to permanent head deformity, increased pressure on the brain, vision problems, seizures, developmental delays, and psychosocial issues as the child grows and interacts with peers^[6]. This is why early recognition and treatment are so important.