Definitions and Epidemiology

Definitions

• Craniosynostosis: premature fusion of 1 ⩲ cranial sutures, causing an abnormal shaping of the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull 
• Scaphocephaly: elongated skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull with frontal bossing, often due to fusion of sagittal sutures 
• Plagiocephaly: flattening of half of the forehead with raising of ipsilateral eyebrow due to unilateral coronal suture fusion
• Trigonocephaly: triangular-shaped forehead with prominent midline ridge caused by fusion of the metopic suture
• Brachycephaly: shortened skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull that is wider and taller than normal due to bilateral coronal suture fusion
• Oxycephaly: tall cranium due to inadequately treated brachycephaly
• Acrocephaly: elevation of the anterior skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull due to combined fusion of lambdoid, sagittal, and coronal sutures

Classification

• Simple versus complex:
  • Simple: A single suture fuses.
  • Complex or compound: Multiple sutures fuse.
• Primary versus secondary:
  • Primary: premature closure due to abnormalities of skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull development
  • Secondary: closure due to failure of brain growth and expansion

Epidemiology

• Incidence:
  • 1 in 2,000 live births in the United States
  • 1 in 2,500 live births worldwide
  • No gender or racial predilection
• Scaphocephaly (sagittal suture) is the most common.
• 85% of cases are simple.
• 10%–20% of cases are associated with genetic syndromes.
• Complex cases tend to be associated with other malformations.

Etiology and Pathophysiology

Etiology

Nonsyndromic:

• Genetic mutations:
  • Caused by gene mutations of fibroblast growth factor (FGF), FGF receptor, or transforming growth factor beta (TGF-β)
  • Alters communication between the dura mater and mesenchyma of suture
  • Can be hereditary
• Environmental influence:
  • Advanced maternal age
  • Nicotine use in pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care
  • Clomiphene citrate in pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care

Syndromic:

• Crouzon syndrome:
  • Most common
  • Bilateral coronal craniosynostosis
  • Midfacial abnormalities
  • Hydrocephalus
  • Exophthalmos 
  • Airway obstruction Airway obstruction Airway obstruction is a partial or complete blockage of the airways that impedes airflow. An airway obstruction can be classified as upper, central, or lower depending on location. Lower airway obstruction (LAO) is usually a manifestation of chronic disease, such as asthma or chronic obstructive pulmonary disease (COPD). Airway Obstruction
  • Mutation Mutation Genetic mutations are errors in DNA that can cause protein misfolding and dysfunction. There are various types of mutations, including chromosomal, point, frameshift, and expansion mutations. Types of Mutations localized in GFR2 gene
• Apert syndrome:
  • Coronal craniosynostosis
  • Hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand, elbow, hip, and knee deformities 
  • Exophthalmos
• Carpenter syndrome:
  • Lambdoid and sagittal craniosynostosis
  • Limb abnormalities (syndactyly) 
• Pfeiffer syndrome:
  • Unicoronal craniosynostosis
  • Facial deformities
  • Limb abnormalities
  • Exophthalmos
  • Hearing loss Hearing loss Hearing loss, also known as hearing impairment, is any degree of impairment in the ability to apprehend sound as determined by audiometry to be below normal hearing thresholds. Clinical presentation may occur at birth or as a gradual loss of hearing with age, including a short-term or sudden loss at any point. Hearing Loss

Pathophysiology

• Skull is made up of 5 separate bones:
  • 2 frontal bones
  • 2 parietal bones
  • Occipital bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones
• In infants → bones are separated by open sutures and fontanelles (anterior and posterior). 
• During childbirth → skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull bones overlap and compress at sutures and fontanelles to allow delivery of head through vaginal canal.
• After birth → sutures remain open to allow for brain growth.
• Craniosynostosis is due to inappropriate closure of sutures.

Diagnosis and Management

Diagnosis

Diagnosis relies on clinical observation, but imaging may be used to further characterize anatomy for classification or surgery

• Ultrasound of the head is preferred due to lack of radiation: can give a prenatal diagnosis
• CT scan of the head
• X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays of skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull
• DNA DNA The molecule DNA is the repository of heritable genetic information. In humans, DNA is contained in 23 chromosome pairs within the nucleus. The molecule provides the basic template for replication of genetic information, RNA transcription, and protein biosynthesis to promote cellular function and survival. DNA Types and Structure testing to look for underlying genetic disorders

Management

Molded helmet:

• For mild cases
• Reshapes head

Surgical intervention: 

• Goals:
  • Give brain room to grow
  • Release developing intracranial pressure (pseudotumor cerebri)
  • Correction of appearance
• Needed in:
  • Hydrocephalus
  • ↑ intracranial pressure
• Options available include:
  • Shunting
  • Ventriculoperitoneal shunting 
  • Ventriculopleural shunting

Prognosis

• Simple cases: 5% risk of recurrence
• Complex cases: up to 50% risk of recurrence
• Recurrence is ↑ in presence of genetic syndromes

Complications

• Permanent facial deformity
• Poor self-esteem
• ↑ intracranial pressure can lead to:
  • Developmental delay
  • Cognitive impairment
  • Lethargy
  • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
  • Death

Differential Diagnosis

• Positional plagiocephaly: a common occurrence in infants that presents as a flat spot on a baby’s head that is caused by the baby spending too much time lying on their back. Positional plagiocephaly does not affect brain development or create increased intracranial pressure Increased Intracranial Pressure Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP). The condition is treated by changing the position of the head and/or using a helmet in severe cases. 
• Infant torticollis: contracture of the sternocleidomastoid muscle due to abnormal fetal positioning or birth trauma. Typically noted by one month of age when the head is tilted to one side. The condition can be associated with facial asymmetry. Treatment is physical therapy and reassuring parents as the condition typically resolves by 6 months of age.