(Disorders of Head Size)
Cephalic disorders affect the central nervous system as it develops. They may also affect the brain and the growth of the skull. These disorders can cause a variety of developmental delays, physical disabilities, and threats to a child’s life. Cephalic disorders begin during pregnancy early in a baby’s development. They are also called neurodevelopmental disorders.
One of the most visible signs of a cephalic disorder is the unusual size or shape of a baby’s head. Problems from these disorders are most likely when a baby’s head is much smaller or larger than the average for their age.
These disorders may range from mild to severe. This depends on the parts of the brain and central nervous system affected. Many people with cephalic disorders live relatively normal lives. But some cephalic disorders are so severe that a baby will die within weeks or months of birth.
There are many different cephalic disorders, including:
Anencephaly. This condition happens when the top of the neural tube doesn’t close as the baby develops during pregnancy. A major part of the brain, skull, and scalp are missing. The brain tissue that remains is often exposed. These babies are born unconscious, deaf, and blind. Babies with this condition often die within hours or days of birth.
Colpocephaly. The back part of the chambers of the brain (the occipital horns) are abnormally large. Babies with this condition have an unusually small head and an intellectual disability. Other symptoms may include muscle spasms, motor abnormalities, and seizures.
Holoprosencephaly. As the baby develops during pregnancy, the brain grows into one single lobe instead of two. There are different grades of severity. A baby may have very mild abnormalities and be able to lead a relatively normal life. Or there may be severe abnormalities and limited function. Many babies with the severe form of this disorder die before or soon after birth. Others may live, but may have severely deformed faces and severe cognitive and neurological impairment.
Hydranencephaly. With this rare condition, the cerebral hemispheres of the brain are missing. They are replaced by pockets of cerebrospinal fluid. These babies may seem normal at birth. But within a few months they become irritable. They don’t develop along a normal timeline. Most of these children have severe neurological and cognitive impairment. They usually die within several years.
Hydrocephalus. This is not really a cephalic disorder, but it can cause a large head size in infants. With this condition, cerebrospinal fluid builds up in the ventricles of the brain. Children usually need a tube (shunt) to drain the excess fluid. The outcome depends on the cause of the hydrocephalus and how early therapy is started.
Iniencephaly. This disorder combines the extreme backward bending of the baby’s head with severe spinal defects. The baby's distorted body may also put the mother’s life in danger. Babies with this disorder rarely live more than a few hours.
Lissencephaly. In normal brain development, nerve cells (neurons) travel to the correct part of the nervous system and connect to each other. This and other related disorders happen when the brain neurons don’t end up in the correct place during development. This causes an unusual brain formation and an extremely small head. There is a range of neurological disability, from mild developmental delay to severe neurologic dysfunction and even death.
Microcephaly. With this condition, a baby’s head is much smaller than normal. Many children with smaller than average heads have normal intelligence and develop correctly. But this condition is common in many known disorders such as Down syndrome. Many children with microcephaly may have an intellectual disability, as well as cerebral palsy, sensory disorders including vision problems, poor motor skills, lack of balance and coordination, and trouble thinking and learning as expected for the child’s age. Microcephaly is also a symptom of other birth defects such as lissencephaly and porencephaly.
Macrencephaly (also called megalencephaly). With this disorder, a baby’s head is much larger than normal. This may be because the brain grows unusually large. Experts believe this disorder may occur because normal cell production in the brain is disrupted. Children may have seizures, developmental delays, and other motor problems. (This disorder is different than macrocephaly, an enlargement of the head without related brain defects. It is usually inherited and has no symptoms.)
Porencephaly. This disorder occurs when a pocket of cerebrospinal fluid forms in the baby’s brain during development. It is believed to be related to an infection or stroke, either during pregnancy or the newborn stage. Some children with this disorder have normal intelligence and few if any developmental problems. Others have motor or cognitive difficulties of varying degrees. The severity depends on the size of the cerebrospinal fluid-filled pockets, and where they are in the brain.
Schizencephaly. This rare disorder happens when slits (clefts) form in one or both hemispheres of the brain. Symptoms will vary depending on how many clefts a child has, and if they are on one or both sides of the brain. Some people with this disorder lead relatively normal lives. Others may have severe developmental delays, motor delays or even paralysis, or seizures.
Symptoms vary depending on the type of cephalic disorder, but may include:
Unusually large or small head
Trouble swallowing or eating
Poor muscle tone
Deformed fingers or toes
Delays in the development of physical abilities or language
To make a diagnosis, the healthcare provider may consider symptoms and health history, and do a physical exam of the skull and body. You will often be referred to a specialist, such as a geneticist to help make a diagnosis. The healthcare provider may also order tests:
CT scan or MRI scans (MRI scans often show more detail)
Head size is often considered during diagnosis. A healthcare provider will use a measuring tape to measure the distance around your baby’s head (circumference). The tape is usually placed just above the eyebrows and around the widest part of the head. This number is compared with standard growth charts.
Head size can change as a baby grows into a toddler or young child. A child’s head size may be measured at every well visit or office visit to see if the head is changing shape. This usually continues until age 3, unless there is a reason to keep track past that age.
Some cephalic disorders are clearly present from birth. Others are not. Call the healthcare provider if you have concerns about your child’s ability to meet developmental milestones. These include starting to roll over, crawl, walk, or speak at the expected age. Also call if you are concerned about the shape of your child’s face or head.
Treatment for cephalic disorders depends on the type of disorder. Treatments may include:
Physical therapy for motion
Speech therapy for language
Medicines, such as antiseizure medicine, for symptoms
Shunts to drain excess fluid off the brain
Surgery to help correct a deformed skull or face
The true cause of cephalic disorders is not fully known. Experts believe that genes may be a factor. Things that happen during a woman’s pregnancy may also play a role. These can include having an infection or being exposed to toxic chemicals.
The best way to try to prevent cephalic disorders is to be as healthy as possible during pregnancy. This means staying away from alcohol, cigarettes, and illegal drugs. It’s also important to eat a varied, healthy diet. Getting enough folic acid has been shown to reduce the risk for certain birth defects, including some cephalic disorders. But many women take good care of themselves during pregnancy and still give birth to a child with a cephalic disorder. Some of these disorders may be caused by intrauterine infection or an injury. Hereditary conditions may also be a factor. Genetic counseling may help you understand your risks in future pregnancies.