(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 handicaps, and threats to a child’s life. Cephalic disorders, which may also be called neurodevelopmental disorders, begin during pregnancy early in a baby’s development.
One of the most noticeable signs of a cephalic disorder is a head of an unusual size or shape. Problems caused by cephalic disorders are most likely when the head is much smaller or larger than the average for a child’s age.
The effect of any given disorder on a specific child may be mild or severe, depending 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.
Here are several types of cephalic disorders:
Anencephaly. This disorder happens when the top of the neural tube doesn’t close during the development of the fetus. This results in a baby developing without the forebrain and cerebrum. The baby may be born without any skull covering the remaining brain. These babies are born unconscious, deaf, and blind. Babies with this defect often die within hours or days of birth.
Colpocephaly. This disorder involves an abnormal enlargement of the occipital horns (rear portion of the lateral ventricles of the brain). Colpocephaly is characterized by an unusually small head and mental retardation. Other symptoms may include muscle spasms, motor abnormalities, and seizures.
Holoprosencephaly. During development in the womb, the brain grows into one single lobe instead of two. There are varying grades of severity ranging from severe abnormalities with limited function, to very mild abnormalities with the ability to lead a relatively normal life. 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 profound cognitive and neurological impairment.
Hydranencephaly. Babies born with this disorder have pockets of cerebrospinal fluid in the place of the two separate lobes of the brain. They may appear normal at birth, but within a few months become irritable and do not develop along a normal timeline. Most of these children have profound neurological and cognitive impairment and usually die within several years.
Hydrocephalus. Not really a cephalic disorder, hydrocephalus can cause a large head size because of the buildup of cerebrospinal fluid in the ventricles of the brain. Because the skull plates in neonates and infants have not yet fused, there is little to prevent the head from enlarging significantly with increased internal pressure. Hydrocephalus is caused by either production of too much fluid, poor resorption of the fluid produced, or an obstruction along the normal pathway of fluid flow in the brain. These children usually need the placement of a shunt to drain the excess fluid. The outcome depends on the cause of the hydrocephalus and how early therapy is started.
Iniencephaly. This disorder is a combination of the extreme backward bending of the head and severe spinal defects. The distortion of the baby's body may also present a danger to the mother's life. Babies with this disorder rarely live more than a few hours.
Lissencephaly. Normal brain development requires that the neurons (nerve cells) migrate to the correct part of the nervous system and connect to each other. Lissencephaly and associated disorders happen when the brain neurons do not end up in the proper place during development. This results in an unusual brain formation and an extremely small head, causing a range of neurological disability, from mild developmental delay to severe neurologic dysfunction and even death.
Microcephaly. This means the head is much smaller than average. Many children with smaller than average heads have normal intelligence and develop correctly. However, microcephaly is common in many known disorders such as trisomy 21 (Down syndrome). In addition to intellectual disability, many children with microcephaly have cerebral palsy, sensory disorders including visual difficulties, poor motor skills, lack of balance and coordination, and difficulty thinking and learning as expected for the child’s age. Other birth defects, such as lissencephaly or porencephaly, also have microcephaly as a symptom.
Macrencephaly. Also called megalencephaly, this is a disorder in which the head is much larger than average. It occurs more often in boys than girls. The large head size may be caused by a brain that grows unusually large. In the process of brain development, after the nerve cells have migrated and connected to each other, a normal process of pruning naturally removes the cells that are not needed. When this neuronal pruning does not happen, megalencephaly can result. Children may have seizures, developmental delays, and other motor difficulties. This disorder is also related to the cephalic disorder called porencephaly. It is important to distinguish this disorder from macrocephaly, which is benign enlargement of the head without associated brain abnormalities and is usually hereditary and without symptoms.
Porencephaly. During development, a pocket of cerebrospinal fluid forms in the baby’s brain, causing this cephalic disorder. This is thought to be related to an infection or stroke, either in utero or during the neonatal period. Some children with this disorder have normal intelligence and few if any developmental problems. Others have motor or cognitive difficulties of varying degrees. This will depend on the location within the brain and the size of the cerebrospinal fluid filled pockets.
Schizencephaly. This rare cephalic disorder results from clefts forming in one or both hemispheres of the brain. Impairment is related to the number and location of the clefts. Some people with this disorder lead relatively normal lives, but 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
Difficulty swallowing or eating
Poor muscle tone
Deformed fingers or toes
Delays in the development of physical abilities or language
In order to make a diagnosis, the healthcare provider may consider symptoms and medical history, and perform a physical exam of the skull and body. You will commonly 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 circumference of the head. That is the distance around the head. 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. Measurement of head size may be done at every well check or office visit in order to find out whether 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 your healthcare provider if you have concerns about your child’s ability to meet milestones as expected, such as 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. At the same time, events during a woman’s pregnancy, such as having an infection or being exposed to toxic chemicals, may also play a role.
Women have the best chance of preventing cephalic disorders by trying to be as healthy as possible throughout their pregnancy. This means avoiding unlawful drugs, alcohol, and cigarettes, and eating a varied, healthy diet. Getting enough folic acid has been shown to reduce the risk for certain birth defects, including some cephalic disorders. Many women, however, take good care of themselves during pregnancy and still give birth to a child with a cephalic disorder, as some of these disorders may be caused by intrauterine infection, trauma, or have a hereditary component. Genetic counseling can sometimes be helpful to determine risks in future pregnancies.
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