Cephalic disorders are a group of related birth defects or congenital disorders involving the developing brain, skull, and central nervous system. These disorders are congenital, meaning they are present during fetal development and at birth.
Definition & Facts
There are at least 20 identified cephalic disorders, and each disorder occurs at different frequencies in populations around the world. The occurrence of these disorders also varies widely between countries and over time.
Anencephaly is the most common cephalic disorder in the United States, occurring at a rate of approximately 1 in 10,000 births, or 1,000 to 2,000 cases per year. In Nigeria, the rate of anencephaly is approximately 3 in 10,000 births.
Microcephaly is generally rare worldwide; however there have been recent surges in the number of cases in specific locations, including the country of Brazil and the US state of Florida due to Zika virus infections.
Cephalic disorders can cause a wide degree of disability in the affected person ranging from death in infancy to profound intellectual disability for life to mild impairment in which the person can live and function with some degree of independence.
Symptoms & Complaints
The most common form, anencephaly, begins between the 23rd and 26th days of gestation when the neural tube does not close properly. This neural tube defect results in a complete absence of major sections of brain, scalp, and skull and severe intellectual disability and physical disability or even death.
In other forms of the disorder, such as megalocephaly, parts of the brain become abnormally large and do not function properly or crowd-out other brain areas. Microcephaly is a disorder affecting the size of the head. The child may be born with an abnormally small head, or the head may fail to grow as the body grows and the condition becomes apparent in the first two or three years of the child’s life.
Newborns with cephalic disorders often have seizures or obvious deformities of the head and face. Severe intellectual impairment, problems with motor function, delayed speech, hyperactivity, convulsions, clumsiness, difficulty swallowing (dysphagia), and dwarfism are also common symptoms of various cephalic disorders.
Cephalic disorders are known to be caused by multiple, independent factors including:
- Hereditary genetic mutations
- Exposure of the mother to environmental toxicants during or before pregnancy, such as radiation exposure and toxic chemicals
- Infections contracted by the mother during pregnancy, such as the mosquito-borne Zika virus
- Vitamin deficiencies before or during pregnancy, particularly folate deficiency
- Use of certain medications during pregnancy
Cephalic disorders almost always begin during the early stages of fetal growth when the nervous system is first developing. The nervous system in human beings begins developing after the first three to four weeks of gestation when specialized cells begin forming the neural tube.
The neural tube contains the brain and spinal cord, and during normal development, it closes up and becomes sealed at about the fourth week of pregnancy. In many forms of cephalic disorder, the neural tube fails to close or closes only partially. In some forms of the disorder, the problems emerge slightly later in gestation when the connecting bones of the skull close too early. Researchers are still seeking to understand all of the causes of cephalic disorders, as well as looking for ways of preventing them and helping people with these conditions.
Diagnosis & Tests
Several types of prenatal tests can reveal the presence of a cephalic disorder in a developing fetus, but sometimes the problem cannot be detected until after birth, or even until the child is a few years old. Ultrasound tests can often detect the most severe cephalic disorders during pregnancy, but milder forms of the disorder will not be visible on an ultrasound test.
After the child is born, diagnosis can be made by consideration of the child’s and parent’s medical histories and the symptoms experienced by the child. Blood tests, magnetic resonance imaging (MRI) scans, and computed tomography (CT) scans can also be used in diagnosis after birth.
When a cephalic condition is suspected, doctors often measure the circumference of the child’s head at the widest part just above the eyebrows. These measurements are then compared to averages for the child’s age or tracked over time up until the age of 3 to identify abnormalities in growth and development and to make a diagnosis of a cephalic disorder. When parents have a history of cephalic hereditary disorders, a doctor may recommend genetic counseling early in the pregnancy or before pregnancy.
Treatment & Therapy
There are no cures or standardized treatments for cephalic disorders, and therapy is usually limited to therapeutic support and management of symptoms. The prognosis is dependent on the form of cephalic disorder the person has. Severe forms often result in a miscarried pregnancy, stillborn birth, or death of the infant shortly after birth.
Each case must be evaluated individually to find the optimum level of therapeutic support for that person. Respiratory problems and convulsions are a common symptoms for many people with cephalic disorders, and when present, can be managed with a variety of treatment options including anticonvulsant medication and antispasmodic drugs.
Prevention & Prophylaxis
Avoidance of exposure to radiation and other toxic insults is also recommended for minimizing the chances of a cephalic disorder in offspring. Health agencies are also recommending that women or men who plan to become parents avoid mosquito bites which could expose a developing fetus to the Zika virus, causing microcephaly. People with a family history or known cephalic genetic disorders are may opt to seek genetic counseling before becoming pregnant.