Cephalic disorders are congenital conditions that stem from damage to or abnormal development of the budding nervous system. Most cephalic disorders are caused by a disturbance that occurs very early in the development of the fetal nervous system. Damage to the developing nervous system is a major cause of chronic, disabling disorders, and sometimes death in infants, children, and even adults. Cephalic disorders may be influenced by hereditary or genetic conditions or by environmental exposures during pregnancy (e.g., medication taken by the mother, maternal infection, exposure to radiation). Some cephalic disorders occur when the cranial sutures (the fibrous joints that connect the bones of the skull) join prematurely.

Cephalic disorders are in which there is an abnormal enlargement of the occipital horns - the posterior or rear portion of the lateral ventricles (cavities or chambers) of the brain. This enlargement occurs when there is an underdevelopment or lack of thickening of the white matter in the posterior cerebrum. Colpocephaly is characterized by microcephaly (abnormally small head) and mental retardation. Other features may include motor abnormalities, muscle spasms and seizures.

Cephalic disorders are not necessarily caused by a single factor but may be influenced by hereditary or genetic conditions or by environmental exposures during pregnancy such as medication taken by the mother, maternal infection, or exposure to radiation. Some cephalic disorders occur when the cranial sutures (the fibrous joints that connect the bones of the skull) join prematurely. Most cephalic disorders are caused by a disturbance that occurs very early in the development of the fetal nervous system.

The human nervous system develops from a small, specialized plate of cells on the surface of the embryo. Early in development, this plate of cells forms a critically important structure called the neural tube, a narrow sheath that closes between the third and fourth weeks of pregnancy to form the brain and spinal cord of the embryo. Four main processes are responsible for the development of the nervous system: cell proliferation, the process in which nerve cells (neurons) divide to form new generations of cells; cell migration, the process in which nerve cells move from their place of origin to the place where they will remain for life; cell differentiation.

Infants born with anencephaly are usually blind, deaf, unconscious, and unable to feel pain. Although some individuals with anencephaly may be born with a rudimentary brainstem, the lack of a functioning cerebrum permanently rules out the possibility of ever gaining consciousness. Reflex actions such as respiration (breathing) and responses to sound or touch may occur. The disorder is one of the most common disorders of the fetal central nervous system. Approximately 1,000 to 2,000 American babies are born with anencephaly each year. The disorder affects females more often than males.

Fusion of the sagittal suture, the joint connecting the two parietal (top and sides of the head) bones of the skull, causing a long, narrow head. This is the most common of the craniostenoses. Unilateral fusion (joining of one side) of the fibrous joint between the occipital and parietal bones, causing asymmetrical (one side) flattening of the skull. It is thought to be caused by a brain malformation, an excessively small or tight intrauterine environment, or a spasm or tightening of the neck muscles.

The degree to which damage to the developing nervous system harms the mind and body varies enormously. Many disabilities are mild enough to allow those afflicted to eventually function independently in society. Others are not. Some infants, children, and adults die; others remain totally disabled; and an even larger population is partially disabled, functioning well below normal capacity.