What is Cephalic Disorder?
Cephalic disorders are congenital conditions that stem from damage to, or abnormal development of, the budding nervous system. Cephalic is a term that means "head" or "head end of the body." Congenital means the disorder is present at, and usually before, birth. Although there are many congenital developmental disorders, this fact sheet briefly describes only cephalic conditions.
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 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 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, the process during which cells acquire individual characteristics; and cell death, a natural process in which cells die. Understanding the normal development of the human nervous system, one of the research priorities of the National Institute of Neurological Disorders and Stroke, may lead to a better understanding of cephalic disorders.
Damage to the developing nervous system is a major cause of chronic, disabling disorders and, sometimes, death in infants, children, and even adults. 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 throughout life.
What are the Different Kinds of Cephalic Disorders?
ANENCEPHALY is a neural tube defect that occurs when the cephalic (head) end of the neural tube fails to close, usually between the 23rd and 26th days of pregnancy, resulting in the absence of a major portion of the brain, skull, and scalp. Infants with this disorder are born without a forebrain - the largest part of the brain consisting mainly of the cerebrum, which is responsible for thinking and coordination. The remaining brain tissue is often exposed - not covered by bone or skin.
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.
The cause of anencephaly is unknown. Although it is believed that the mother's diet and vitamin intake may play a role, scientists agree that many other factors are also involved.
There is no cure or standard treatment for anencephaly and the prognosis for affected individuals is poor. Most infants do not survive infancy. If the infant is not stillborn, then he or she will usually die within a few hours or days after birth. Anencephaly can often be diagnosed before birth through an ultrasound examination.
Recent studies have shown that the addition of folic acid to the diet of women of child-bearing age may significantly reduce the incidence of neural tube defects. Therefore it is recommended that all women of child-bearing age consume 0.4 mg of folic acid daily.
COLPOCEPHALY is a disorder 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.
HOLOPROSENCEPHALY is a disorder characterized by the failure of the prosencephalon (the forebrain of the embryo) to develop. During normal development the forebrain is formed and the face begins to develop in the fifth and sixth weeks of pregnancy. Holoprosencephaly is caused by a failure of the embryo's forebrain to divide to form bilateral cerebral hemispheres (the left and right halves of the brain), causing defects in the development of the face and in brain structure and function.
There are three classifications of holoprosencephaly. Alobar holoprosencephaly, the most serious form in which the brain fails to separate, is usually associated with severe facial anomalies. Semilobar holoprosencephaly, in which the brain's hemispheres have a slight tendency to separate, is an intermediate form of the disease. Lobar holoprosencephaly, in which there is considerable evidence of separate brain hemispheres, is the least severe form. In some cases of lobar holoprosencephaly, the patient's brain may be nearly normal.
Lissencephaly may be diagnosed at or soon after birth. Diagnosis may be confirmed by ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI).
Lissencephaly may be caused by intrauterine viral infections or viral infections in the fetus during the first trimester, insufficient blood supply to the baby's brain early in pregnancy, or a genetic disorder. There are two distinct genetic causes of lissencephaly - X-linked and chromosome 17-linked.
The spectrum of lissencephaly is only now becoming more defined as neuroimaging and genetics has provided more insights into migration disorders. Other causes which have not yet been identified are likely as well.
Lissencephaly may be associated with other diseases including isolated lissencephaly sequence, Miller-Dieker syndrome, and Walker-Warburg syndrome.
Treatment for those with lissencephaly is symptomatic and depends on the severity and locations of the brain malformations. Supportive care may be needed to help with comfort and nursing needs. Seizures may be controlled with medication and hydrocephalus may require shunting. If feeding becomes difficult, a gastrostomy tube may be considered.
The prognosis for children with lissencephaly varies depending on the degree of brain malformation. Many individuals show no significant development beyond a 3- to 5-month-old level. Some may have near-normal development and intelligence. Many will die before the age of 2.Respiratory problems are the most common causes of death.
MEGALENCEPHALY, also called macrencephaly, is a condition in which there is an abnormally large, heavy, and usually malfunctioning brain. By definition, the brain weight is greater than average for the age and gender of the infant or child. Head enlargement may be evident at birth or the head may become abnormally large in the early years of life.
Megalencephaly is thought to be related to a disturbance in the regulation of cell reproduction or proliferation. In normal development, neuron proliferation - the process in which nerve cells divide to form new generations of cells - is regulated so that the correct number of cells is formed in the proper place at the appropriate time.
Symptoms of megalencephaly may include delayed development, convulsive disorders,corticospinal (brain cortex and spinal cord) dysfunction, and seizures. Megalencephaly affects males more often than females.
The prognosis for individuals with megalencephaly largely depends on the underlying cause and the associated neurological disorders. Treatment is symptomatic. Megalencephaly may lead to a condition called macrocephaly (defined later in this fact sheet). Unilateral megalencephaly or hemimegalencephaly is a rare condition characterized by the enlargement of one-half of the brain. Children with this disorder may have a large, sometimes asymmetrical head. Often they suffer from intractable seizures and mental retardation. The prognosis for those with hemimegalencephaly is poor.
MICROCEPHALY is a neurological disorder in which the circumference of the head is smaller than average for the age and gender of the infant or child. Microcephaly may be congenital or it may develop in the first few years of life. The disorder may stem from a wide variety of conditions that cause abnormal growth of the brain, or from syndromes associated with chromosomal abnormalities.
Infants with microcephaly are born with either a normal or reduced head size. Subsequently the head fails to grow while the face continues to develop at a normal rate, producing a child with a small head, a large face, a receding forehead, and a loose, often wrinkled scalp. As the child grows older, the smallness of the skull becomes more obvious, although the entire body also is often underweight and dwarfed. Development of motor functions and speech may be delayed. Hyperactivity and mental retardation are common occurrences, although the degree of each varies. onvulsions may also occur. Motor ability varies, ranging from clumsiness in some to spastic quadriplegia in others.
For more information about disorders of the developing nervous system, cephalic disorders, or birth defects in general, you may wish to contact:
National Organization for Rare Disorders, Inc. (NORD)
55 Kenosia Avenue
P.O. Box 1968
Danbury, CT 06813-1968
(203) 744-0100
(800) 999-6673 (voicemail only)
Fax: (203) 798-2291
http://www.rarediseases.org/
The Lissencephaly Network, Inc.
716 Autumn Ridge Lane
Fort Wayne, Indiana 46804-6402
(219) 432-4310
http://www.lissencephaly.org/
The March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, New York 10605
(914) 428-7100
(888) MODIMES (663-4637)
http://www.modimes.org/
Association of Birth Defects Children
930 Woodcock Rd.
Orlando, Florida 32803
(407) 245-7035
(800) 313-ABDC (2232)
http://www.birthdefects.org/
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