Macrocephaly is a condition in which the head is larger than normal.
Also called macrocephalia and megalocephaly, macrocephaly is diagnosed when the circumference of the head is more than two standard deviations above average for the child's age, sex, race, and period of gestation. The fontanelle (soft spot) of the newborn is wide, but facial features are usually normal. Macrocephaly is distinguished from hydrocephalus in that there is no increase in pressure within the head; however, hydrocephalus can result in macrocephaly in some children. The disorder can result from a defect in formation during the embryonic stage, as a result of certain degenerative diseases, as a part of various genetic syndromes, or as an inherited family trait. Mental deficiency, seizures, and movement disorders are common in macrocephalic children.
Because of the many conditions that cause macrocephaly, a true assessment of its incidence is difficult. It is a relatively rare condition that does not appear to affect children of any particular race, gender, or nationality with more frequency.
Causes and symptoms
Macrocephaly may be caused by many conditions. The most common causes for an enlarged head are megalencephaly, or an enlarged brain, and hydrocephalus, or excessive cerebrospinal fluid ( CSF ) in the brain.
When macrocephaly is a result of megalencephaly, it is often impossible to determine the cause. However, megalencephaly is often associated with metabolic diseases such as Canavan's disease or Alexander's disease or with syndromes such as gigantism , achondroplasia ( dwarfism or small stature), osteogenesis imperfecta , neurofibromatosis , and some chromosomal anomalies. In each of these disorders, there is an enlargement of brain tissues.
In hydrocephalus, excess CSF collects in the large sections of the brain called the ventricles. This may occur for many reasons, including Chiari malformation , abnormal cysts within the brain, and infections such as meningitis .
In some cases, a child may have benign macrocephaly. In these children, the only abnormality is an enlarged head. Usually there are other family members with large heads, and the condition is considered a family trait. These children do not have an underlying condition and usually do not have any additional complications.
The major symptom of macrocephaly is an enlarged head circumference. Other symptoms can include, delay in reaching developmental milestones, mental retardation , rapid head growth, and slowed growth of the rest of the body.
Macrocephaly is usually diagnosed by the pediatrician during a physical examination. In some cases this may be the only diagnosis necessary. Some children will require additional diagnostic imaging procedures, such as computed tomography scan (CAT scan), x ray, and magnetic resonance imaging (MRI), to determine the cause of the macrocephaly and the appropriate treatment.
There is no specific treatment for macrocephaly. Medical care for children with macrocephaly focuses on management of specific symptoms such as developmental delays and mental retardation and treatment of the primary diagnosis responsible for the macrocephaly.
For children with benign familial macrocephaly, the prognosis is excellent. These children usually do not have any complications and have normal intelligence . For other children with macrocephaly, the prognosis is dependent upon the cause. In children with hydrocephalus, the prognosis can be excellent depending on what type of hydrocephalus they have. Unfortunately, many children with macrocephaly experience delayed development, slow growth, seizure disorders, and limited intelligence. All of these are related to the underlying condition that caused the macrocephaly.
Macrocephaly is often present at birth or is a result of conditions that are present at birth. As of 2004 there was no known prevention.
Achondroplasia —A congenital disturbance of growth plate development in long bones that results in a person having shortened limbs and a normal trunk.
Alexander's disease —A progressive, degenerative disorder of the central nervous system.
Canavan disease —A serious genetic disease more common in the Eastern European Jewish population that causes mental retardation and early death. Canavan disease is caused by the lack of an enzyme called aspartoacylase.
Chiari II anomaly —A structural abnormality of the lower portion of the brain (cerebellum and brainstem) associated with spina bifida. The lower structures of the brain are crowded and may be forced into the foramen magnum, the opening through which the brain and spinal cord are connected.
Computed tomography (CT) —An imaging technique in which cross-sectional x rays of the body are compiled to create a three-dimensional image of the body's internal structures; also called computed axial tomography.
Fontanelle —One of several "soft spots" on the skull where the developing bones of the skull have yet to fuse.
Gigantism —Excessive growth, especially in height, resulting from overproduction of growth hormone during childhood or adolescence by a pituitary tumor. Untreated, the tumor eventually destroys the pituitary gland, resulting in death during early adulthood. If the tumor develops after growth has stopped, the result is acromegaly, not gigantism.
Magnetic resonance imaging (MRI) —An imaging technique that uses a large circular magnet and radio waves to generate signals from atoms in the body. These signals are used to construct detailed images of internal body structures and organs, including the brain.
Megalencephaly —A condition in which the brain is abnormally large.
Megalocephaly —An abnormally large head.
Neurofibromatosis —A progressive genetic condition often including multiple café-au-lait spots, multiple raised nodules on the skin (neurofibromas), developmental delays, slifhtly larger head size, and freckles in the armpits, groin, and iris. Also known as von Recklinghausen's disease.
Osteogensis imperfecta —An inherited disorder of the connective tissue which involves multiple symptoms, including weakened bones that break easily.
Standard deviation —A measure of the distribution of scores around the average (mean). In a normal distribution, two standard deviations above and below the mean includes about 95% of all samples.
When mental deficiency and the attendant diseases or disorders are severe, the child may require a life-support system. When the mental deficiency is less severe, the child may be diagnosed with minimal brain dysfunction or as neurologically handicapped. Minimal brain dysfunction can include any or all of the following: memory and language problems, neuromotor functioning problems, and behavior and social problems. The degree of dysfunction is a key factor in parents' deciding whether the child can continue to live at home and what type of schooling is appropriate. Parents and teachers need to be cognizant of the nature of the child's dysfunction. What was once seen as laziness and lack of motivation on the child's part has begun in the early 2000s to be recognized as a medical condition that can be corrected or modified through psychotherapy. Sometimes, though, a child may suffer several years of frustrating failure and abnormal development or behavior before the problem is recognized and he or she is properly diagnosed.
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Deborah L. Nurmi, MS