Increased head circumference

Alternative names:

macrocephaly

Definition:

Increased head circumference is determined when the measurement of the distance around the widest part of the skull is greater than expected for the age and sex of the child.

Considerations:

Increase in head circumference during infancy and childhood normally represent growth of the brain. Normal growth parameters have been determined by years of measuring infants and children. An increasing head circumference that exceeds the normal and well-established standards is frequently a cause for concern that something is causing the above normal head size other than normal brain growth.As a rule of thumb, a newborn's head is usually about 2 centimeters larger than the chest size. Between 6 months and 2 years old, both measurements are about equal, after 2 years old the chest size becomes larger than the head.

Head circumferences usually are obtained from birth up to 18 months while the head is growing and the bones of the head have not yet fused. These measurements are plotted by the physician on a graph along with the child's height and weight. A series of measurements over time, such as those done during routine well-baby visits, that show an abnormally increased rate of head growth often can provide more valuable information than a single measurement that is larger than expected. The first step is to determine if the increased circumference is simply a normal variant such as coming from a family with a history of large heads or if there is some other cause for the increased size. Once it is determined that the cause is an abnormal condition, then a diagnosis must be made.

See also bulging fontanels.

Common causes:

Genetic (one or more members of the immediate family with larger than average head sizes

• familial large head

Although rare, the following are the more common causes of increased head circumference:

• hydrocephalus - this condition occurs when fluid collects in the ventricles of the brain and around the brain. In infants and children less than 18 months (before the bones of the head fuse together) it can cause a slow to rapid increase in head size. Hydrocephalus can have many causes (congenital, post-traumatic, or obstructive)
• achondroplasia (a genetic condition with an incidence of approximately 1 in 20,000 to 1 in 25,000 births)
• neurofibromatosis (a genetic condition with an incidence of approximately 1 in 3000 to 1 in 4000)

The following is a list of extremely rare causes of increased head circumference:

• cerebral gigantism (Sotos syndrome)
• Canavan disease
• Hurler syndrome
• Morquio syndrome

Note: There may be other causes of increased head circumference. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as location, quality, time course, aggravating factors, relieving factors, and associated complaints.