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Increased head circumference is when the measured distance around the widest part of the skull is larger than expected for the child's age and background.
A newborn's head is usually about 2 centimeters larger than the chest size. Between 6 months and 2 years, both measurements are about equal. After 2 years, the chest size becomes larger than the head.
Measurements over time that show an increased rate of head growth often provide more valuable information than a single measurement that is larger than expected.
Increased pressure inside the head (increased intracranial pressure) often occurs with increased head circumference. Symptoms of this condition include:
The health care provider usually finds macrocephaly during a routine well-baby exam.
The health care provider will take a medical history and will perform a physical examination.
Medical history questions may include:
A careful physical exam will be done. Other milestones for growth and development will be checked.
In some cases, a single measurement is enough to confirm that there is a size increase that needs to be tested further. More often, repeated measurements of the head circumference over a period are needed to confirm that the head circumference is increased and the problem is getting worse.
Diagnostic tests that may be ordered include:
Cohen MM Jr. Overgrowth syndromes. In: Gilbert-Barness E, Kapur RP, Oligny LL, et al., eds. Potter's Pathology of the Fetus, Infant and Child. Philadelphia, PA: Elsevier Mosby; 2007:chap 41.
Kinsman SL, Johnston MV. Congenital anomalies of the central nervous system. In: Kliegman RM, Stanton BF, St. Geme JW III, et al., eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 585.
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