Macrocephaly can be normal or caused by genetic disorders or other disorders.
Diagnosis is made before birth through routine ultrasound tests or after birth by measuring the head circumference.
Doctors usually do imaging tests to look for brain abnormalities and sometimes blood tests to look for a cause.
Treatment for macrocephaly depends on the cause, and sometimes, if no problems are found, no treatment is necessary.
(See also Overview of Brain and Spinal Cord Birth Defects Overview of Brain and Spinal Cord Birth Defects Birth defects of the brain and spinal cord can occur in early or late fetal development. Typical symptoms include intellectual disability, paralysis, incontinence, or loss of sensation in some... read more .)
Infants with macrocephaly have a head circumference Head Circumference Physical growth refers to an increase in body size (length or height and weight) and in the size of organs. From birth to about age 1 or 2 years, children grow rapidly. After this rapid infant... read more that is considerably larger than others of the same age.
Macrocephaly can be classified as
Disproportionate: The head is larger than appropriate for the child's overall size.
Proportionate: The head appears appropriately sized for the body (in other words, the child has a large body and a large head).
Many people with large heads or large skulls are healthy.
Abnormal macrocephaly may be due to an enlarged brain (megalencephaly), water on the brain (hydrocephalus Hydrocephalus Hydrocephalus is an accumulation of extra fluid in the normal spaces within the brain (ventricles) and/or between the inner and middle layers of tissues that cover the brain (the subarachnoid... read more 
), overgrowth of the bones of the skull (cranial hyperostosis), or other conditions. These conditions may be the result of genetic disorders or disorders the child acquired before or after birth.
Diagnosis of Macrocephaly
Before birth, ultrasound
After birth, physical examination, including measurement of head circumference and sometimes imaging tests and blood tests
Before birth, the diagnosis of macrocephaly sometimes is made with a routine prenatal ultrasound test Ultrasonography Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more done late in the 2nd trimester or early in the 3rd trimester.
After birth, doctors measure a baby's head circumference Head Circumference Physical growth refers to an increase in body size (length or height and weight) and in the size of organs. From birth to about age 1 or 2 years, children grow rapidly. After this rapid infant... read more (the measurement of the head around its largest area) during routine physical examinations. They diagnose macrocephaly when the head circumference is significantly larger than the normal range for babies of the same sex, age, and ethnic group in the region where the baby lives. When making the diagnosis, doctors also take into account the head circumference of the baby's parents and grandparents because a slightly larger head size may run in the family.
If macrocephaly is present, doctors usually do computed tomography Computed Tomography (CT) In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more 
(CT) or magnetic resonance imaging Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more 
(MRI) of the head to look for brain abnormalities. Doctors also evaluate the newborn and parents to look for possible causes of macrocephaly and then test for any causes they suspect. Sometimes the doctor may request blood tests to help determine the cause.
Treatment of Macrocephaly
Depends on the cause
Treatment of macrocephaly depends on the cause. Sometimes, no treatment is necessary. If the cause is an abnormality, such as hydrocephalus, treatment, including surgery, may be necessary.
