Cranial ultrasound uses reflected sound waves to produce pictures of the brain and the inner fluid chambers (ventricles) through which cerebrospinal fluid (CSF) flows. This test is most commonly done on babies to evaluate complications of premature birth. In adults, cranial ultrasound may be done to visualize brain masses during brain surgery.

Ultrasound waves cannot pass through bones; therefore, an ultrasound to evaluate the brain cannot be done once the bones of the skull (cranium) have grown together. Cranial ultrasound can be done on babies before the bones of the skull have grown together or on adults after the skull has been surgically opened. It may be used to evaluate problems in the brain and ventricles in babies up to 18 months old.

Cranial ultrasound for babies

Complications of premature birth include bleeding in the brain (intraventricular hemorrhage, or IVH) and periventricular leukomalacia (PVL). PVL is a condition in which the brain tissue around the ventricles is damaged, possibly from decreased oxygen or blood flow to the brain that may have occurred before, during, or after delivery. Both IVH and PVL increase a baby's risk of developing disabilities that may range from mild learning or gross motor delays to cerebral palsy or mental retardation.

IVH is more common in premature babies than in full-term babies. When it occurs, it most commonly develops in the first 3 to 4 days after birth. Most cases of IVH can be detected by cranial ultrasound by the first week after delivery. By contrast, PVL can take several weeks to detect. For this reason, cranial ultrasound may be repeated between 4 and 8 weeks after delivery if PVL is suspected. Several cranial ultrasound tests may be done to evaluate areas in the brain.

Cranial ultrasound may also be done to evaluate a baby's large or increasing head size, detect infection in or around the brain (such as from encephalitis or meningitis), or screen for brain problems that are present from birth (such as congenital hydrocephalus). See an illustration of congenital hydrocephalus.

Cranial ultrasound for adults

Cranial ultrasound may be done on an adult to help locate a brain mass. Because cranial ultrasound cannot be done once the skull bones have fused, it is only done once the skull has been surgically opened during brain surgery.

Why It Is Done

Cranial ultrasound usually is done only on babies:

• As part of routine screening of babies born prematurely to detect bleeding in the brain, such as intraventricular hemorrhage (IVH).
• To monitor any complications or to detect periventricular leukomalacia (PVL). IVH and PVL increase a baby's risk of developing disabilities, including cerebral palsy or mental retardation. See an illustration of a child's cranial ultrasound.
• To screen for brain problems that may be present from birth (such as congenital hydrocephalus).
• To evaluate an enlarging head.
• To detect infection or abnormal growths in or around the brain.

In adults, cranial ultrasound may be done during brain surgery to help locate a brain mass.