Cranial Ultrasound

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.

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.

No special preparation is required before having this test.

If an older baby is having the test, it may help to have the baby be a little hungry. The baby can be fed during the test, which will help the baby be comforted and hold still during the test.

This test is done by a doctor who specializes in interpreting imaging tests (radiologist) or by an ultrasound technologist (sonographer) who is supervised by a radiologist. For a baby, cranial ultrasound may be done at your baby's bedside in the neonatal intensive care unit (NICU). With the baby lying on his or her back, the transducer is moved across the soft spot (fontanelle) on top of the head. You may be asked to hold your baby during the test. Several pictures of the brain and inner fluid chambers (ventricles) can be seen on a video monitor.

For an adult, cranial ultrasound is done during brain surgery to help locate a brain mass.

A cranial ultrasound usually takes 15 to 30 minutes.

There is usually no discomfort involved with having a cranial ultrasound test. The gel may feel cold when it is applied to the skin unless it is first warmed to body temperature.

There are no known risks associated with a cranial ultrasound test.

Cranial ultrasound uses reflected sound waves to produce pictures of the brain and the inner fluid chambers (ventricles) through which cerebrospinal fluid (CSF) flows.

Factors that can interfere with your test and the accuracy of the results include:

• The baby not remaining still during the test.
• Having an open wound or recent surgical wound in the area being viewed.

• Because ultrasound cannot penetrate bone, cranial ultrasound can be performed only on babies whose skull (cranial) bones have not yet grown together. However, duplex Doppler ultrasound can be done to evaluate blood flow and vessel spasms in the brain in children and adults. For more information, see the medical test Doppler Ultrasound.
• Periventricular leukomalacia (PVL) is not usually detectable until several weeks after birth. For this reason, cranial ultrasound is generally done between 4 and 8 weeks after delivery. Because cranial ultrasound may detect suspicious areas in the brain that may or may not be PVL, ultrasound testing may be repeated over several weeks. Babies with PVL or intraventricular hemorrhage (IVH) may develop normally or may have varying levels of disability, including cerebral palsy or mental retardation.
• Magnetic resonance imaging (MRI) scanning may be done instead of cranial ultrasound to evaluate PVL or IVH in babies born prematurely. For more information, see the medical test Magnetic Resonance Imaging (MRI) of the Head.
• Fetal ultrasound is used during pregnancy to view a baby (fetus) and the placenta. For more information about ultrasound during pregnancy, see the medical test Fetal Ultrasound.

Other Works Consulted

• National Guideline Clearinghouse (2004). Transcranial Doppler ultrasonography: Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Available online: http://www.guideline.gov/summary/summary.aspx?view_id=1&doc_id=5331.