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, so an ultrasound to evaluate the brain cannot be done after 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 about 18 months old.
Cranial ultrasound for babies
Complications of premature birth include periventricular leukomalacia (PVL) and bleeding in the brain, including intraventricular hemorrhage (IVH). 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. 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 an intellectual disability.
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. In contrast, PVL can take several weeks to detect. For this reason, cranial ultrasound may be repeated 4 to 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 ).
Cranial ultrasound for adults
Cranial ultrasound may be done on an adult to help locate a brain mass. Because cranial ultrasound cannot be done after the skull bones have fused, it is only done after the skull has been surgically opened during brain surgery.
Why It Is Done
In babies, cranial ultrasound usually is only done:
- 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 look for periventricular leukomalacia (PVL). IVH and PVL increase a baby's risk of developing disabilities, including cerebral palsy or an intellectual disability.
- To screen for brain problems that may be present from birth (such as congenital hydrocephalus).
- To evaluate an enlarging head.
- To look for 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.
How To Prepare
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 to be comforted and to hold still during the test.
How It Is Done
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. 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 find a brain mass.
A cranial ultrasound usually takes 15 to 30 minutes.
How It Feels
There are no known risks linked with a cranial ultrasound test.
The size and shape of the brain appear normal.
The size of the brain's inner fluid chambers (ventricles) is normal.
Brain tissue appears normal. No bleeding, suspicious areas (lesions), abnormal growths, or evidence of infection are present.
Bleeding in the brain may be present, which may indicate intraventricular hemorrhage (IVH). Repeated tests are often done to check the bleeding or to look for problems caused by the bleeding.
Suspicious areas or lesions around the brain's ventricles may be present. This may be a sign of periventricular leukomalacia (PVL), a condition in which the brain tissue around the ventricles is damaged.
The brain and ventricles may be enlarged from the buildup of excessive amounts of cerebrospinal fluid (CSF). This may point to hydrocephalus.
Abnormal growths may be present, which may point to a tumor or cyst.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- The baby does not remain still during the test.
- Having an open wound or recent surgical wound in the area being viewed.
What To Think About
- Because ultrasound cannot penetrate bone, cranial ultrasound can be performed only on babies whose skull (cranial) bones have not yet grown together. But duplex Doppler ultrasound can be done to evaluate blood flow in the brain in children and adults. To learn more, see the topic Doppler Ultrasound.
- Periventricular leukomalacia (PVL) is not usually detectable until several weeks after birth. For this reason, cranial ultrasound is generally done 4 to 8 weeks after delivery. Because cranial ultrasound may find 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 an intellectual disability.
- Magnetic resonance imaging (MRI) scanning may be done instead of cranial ultrasound to evaluate PVL or IVH in babies born prematurely. To learn more, see the topic Magnetic Resonance Imaging (MRI) of the Head.
- Fetal ultrasound is used during pregnancy to view a developing baby (fetus) and the placenta. To learn more about ultrasound during pregnancy, see the topic Fetal Ultrasound.
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
Sloan MA, et al. (2004). Assessment: Transcranial Doppler ultrasonography. Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Neurology, 62(9): 1468-1481. Also available online: http://neurology.org/content/62/9/1468.full.
Primary Medical ReviewerKathleen Romito, MD - Family Medicine
Specialist Medical ReviewerHoward Schaff, MD - Diagnostic Radiology
Current as ofSeptember 9, 2014