Test Overview
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. See two newborn babies'
cranial ultrasound images.
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 a picture 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 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 be comforted and 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 is usually no discomfort involved
with having a cranial ultrasound test. Unless the gel is first warmed to body
temperature, it may feel cold when it is put on the skin.
Risks
There are no known risks linked with a
cranial ultrasound test.
Results
Cranial
ultrasound uses reflected sound waves to produce
pictures of the brain and the inner fluid chambers (ventricles) through which
cerebrospinal fluid (CSF) flows.
Cranial ultrasound
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Normal:
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The size and shape of the brain appear
normal.
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The size of the brain's inner fluid
chambers (ventricles) is normal.
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Brain tissue appears normal. No bleeding,
suspicious areas (lesions), abnormal growths, or evidence of infection are
present.
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Abnormal:
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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.
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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.
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The brain and ventricles may be enlarged
from the buildup of excessive amounts of cerebrospinal fluid (CSF). This may
point to
hydrocephalus.
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Abnormal growths may be present, which may
point to a tumor or
cyst.
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Suspicious findings may be present, which
may point to
encephalitis or
meningitis.
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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. For more information,
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. For more information, 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. For more information about ultrasound during
pregnancy, see the topic
Fetal Ultrasound.
References
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.
Credits
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By
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Healthwise Staff |
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Primary Medical Reviewer
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Kathleen Romito, MD - Family Medicine |
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Specialist Medical Reviewer
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Howard Schaff, MD - Diagnostic Radiology |
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Last Revised
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November 29, 2012 |