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; 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.