A cranial ultrasound is an imaging study of the contents of the skull performed with the use of reflected sound waves. Ultrasound imaging cannot penetrate bone and thus this test can only be used on infants and young children with incompletely fused skulls, or adults undergoing brain surgery, where the surgeon opens the cranium to access the brain. A doctor may recommend a cranial ultrasound to identify or follow up on abnormalities in the brain.
Before babies are born, it is possible to get an image of the skull and contents through prenatal ultrasound, and this may allow a doctor to identify early warning signs of conditions like hydrocephalus, where fluid builds up on the brain. It is also possible to identify serious congenital abnormalities like ancephaly, where no brain develops. This type of cranial ultrasound may be part of routine prenatal ultrasounds, and a doctor can also request a closer look if there are specific concerns.
After birth, a doctor can request a cranial ultrasound to evaluate a baby for birth complications, congenital conditions not caught earlier, and other issues. In the cranial ultrasound, the doctor or technician moves a probe across the skull. The probe transmits and receives sound waves to create an image of the brain. As the plates of the skull fuse, the resolution will decline, until the skull is solid bone and it is no longer possible to perform a cranial ultrasound. Other imaging options like magnetic resonance imaging may need to be considered for older children and adults.
Adult cranial ultrasound may be used during surgery. The surgeon can ask for an ultrasound evaluation of the brain after opening the skull to identify masses and other abnormalities. These should be visible on other imaging studies prior to surgery, but additional imaging during surgery can help the surgeon get oriented in the brain. The surgeon can also check for any missed masses before closing, to reduce the risk of a repeat surgery.
As with other ultrasound examinations, copies of images may be kept on file for reference. Patients can ask to look at these and can also ask for guidance from a health care professional familiar with ultrasound interpretation. A doctor or technician can discuss the visible structures, any abnormalities in the image, and the results of the test. Some patients and family may find it helpful to look at a cranial ultrasound while they discuss a diagnosis, prognosis, and treatment plan.