Ultrasound of the spine in neonates

Who should get an ultrasound of the spine? And when should it be done?

The primary indication for ultrasound of the spine in neonates is usually a finding in the skin, or just beneath the skin of the back, such as a dimple or mass, hair tuft or change in colour.
Usually, these findings are seen following birth at the nursery or during the newborn’s first visit to the pediatrician’s office.

How common are the above-mentioned findings in infants?

The prevalence of skin findings on the back of an infants is quite common and is seen in about 3-8% of babies. As mentioned above, this is the main indication for spinal ultrasound in neonates.
Different studies have shown that the chances of having an anormal finding in the spinal cord decrease when there is a single finding in the skin (compared to multiple), when the finding is smaller than 2.5cm, when it is located closer to the anus and when it is more central and closer to the midline.

What is an ultrasound imaging test and who performs it?

Ultrasound machines use sound waves to demonstrate structures in the human body. The most important aspect of this machine is that it is free of radiation and is therefore safe for use in all age groups.
Spinal ultrasound tests performed on neonates are only performed by pediatric radiologists (a physician who has specialized in radiology) as it requires a certain level of expertise and skills in ultrasound examinations, a good understanding of the anatomy of the area and high level of experience in spinal abnormalities of the neonate.

What is the association between the findings on the skin and the abnormalities in the spinal cord?

The bony structure of the vertebral column is made up of vertebral bodies and posterior (back) elements (an arch, lamina and pedicle) that create a bony canal for the spinal cord and its enveloping membranes.
During the beginning of fetal development, there are three types of prototypic cells that are responsible for the development of different tissues in the body (cells of the endoderm, mesoderm and ectoderm).
The first ectodermal cells produce the central and peripheral nervous system and the skin tissue, and this is where the association between the two lies. A finding on the skin of the back of a child can imply a congenital migrating abnormality in the development of the spinal cord and its membranes.
An additional possibility is a disorder in the development of the bony structure, such as the absence of closure of the posterior arch (spina bifida), with or without involvement of the spinal cord and its membranes. In such cases, the skin manifestation can be a hair tuft.

Does this mean that every time we find an abnormality in the back there will likely be a problem with the spinal cord?

No. In most cases the ultrasound test will be normal. A finding along the spinal cord in the presence of an abnormal finding in the skin is not common and is found in only about 1-1.5% of all neonates, and in about 5-6% of those with a finding on the back.
However, if there is a structural developmental disorder. it is very important to detect it early, prior to the closure of the bony structures, for the purpose of early assessment and treatment.

But we did an anatomical scan during pregnancy and no abnormalities were detected – is there still a chance for a significant finding?

The answer to this question is slightly complicated because the anatomical scans performed during pregnancy are quite limited compared to the spinal ultrasound that can be done on a newborn.
First of all, the routine anatomical scan is performed during the early weeks of pregnancy (around 20th-22nd week of gestation) and it is important to realize that at this time not all the structures of the vertebral column, spinal cord, and adjacent structures have completely matured to their final shape. Afterall, there is still another half of the pregnancy to go through at this stage.
Secondly, the resolution at which the fetal tests are performed is lower than that of the newborn baby because of the simple reason that the fetus is much smaller than the full-grown baby and the fetus is inside an amniotic sac, far away from the ultrasound machine, while the newborn baby can be held by the physician, close to the probe of the ultrasound.
Thirdly, a detailed and extended anatomical scan requires a high level of skill and expertise, beyond the routine anatomical scan performed.
So, the answer is yes. There can certainly be a situation where a routine anatomical skin during the 20th week of gestation was normal while abnormalities are detected in the spinal cord following birth. One of the ways to avoid this is to get a detailed and extended anatomical scan done by a specialist in the field, and to get an additional ultrasound test in the third trimester, in order to try and examine the spinal column again. This is not a routine examination in most countries.

What is the best time to perform a spinal ultrasound on a neonate after birth?

The ideal timing for this imaging test is between birth and 4-5 months of age, and if the baby was born prematurely, sometimes it is possible to perform this test also at the age of 6 months. Following this time period, the posterior elements undergo partial or full closure which limits or masks the structure of the spinal column and reduces the diagnostic abilities of this test.
However, despite this (relatively) long timeframe, I always recommend patients to get it done as soon as possible after birth and not to wait till the infant is several months old.
In addition, it is possible to perform the spinal ultrasound together with the ultrasound for the hip joints, an important imaging test that you can read more about here.

How is this ultrasound done?

There is no need to prepare for this imaging test (such as fasting, etc.).
Usually, the infant is laid down on their abdomen. A pillow or soft voluminous sheet is placed underneath the abdomen in order to produce an arching of the spinal column. Another way to perform this test is by placing the infant on their side in a fetal position, with the knees bent towards their abdomen. Only when the baby is calm and quiet are the upper and lower parts of the back are exposed.
Afterwards, a gel is applied on the area that is to be examined and the test is started. If there are no findings, a skilled physician is able to complete the test within 15-20 minutes.

What exactly is being examined during an ultrasound of the spine?

Just like any other ultrasound test it is important to do the test properly, according to the guidelines and criteria (checklist) for examination, to make sure that all the relevant components have been examined and nothing was missed.
The main purpose of the examination is to rule out a tethered spinal cord – this is when the spinal cord ends in an abnormally low area and is often attached to abnormal tissue under vertebral body L3. In addition, it is important to assess the spinal cord and membranes to rule out the presence of lesions/masses or abnormal tissue along the cord and to ensure free movement of the ends of the spinal cord (cauda equina).
It is then important to examine the bony structure of the spinal column – it is important to make sure that the bony structure fits the age of the infant, both in position and appearance and that there are no missing structures.
Finally, the soft tissue surrounding the spinal column such as the skin and the subcutaneous fat tissue are examined, and the examiner makes sure that the different tissues are properly separated from the structures of the spinal column.

What happens if there is an abnormal finding in the imaging test?

As mentioned above, the prevalence of abnormal findings is not very high.
If an abnormality is detected in the bony structure or along the spinal cord, either a neurosurgical or orthopedic consult will be needed, depending on the finding. In addition, a more advanced imaging test will be needed such as an MRI to characterize the abnormality along the spinal cord or an X-ray/CT if there is an abnormality in the bone.

In summary, a finding on the skin on the lower back of an infant is common and presents the primary indication for spinal ultrasounds in neonates. Ultrasound imaging tests in infants is a test that must be performed by a pediatric radiologist, as it requires skill and knowledge, and it is limited to the first 4-5 months of life. The rate of abnormal findings or developmental disorders along the spinal cord is not high, but if present it requires further investigation using advanced imaging techniques and management by a specialist depending on the source of the abnormality.
Wishing you all health!