Spinal Ultrasound -Normal Variants -part 2

pediatricultrasound ♦ June 5, 2019

In a previous post about normal variants of the neonatal spinal cord, two of the more common variants were covered, a ventriculus terminalis and a filar cyst. In this post the remaining two spinal cord variants which are detected under ultrasound are covered. They are the prominent filum terminale and the pseudo sinus tract.
The filum terminale is a thin fibrous tissue extension of the pia mater that connects the tip of the conus medullaris to the coccyx bone and anchors the spinal cord within the spinal canal. The filum terminale should measure less than 2mm PA dimension. A prominent filum terminale will appear visually thick but still measure less than 2mm. This is considered to be a normal variant and will not inhibit the spinal cord from ascending to its correct level as a true thickened filum terminale over 2mm will.
A pseudo sinus tract is a hypoechoic tract that runs from the skin surface, usually from a sacral dimple, and tracts towards the coccyx. It will have no mass associated with it and will not have a fluid filled cavity as in a true dermal sinus which contains CSF and typically run in a cranial direction towards sacrum. Both prominent filum terminale and pseudo sinus tracts are thought to have no clinical significance and require no follow-up.