Ligament
Filum terminale
Slender connective attachment from the conus toward the coccyx
High-yield
This is a supporting strand, distinct from the surrounding nerve roots. Although usually described as a pial extension, its tissue is more complex and can include glial and other cellular remnants.
Overview
The filum terminale extends downward from the conus among the cauda equina roots. Its internal part lies inside the dural sac; near the sac's lower end, around S2, it joins the dura and continues toward the coccyx as the external part.
Reference facts
- Attachments
- Conus tip to the lower dural sac as the filum terminale internum, then onward with a dural contribution toward coccygeal attachments as the externum
- Function
- Contributes to longitudinal support of the lower cord and dural sac while accommodating movement
- Clinical point
- A thickened or fatty filum can accompany tethering, but fat within the filum is often an incidental MRI finding and does not alone establish symptomatic tethered cord
Clinical correlation
Abnormal tethering can restrict cord movement and cause stretching, with pain, weakness, gait changes or bladder problems. It can arise from developmental abnormalities or acquired scarring. Symptoms and imaging must be considered together.
Frequently asked questions
Where does the filum terminale attach?
Conus tip to the lower dural sac as the filum terminale internum, then onward with a dural contribution toward coccygeal attachments as the externum.
What does the filum terminale do?
Contributes to longitudinal support of the lower cord and dural sac while accommodating movement.
Why does the filum terminale matter clinically?
A thickened or fatty filum can accompany tethering, but fat within the filum is often an incidental MRI finding and does not alone establish symptomatic tethered cord.