The filum terminale ('terminal thread') is a delicate strand of fibrous tissue, about 20 cm in length, extending inferiorly from the apex of the conus medullaris to attach onto the coccyx. The filum terminale acts to anchor the spinal cord and spinal meninges inferiorly.
The upper portion of the filum terminale is formed by spinal pia mater within a dilated dural sac, while the lower portion is formed by both pia and dura mater (with the outer dural layer closely adhering to the inner pial component).
Anatomy
The proximal/superior partthe filum terminale internum or pial part of terminal filum to blend with the coccygeal periosteum.
The central canal of the spinal cord extends inferiorly into the superior part of the filum terminale.