Glossary term:

Filum terminale

Of the three membranous layers that invest the brain and spinal cord, the inner-most, known as the “pia”, can be likened to a thin skin, which is closely applied to the brain and cord tissue. At the lower end of the spinal cord, where it tapers down to the conus, the pia continues on, in a downward direction, becoming the filum terminale, often referred to simply as the filum.