The filum terminale is an anatomic structure at the end of the spinal cord.
The pia mater that surrounds the spinal cord, projects directly downward, forming a slender filament called the filum terminale, which connects the conus medullaris to the back of the coccyx. The tension that the filum terminale provides between the conus medullaris and the coccyx stabilizes the entire spinal cord.
Neoplasms in the region of filum terminale are not uncommon. Myxopapillary ependymoma is the commonest tumor at this location. The differentials reported for this entity are nerve sheath tumor, meningioma, paraganglioma, intradural metastases, lymphoma, other varieties of ependymoma, subependymoma, astrocytoma, ganglioglioma, hemangioblastoma, and primitive neuroectodermal tumor (PNET). PNET may very rarely present as an intradural thoracolumbar mass.
Thoriya et al. present pre- and post-therapy magnetic resonance imaging (MRI) features of a patient with proven primary spinal primitive neuroectodermal tumor (PSPNET) of peripheral subtype 1)