What is "conus medullaris"

The conus medullaris (Latin for "medullary cone") is the tapered, lower end of the spinal cord. It occurs near lumbar vertebral levels 1 (L1) and 2 (L2), occasionally lower. The upper end of the conus medullaris is usually not well defined.

After the spinal cord tapers out, the spinal nerves continue to branch out diagonally, forming the cauda equina.

The pia mater that surrounds the spinal cord, however, 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.