The conus medullaris (Latin for “medullary cone”) or conus terminalis is that the tapered, lower end of the medulla spinalis . It occurs near lumbar vertebral levels 1 (L1) and a couple of (L2), occasionally lower. The upper end of the conus medullaris is typically not well defined, however, its corresponding medulla spinalis segments are usually S1-S5.
After the medulla spinalis tapers out, the spinal nerves still diversify diagonally, forming the cauda equina.
The meninx that surrounds the medulla spinalis , however, projects directly downward, forming a slender filament called the filum terminale, which connects the conus medullaris to the rear of the coccyx. The filum terminale provides a connection between the conus medullaris and therefore the coccyx which stabilizes the whole medulla spinalis .
The blood supply consists of three spinal arterial vessels— the anterior median longitudinal arterial trunk and therefore the right and left posterior spinal arteries. Other less prominent sources of blood supply include radicular arterial branches from the aorta, lateral sacral arteries, and therefore the fifth lumbar, iliolumbar, and middle sacral arteries. The latter contribute more to the vascular supply of the cauda equina.
Conus medullaris syndrome may be a collection of signs and symptoms related to injury to the conus medullaris. It typically causes back pain and bowel and bladder dysfunction, spastic or flaccid weakness counting on the extent of the lesion, and bilateral sensory loss . Comparatively, cauda equina syndrome may cause radicular pain, bowel/bladder dysfunction, patchy sensory loss or saddle anesthesia and lower extremity weakness at the extent of the lumbar and sacral roots.