Conus medullaris


Refers to the tapered, lower end of the spinal cord.

The conus medullaris is a concentrated region of cell bodies for existing lumbosacral nerve roots from L5 to S3.

It occurs near lumbar vertebral levels 1 (L1) and 2 (L2), and occasionally lower.

The upper end of the conus medullaris is not well defined.

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

A thin layer of non-neural fibrous tissue known as the filum terminals extends from the conus medullaris and attaches to the sacrum.

The pia mater surrounding 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. which stabilizes the entire spinal cord

Blood supply to the conus medullaris consists of three spinal arterial vessels― the anterior median longitudinal arterial trunk and the right and left posterior spinal arteries.

Other less important sources of blood supply include radicular arterial branches from the aorta, lateral sacral arteries, and the fifth lumbar, iliolumbar, and middle sacral arteries.

Conus medullaris syndrome typically causes back pain and bowel and bladder dysfunction but weakness and sensory loss is uncommon.

Comparatively, cauda equina syndrome may cause radicular pain, bowel/bladder dysfunction, saddle anesthesia and lower extremity weakness at the level of the lumbar and sacral roots.

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