The conus medullaris (Latin for "medullary cone") or conus terminalis is the tapered, lower end of the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

. 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, however, its corresponding spinal cord segments are usually S1–S5. After the spinal cord tapers out, the spinal nerves continue to branch out diagonally, forming the

cauda equina The cauda equina () is a bundle of spinal nerves and spinal nerve rootlets, consisting of the second through fifth lumbar nerve pairs, the first through fifth sacral nerve pairs, and the coccygeal nerve, all of which arise from the lumbar enl ...

. The

pia mater Pia mater ( or ),Entry "pia mater"
in
filum terminale The filum terminale ('terminal thread') is a delicate strand of fibrous tissue, about 20 cm in length, extending inferiorly from the apex of the conus medullaris to attach onto the coccyx. The filum terminale acts to anchor the spinal cord ...

, which connects the conus medullaris to the back of the

coccyx The coccyx (: coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horse anatomy, horses. In tailless primates (e.g. hum ...

. The filum terminale provides a connection between the conus medullaris and the coccyx which stabilizes the entire spinal cord.

Blood supply

The blood supply consists of three spinal arterial vessels—the anterior median longitudinal arterial trunk and the right and left posterior spinal arteries. Other less prominent sources of blood supply include radicular arterial branches from the

aorta The aorta ( ; : aortas or aortae) is the main and largest artery in the human body, originating from the Ventricle (heart), left ventricle of the heart, branching upwards immediately after, and extending down to the abdomen, where it splits at ...

, lateral sacral arteries, and the fifth lumbar, iliolumbar, and middle sacral arteries. The latter contribute more to the vascular supply of the cauda equina.

Pathology

Conus medullaris syndrome is a collection of signs and symptoms associated with injury to the conus medullaris. It typically causes back pain and bowel and bladder dysfunction, spastic or flaccid weakness depending on the level of the lesion, and bilateral sensory loss. Comparatively,

cauda equina syndrome Cauda equina syndrome (CES) is a condition that occurs when the bundle of nerves below the end of the spinal cord known as the cauda equina is damaged. Signs and symptoms include low back pain, sciatica, pain that radiates down the leg, numbness ...

may cause radicular pain, bowel/bladder dysfunction, patchy sensory loss or saddle anesthesia and lower extremity weakness at the level of the lumbar and sacral roots.

Pediatric Pediatrics (American English) also spelled paediatrics (British English), is the branch of medicine that involves the medical care of infants, children, adolescents, and young adults. In the United Kingdom, pediatrics covers many of their youth ...

patients may have a

syrinx In classical Greek mythology, Syrinx () was an Arcadian nymph and a follower of Artemis, known for her chastity. Being pursued by Pan, she fled into the river Ladon, and at her own request was metamorphosed into a reed from which Pan then mad ...

associated with their Chiari malformation and the conus medullaris will be located at or below the L2–L3

lumbar vertebrae The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe t ...

disk space. Isolated infarcts of the conus medullaris are rare, but should be considered in patients with acute cauda equina syndrome, especially in females. According to a 2021 paper by You-Jiang Tan, et al., those with demonstrated causes or with vascular risk factors are less likely to walk without assistance.

References

External links

* – "Lower Third of Spinal Cord, MRI" {{Authority control Spinal cord