Conus medullaris

The tapered, lower end of the spinal cord

Diagram of the spinal cord showing the conus medullaris

The conus medullaris is the tapered, lower end of the spinal cord. It occurs near the lower back, at the level of the first or second lumbar vertebra (L1 or L2), although the exact position can vary among individuals. The conus medullaris is an important anatomical structure as it marks the transition from the central nervous system to the peripheral nervous system.

Anatomy

The conus medullaris is the terminal end of the spinal cord, which is a long, thin, tubular structure made up of nervous tissue. The spinal cord itself is part of the central nervous system and extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column.

The conus medullaris is located at the level of the L1 or L2 vertebra in adults, but in infants, it is positioned at a lower level, around L3. This difference is due to the differential growth rates of the spinal cord and the vertebral column during development.

Function

The conus medullaris is responsible for transmitting neural signals between the brain and the lower parts of the body. It contains the lower segments of the spinal cord, which are involved in controlling the lower limbs and pelvic organs. The nerves that emerge from the conus medullaris form part of the cauda equina, a bundle of spinal nerves and spinal nerve rootlets.

Clinical Significance

The conus medullaris is clinically significant because it is a common site for certain types of spinal cord injuries and conditions. Damage to the conus medullaris can result in a condition known as conus medullaris syndrome, which is characterized by a combination of symptoms including lower back pain, bladder and bowel dysfunction, and lower limb weakness.

Conus medullaris syndrome can be caused by trauma, tumors, or infections that affect the lower spinal cord. It is important to differentiate this condition from cauda equina syndrome, which involves compression of the nerve roots below the conus medullaris.

Related pages

• Spinal cord
• Cauda equina
• Lumbar vertebrae
• Conus medullaris syndrome