Which spinal cord anatomical features are useful in understanding cauda equina and conus medullaris syndrome?

Updated: Jun 14, 2018
  • Author: Segun Toyin Dawodu, JD, MD, MS, MBA, LLM, FAAPMR, FAANEM; Chief Editor: Nicholas Lorenzo, MD, CPE, MHCM, FAAPL  more...
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The spinal cord, which is the downward continuation of medulla that starts just below the foramen magnum, serves as a conduit for the ascending and descending fiber tracts that connect the peripheral and spinal nerves to the brain. The cord projects 31 pairs of spinal nerves on either side (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal) that are connected to the peripheral nerves.

A cross-section of the spinal cord reveals butterfly-shaped gray matter in the middle, surrounded by white matter. As in the cerebrum, the gray matter is composed of cell bodies. The white matter consists of various ascending and descending tracts of myelinated axon fibers, each with specific functions.

During development, the vertebral column grows more rapidly than the spinal cord. Spinal nerves exit the vertebral column at progressively more oblique angles because of the increasing distance between the spinal cord segments and the corresponding vertebrae. Lumbar and sacral nerves travel nearly vertically down the spinal canal to reach their exiting foramen.

The spinal cord ends at the intervertebral disc between the first and second lumbar vertebrae as a tapered structure called the conus medullaris, consisting of sacral spinal cord segments. The upper border of the conus medullaris is often not well defined. The fibrous extension of the cord, the filum terminale, is a nonneural element that extends down to the coccyx.

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