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Cauda Equina and Conus Medullaris Syndromes


The spinal cord tapers and ends at the level between the first and second lumbar vertebrae in an average adult. The most distal bulbous part of the spinal cord is called the conus medullaris, and its tapering end continues as the filum terminale. Distal to this end of the spinal cord is a collection of nerve roots, which are horsetail-like in appearance and hence called the cauda equina (Latin for horse’s tail). (See the image of cauda equina anatomy below.)

Illustration demonstrating the relevant anatomy of

Illustration demonstrating the relevant anatomy of the cauda equina region

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See Back Pain: Find the Cause, Watch for the Comeback, a Critical Images slideshow, to help diagnose and manage this common problem.

These nerve roots constitute the anatomic connection between the central nervous system (CNS) and the peripheral nervous system (PNS). They are arranged anatomically according to the spinal segments from which they originated and are within the cerebrospinal fluid (CSF) in the subarachnoid space with the dural sac ending at the level of second sacral vertebra.

Cauda equina syndrome refers to a characteristic pattern of neuromuscular and urogenital symptoms resulting from the simultaneous compression of multiple lumbosacral nerve roots below the level of the conus medullaris (see the image below). These symptoms include low back pain, sciatica (unilateral or, usually, bilateral), saddle sensory disturbances, bladder and bowel dysfunction, and variable lower extremity motor and sensory loss (see Clinical).

Although the lesion is technically involves nerve roots and represents a “peripheral” nerve injury, damage may be irreversible and cauda equina syndrome may be a surgical emergency (see Treatment).

Illustration demonstrating an example of cauda equ

Illustration demonstrating an example of cauda equina syndrome secondary to a spinal neoplasm

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Lesions involving the termination of the spinal cord (conus medullaris) are not discussed in this article. Please see the article Spinal Cord Injuries.

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