View source for Cauda equina

{{Short description|Anatomical structure}}
{{More citations needed|date=January 2020}}
{{Infobox anatomy
| Name        = Cauda equina 
| Latin       = cauda equina
| Image       = Gray662.png
| Caption     = Cauda equina and [[filum terminale]] seen from behind.
| Image2      = Human caudal spinal chord anterior view description.JPG
| Caption2    = Human caudal spinal cord anterior view
| Width       = 200
| Precursor   =
| System      =

| Artery      = [[Iliolumbar artery]]
| Vein        =
| Nerve       =
| Lymph       =
}}
The '''cauda equina''' ({{ety|la|[[Tail (horse)|tail of horse]]}}) 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 enlargement]] and the [[conus medullaris]] of the [[spinal cord]]. The cauda equina occupies the [[Subarachnoid_cisterns#Cisterns|lumbar cistern]], a [[subarachnoid]] space inferior to the [[conus medullaris]]. The [[Nerve|nerves]] that compose the cauda equina innervate the [[Pelvic cavity|pelvic organ]]s and [[human leg|lower limbs]] to include [[motor innervation]] of the [[hip]]s, [[knee]]s, [[ankle]]s, [[foot|feet]], [[Sphincter ani internus muscle|internal anal sphincter]] and [[Sphincter ani externus muscle|external anal sphincter]]. In addition, the cauda equina extends to [[sensory innervation]] of the [[perineum]] and, partially, [[parasympathetic]] [[innervation]] of the [[bladder]].<ref>{{cite web|url= http://www.medschool.lsuhsc.edu/search/default.aspx?cx=012989503401987579181:dorjvt5fw4i&cof=FORID:10&ie=UTF-8&q=cauda+equina|title=LSUHSC School of Medicine - Search Results|website=www.medschool.lsuhsc.edu}}</ref>

==Structure==
In [[adulthood]], the cauda equina is made of [[Vertebral column|lumbosacral]] [[Spinal nerve root|spinal nerve roots]].<ref name=":0">{{Citation|last=Lavyne|first=M. H.|title=Cauda Equina|date=2014-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780123851574011283|encyclopedia=Encyclopedia of the Neurological Sciences (Second Edition)|pages=613|editor-last=Aminoff|editor-first=Michael J.|place=Oxford|publisher=Academic Press|language=en|isbn=978-0-12-385158-1|access-date=2021-01-06|editor2-last=Daroff|editor2-first=Robert B.}}</ref>

===Development===
In [[Human|humans]], the [[spinal cord]] stops growing in [[Infant|infancy]].  At birth the end of the spinal cord is about the level of the third [[lumbar vertebrae|lumbar vertebra]], or L3. Because the [[Bone|bones]] of the [[vertebral column]] continue to grow, by about 12 months of age the end of the cord reaches its permanent position. Typically this is at the level of L1 or L2 (closer to the head),<ref name=":0" /> ranging due to normal [[anatomical]] variations anywhere from the twelfth [[thoracic vertebrae|thoracic vertebra]] (T12) to L3. Individual [[Spinal nerve root|spinal nerve roots]] arise from the cord as they get closer to the head, but as the differential growth occurs, the top end of the nerve stays attached to the spinal cord while the lower end of the nerve exits the [[spinal column]] at its proper level. This results in a "bundle"-like structure of [[nerve fibers]] that extends [[caudally]], within the spinal column, from the end of the spinal cord, gradually declining in number further down as individual pairs leave the spinal column.<ref name=":0" />

==Clinical significance==

=== Needle insertion ===
The cauda equina exists within the [[cistern (neuroanatomy)|lumbar cistern]], a gap between the [[arachnoid membrane]] and the [[pia mater]] of the spinal cord, called the [[subarachnoid space]]. [[Cerebrospinal fluid]] also exists within this space. Because the spinal cord terminates at level L1/L2, [[lumbar puncture]] (or colloquially, "[[Spinal tap (medical procedure)|spinal tap]]") is performed from the [[lumbar cistern]] between two [[Vertebra|vertebrae]] at level L3/L4, or L4/L5, where there is no risk of accidental injury to the spinal cord, when a sample of CSF is needed for clinical purposes.

=== Cauda equina syndrome ===
[[Cauda equina syndrome]], a rare disorder affecting the bundle of nerve roots (cauda equina) at the lower (lumbar) end of the spinal cord, is a surgical emergency.<ref name="aaos.org">{{cite web|url=http://orthoinfo.aaos.org/topic.cfm?topic=a00362|title=Cauda Equina Syndrome-OrthoInfo - AAOS|website=orthoinfo.aaos.org}}</ref> Cauda equina syndrome occurs when the [[Nerve root|nerve roots]] in the lumbar spine are compressed, disrupting sensation and movement.<ref name="aans.org">{{cite web |title=Cauda Equina Syndrome – Symptoms, Causes, Diagnosis and Treatments |url=https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Cauda-Equina-Syndrome |website=www.aans.org |publisher=American Association of Neurological Surgeons |access-date=28 August 2020 |language=en}}</ref> Nerve roots that control the function of the [[bladder]] and [[bowel]] are especially vulnerable to damage. It can lead to permanent [[paralysis]], impaired bladder and/or bowel control, loss of [[sexual sensation]], and other problems if left untreated. Even with immediate treatment, some patients may not recover complete function.<ref name="aaos.org"/>

Cauda equina syndrome most commonly results from a massive [[disc herniation]] in the lumbar region.<ref>{{cite web|url= http://www.columbianeurosurgery.org/conditions/cauda-equina-syndrome/|title=Cauda Equina Syndrome – The Spine Hospital at The Neurological Institute of New York|date=29 April 2021}}</ref> A disc herniation occurs when one of the soft flexible discs that functions as an elastic shock absorber between the bones of the spinal column displaces from its normal position. The herniation occurs after the disc begins to break down with [[Ageing|aging]] and can be precipitated by stress or a mechanical problem in the spine. The result is that the softer, center portion of the disc pushes out and causes pressure on the nerve roots in the lumbar spine. Other causes include spinal [[Lesion|lesions]] and [[tumors]], spinal infections or [[inflammation]], [[lumbar spinal stenosis]], trauma to the lower back, birth abnormalities, spinal arteriovenous malformations (AVMs), spinal hemorrhages ([[subarachnoid]], subdural, epidural), narrowing of the [[spinal canal]], [[postoperative]] lumbar spine surgery complications or [[Spinal anaesthesia|spinal anesthesia]].<ref name="aans.org"/> Cauda equina syndrome can often be mistaken for conditions such as [[spinal stenosis]], [[Herniated disc|herniated discs]] and [[nerve root]] compression.<ref>{{cite web|url= https://www.caudaequina.co.uk/|title=Cauda Equina Syndrome|website=caudaequina.co.uk}}</ref>

=== Radiculopathy ===
The cauda equina is vulnerable to being compressed, causing a [[radiculopathy]].<ref name=":0" />

==History==
The cauda equina was named after its resemblance to a horse's tail ({{langx|la|cauda equina}}) by the [[French language|French]] [[anatomist]] Andreas Lazarus ([[André du Laurens]]) in the 17th century.

==See also==
{{Anatomy-terms}}
* [[Spinal cord]]
* [[Cauda equina syndrome]]
* [[Conus medullaris]]

==References==
{{Reflist}}
* Saladin, Kenneth S. Anatomy and Physiology The Unity of Form and Function
* Smith's Anesthesia for infants and children. 8th edition, Chapter 1, Page 8.

==External links==
* {{MedlinePlusImage|19504}}
* {{SUNYAnatomyLabs|02|08|01|06}}
* {{ViennaCrossSection|pembody/body12a}}
* [http://anatomyguy.com/deep-back-and-spinal-cord-review/ Dissection of deep back and spinal cord video: great view of the Cauda Equina]
* https://web.archive.org/web/20170617012537/http://www.caudaequinauk.com/welcome.php - Cauda Equina Syndrome UK Charity social network

{{Spinal cord}}
{{Authority control}}

[[Category:Spinal nerves| Cauda equina]]
[[Category:Bones of the vertebral column]]