Editing Sciatica (section)

=== Intraspinal sciatica ===
[[File:728 Herniated Disk.jpg|thumb|348x348px|Left: Illustration of herniated spinal disc, superior view. Right: MRI showing herniated L5-S1 disc (red arrow tip), sagittal view.]]
Intraspinal, or discogenic sciatica refers to sciatica whose pathology involves the spine. In 90% of sciatica cases, this can occur as a result of a spinal disc bulge or [[spinal disc herniation|herniation]].<ref name=":3" /><ref>{{cite journal |vauthors=((Siddiq MAB)), Clegg D, Hasan SA, Rasker JJ |date=October 2020 |title=Extra-spinal sciatica and sciatica mimics: a scoping review |url= |journal=Korean J Pain |volume=33 |issue=4 |pages=305–317 |doi=10.3344/kjp.2020.33.4.305 |pmc=7532296 |pmid=32989195}}</ref> Sciatica is generally caused by the compression of [[lumbar nerves]] L4 or L5 or [[sacral nerves|sacral nerve]] S1.<ref name=":4">{{Cite book|title=Practical Office Orthopedics|last=Parks|first=Edward|publisher=McGraw-Hill|year=2017|isbn=9781259642876|location=[New York, N.Y.]|pages=Chapter 6: Low Back Pain|oclc=986993775}}</ref> Less commonly, [[sacral nerves]] S2 or S3 may cause sciatica.<ref name=":4" />

Intervertebral spinal discs consist of an outer [[Anulus fibrosus disci intervertebralis|anulus fibrosus]] and an inner [[Intervertebral disc|nucleus pulposus]].<ref name=":3" /> The [[Anulus fibrosus disci intervertebralis|anulus fibrosus]] forms a rigid ring around the [[Intervertebral disc|nucleus pulposus]] early in human development, and the gelatinous contents of the nucleus pulposus are thus contained within the disc.<ref name=":3" /> Discs separate the spinal vertebrae, thereby increasing spinal stability and allowing nerve roots to properly exit through the spaces between the vertebrae from the spinal cord.<ref>{{Cite book|url=https://accessmedicine.mhmedical.com/book.aspx?bookID=980|title=Schwartz's Principles of Surgery|last=Halpern|first=Casey H.|publisher=McGraw-Hill|others=Grady, M. Sean|year=2015|isbn=9780071800921|edition=   Tenth |location=[New York]|pages=Chapter 42: Neurosurgery|oclc=892490454}}</ref> As an individual ages, the [[Anulus fibrosus disci intervertebralis|anulus fibrosus]] weakens and becomes less rigid, making it at greater risk for tear.<ref name=":3" /> When there is a tear in the [[Anulus fibrosus disci intervertebralis|anulus fibrosus]], the [[Intervertebral disc|nucleus pulposus]] may extrude through the tear and press against spinal nerves within the spinal cord, [[cauda equina]], or exiting [[nerve root]]s, causing inflammation, numbness, or excruciating pain.<ref name=":1">{{Cite book |editor-last=LeBlond |editor-first=Richard F. |editor2-last=Brown |editor2-first=Donald D. |editor3-last=Suneja |editor3-first=Manish |editor4-last=Szot |editor4-first=Joseph F. |year=2015 |chapter=Chapter 13: The Spine, Pelvis, and Extremities |title=DeGowin's Diagnostic Examination |url=https://accessmedicine.mhmedical.com/book.aspx?bookid=1192 |edition=Tenth |location=New York |publisher=McGraw-Hill Education |isbn=9780071814478 |oclc=876336892}}</ref> Inflammation of spinal tissue can then spread to adjacent facet joints and cause [[facet syndrome]], which is characterized by lower back pain and referred pain in the [[Posterior compartment of thigh|posterior thigh]].<ref name=":3" />

Other causes of sciatica secondary to spinal nerve entrapment include the roughening, enlarging, or misalignment (''[[spondylolisthesis]]'') of [[vertebra]]e, or [[degenerative disc disease|disc degeneration]] that reduces the diameter of the lateral foramen through which nerve roots exit the spine.<ref name=":3" /> When sciatica is caused by compression of a [[dorsal nerve root]], it is considered a lumbar [[radiculopathy]] or [[radiculitis]] when accompanied by an inflammatory response.<ref name=":2" />