Editing Sciatica (section)

==Causes==
===Risk factors===
Modifiable risk factors for sciatica include [[smoking]], [[obesity]], occupation,<ref name=Cook2014 /> and physical sports where back muscles and heavy weights are involved. Non-modifiable risk factors include increasing age, being male, and having a personal history of [[low back pain]].<ref name=Cook2014 />

===Spinal disc herniation===
{{main|Spinal disc herniation}}
[[Spinal disc herniation]] pressing on one of the [[lumbar nerve|lumbar]] or [[sacral nerve]] roots is the most frequent cause of sciatica, being present in about 90% of cases.<ref name=Valat2010/> This is particularly true in those under age 50.<ref name=tarulli_radiculopathy>{{cite journal | vauthors = Tarulli AW, Raynor EM | title = Lumbosacral radiculopathy | journal = Neurologic Clinics | volume = 25 | issue = 2 | pages = 387–405 | date = May 2007 | pmid =  17445735 | doi = 10.1016/j.ncl.2007.01.008 | s2cid = 15518713 | url = http://pdfs.semanticscholar.org/27a9/f13596f9bc2fdb873eb83302d14aaa176381.pdf | archive-url = https://web.archive.org/web/20190220113056/http://pdfs.semanticscholar.org/27a9/f13596f9bc2fdb873eb83302d14aaa176381.pdf | url-status = dead | archive-date = 2019-02-20 }}</ref> Disc herniation most often occurs during heavy lifting.<ref name=":3">{{Cite book|url=https://accessmedicine.mhmedical.com/book.aspx?bookID=564|title=Morgan & Mikhail's Clinical Anesthesiology|last=Butterworth IV|first=John F.|date=2013|publisher=McGraw-Hill|others=David C. Mackey, John D. Wasnick|isbn=9780071627030|edition=   5th.|location=New York|pages=Chapter 47. Chronic Pain Management|oclc=829055521}}</ref> Pain typically increases when bending forward or sitting, and reduces when lying down or walking.<ref name=tarulli_radiculopathy/>

===Spinal stenosis===
{{main|Lumbar spinal stenosis}}
Other compressive spinal causes include [[lumbar spinal stenosis]], a condition in which the [[spinal canal]], the space the spinal cord runs through, narrows and compresses the spinal cord, [[cauda equina]], or sciatic nerve roots.<ref name=":2" /> This narrowing can be caused by [[Exostosis|bone spurs]], [[spondylolisthesis]], [[inflammation]], or a [[herniated disc]], which decreases available space for the spinal cord, thus pinching and irritating nerves from the spinal cord that become the sciatic nerve.<ref name=":2" /> This is the most frequent cause after age 50.<ref name=tarulli_radiculopathy/> Sciatic pain due to spinal stenosis is most commonly brought on by standing, walking, or sitting for extended periods of time, and reduces when bending forward.<ref name=tarulli_radiculopathy/><ref name=":2" /> However, pain can arise with any position or activity in severe cases.<ref name=":2" /> The pain is most commonly relieved by rest.<ref name=":2" />

===Piriformis syndrome===
{{main|Piriformis syndrome}}
Piriformis syndrome is a condition that, depending on the analysis, varies from a "very rare" cause to contributing up to 8% of low back or buttock pain.<ref name=Miller2012>{{cite journal |vauthors=Miller TA, White KP, Ross DC |title=The diagnosis and management of Piriformis Syndrome: myths and facts |journal=Can J Neurol Sci |volume=39 |issue=5 |pages=577–83 |date=September 2012 |pmid=22931697 |doi= 10.1017/s0317167100015298|doi-access=free }}</ref> In 17% of people, the sciatic nerve runs through the [[piriformis muscle]] rather than beneath it.<ref name=":2" /> When the piriformis shortens or spasms due to trauma or overuse, it is posited that this causes compression of the sciatic nerve.<ref name=Miller2012/> Piriformis syndrome has colloquially been referred to as "wallet sciatica" since a [[wallets|wallet]] carried in a rear hip pocket compresses the buttock muscles and sciatic nerve when the bearer sits down. Piriformis syndrome may be suspected as a cause of sciatica when the spinal nerve roots contributing to the sciatic nerve are normal and no herniation of a spinal disc is apparent.<ref name="pmid19466717">{{cite journal | vauthors = Kirschner JS, Foye PM, Cole JL | title = Piriformis syndrome, diagnosis and treatment | journal = Muscle Nerve | volume = 40 | issue = 1 | pages = 10–18 | date = July 2009 | pmid = 19466717 | doi = 10.1002/mus.21318 | s2cid = 19857216 }}</ref><ref name="pmid17030664">{{cite journal | vauthors = Lewis AM, Layzer R, Engstrom JW, Barbaro NM, Chin CT | title = Magnetic resonance neurography in extraspinal sciatica | journal = Arch. Neurol. | volume = 63 | issue = 10 | pages = 1469–72 | date = October 2006 | pmid = 17030664 | doi = 10.1001/archneur.63.10.1469 | s2cid = 6634301 | doi-access =  }}</ref>

=== Deep gluteal syndrome ===
{{Main|Deep gluteal syndrome}}
Deep gluteal syndrome is non-discogenic, extrapelvic sciatic [[Nerve compression syndrome|nerve entrapment]] in the deep gluteal space.<ref name=":5" /> Piriformis syndrome was once the traditional model of sciatic nerve entrapment in this anatomic region. The understanding of non-discogenic sciatic nerve entrapment has changed significantly with improved knowledge of posterior hip anatomy, nerve kinematics, and advances in [[Endoscopy|endoscopic]] techniques to explore the sciatic nerve.<ref name=":6" /><ref name=":7">{{cite journal |vauthors=Hernando MF, Cerezal L, Pérez-Carro L, Abascal F, Canga A |date=July 2015 |title=Deep gluteal syndrome: anatomy, imaging, and management of sciatic nerve entrapments in the subgluteal space |url= |journal=Skeletal Radiol |volume=44 |issue=7 |pages=919–34 |doi=10.1007/s00256-015-2124-6 |pmid=25739706}}</ref> There are now many known causes of sciatic nerve entrapment, such as fibrous bands restricting nerve mobility, that are unrelated to the piriformis in the deep gluteal space. Deep gluteal syndrome was created as an improved classification for the many distinct causes of sciatic nerve entrapment in this anatomic region.<ref name=":7" /> Piriformis syndrome is now considered one of many causes of deep gluteal syndrome.<ref name=":6" />

===Endometriosis===
Sciatic [[endometriosis]], also called catamenial or cyclical sciatica, is a sciatica whose cause is endometriosis. Its incidence is unknown. Diagnosis is usually made by an [[Magnetic resonance imaging|MRI]] or CT-[[myelography]].<ref name="Gandhi Wilson Liang Weissbart pp. 3–9">{{cite journal | last1=Gandhi | first1=Jason | last2=Wilson | first2=Anthony L | last3=Liang | first3=Raymond | last4=Weissbart | first4=Steven J | last5=Khan | first5=Sardar Ali | title=Sciatic endometriosis: A narrative review of an unusual neurogynecologic condition | journal=Journal of Endometriosis and Pelvic Pain Disorders | publisher=SAGE Publications | volume=13 | issue=1 | date=2020-11-11 | issn=2284-0265 | doi=10.1177/2284026520970813 | pages=3–9| s2cid=228834273 }}</ref>

===Pregnancy===
Sciatica may also occur during pregnancy, especially during later stages, as a result of the weight of the [[fetus]] pressing on the sciatic nerve during sitting or during leg spasms.<ref name=":2" /> While most cases do not directly harm the woman or the fetus, indirect harm may come from the numbing effect on the legs, which can cause loss of balance and falls. There is no standard treatment for pregnancy-induced sciatica.<ref>[http://americanpregnancy.org/pregnancy-health/sciatic-nerve-pain-during-pregnancy/ Sciatic Nerve Pain During Pregnancy: Causes and Treatment]. American Pregnancy Association. Published September 20, 2017. Accessed November 12, 2018.</ref>

===Other===
Pain that does not improve when lying down suggests a nonmechanical cause, such as [[cancer]], [[inflammation]], or [[infection]].<ref name=tarulli_radiculopathy/> Sciatica can be caused by [[tumors]] impinging on the spinal cord or the nerve roots.<ref name=Valat2010/> Severe back pain extending to the hips and feet, loss of bladder or bowel control, or muscle weakness may result from [[spinal tumor]]s or [[cauda equina syndrome]].<ref name=":2" /> Trauma to the spine, such as from a car accident or hard fall onto the heel or buttocks, may also lead to sciatica.<ref name=":2" /> A relationship has been proposed with a latent ''[[Cutibacterium acnes]]'' infection in the intervertebral discs, but the role it plays is not yet clear.<ref name=GankoRao2015>{{cite journal | vauthors = Ganko R, Rao PJ, Phan K, Mobbs RJ | title = Can bacterial infection by low virulent organisms be a plausible cause for symptomatic disc degeneration? A systematic review | journal = Spine | volume = 40 | issue = 10 | pages = E587–92 | date = May 2015 | pmid = 25955094 | doi = 10.1097/BRS.0000000000000832 | s2cid = 23436352 }}</ref><ref name=ChenZhou2016>{{cite journal| vauthors=Chen Z, Cao P, Zhou Z, Yuan Y, Jiao Y, Zheng Y| title=Overview: the role of Propionibacterium acnes in nonpyogenic intervertebral discs. | journal=Int Orthop | year= 2016 | volume= 40 | issue= 6 | pages= 1291–8 | pmid=26820744 | doi=10.1007/s00264-016-3115-5 | s2cid=889041 | type=Review }}</ref>