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Caption = Nerves of the right lower extremity Posterior view.
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eMedicineTopic = 106
Piriformis syndrome is a
neuromusculardisorder that occurs when the sciatic nerveis compressedor otherwise irritated by the piriformis muscle. This causes pain, tingling and numbness in the buttocksand along the course of the sciatic nerve. The syndrome may result from anatomicalvariations in the muscle-nerve relationship, or from overuse or strain.
uncontrolled studiesadvanced theories behind the disorder. However, following a large scale formal prospective outcome trial using Class A studydesign as outlined by the American College of Physicians, the weight of the evidence-based medicine is that piriformis syndromeshould be considered as a possible diagnosiswhen sciaticaoccurs without a clear spinal cause cite journal |author=Filler AG, Haynes J, Jordan SE, "et al" |title=Sciatica of nondisc origin and piriformis syndrome: diagnosis by magnetic resonance neurography and interventional magnetic resonance imaging with outcome study of resulting treatment |journal=Journal of neurosurgery. Spine |volume=2 |issue=2 |pages=99–115 |year=2005 |pmid=15739520 |doi=] cite journal |author=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 |year=2006 |pmid=17030664 |doi=10.1001/archneur.63.10.1469]
The need for
controlled studiesis supported by studies of spinal disk diseasethat show a high frequency of abnormal disksin asymptomaticpatients.cite journal |author=Deyo RA, Weinstein JN |title=Low back pain |journal=N. Engl. J. Med. |volume=344 |issue=5 |pages=363–70 |year=2001 |pmid=11172169 |doi=10.1056/NEJM200102013440508] [cite web |url=http://content.nejm.org/cgi/content/full/344/5/363/T2 |title=NEJM -- Table 2 |accessdate=2007-11-16 |format= |work=] Pathophysiology
In 15% of the population the sciatic nerve passes through the
piriformis muscle, [ [http://www.geocities.com/akramjfr/sciatic_2_roots.html sciatic_2_roots ] ] rather than underneath it. These people have been reported by some studies to have a greater incidence of piriformis syndrome than does the general population. Some researchers discount the importance of this relationship in the etiologyof the syndrome.cite journal |author=Benzon HT, Katz JA, Benzon HA, Iqbal MS |title=Piriformis syndrome: anatomic considerations, a new injection technique, and a review of the literature |journal=Anesthesiology |volume=98 |issue=6 |pages=1442–8 |year=2003 |pmid=12766656 |doi=]
glutealmuscles also facilitate development of the syndrome. These are important in both hip extensionand in aiding the piriformisin external rotationof the femur. A major cause for inactive gluteals is unwanted reciprocal inhibitionfrom overactive hip flexors( psoas major, iliacus, and rectus femoris). This imbalance usually occurs where the hip flexors have been trained to be too short and tight, such as when someone sits with hips flexed, as in sitting all day at work. This deprives the glutealsof activation, and the synergiststo the gluteals ( hamstrings, adductor magnus, and piriformis) then have to perform extra roles they were not designed to do. Resulting hypertrophy of the piriformisthen produces the typical symptoms.
purportedcause for piriformis syndrome is stiffness, or hypomobility, of the sacroiliac joints. The resulting compensatorychanges in gaitwould then result in shearing of one of the origins of the piriformis, and possibly some of the gluteal muscles as well, resulting not only in piriformis malfunction but in other low back pain syndromes as well.
Piriformis syndrome can also be caused by overpronation of the foot. [cite web |url=http://www.coloradorunnermag.com/features/Issue1_Sciatica.html |title=Colorado Runner -- Feature Article |accessdate=2007-11-16 |format= |work=] When a foot overpronates it causes the
kneeto turn medially, causing the piriformisto activiate to prevent over-rotating the knee. This causes the piriformis to become overused and therefore tight, eventually leading to piriformis syndrome.
It is most frequently associated with falling injury.cite journal |author=Kuncewicz E, Gajewska E, Sobieska M, Samborski W |title=Piriformis muscle syndrome |journal=Annales Academiae Medicae Stetinensis |volume=52 |issue=3 |pages=99–101; discussion 101 |year=2006 |pmid=17385355 |doi=]
In addition to causing
glutealpain that may radiate down the leg, the syndrome may present with pain that is relieved by walking with the foot on the involved side pointing outward. This position externally rotates the hip, lessening the stretch on the piriformis and relieving the pain slightly. Piriformis syndrome is also known as "wallet sciatica" or "fat wallet syndrome," as the condition can be caused or aggravated by sitting with a large walletin the rear pocket. [ [http://iach.amedd.army.mil/sections/clinics/physicalTherapy/pdf/PIRIFORMIS%20SYNDROME.pdf Piriformis Syndrome (Hip/Buttocks Pain) ] ]
Piriformis syndrome is diagnosed by the presence of sciatica - radiating pain in the posterior thigh and lower leg - and the physical exam finding of tenderness in the area of the sciatic notch.
Magnetic resonance neurographyis a medical imaging technique that can show the presence of irritation of the sciatic nerve at the level of the sciatic notch where the nerve passes under the piriformis muscle. Neurography can also determine whether or not a patient has a split sciatic nerve or a split piriformis muscle - this may be important in getting a good result from injections or surgery. Image guided injections carried out in an Open MRI scanner can accurately relax the piriformis muscle to test the diagnosis. Other injection methods such as blind injection, flouroscopic guided injection, ultrasound, or EMG guidance can work but are not as reliable. Unlike spine injections, there is no bony target that can show up on X-ray, so fluoroscopy can't show the injection target. It has been difficult to achieve reliable injections with EMG and ultrasound because these methods are not specific to the piriformis muscle. CT guided injections can work well but provide a very high dose of radiation to the pelvis and there is no possibility of shielding sensitive tissues from the radiation.
Treatment usually begins with stretching exercises and massage, and avoidance of contributory activities, such as running and bicycling. Some clinicians recommend formal
physical therapy, including the teaching of stretching techniques, massage, and strengthening of the core muscles(abs, back, etc.) to reduce strain on the piriformis. Stretches exercises will target the piriformis, but may also include the hamstringsand hip muscles, in order to adequately reduce pain and increase range of motion.
Patients with piriformis syndrome may also find relief from ice and heat. Ice can be helpful when the pain starts, or immediately after an activity that causes pain. This may be simply an ice pack, or ice massage. Alternating heat and ice is often helpful.
Anti-inflammatorydrugs and/or corticosteroidinjections can be used. Rarely surgery may be recommended. The prognosisis generally good. Custom foot orthoticsalso help with both treatment and prevention. Gaitcorrection can reduce the use of the piriformis, allowing the muscle to relax and heal itself. Ultrasoundis another option, providing deeper heat than heat packs alone. Minimal access surgeryusing newly-reported techniques has also proven successful in a large-scale formal outcome published in 2005. [ [http://www.jnsonline.org/spine/issues/v2n2/toc.html JNS: Spine Table of Contents Menu ] ]
* [http://www.neurography.com/Images/Piriformis/Piriformis1.htm Piriformis syndrome] information including MRI scans at neurography.com
* [http://www.nervemed.com/nerve-piriformis.html Piriformis diagnosis] information on diagnosis and treatment at nervemed.com
* [http://www.sciatica.org/piriformis.html Treatment and Diagnoisis of Piriformis Syndrome] Medical Paper at sciatica.org
* [http://drpribut.com/sports/piriformis.html Piriformis Syndrome: Evaluation and Treatment in Athletes] at drpribut.co
* [http://www.sciatica.org/research.html Using Botox for treatment] at sciatica.org
* [http://sciatica-hurts.blogspot.com Piriformis syndrome blog] at blogger.com
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