Piriformis Syndrome
| Piriformis Syndrome | |
|---|---|
| Epidemiology | Unknown |
| Causes | Entrapment neuropathy |
| DDX | Lumbar radicular pain, lumbar somatic referred pain, sacroiliac joint pain. |
| Treatment | Physical therapy, injections, piriformis tenotomy |
Piriformis Syndrome is a controversial entity that describes extra-spinal entrapment neuropathy of the sciatic nerve by the piriformis muscle. The condition is also known as Deep Gluteal Syndrome, but some denote Piriformis Syndrome a subset of Deep Gluteal Syndrome. See Marin et al for a recent open source review [1]
Controversy
It is the opinion of the author and colleagues that this condition is over-diagnosed in New Zealand and that most cases of purported piriformis syndrome can be explained by either misreading MRI imaging (such as not recognising lateral recess stenosis) or by somatic referred pain from other structures such as a lumbar disc, lumbar facet joint, or sacroiliac joint. Complicating matters is that there is no gold standard for diagnosis and so different studies use different inclusion criteria. The research literature is dominated by case studies and review articles.
Epidemiology
The author has not found any reliable sources evaluating the prevalence of this condition in those with chronic low back pain or sciatica. A 1983 study by P Hallin is often quoted by review authors stating that piriformis syndrome accounts for between 6% to 8% of all sciatica cases.[2] However in the Hallin article there is no discussion or study of the prevalence whatsoever.[3]
Aetiology
The sciatic nerve typically passes immediately anterior to the piriformis muscle. Sciatic nerve entrapment may occur subsequent to buttock trauma or sprain of the piriformis muscle which is purported to cause perineural fibrosis. Another mechanism is through anatomical variation where the sciatic nerve branches pass through a bifid piriformis muscle. Both the piriformis muscle and sciatic nerve exit the pelvis through the greater sciatic notch. An accessory piriformis muscle can be implicated.
During downhill running or sprinting, the piriformis muscle undergoes eccentric contraction and some runners may develop the syndrome via this mechanism.
Clinical Manifestations
Buttock pain that increases with sitting is the most common presenting symptom. The "wallet sign" has been described which describes a male patient finding he cannot sit on his wallet without symptoms occurring. Classic radicular symptoms are not common, but paraesthesias may be reported.
Diagnosis
The Freiburg test is performed with placing the hip in extension and internal rotation, and then resisting external rotation. A positive test is the production of pain or radicular symptoms. It has questionable clinical value.
The Pace test has the patient in a seated position. The patient then resists abduction and external rotation. A positive test is the production of pain or typical symptoms. This test also is of questionable clinical value.
Endoscopic evaluation has been used for diagnosis.
Another diagnostic method is the injection of local anaesthetic into the piriformis muscle with a positive result being resultant pain reduction by a significant but arbitrary percentage.
Imaging
MRI and x-rays can help evaluate for other causes of symptoms. Often MRI of the piriformis muscle is normal, however an accessory piriformis muscle can be identified, and if there is relatively acute sprain or inflammation then there may be an increased T2 signal. Neurophysiology studies are not typically helpful. In one small study, ultrasound evaluation showing increased piriformis thickness was found to be helpful in diagnosis in those without lumbosacral radiculopathy on MRI.[4]
Treatment
Treatment options include physiotherapy, corticosteroid injections, botulinum toxin injections, and piriformis tenotomy.
Resources
See review by US physiotherapist here
References
- ↑ Martin et al.. Deep gluteal syndrome. Journal of hip preservation surgery 2015. 2:99-107. PMID: 27011826. DOI. Full Text.
- ↑ Probst et al.. Piriformis Syndrome: A Narrative Review of the Anatomy, Diagnosis, and Treatment. PM & R : the journal of injury, function, and rehabilitation 2019. 11 Suppl 1:S54-S63. PMID: 31102324. DOI.
- ↑ Hallin. Sciatic pain and the piriformis muscle. Postgraduate medicine 1983. 74:69-72. PMID: 6878094. DOI.
- ↑ Zhang et al.. Ultrasound appears to be a reliable technique for the diagnosis of piriformis syndrome. Muscle & nerve 2019. 59:411-416. PMID: 30663080. DOI. Full Text.
Literature Review
Literature Review
- Reviews from the last 7 years: review articles, free review articles, systematic reviews, meta-analyses, NCBI Bookshelf
- Articles from all years: PubMed search, Google Scholar search.
- TRIP Database: clinical publications about evidence-based medicine.
- Other Wikis: Radiopaedia, Wikipedia Search, Wikipedia I Feel Lucky, Orthobullets,
