Is it painful to be different? Sciatic nerve anatomical variants on MRI and their relationship to piriformis syndrome
To investigate the purported relationship between sciatic nerve variant anatomy and piriformis syndrome.
Over 49 months, 1039 consecutive noncontrast adult hip MRIs were completed for various clinical indications. Repeat and technically insufficient studies were excluded. Radiologists categorized sciatic nerve anatomy into Beaton and Anson anatomical types. Chart review using our institution’s cohort search and navigation tool determined the prevalence of the explicit clinical diagnosis of piriformis syndrome (primary endpoint) and sciatica and buttock pain (secondary endpoints). A Z-test compared the prevalence of each diagnosis in the variant anatomy and normal groups.
Seven hundred eighty-three studies were included, with sciatic nerve variants present in 150 hips (19.2%). None of the diagnoses had a statistically significant difference in prevalence between the variant and normal hip groups. Specifically, piriformis syndrome was present in 11.3% of variant hips compared with 9.0% of normal hips (p = 0.39).
There were no significant differences in the prevalence of piriformis syndrome, buttock pain, or sciatica between normal and variant sciatic nerve anatomy. This large-scale correlative radiologic study into the relationship between sciatic nerve variants and piriformis syndrome calls into question this purported relationship.
• Large retrospective study relating variant sciatic nerve anatomy, present in 19.2% of hip MRIs, and piriformis syndrome
• While sciatic nerve variant anatomy has previously been implicated in piriformis syndrome in small studies, no relationship was identified between sciatic nerve variants and piriformis syndrome
KeywordsPiriformis muscle syndrome Sciatic neuropathy Magnetic resonance imaging Cross-sectional anatomy Peripheral nerves
The authors greatly appreciate the original anatomy sketch provided by Amy N. Thomas.
Early preliminary data from this study were presented as a poster by Dr. Bartret at RSNA 2016.
The authors state that this work has not received any funding.
Compliance with ethical standards
The scientific guarantors of this publication are Adam Bartret and Amelie Lutz.
Conflict of interest
The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.
Statistics and biometry
No complex statistical methods were necessary for this paper.
Written informed consent was waived by the Institutional Review Board.
Institutional Review Board approval was obtained.
Study subjects or cohorts overlap
Part of the MR imaging findings of approximately 250 subjects of this cohort (without symptom correlation) have been previously reported in:
Varenika V, Lutz AM, Beaulieu CF, Bucknor MD. Detection and prevalence of variant sciatic nerve anatomy in relation to the piriformis muscle on MRI. Skeletal Radiol 2017;46:751–757.
• performed at one institution
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