What is the role of imaging studies in the workup of piriformis syndrome?

Updated: Sep 16, 2020
  • Author: Milton J Klein, DO, MBA; Chief Editor: Ryan O Stephenson, DO  more...
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Answer

Diagnostic imaging of the lumbar spine may be helpful in excluding associated diskogenic and/or osteoarthritic contributing pathology should conservative treatment of clinically diagnosed piriformis syndrome fail to provide therapeutic benefit.

Reports in the literature on the piriformis muscle describe imaging by nuclear diagnostic studies and MRI of the pelvis, [16] but these tests are neither practical nor reliable approaches to the diagnosis of piriformis syndrome. The history and clinical diagnostic examination provide the greatest and most specific diagnostic yield for the disorder.

Magnetic resonance neurography

Magnetic resonance neurography is a newer, sensitive imaging technique that increases nerve conspicuity by suppressing the signal from adjacent soft tissue, including fat, bone, and muscle. [17] The nerve itself contains minimal fat, and its signal is unsuppressed. According to Filler and colleagues, MR neurography demonstrated piriformis muscle asymmetry and sciatic nerve hyperintensity at the sciatic notch with 93% specificity. [18] The investigators also found that the technique had a sensitivity of 64% with regard to distinguishing patients with piriformis syndrome from persons who, despite having similar symptoms, did not have the condition (p< 0.01).

Ultrasonography

Diagnostic ultrasonographic imaging of the piriformis muscle for the assessment of muscle morphology has demonstrated a significant correlation of piriformis muscle morphology abnormality, especially in patients with lumbosacral/buttock pain and pain ascending stairs, referred pain to the posterior thigh on the symptomatic side, and reproduction of pain with needling of the piriformis muscle.


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