How is piriformis syndrome classified?

Updated: Sep 16, 2020
  • Author: Milton J Klein, DO, MBA; Chief Editor: Ryan O Stephenson, DO  more...
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Papadopoulos and colleagues proposed the following classifications for piriformis syndrome [13] :

  • Primary piriformis syndrome - This designation would apply to piriformis syndrome resulting from intrinsic pathology of the piriformis muscle itself, such as myofascial pain, anatomic variations, and myositis ossificans.

  • Secondary piriformis syndrome (pelvic outlet syndrome) - This classification would encompass all other etiologies of piriformis syndrome, with the exclusion of lumbar spinal pathology.

In an imaging study of 74 patients who demonstrated pathologies associated with piriformis syndrome, Vassalou et al found a greater incidence of secondary causes than primary etiologies, with the condition most often caused by space-occupying lesions in the piriformis area. The study, which employed magnetic resonance imaging (MRI) and/or computed tomography (CT) scanning, reported the most frequent imaging finding to be piriformis muscle enlargement. [14]

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