Piriformis syndrome--an attempt to understand its pathology.

Objective: Gross anatomy of the hip rotators and histology of the sciatic nerves in adult cadavers were studied, aiming to the identification of possible pathologic changes related to the piriformis syndrome (PS).

Material: 50 cadavers were dissected; in 17 cases with macroscopical findings the sciatic nerves were harvested (34 sciatic nerves; 17 cadavers). History of low back or leg pain was not available.

Method: Site anatomy and additional findings at the harvesting sites were recorded, such as anatomical variations, adhesions, hematomas etc. All nerves were additionally microscopically analyzed. In cases with findings at the dissection, the contralateral unaffected nerves served as controls. All the dissected nerves were conserved in 10% formalin solution, embedded in paraffin, stained with Hematoxylin and Eosin (H&E) and immunolabeled with antibodies against Neurofilament (NF).

Results: Both the H&E staining as well as the performed immunohistochemistry showed, to a variable degree, significant alterations in the structure of the affected nerves compared to the controls.

Conclusions: These findings both in the local anatomy and sciatic nerve correspond to lesions that are expected in PS. Nevertheless, since this was a cadaveric study, unassociated to a certain pain patient's history, results should be considered and interpreted as an indication of a sciatic nerve injury in PS.