Anatomical, clinical and electrical observations in piriformis syndrome

Abstract

Background: We provided clinical and electrical descriptions of the piriformis syndrome, contributing to better understanding of the pathogenesis and further diagnostic criteria.

Methods: Between 3550 patients complaining of sciatica, we concluded 26 cases of piriformis syndrome, 15 females, 11 males, mean age 35.37 year-old. We operated 9 patients, 2 to 19 years after the onset of symptoms, 5 had piriformis steroids injection. A dorsolumbar MRI were performed in all cases and a pelvic MRI in 7 patients. The electro-diagnostic test was performed in 13 cases, between them the H reflex of the peroneal nerve was tested 7 times.

Results: After a followup 1 to 11 years, for the 17 non operated patients, 3 patients responded to conservative treatment. 6 of the operated had an excellent result, 2 residual minor pain and one failed. 3 new anatomical observations were described with atypical compression of the sciatic nerve by the piriformis muscle.

Conclusion: While the H reflex test of the tibial nerve did not give common satisfaction in the literature for diagnosis, the H reflex of the peroneal nerve should be given more importance, because it demonstrated in our study more specific sign, with six clinical criteria it contributed to improve the method of diagnosis. The cause of this particular syndrome does not only depend on the relation sciatic nerve-piriformis muscle, but the environmental conditions should be considered with the series of the anatomical anomalies to explain the real cause of this pain.

Figure 1

Electro-diagnostic test of a 22 year-old female patient complaining of right sided piriformis muscle syndrome since 6 years. (A-1) The H reflex of the tibial nerve, the leg in a straight position, was normal, (A-2) showed slight disturbance of the H wave, during the stress maneuver of flexion and internal rotation of the lower limb. (B-1) the H-reflex of the common peroneal nerve, the leg in a straight position, was normal, (B-2) noted the complete extinction of the H wave, during the painful maneuver of forced adduction-internal rotation, (B-3) the H reflex reappeared when the leg was returned in the relieved straight position.

Figure 2

A 23-year-old female complaining of right sided piriformis muscle syndrome since 4 years. We noted intraoperatively a bifid sciatic nerve passing under the hypertrophied piriformis muscle.

Figure 3

32-year-old female complaining of left sided piriformis muscle syndrome since 7 years. We noted intraoperatively a bifid piriformis muscle and a bifid sciatic nerve, one branch of the nerve passing proximal to the muscle and the other one through the split

Figure 4

A 65-year-old female complaining of right sided piriformis muscle syndrome since 19 years. Note the impingement of the sciatic nerve in contact with the sacrospinous ligament.

Figure 5

A 58-year-old male complaining of left sided piriformis muscle syndrome since 3 years. Note the transverse fibrous band squeezing the sciatic nerve.