We read with interest the correspondence by Palamar et al. regarding our previously published study. We are grateful for the proposed discussion. The authors raise interesting challenges with regard to our daily practice. We would like to comment on the points mentioned.

Piriformis muscle syndrome (PMS) is probably an underestimated entity . The main difficulty in establishing diagnosis is the lack of a gold standard. We aimed to develop a clinical score to select patients and then propose oriented therapeutic management. In many publications , this specific oriented management consists in performing a therapeutic test to confirm the diagnosis.

By definition, this probable entrapment neuropathy associates a classical range of symptoms corresponding to truncal sciatica with frequently fluctuating pain, initially in the muscles of the buttocks. In our work , to respect this definition, we favoured the existence of distal fluctuating and positional symptoms. In this context, the nosology of PMS should be clarified to include buttock pain associated with irradiation in the territory of the posterior thigh nerve. These clinical symptoms prompted us to consider compression at the infra-piriformis foramen. Therefore, PMS must be distinguished from isolated buttock pain, in which the piriformis muscle can sometimes be incriminated, but the pathophysiologic features differ. Furthermore, many spinal or hip pathologies can cause pain around the piriformis muscle.

In this context, a diagnostic test with anesthetics delivered to the piriformis muscle is of interest to identify the muscle responsible for the buttock pain . However, this test does not allow for evaluating the sciatica, for which the main differential diagnosis remains its disco-radicular origin. An anesthetic test at the infrapiriform foramen does not allow for identifying the precise origin of the nerve root compression or the sciatic nerve itself.

Topographic features are important for identifying the piriformis muscle. Inserted proximally on the ventral side of the sacrum, the fibers travel into the gluteal area and pass into the large sciatic notch to fit into the posterior part of the greater trochanter. Thus, for clinical identification, the patient is placed in the lateral decubitus position on the side contralateral to pain. The knee is placed with the painful side down and flat on the table, with the foot hooked behind the contralateral leg. We then draw a triangle whose base comprises the line joining the posterior superior iliac spine (PSIS) and the top of the inter-gluteal fold. The apex of this triangle is represented by the posterior edge of the greater trochanter. The piriformis muscle is projected on the line joining the middle of the PSIS segment–the top of the inter-gluteal fold to the greater trochanter. We usually inject botulinum toxin into a proximal site and a distal site. Electromyography is used to detect “spontaneous” electrical activity of this muscle and activity, by asking the patient to perform an active lateral rotation (lifting the knee off the exam table) . In recent years, we have coupled this electrical identification with ultrasound guidance, to associate additional morphological data with functional identification. The combination of these two technologies is inexpensive, does not involve radiation and is easy to implement.

In addition to the anatomical variants advanced by some authors to discuss the indication for surgery , most authors retain the abnormal contracture of the piriformis muscle, although sometimes without finding any specific risk factor. Thus, botulinum toxin (shown to decrease muscle hyperactivity) seems to be the ideal product to decrease this state of contracture . The main objective is to influence the compression of the sciatic nerve by muscle relaxation. In addition, the effect of the toxin indirectly generates partial and secondary atrophy of the piriformis muscle, especially if injections are repeated. We have demonstrated this process in further work .

The toxin has satisfactory muscle-relaxant action on the piriformis muscle. Changing the volume of the piriformis muscle and indirectly optimizing the ratio of content to container at the infra-piriformis foramen remains an attractive therapeutic option. All patients were monitored and evaluated in terms of muscle strength on the gluteal lateral rotator muscles, and no deficit was observed.

The first 10 patients we recruited received a cortisone injection. The benefit was not consistent and never observed beyond day 10. Therefore, we proposed to use botulinum toxin for management. The superiority of botulinum toxin was confirmed in various publications . Although the effect was sometimes equivalent, a significant superiority of corticosteroids associated with an anesthetic over botulinum toxin has never been reported.