I read with great interest the article by Michel et al. and letter by Palamar et al. on piriformis muscle syndrome (PMS). The authors have clearly discussed the diagnostic and treatment approaches of this rarely seen syndrome.

The authors discuss proximal nerve conduction (H-reflex), a simple, non-invasive and supportive technique for the differential diagnosis of PMS. Recently, H-reflex of the peroneal nerve was considered a more specific sign for the diagnosis of PMS . Comparing the H-reflex latency between the hip in the neutral position and the flexion, adduction, internal rotation (FAIR) position is suggested for the differential diagnosis of PMS . The FAIR manoeuvre is defined as moving the patient’s leg passively into flexion (90°), adduction, and internal rotation. A positive test result occurs when pain is produced in the sciatic or gluteal region. The FAIR test coupled with injection and physical therapy is an effective tool to diagnose and treat PMS .

Michel et al. show a delay in the proximal nerve conduction (H-reflex) on the pathological side as compared with the healthy side in the neutral position in PMS patients. An additional delay was also obtained with the FAIR manoeuvre on the pathologic side as compared with the healthy side. The delay measured by the FAIR manoeuvre seemed a reasonable result for PMS, but the delay in the neutral position was an unexpected finding. As is known, lumbar radiculopathy and PMS may coexist as “double crush” syndrome: after nerve entrapment at any side, the nerve actually becomes more prone to irritation at other sites, which leads to double entrapment of a nerve, called double crush syndrome . Could the delay in the neutral position Michel et al. found be a sign of double crush syndrome in PMS with lumbar radicular compression?

The authors reported that electromyography findings were normal in PMS patients, which indicated the absence of L5 and S1 neurologic signs. Perhaps because the delay in the neutral position was mild, they considered it normal, but it could be a sign of accompanying mild radicular compression. In cases of no response to therapy, a possible double crush syndrome of PMS with mild radiculopathy should be kept in mind.