Comment on “Piriformis muscle syndrome: Diagnostic criteria and treatment of a monocentric series of 250 patients” by F. Michel et al. Ann Phys Rehabil Med 2013;56:371–83

Dear Editor: we read with interest the article in this journal by Michel et al. . The authors aimed to devise a clinical assessment score for diagnosis of piriformis muscle syndrome (PMS) . They used a range of tests to produce a diagnostic score for PMS; however, to confirm the diagnosis, no diagnostic test such as local piriformis muscle (PM) injection was used. The diagnosis of PMS is difficult on clinical grounds alone and often difficult to treat. However, local injection of an anesthetic and corticosteroids into the PM to relieve pain may also reconfirm the diagnosis in terms of therapeutic success . The marked and almost immediate relief of pain produced by infiltration of the PM is considered a diagnostic aid for PMS . Therefore, PMS should be diagnosed on the basis of clinical symptoms, specific physical examinations, and positive response to local injection.

Older injection techniques were done blindly , whereas currently, nerve stimulation, electromyography (EMG), fluoroscopy, CT, MRI and ultrasonography are used to guide the PM injection . Michel et al. identified the PM by EMG. The confirmatory techniques the authors used may not be considered highly accurate for positioning, because nearby muscles with similar actions as the PM can produce an artifact . Positioning should be validated with imaging techniques in which the muscle and the injected material are identified with certainty .

In some studies, injections of botulinum toxin (BTX) seem safe and effective for PMS and have given more relief from pain than lidocaine with steroids or placebo , but another study found no significant differences between BTX and 0.5% bupivacaine . Furthermore, in one study, BTX led to atrophy and fatty degeneration of the PM that could be quantified by MRI . Therefore, considering the high cost and potential risks of BTX, its use as first-line treatment does not seem appropriate. Instead, injecting the PM with a local anesthetic with or without corticosteroids should be considered earlier for therapeutic and diagnostic purposes .

Disclosure of interest

The authors declare that they have no conflicts of interest concerning this article.

References

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