Botulinum toxin injection strategy of intractable and relapsed piriformis syndrome: A case report.

[RATIONALE] Piriformis syndrome (PS) is neuromuscular disorder caused by sciatic nerve compression by piriformis muscle and related to sciatic-type pain. When the conservative care fails, local injection or surgery can be also performed into piriformis. In recent years, botulinum toxin (BoNT) has also been considered as a new therapeutic option of piriformis syndrome.

[PATIENT CONCERNS] A man in his late 40s came to pain clinic for left low back pain. The symptom was aggravated with sitting position.

[DIAGNOSIS] Piriformis syndrome.

[INTERVENTIONS] The patient underwent BoNT injection with 100 IU with 2 mL into piriformis muscle for piriformis syndrome treatment, and his pain was relieved. However, it recurred 8 months later. BoNT injection was repeated with 100 IU with 5 mL.

[OUTCOMES] At the time of this writing, his pain was reduced for 2 years without any medication.

[LESSONS] We report a case of treating relapsed piriformis syndrome with BoNT injection of different dilution volume, suggesting that the higher the dilution volume, the more effective for therapeutic effect of BoNT.