Guidelines for botulinum neurotoxin injections in piriformis syndrome

Kyu Ho Yi, Kyu Lim Lee, Ji Hyun Lee, Hye Won Hu, Kangwoo Lee, Kyle K. Seo, Hee Jin Kim

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


Background: The piriformis muscle is normally involved in piriformis syndrome and can be treated with botulinum neurotoxin using several different injection methods. However, definitive injection guidelines for the muscle have not been reported previously. Aims: This study aimed to determine the ideal area for injections based on the intramuscular nerve distribution as obtained using a modified Sihler's staining technique. Materials and Methods: A modified Sihler's method was applied to the piriformis muscle in 15 specimens. The intramuscular arborization areas were identified based on two anatomical landmarks: (a) the lateral border of the sacrum bone and (b) the greater trochanter. Results: The nerve entry point for both piriformis muscles was found in the area between the lateral border of the sacrum and one-fifth of the distance toward the greater trochanter. The intramuscular nerve distribution for the piriformis muscle had the largest arborization patterns between one-fifth and two-fifths of the distance from the sacrum to the greater trochanter. The piriformis muscle was tendinous from two-fifths of the distance to the greater trochanter. Discussion: This study has yielded suggested optimal injection locations for the piriformis muscle relative to external anatomical landmarks. Conclusion: Clinicians can use these guidelines to ensure the effectiveness of not only botulinum neurotoxin injections but also other agents such as steroids, anesthetics, and normal saline. These guidelines will also help to avoid adverse outcomes of injection treatments.

Original languageEnglish
Pages (from-to)1028-1034
Number of pages7
JournalClinical Anatomy
Issue number7
Publication statusPublished - 2021 Oct

Bibliographical note

Funding Information:
Korean government (MSIP), Grant/Award Number: NRF‐2020R1A2B5B0100223811; National Research Foundation of Korea (NRF) Funding information

Funding Information:
The authors thank Eun-Byul Yi from Eonbuk elementary school for illustrations. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (NRF-2020R1A2B5B0100223811). The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind's overall knowledge that can then improve patient care. Therefore, these donors and their families deserve our highest gratitude.

Publisher Copyright:
© 2020 American Association of Clinical Anatomists

All Science Journal Classification (ASJC) codes

  • Anatomy
  • Histology


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