Chanwit Maneenin; Naowarat Maneenin; Chananya Jirapornkul; Surasak Wanram; Phatthiraporn Aorachon; Sitthichai Iamsaard

Clinically, it is known that the sciatic nerve-piriformis muscle variants (SPV) can increase the susceptibility to piriformis syndrome and gluteal pain syndromes. Specialized medical care might be required for patients with piriformis syndrome due to their unique SPVs. Different patterns and prevalence of such variations have been reported in many populations, but not in Northeastern Thais. This recent study aimed to investigate the types and incidence of SPV in Thai body donors. In this study, 33 embalmed body donors (66 lower limbs in total) were examined to collect anatomical variations between the sciatic nerve (SCN) and piriformis muscle (PM) before classifying their specific types. The results showed that SPV could be classified into 6 types with a novel pattern (Type I; undivided SCN passes below PM, Type II; divided SCNs pass below PM, Type III; divided SCNs pass between & below PM, Type IV; divided SCNs pass above PM, Type V; divided SCNs pass above & below PM, and Type VI; trifurcates of SCN (Y-shape common fibular & tibial nerves) pass above PM, respectively). The incidence of such SPVs is 83.33 % (Type I), 7.57 % (Type II), 1.51 % (Type III), 3.03 % (Type IV), 3.03 % (Type V), and 1.51 % (Type VI), respectively. In conclusion, these population-specific data have enhanced regional anatomical knowledge and underscore the critical need for preoperative recognition of SPV to mitigate surgical complications in the gluteal region, particularly for the management of piriformis syndrome in the Northeastern Thai population.

KEY WORDS: Piriformis,; Sciatic nerve; Piriformis syndrome; Northeastern Thais.

MANEENIN, C.; MANEENIN, N.; JIRAPORNKUL, C.; WANRAM, S.; AORACHON, P. & IAMSAARD, S. Six intriguing sciatic nerve-piriformis muscle variants investigated in the Northeastern Thai population. Int. J. Morphol.,43(6):2056-2061, 2025.