A Novel Type and Classification System for Sciatic Nerve High Division

Background: High division of the sciatic nerve (SN) occurs in approximately 16.9% of individuals and often has significant clinical implications, such as failed SN blocks for anesthesia or nerve injuries during deep intramuscular procedures.1,2 Existing literature classifies SN high division and provides large-scale prevalence data; however, this case study reports a unique type of SN high division discovered in a sample of 28 cadavers with an unusually high prevalence of SN high division.1,3,4 Methods: This study examines the SNs in 56 limbs from 28 cadavers dissected in cadaver labs at Liberty University. Among these, 17 cases of SN high division were identified, nearly doubling the prevalence reported in existing literature.1 Notably, three cases involved unique types of high division (Figures 1 & 2) where the common fibular nerve (CFN) forms from two branches distal to the piriformis muscle (PM), a variation not described in the conventional Beaton and Anson classification system.2,3 This study documents these findings and proposes a new classification for the observed variation. Results: The prevalence of SN high division in this sample was 30.4%, significantly higher than the literature-reported 16.9%.1 Of the 17 cases, 13 were type B high division (Figures 5), 1 was type C, and 3 were unclassifiable according to existing systems.3 Comparative analysis of the 3 unique cases led to the discovery of a common pattern, and the development of a new type for addition to traditional classification systems. Discussion: The heightened prevalence observed in this sample may be linked to embryological factors, though the exact cause remains unknown. The unclassifiable cases may result in clinical symptoms distinct from traditional piriformis syndrome, as the tibial nerve remains unaffected.4,5 This study proposes a new classification type which accounts for these variations and discusses areas for future studies on SN high division prevalence and its clinical implications. Conclusion: While SN abnormalities are not life-threatening, they carry significant clinical risks.1,2 This study highlights the need for awareness and further research into the prevalence and impact of SN high division.