Variations in sural nerve formation and course in fetuses

Area of Science:

• Anatomy
• Embryology
• Human Morphology

Background:

• The sural nerve (SN) is crucial for sensory innervation of the lower leg.
• Understanding its anatomical variations is important for surgical procedures and clinical diagnosis.
• Previous studies have described various patterns, but detailed analysis in specific populations is needed.

Purpose of the Study:

• To investigate and classify the formation patterns and anatomical course of the sural nerve (SN).
• To analyze potential associations between SN variations, lower limb laterality, and sex.

Main Methods:

• Dissection of 120 lower limbs from 60 Brazilian fetuses (16-34 weeks gestational age).
• Detailed examination of the sural nerve's formation and course through multiple incisions.
• Statistical analysis using the Chi-square test to assess laterality and sex correlations.

Main Results:

• Eight distinct sural nerve formation patterns were identified.
• Type 4, formed by the union of the medial sural cutaneous nerve (MSCN) and lateral sural cutaneous nerve (LSCN), was the most frequent pattern.
• A statistically significant association was found between sural nerve formation patterns and sex (p=0.03973), but not with lower limb laterality (p=0.9725).
• The junction of the main branches typically occurred in the distal leg (53.75%).
• The SN consistently coursed medially to laterally across the calcaneal tendon.

Conclusions:

• The sural nerve's formation and course exhibit significant variations, particularly in relation to sex.
• The common pattern involves the MSCN and LSCN joining in the distal leg.
• These anatomical findings contribute to a better understanding of lower limb neuroanatomy and potential clinical implications.