Journal of Anatomical Variation and Clinical Case Report Vol 3, Iss 1
Case Report
High Division of the Sciatic Nerve Split by the Superior Gemellus
Muscle: A Case Review and Clinical Implications
Omar Noori, Hongsheen Kim, Jay Parikh, Si L. Chen and Macario Llamas*
Anatomy and Clinical Medicine, Kirk Kerkorian School of Medicine at UNLV, Las Vegas, USA
ABSTRACT
Anatomical variations of the sciatic nerve (SN) are clinically significant due to their implications in surgery and
neuropathy management. A rare variant, the high division of the SN split by the superior gemellus muscle (SGM), was
observed bilaterally during routine dissection, with the two components passing superior and inferior to the SGM. This
finding contributes to the existing anatomical knowledge of this rare variant. By consolidating these findings, this
review aims to enhance anatomical understanding, refine surgical approaches, and improve patient outcomes.
Keywords: Anatomical variation; Calot's Triangle; Cystic artery origin; Laparoscopic cholecystectomy
V
Keywords: Sciatic nerve variation; Superior gemellus muscle; Nerve compression; Anatomical dissection; Clinical
anatomy
*
Correspondence to: Dr. Macario Llamas, Associate Professor, Anatomy and Clinical Medicine, Kirk Kerkorian School of Medicine at UNLV,
USA
Received: Apr 23, 2025; Accepted: May 01, 2025; Published: May 08, 2025
Citation: Noori O, Kim H, Parikh J, Chen SL, Llamas M (2025) High Division of the Sciatic Nerve Split by the Superior Gemellus Muscle: A
Case Review and Clinical Implications. J Anatomical Variation and Clinical Case Report 3:118.
DOI: https://doi.org/10.61309/javccr.1000118
Copyright: ©2025 Noori O. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which
permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
INTRODUCTION
The sciatic nerve (SN), the largest in the human
piriformis syndrome (PS) [1]. In 10-15% of the
body, transmits motor and sensory signals between
population, these variations, which include the SN
the spinal cord and lower extremities. It arises from
passing through or above the PM, increase the
the L4 to S3 spinal nerve roots and exits the pelvis
likelihood of SN compression, causing symptoms,
through the greater sciatic foramen (GSF), traveling
such as pain, tingling, and numbness along the SN’s
deep to the gluteus maximus muscle (GMM) and the
distribution [1,2]. Misdiagnosis can occur when
piriformis muscle (PM). Typically, the SN bifurcates
attempting to differentiate PS from other causes of
into the tibial nerve (TN) and common fibular
sciatica due to an overlap in symptomology. Another-
(peroneal) nerve (CFN) branches behind the popliteal
less commonly understood variation, the superior
fossa, each responsible for different leg and foot
gemellus muscle (SGM) SN split, accounts for a
functions.
SN,
small fraction of cases but is important for both
especially in relation to the PM, may contribute to
clinical and anatomical understanding [2]. Early
Anatomical
Noori O et al.
variations
in
the
Journal of Anatomical Variation and Clinical Case Report Vol 3, Iss 1
Case Report
recognition of these variations is essential for
The SN was identified posteriorly after its formation
accurate diagnosis and effective treatment [3].
at the level of the QFM, where the TN and CFN
components unite. From this point, the SN was
CASE PRESENTATION
carefully traced distally, running deep to the GMM
During the routine dissection of the right and left
and coursing parallel to the femur within the
gluteal regions and upper posterior thighs of a 70-
posterior compartment of the thigh. It was observed
year-old female donor, a bilateral variation of the SN
to bifurcate into its terminal branches: the TN and the
configuration was observed. In both legs, the SN
CFN within the popliteal fossa, specifically at the
exited the pelvis at the greater sciatic foramen as a
superior angle of the popliteal triangle.
single structure and bifurcated at the SGM into the
The TN was then followed distally, continuing its
TN and CFN components. Immediately superior to
course through the posterior compartment of the leg.
the SGM, the branches separated and followed
During dissection, it was noted to give off articular
distinct paths. Inferior to the SGM, however, the TN
branches, including the superior medial genicular
and CFN reunited into the SN at the level of the
nerve and the middle genicular nerve, which supply
quadratus femoris muscle (QFM), then bifurcated
the knee joint capsule.
again within the popliteal fossa, continuing distally as
The CFN was traced laterally along the border of the
the TN and CFN branches with their standard
biceps femoris muscle. Dissection continued until the
innervations (Figure 1).
nerve curved around the neck of the fibula, where it
was seen to divide into the superficial fibular nerve
and the deep fibular nerve. Additionally, the sural
communicating branch was identified, contributing to
the formation of the sural nerve, which was traced
running
superficially
down
the
posterior
leg
alongside the small saphenous vein.
No other neurovascular or musculoskeletal variations
were noted in the dissected areas, and no signs of
pathology or previous surgical procedures were
observed.
CLINICAL SIGNIFICANCE AND MPLICATIONS
The high division of the SN split by the SGM can
Figure 1: High division of the sciatic nerve at the level of the
have clinical consequences, primarily due to its
superior gemellus muscle. The tibial and common fibular nerves
potential for nerve entrapment or compression. The
separate early, with the common fibular nerve taking a more lateral
presence of the SGM between the TN and the CFN
course alongside the superior gemellus. FN = Fibular Nerve; I.
Gemellus = Inferior Gemellus Muscle; Obturator i = Tendon to
branches can result in atypical symptoms, including
Obturator Internus Muscle; Quadratus = Quadratus Femoris
pain, weakness, or sensory deficits in the lower limb.
Muscle; S. Gemellus = Superior Gemellus Muscle; TN = Tibial
Patients may present with atypical sciatica or nerve
Nerve.
Noori O et al.
Journal of Anatomical Variation and Clinical Case Report Vol 3, Iss 1
Case Report
dysfunction that does not conform to the typical
CONCLUSION
distribution of either the TN or CFN [2]. From a
The high division of the SN split by the SGM is a
surgical perspective, awareness of this anatomical
rare but clinically significant anatomical variant. Its
variant is crucial for procedures involving the hip and
clinical relevance is primarily associated with
pelvis, including hip arthroplasty, PM release
potential
surgeries, and nerve block injections. Inadvertent
challenges in surgical intervention. As such, both
injury or compression of the SN branches during
clinicians and surgeons must maintain a high index of
these
postoperative
suspicion for this variation when encountering
neuropathy,
unusual patterns of lower limb neuropathy or
impaired gait, or chronic pain [3]. Furthermore,
performing hip-related surgeries. Future research
failure to recognize this variant can complicate the
with larger case series and detailed anatomical
diagnosis of conditions, such as sciatica, as the
dissections will help clarify the prevalence, clinical
distribution of sensory and motor deficits may not
outcomes, and best management strategies for this
align with classical patterns [1].
rare variant.
PREVALENCE AND RECOGNITION OF THE
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