A Study on the bifurcation of sciatic nerve with its clinical

Transcription

Indian Journal of Basic and Applied Medical Research; June 2015: Vol.-4, Issue- 3, P. 34-44
Original article
A Study on the bifurcation of sciatic nerve with its clinical significance
1Dr.
Satyajit Sangram , 2Dr. Chiranjit Samanta , 3Dr. Mithu Paul , 4Dr. Susumna Biswas , 5Dr. Reshma
Ghosh , 6Dr. Amitava Sarkar , 7Dr. Saktipada Pradhan , 8 Prof. (Dr.) Sudeshna Majumdar
1,2,3,5,6,7
4
Junior Resident, Department of Anatomy,Nilratan Sircar Medical College, Kolkata – 700014, West Bengal, India
Demonstrator, Department of Anatomy, Nilratan Sircar Medical College, Kolkata – 700014, West Bengal, India.
8 Professor,
Department of Anatomy, Nilratan Sircar Medical College, Kolkata -700014, West Bengal, India.
Corresponding author: Dr. Sudeshna Majumdar
Abstract:
Introduction: The sciatic nerve (SN) arises from the sacral plexus. It usually appears in the gluteal region below the piriformis
muscle, passes along the back of the thigh and divides into tibial and the common fibular (peroneal) nerves near the apex of the
popliteal fossa. But the point of bifurcation of the sciatic nerve is very much variable.
Methods: A study was conducted on the division of the sciatic nerve, in the Department of Anatomy, NRS Medical College,
Kolkata, over two years, from December, 2012 to the November, 2014. 50 inferior extremities of 25 cadavers were dissected for
this study. The dissections were done while teaching MBBS Students in the said department. The relevant structures were
observed minutely and photographs were taken.
Observations: Among the fifty inferior extremities, in the sciatic nerve was found to be divided into tibial and common peroneal
nerves in different levels (in the pelvis, gluteal region etc.)
Results: Out of fifty lower limbs, in forty one cases (82%) the sciatic nerve divided in the back of the thigh, near the apex of the
popliteal fossa according to normal anatomy. In nine lower limbs (18% cases), the nerve divided high above, either in the sacral
fossa (14% cases) or in the gluteal region (4% cases).
Conclusion: This high division of the sciatic nerve may result in nerve injury during deep intramuscular injections in the gluteal
region, sciatica, piriformis syndrome etc. So this variation has importance in gross and clinical anatomy.
Key Words: Division of Sciatic Nerve, tibial nerve, common peroneal nerve, piriformis muscle
Introduction
nerve leaves the pelvis via the greater sciatic
Sciatic is a Greek word derived from ‘ischiadicus’.
foramen, below the piriformis and above the superior
Sciatic nerve is also known as ischiadic nerve or
gemellus muscle, descends in the gluteal region
ischiatic nerve, is a large nerve in humans and other
between
animals1. Sciatic nerve (SN) is the nerve of the
tuberosities. Then it runs along the back of the thigh
posterior compartment of the thigh and via its major
dividing into tibial and the common peroneal
branches of all the compartments of leg and foot. It is
(fibular) nerves at a varying level proximal to the
typically 2cm. wide at its origin and is the thickest
knee joint. The point of bifurcation of the sciatic
nerve in the human body with the root value: L4, 5,
nerve is very much variable 2. The common site is at
S1-3. Formed in the pelvis from the ventral rami of
the junction of the middle third and lower third of the
fouth lumbar to third sacral spinal nerves, the sciatic
back of the thigh, near the apex of the popliteal fossa
the
greater
trochanter
and
ischial
34
www.ijbamr.com P ISSN: 2250-284X , E ISSN : 2250-2858
(85-89% cases), but division may occur at any point
1, 2
Materials and methods
. The
A study was undertaken to detect different variations
tibial and common proneal nerves are structurally
in the bifurcation of sciatic nerve, in the Department
separate and only loosely held together within the
of Anatomy, NRS Medical College, Kolkata, over
sciatic nerve. Dorsal divisions of ventral rami of L4-5,
two years, from December, 2012 to the November,
S1-2 form the common peroneal component and the
2014. 50 inferior extremities of 25 cadavers were
ventral divisions of ventral rami of L4-5, S1-3 form the
dissected minutely for this study while teaching
above this and rarely may occur below it
2
tibial component of the sciatic nerve . Very often
MBBS Students. The cadavers belonged to the adult
these two nerves arise separately from the sacral
age group (within 50 to 70 years age group); twenty
plexus and at that time, the common peroneal nerve
male and five female cadavers were included in this
may pass through the piriformis muscle and the tibial
study.
2
nerve below the muscle .
The relevant structures were observed carefully and
The piriformis is a flat muscle, pyramidal in shape,
photographs were taken. Variations were noted with
lying below the posterior margin of the gluteus
calculation of their percentage.
medius. It arises from the front of the sacrum by three
Observations
fleshy digitations and partly from the greater sciatic
Among the fifty inferior extremities, in twenty-five
foramen and sacrotuberous ligament. The muscle
cadavers, the sciatic nerve was found to be divided
comes out of the pelvis through the greater sciatic
into tibial and common peroneal nerves in different
foramen and is inserted by a rounded tendon to the
levels (in the pelvic cavity, gluteal region etc.).
upper border of the greater trochanter of femur2.
In forty one cases the sciatic nerve divided in the
Piriformis syndrome is a controversial condition in
lower part of the back of the thigh, near the apex of
which the anomalous relationship between piriformis
the popliteal fossa, according to normal anatomy. So
and sciatic nerve is thought to cause pain in buttocks
in 82% cases the nerve was found to be bifurcated in
2
and along the course of the sciatic nerve . Piriformis
the posterior compartment of the thigh above the
syndrome may be caused by an entrapment of the
knee joint. This normal bifurcation of SN occurred in
sciatic nerve as it exits the greater sciatic notch in the
three female cadavers bilaterally (6 cases), in two
gluteal region
3,4,5
unilaterally (2cases) and in fifteen male cadavers
.
The high division of SN may give rise to
bilaterally (30 cases), and in three unilaterally (3
complications
cases).
during
intramuscular
injections,
anaesthesia or surgery in the gluteal region3,4,6 . The
In nine lower limbs (18% cases), the sciatic nerve
sciatic nerve may be damaged in misplaced
divided high above into tibial and common peroneal
therapeutic injections in the gluteal region and the
nerves, either in the sacral fossa or in the gluteal
nerve is vulnerable in posterior dislocation of hip
region. In two cadavers the sciatic nerve bifurcated in
2
joint .
the pelvis bilaterally and in the inferior extremities of
The present study was planned to describe the
the other five cadavers, high division of the nerve
variations in the division of the sciatic nerve at
was unilateral.
different levels with the clinical implications.
35
Among these nine cases, in seven of them (14%), the
region unilaterally. In both the cases, the nerve
nerve bifurcated while in the pelvic cavity and tibial
passed through the piriformis muscle dividing it into
and common peroneal components emerged in the
superior and inferior slips to appear in the gluteal
gluteal region below the lower border of piriformis
region. Then after a short distance the sciatic nerve
separately. Four were right sided cases and three
divided in each case into tibial and common peroneal
were left sided. Among these seven cases, there was a
nerves. In the female cadaver, the left lower limb and
female cadaver with unilateral variation (1case) and
in the male cadaver, the right lower limb was
four male cadavers, where two of them had bilateral
concerned with this variation.
variation (4 cases) and two had unilateral variation (2
The photographs of eight cases with one normal
cases) of high division of SN in pelvis.
bifurcation of the SN are presented in this article, the
In the two other cadavers (4% cases), one male and
other case was similar to figure - 5.
one female, sciatic the nerve bifurcated in the gluteal
Table – 1 Different levels of bifurcation of the sciatic nerve with percentage:
Level of
Number of total
Bilateral
Unilateral
Bifurcation of SN
cases with
In 3 female cadavers –
In 2 female cadavers – 2 cases
sciatic nerve near
6 cases,
(one right and one left sided case).
the apex of the
In 15 male cadavers –
In 3 male cadavers –3 cases (two
popliteal fossa
30 cases.
left and one right sided case).
Total 36 (72% cases).
Total 5 (10% cases).
percentage
Division of the
41 (82%) cases.
In one female cadaver – 1 case
Division of the
7 cases (14%)
sciatic nerve in the
In 2 male cadavers – 4 cases
(right sided).
(8%).
In 2 male cadavers – 2 cases (one
right & one left).
pelvis
Total – 3 cases (6%).
Division of the
2 cases (4%)
Nil.
In one female cadaver – 1 case
sciatic nerve in
(left sided).
gluteal region
In 1 male cadaver – 1 case (right
sided).
Total – 2 cases (4%).
36
Figures
Figure - 1;
In a right sided lower limb of a female cadaver, the sciatic nerve (SN) passed between the two heads of the biceps
femoris and divided into tibial and common peroneal nerves in the back of the knee joint.
Index: A – Sciatic nerve, B - Tibial nerve, C - Common Peroneal nerve, D- Hamstring group of muscles, E –
Lateral head of Gastrocnemius, F – Biceps Femoris muscle.
Figure – 3;
In a left sided lower limb of a male cadaver, the sciatic nerve divided into tibial and common peroneal nerves in the
pelvis and they emerged in the gluteal region below the piriformis muscle separately.
Index : A – Piriformis muscle, B – Gluteus maximus muscle, C - Tibial nerve, D - Common Peroneal nerve, E –
Tibial and Common Peroneal nerves running side by side from the gluteal region to the back of the thigh, F –
Gluteus medius muscle.
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35
Figure – 4;
The two components of SN (Tibial and Common Peroneal nerves) running side by side in the back of the left thigh
of a male cadaver.
Index : A- Tibial nerve, B- Common Peroneal nerve, C- Hamstring group of muscles.
Figure – 4
The two components of SN (Tibial and Common Peroneal nerves) running side by side in the back of the left thigh
of a male cadaver. These two nerves seemed to have united as they ran very close to each other.
Index : A- Tibial nerve, B- Common Peroneal nerve, C- Biceps femoris muscle, D – Semitendinosus muscle.
36
38
Figure -5; In a right sided lower limb of a male cadaver, the tibial and common peroneal nerves emerged in the
gluteal region below the piriformis muscle separately as the sciatic nerve bifurcated in the pelvis.
Index : A – Tibial nerve, B – Common Peroneal nerve, C - Gluteus maximus muscle, D - Piriformis muscle, E –
tricipital tendons of gemellus superior, obturator internus, gemellus inferior, G –Biceps femoris muscle, F –
Semitendinosus muscle.
Figure - 6 ; In the right sided lower limb of a female cadaver, the sciatic nerve divided into tibial and common
peroneal nerves in the pelvic cavity and emerged in the gluteal region below the piriformis separately to run in the
back of the thigh passing deep to the origin of the long head of biceps femoris.
Index : A – Tibial nerve, B – Common Peroneal nerve (both in the gluteal region and back of thigh), C - Piriformis
muscle , D - Gluteus maximus muscle, E – Long head of Biceps Femoris muscle, F – Semimembranosus muscle.
39
37
Figure– 7; Two divisions of the Sciatic Nerve (Tibial and Common Peroneal) emerged below the piriformis muscle
in the gluteal region, passed to the back of the thigh deep to the origin of the Hamstring Muscles in the right lower
limb of a male cadaver.
Index : A – Tibial nerve, B – Common Peroneal nerve (both in the gluteal region and back of thigh), C - Piriformis
muscle , D - Gluteus maximus muscle,
E – Inferior gluteal vessels and nerve, F- Long head of Biceps Femoris
muscle, G – Semitendinosus muscle, H- Semimembranosus muscle.
Figure - 8 ;In a leftt sided lower limb of a female cadaver, the Sciatic nerve emerged in the gluteal region through
the divided piriformis and after a short distance divided into tibial and common peroneal nerves which ran in the
back of the thigh.
Index: A – Sciatic Nerve, B - Common Peroneal nerve, C - Tibial nerve, D – Long head of Biceps femoris, E –
Semitendinosus, F – Semimembranosus.
40
38
Figure – 9; The sciatic nerve emerged between the two slips of the piriformis muscle in the right sided gluteal
region and then it was divided into tibial and common peroneal nerves in the same region in a male cadaver.
Index: A- Sciatic Nerve,
B - Tibial nerve, C - Common peroneal nerve, D - piriformis muscle with upper and
lower slips, E – Gemellus superior, F - Gluteus medius muscle.
Kirci et al in 1999, described a case with unilateral
Discussion
double piriformis and high division of sciatic nerve
A number of variations in the course and distribution
where the common peroneal nerve passed between
of the sciatic nerve (SN) has been reported.
the two parts of piriformis and the tibial nerve
Bifurcation into its two major divisions (common
emerged under the lower border of inferior piriformis
peroneal and tibial) may occur anywhere between the
9
sacral plexus and the lower part of the thigh. The two
In a case presented by Paval et al in 2008, bifurcation
terminal branches of the sciatic may arise directly
of the sciatic nerve in pelvis was found bilaterally in
from the sacral plexus7.
a 70 year old male cadaver. Common peroneal nerve
In 85-89% cases, the nerve divides into the terminal
1
.
pierced the piriformis dividing the muscle into upper
branches at the apex of the popliteal fossa ; in the
and lower slips whereas the tibial nerve emerged
present study this percentage is 82%.
below the lower slip of the piriformis on both sides 4.
Smoll compiled the results of 18 previous studies
Khan et al (2011) found a case where on the left side
and 6,062 cadavers to find that the prevalence of high
common peroneal nerve passed between the two
division of sciatic nerve in cadavers was 16.9% and
divisions of piriformis and tibial nerve passed below
8
in surgical case series was 16.2% . In the present
the inferior piriformis5. In all these three cases, the
study, the prevalence of this variation (high division
sciatic nerve divided inside the pelvis before
of SN) was 18%. According to Smoll again, the
emerging in the gluteal region.
piriformis and SN variations have ranged from 1.5 –
8
In 2013, Bhattacharya et al presented a case with
3.58% in dissected human cadavers and in our study
double piriformis and division of the sciatic nerve in
this variation is present in 4% cases.
pelvis; the common peroneal nerve emerged between
the two piriformis muscles, whereas the tibial nerve
39
41
emerged below the lower piriformis on a left inferior
also be caused by directly due to a lumbar disc
extremity. On the right side sciatic nerve divided in
pressing on the sciatic nerve as it exits the
the gluteal region after emerging from the lower
intervertebral foramen in the lumbar spine3,13,14 .
border of piriformis 10.
Investigations like CT scan, MRI, EMG, nerve
In 2014, Saritha et al described few variations of
conduction test are routinely done to detect nerve
Sciatic nerve bifurcation in 4 cadavers from their
pathology1.
study and their findings have similarities with those
In piriformis syndrome, the sciatic nerve can be
revealed in the present study like SN dividing in the
entrapped between the gemellus superior and
1
4,15
pelvis .In 2014, Patil et al described an unique case
piriformis muscles
. Another common site of
where dorsal and ventral divisions of ventral rami of
entrapment is when the sciatic nerve or one of its
lower lumbar and sacral spinal nerves passed ventral
branches pierces the piriformis muscle and this can
and dorsal to the piriformis muscle respectively.
occur in about 1% to 5% of all humans4,13,16. In that
These divisions joined each other below the
case myospasm and or contraction of the piriformis
piriformis muscle to form sciatic nerve. This low
muscle itself can lead to pain along the buttock, back
formation of sciatic nerve was observed in distal part
of the thigh to the knee, loss of sensation or
of left gluteal region of a 50-year-old male cadaver.
numbness and tingling into the leg and sole of the
The sciatic nerve then passed caudally into back of
foot3,11. Piriformis syndrome is often misdiagnosed as
thigh and divided into tibial and common peroneal
sciatica due to similar symptoms 4, 13,14,17 .
nerves in the upper part of popliteal fossa. Such
Some workers consider piriformis syndrome to be
variations may lead to piriformis syndrome or non-
a form of myofascial pain syndrome 3,4,5. A history of
discogenic sciatica11.
trauma may be present in approximately 50% of
Most of the text books of Anatomy, Surgery and
cases of the syndrome. The trauma is not usually
Orthopaedics state that the sciatic nerve bifurcation
sudden in onset and may occur several months before
1
levels are important in clinical and treatment aspects .
the initial symptoms treated in the orthopaedics or
This high division of sciatic nerve can cause nerve
physical
Medicine
1,18
department
along
with
entrapment under other anatomic structures, resulting
rehabilitation
in non-discogenic sciatica, piriformis syndrome or
among the athletes as a part of sport injury 19. It may
coccydynia and muscle atrophy
1,5
. This variation of
also
follow
. This syndrome can also be present
total
hip
replacement
surgery3,4.
sciatic nerve may result in nerve injury during deep
Complete medical history and physical examination
intramuscular injections in the gluteal region,
are necessary for differential diagnosis of this
sciatica, piriformis syndrome, failed SN block in
syndrome 4,18.
anesthesia
or incomplete block of SN during
The management of piriformis syndrome includes
anesthesia, injury during posterior
analgesic, muscle relaxants, injection of local
hip operations and other surgery in the gluteal region
anesthetic agents, steroid (like methylprednisolone)
1,4, 6,9,12
or botulinum toxin into the piriformis muscle; liquid
popliteal block
.
Low back pain, caused by a compression or irritation
1
of the sciatic nerve is called sciatica . Sciatica may
anaesthetic agents can be injected to the area of
sciatic nerve even3,4,5, 10,15,18 . To avoid blind injection
42
35
in
the gluteal region,
Anatomical landmarks,
the surrounding muscles like obturator internus,
electromyography or computed tomography (CT),
gemelli, or quadratus femoris, as these muscles have
fluoroscopic guidance will be helpful to identify the
common insertions like piriformis muscle4,5,10.
piriformis muscle and a nerve stimulator can be used
The knowledge and Information about different
for sciatic nerve identification
4,5, 10,12,13
. Surgery
variations of sciatic nerve bifurcation, will not only
may be considered when the piriformis is involved in
make the surgeons careful, but will also help them
the sciatic nerve entrapment. The muscle may be
regarding proper planning for surgical intervention in
thinned, divided or excised to be compensated with
the gluteal region or in the thigh 6 .
Table – 2 Findings of the present study and the previous studies Variations of SN
Findings of the present study
Findings of the previous studies
Sciatic nerve (SN) bifurcated at
82% cases
85-89% cases1
18% cases
16.9% cases in cadavers8
the apex of the popliteal fossa
Sciatic nerve bifurcated high
16.2% surgical cases8
above
Piriformis and SN variations
4% cases
1.5 – 3.58% cases8
Conclusion
especially among the athletes. This study will also
The variations of the bifurcation of sciatic nerve have
enhance our knowledge in Gross Anatomy and
clinical implications regarding deep intramuscular
Clinical Anatomy.
injections, popliteal block anaesthesia, hip surgery,
Acknowledgement
practice of neurology etc. Moreover, this study will
We are grateful to Professor Hasi Dasgupta, Dr.
have a contribution in Sports Medicine and
Manotosh Banerjee and other members of the
rehabilitation as the high level of division of the
Department of Anatomy, Nilratan
sciatic nerve and variation in the piriformis muscle
College, Kolkata, India, for their kind co-operation to
may be the causes of soft tissue problems of hip,
complete this study.
Sircar Medical
References
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girdle, gluteal region and thigh. 40th Edition. Spain, Philadelphia; Churchill Livingstone Elsevier. 1337-1338,
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A Study on the bifurcation of sciatic nerve with its clinical

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