Download Additional lateral root of the Ulnar and Median nerves

Additional lateral root of the Ulnar
and Median nerves - Case study
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Dorian Wolff - Amandine Labarthe
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Coordinator: Dr. Kory-Mercea Bogdan
UMF Cluj – Department of Anatomy, Cluj-Napoca, Romania
Introduction:
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Brachial plexus
Formation: Ventral rami of the lower cervical and upper
thoracic nerve roots between C5 and T1.
Course: Neck, axilla and upper part of the arm.
Territories: Cutaneous and muscular innervation of the upper
limb.
Brachial Plexus:
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The five anterior rami of the spinal nerves merge to form
three trunks: superior (C5-C6), middle (C7), inferior (C8T1).
Brachial Plexus:
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Each of these trunks splits in two branches, one anterior,
and one posterior.
Brachial Plexus:
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Anterior divisions of
the upper and middle
trunks will form the
lateral cord.
The three posterior
divisions will regroup
to form the posterior
cord
(which
is
posterior
to
the
axillary artery).
Anterior division of the
lower trunk will form
the medial chord.
1) Lateral cord
- Lateral root of the median
nerve
-Musculocutaneous nerve
2) Medial cord:
- Medial root of the median
nerve
- Ulnar nerve
-Medial brachial and
antebrachial nerves
3) Posterior cord:
-Radial nerve
-Axillary nerve
Divisions of cords:
Objectives:
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This study presents a case of an additional
lateral root of the Ulnar and Median nerves.
It could provide important informations about the
variations of these nerves and their origins, in
order to avoid injuries and possible impairment of
a patient during surgical procedures of axillary
region.
Materials and methods:
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Adult male cadaver
Dissected by classical dissection in the
Department of Anatomy, UMF Cluj-Napoca,
Romania.
The entire upper arm and the axillary region were
dissected carefully.
The variations from the usual pattern were noted.
Results:
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A lateral root of the ulnar nerve, which originated
from the lateral cord, was found.
Usually the lateral cord only gives three
branches: lateral pectoral nerve, lateral root of
median nerve and musculocutaneous nerve.
The fourth branch of the lateral cord splits in two,
posteriorly to the origin of median nerve.
Results:
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One
of
the
two
branches courses to
the medial nerve ->
Lateral origin of the
right ulnar nerve.
The branch that made
an anastomosis with
the median nerves
forms a third origin of
the
right
median
nerve (second lateral
origin).
The additional branch :
approximately 3.5 cm
long.
Fig. 1: Right Arm: View of the Lateral Root of the
Ulnar Nerve - Closeup
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The branch coming
from the lateral cord,
passes
under
the
medial root of Median
nerve.
Divides
in
two
branches, one going
back to the median
nerve, and the other
forming the lateral root
of the ulnar nerve.
Fig. 1: Right Arm: View of the Lateral Root of the
Ulnar Nerve
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Musculocutaneous
can be seen.
nerve
The insertion of the lateral
root of ulnar nerve is in its
lateral side.
The third root of the median
nerve joins him between the
two other roots.
The fourth branch of lateral
cord runs inferiorly to medial
root of the median nerve.
Drawing of the variation:
Results:
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Apart from the fourth branch emerging from
the lateral chord, the rest of the brachial
plexus follows the regular pattern, and no
other variation can be observed.
Discussion:
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The fourth branch
divides itself in two parts:
One
towards
nerve.
median
One towards ulnar nerve.
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The anatomical variant
of this brachial plexus
consists
in
the
presence of the fourth
abnormal branch.
Discussion
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On
a
plexus:
usual
This fourth branch
does not exist.
The ulnar nerve
does not have
any lateral origin.
Discussion:
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There wasn't any living subject bearing this anomaly
available for our study,
We cannot be sure about the
consequences that it could have.
possible
functional
We are not yet in possession of any method that could
permit us to find out what those consequences would be on
a living subject.
Discussion:
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We do know that both the nerves Ulnar and Median
carry motor and cutaneous sensitive functions,
especially in the forearm and the hand.
Both muscular and sensitive functions of the territories
innervated by the Ulnar and Median nerves could be
altered in one or another way.
Discussion:
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Most common brachial plexus variation are at root, but
they can also be found at division of a trunk, formation of
a cord, or at the root of a nerve.
These variations could be damaged during the neck
dissection or during axillary surgery, thus it's important
for surgeons and anatomists to know about their
presence.
Discussion:
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Anatomic variants often happen in the brachial plexus.
(according to Valeria Paula et al. - Brachial plexus
variation in its formation and main branches. Acta Cir.
Bras. 2003; 18:5.).
Errors of migration of nerve cells axons are corrected
distally in the arm, thus the brachial plexus often carries
anatomical variations.
Discussion:
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According to F.K. Fuss (Fuss FK. Acta Anatomica.
134(3):199-205) a lateral branch of the ulnar nerve is
normal, and is not an anatomic particularity but is more of a
variant as it was found in 56% of the brachial plexuses he
investigated.
Discussion:
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According to T.W. Sadler (Langmans Medical Embryology.
9th edition, 2004, Luppincott Williams & Wilkins, 202-206)
during the formation of the Brachial Plexus, the nerve cells
remain with their original muscles as they migrate.
Hypothesis:
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Based on the embryologic argument: Every muscle bud
migrates, preserving it's own innervation.
The nervous fibers may eventually group differently from the
general pattern, but every muscle preserves the fibers
coming from a certain neuromere.
It could mean that the median nerve has a smaller than
usual muscular territory and the ulnar nerve a bigger one.
Hypothesis:
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Previous hypothesis can also be considered about the
sensitive territories of the two nerves:
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The ulnar nerve would have a greater territory.
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The median nerve would have a smaller territory.
Conclusions:
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We have to pay particular attention to this zone in case of
injury (accidental or surgical) of the axillary region.
The reason: during the surgery of this zone, the abnormal
roots of these nerves can be injured.
Furthermore, there is no exterior sign that could signal the
presence of this variation, so when working on the axillary
region, we can't be sure if the brachial plexus follows the
regular pattern.