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Case report
Clinical Anatomy
Clinically important unilateral accessory tendinous slip
from the short head of biceps brachii muscle merged
with medial intermuscular septum: a case report
Abstract
Introduction
Biceps brachii is a muscle of the anterior compartment of arm, which is a
lexor and supinator of the forearm,
having two heads: short head and
long head. The aim of this report is
to discuss a rare case of bicep brachii
muscle merging with medial intermuscular septum.
Case report
During a routine dissection class
held for medical students, we came
across an unusual unilateral variation in the right arm of a male
cadaver aged about 50 years. A tendinous slip or cord was arising from
the medial surface of the proximal
part of short head of biceps brachii
muscle and its tendon. The accessory
tendon emerged from the medial
side of right biceps brachii muscle,
and after crossing the brachial artery
and median nerve it blended with
the upper part of medial intermuscular septum. This variant tendon
was very thick and was tense enough
to compress the structures passing
deep into it.
Discussion
During certain arm movements,
compression of brachial artery and
median nerve may lead to various
neurovascular syndromes. Such
accessory tendons can also be used
for tendon grafts and can be obtained
with ease because of its super icial
position in the arm.
*Corresponding author
Email: [email protected].
Department of Anatomy, Melaka Manipal
Medical College, Manipal University, Manipal
576 104, Karnataka, India
Conclusion
This case report can be useful for clinicians attending patients of neurovascular compression syndromes in
upper limb and surgeons performing
tendon grafts.
Introduction
Biceps brachii muscle is a prime
supinator of the forearm and a powerful lexor at the elbow joint, supported by musculocutaneous nerve
and brachial and anterior circum lex
humeral arteries. It has two heads:
short head and long head. The long
head originates from the supraglenoid tubercle of scapula and the
short head from its coracoid process.
The two heads distally join to form
a muscle belly. The tendon from
biceps brachii muscle belly inserts
into the radial tuberosity, and bicipital aponeurosis from tendon is fused
with the deep fascia of forearm1.
Muscular anomalies are common
in the upper limb and may be due
to minor disturbances arising during critical stages of normal development of upper-limb muscles2.
Numerous studies and case reports
are available, which predominantly
mention additional heads of biceps
brachii muscle3. The present study
reports on a rare, unusual and clinically important variation associated
with biceps brachii muscle.
Case report
During a routine dissection class for
medical students, we came across
an unusual unilateral variation in
the right arm of a male cadaver aged
about 50 years. A tendinous slip or
cord was arising from the medial
surface of the proximal part of the
short head of biceps brachii muscle
and its tendon. This accessory tendinous slip passed medially and distally
towards the medial side of the arm
super icially crossing the brachial
artery, venae comitantes of brachial
artery and the median nerve. When
traced distally, we found it was blending with medial intermuscular septum at a distance of 13.6 cm above
the medial epicondyle of humerus.
Origin, insertion and number of heads
of biceps brachii muscle were found
to be normal. The superior ulnar collateral artery, which is a branch of
brachial artery, passed deep into the
distal end of accessory tendon and
entered the posterior compartment
of the arm after piercing the medial
intermuscular septum (Figure 1).
This accessory tendon was a thick,
cord-like structure, was tensed and
was compressing the brachial artery,
venae comitantes and the median
nerve. Variant tendon emerged from
the proximal part of biceps brachii
muscle at a distance of about 11 cm
from the coracoid process, and, distally, it ended on the medial intermuscular septum at a distance of about
13.6 cm above the medial epicondyle
of humerus. Total length of the tendon was about 7.4 cm (Figure 2).
Discussion
Variation in the morphology of biceps
brachii muscle is common. A study
regarding the variation of this muscle
indicates that supernumerary heads
of biceps brachii are present in 15%
of subjects in the South Indian population3. In addition to the supernumerary head, other variations have
Licensee OA Publishing London 2013. Creative Commons Attribution Licence (CC-BY)
F
: Swamy RS, Nayak SB, Rao MKG, Rao RT, Sirasanagandla SR, Kumar N, et al. Clinically
important unilateral accessory tendinous slip from short head of biceps brachii muscle merged with medial
intermuscular septum: a case report. OA Anatomy 2013 May 01;1(2):16.
CompeƟng interests: none declared. Conflict of interests: none declared.
All authors contributed to the concept on, design, and preparaƟon of the manuscript, as well as read and approved the final manuscript.
All authors abide by the AssociaƟon for Medical Ethics (AME) ethical rules of disclosure.
RS Swamy, SB Nayak, MKG Rao, RT Rao, SR Sirasanagandla*, N Kumar, J Patil, P Abhinitha,
A Guru
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Case report
CP
11 cm
SBBM
BBMS = short head of biceps brachii muscle, DM = deltoid muscle, MN = median nerve,
VC = venae comitantes, MIS = medial intermuscular septum, UN = ulnar nerve, TM = triceps
muscle, LDM = latissimus dorsi muscle
*Variant anomalous tendon.
**Superior ulnar collateral artery, BV = basilic vein.
also been mentioned4. Some case
reports regarding variations of biceps
brachii muscle and their implications
include the following: (i) biceps brachii arising from the medial intermuscular septum compressing the
brachial artery and median nerve5,
(ii) brachial artery entrapment syndrome caused by supracondylar process during hyperextension of the
arm6, and (iii) supracondylar spur
with Struthers ligament compressing the brachial artery7. Median
nerve entrapment due to a third
head of biceps brachii has also been
reported earlier8. Almost similar to
the present case, a case of variant
muscle fasciculus from the medial
side of biceps brachii, which continues as a narrow tendinous slip and
gets inserted into the medial supracondylar ridge of humerus, has been
reported. This tendinous slip was
found compressing the median nerve,
causing pain, paresthesia and numbness in the palm, diminishing of sensory and motor functions, along with
weakness in grip strength or atrophy
of thenar eminence. Anterior interosseous nerve syndrome can also
be observed in such cases9. Median
nerve compression or entrapment
leads to syndromes such as carpal
tunnel syndrome, pronator teres
syndrome and anterior interosseous
syndrome10. In addition to variants of
biceps brachii muscle, variable insertion of coracobrachialis into the distal
medial border of humerus can also
compress median nerve and brachial
artery11. Thus, numerous types of variant biceps brachii muscle mentioned
in the foregoing cases can lead to neurovascular compression syndromes.
The accessory tendinous slip in
our case was crossing super icial to
13.6 cm
Figure 1: Dissection of right upper arm demonstrating the accessory tendon
emerging from the medial side of short head of biceps brachii muscle, passing super icial to the brachial artery, venae comitantes of brachial artery and
median nerve. Distal blending of this accessory tendon with medial intermuscular septum is also seen.
ME
Figure 2: Diagrammatic representation of the variant anomalous tendon
along with its measurements. The
length of variant anomalous tendon
is 7.4 cm, distance between the tip
of coracoid process and the proximal
end of variant tendon is 11 cm and
the distance between the distal end
of variant tendon and medial epicondyle of humerus is 13.6 cm.
SBBM = short head of biceps brachii muscle,
ME = medial epicondyle of humerus, CP = tip
of coracoid process of scapula.
*Variant anomalous tendon.
**Medial intermuscular septum.
the brachial artery, venae comitantes
and median nerve. This accessory
tendinous slip was a thick, cord-like
structure and was tensed enough
to compress the structures passing
deep into it. As this accessory tendon was emerging from the medial
Licensee OA Publishing London 2013. Creative Commons Attribution Licence (CC-BY)
F
: Swamy RS, Nayak SB, Rao MKG, Rao RT, Sirasanagandla SR, Kumar N, et al. Clinically
important unilateral accessory tendinous slip from short head of biceps brachii muscle merged with medial
intermuscular septum: a case report. OA Anatomy 2013 May 01;1(2):16.
CompeƟng interests: none declared. Conflict of interests: none declared.
All authors contributed to the concept on, design, and preparaƟon of the manuscript, as well as read and approved the final manuscript.
All authors abide by the AssociaƟon for Medical Ethics (AME) ethical rules of disclosure.
*
7.4 cm
**
Page 3 of 3
surface of the short head of biceps
brachii muscle, hyperextension of the
arm at the shoulder joint can lead to
overstretching of this variant tendon,
further compressing the structures
passing deep into it. In such cases,
compression of brachial artery may
lead to ischemia during the hyperextension of upper limb, showing
atypical arterial symptoms similar
to thoracic outlet syndrome or brachial artery entrapment syndrome
in the upper limb. Compression of
median nerve may lead to alterations
in sensory functions, such as pain,
paresthesia and numbness in palm,
accompanied by motor dysfunctions
such as diminished grip strength or
atrophy of muscles of thenar eminence. Signs and symptoms similar to pronator teres syndrome and
anterior interosseous syndrome may
appear with accessory tendinous
slip as mentioned in our present
case. Thus, patients with symptoms
of neurovascular compression syndrome should be investigated for the
presence of anomalies as mentioned
in our present case. Such variant
anomalous tendons can also be used
for tendon grafts.
The accessory tendinous slip from
the biceps brachii muscle is said to
be a remnant of various muscular or
tendinous slips from the distal end of
the muscle attached to the lower end
of humerus, ulna, fascia or neighbouring muscles during the development
of foetus in the fourth month of intrauterine life, and thus, occasionally
leading to such variations12.
Conclusion
Variant anomalous tendinous slips
from biceps brachii muscle can compress vital structures such as brachial artery and median nerve during
hyperextension of the arm at the
shoulder joint, which may lead to various neurovascular compression syndromes in the upper limb. This case
report can thus be useful for clinicians
attending patients of neurovascular
compression syndromes in the upper
limb and surgeons performing tendon
grafts.
References
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10. Rodrigues V, Nayak S, Somayaji N,
Vollala VR. Median nerve and brachial
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2008;1:28–9.
11. El-Naggar MM, Al-Saggaf S. Variant of
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Clin Anat. 2004 Mar;17(2):139–43.
12. Bryce TH. Myology. The muscles and
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In: Sharpey SE, Symington J, Bryce TH,
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11th ed. London: Longmans, Green & Co;
1923.p121.
Licensee OA Publishing London 2013. Creative Commons Attribution Licence (CC-BY)
F
: Swamy RS, Nayak SB, Rao MKG, Rao RT, Sirasanagandla SR, Kumar N, et al. Clinically
important unilateral accessory tendinous slip from short head of biceps brachii muscle merged with medial
intermuscular septum: a case report. OA Anatomy 2013 May 01;1(2):16.
CompeƟng interests: none declared. Conflict of interests: none declared.
All authors contributed to the concept on, design, and preparaƟon of the manuscript, as well as read and approved the final manuscript.
All authors abide by the AssociaƟon for Medical Ethics (AME) ethical rules of disclosure.
Case report