Three-headed biceps brachii muscle associated with duplicated musculocutaneous nerve.

Abstract

A unilateral three-headed biceps brachii muscle coinciding with an unusual variant of the musculocutaneous nerve was found during routine dissection of a 79-year-old male cadaver. The supernumerary bicipital head originated from the antero-medial surface of the humerus just beyond the insertion of the coracobrachialis, and inserted into the conjoined tendon of biceps brachii. Associated with this muscular variant was a duplicated musculocutaneous nerve. The proximal musculocutaneous nerve conformed to the normal pattern only in its proximal part, and terminated after innervating the coracobrachialis and biceps brachii muscles. The distal musculocutaneous nerve arose from the median nerve in the lower arm, then passed laterally between the supernumerary bicipital head and the brachialis muscles, supplying both and terminating as the lateral cutaneous nerve of the forearm. The supernumerary bicipital head and the accompanying anomaly of the musculocutaneous nerve seem to be unique in literature.

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CASE REPORT
Three-Headed Biceps Brachii Muscle Associated
With Duplicated Musculocutaneous Nerve
MARWAN F. ABU-HIJLEH*
Department of Anatomy, College of Medicine and Medical Sciences, Arabian Gulf University,
Manama, Kingdom of Bahrain
A unilateral three-headed biceps brachii muscle coinciding with an unusual variant of the
musculocutaneous nerve was found during routine dissection of a 79-year-old male cadaver.
The supernumerary bicipital head originated from the antero-medial surface of the humerus
just beyond the insertion of the coracobrachialis, and inserted into the conjoined tendon of
biceps brachii. Associated with this muscular variant was a duplicated musculocutaneous
nerve. The proximal musculocutaneous nerve conformed to the normal pattern only in its
proximal part, and terminated after innervating the coracobrachialis and biceps brachii
muscles. The distal musculocutaneous nerve arose from the median nerve in the lower arm,
then passed laterally between the supernumerary bicipital head and the brachialis muscles,
supplying both and terminating as the lateral cutaneous nerve of the forearm. The super-
numerary bicipital head and the accompanying anomaly of the musculocutaneous nerve
seem to be unique in literature. Clin. Anat. 18:376–379, 2005.
V V
C2005 Wiley-Liss, Inc.
Key words: biceps brachii; musculocutaneous nerve; neuro-muscular anoma-
lies; anatomical variations
INTRODUCTION
Neuromuscular anomalies are common in the upper
limbs. Such variations may present clinically or be
detected at cadaveric dissection, autopsy, and surgery
(Abu-Hijleh, 1993). In terms of the number and mor-
phology of its heads, the biceps brachii is one of the
most variable muscles in the human body (Bergman
et al., 1988; Nakatani et al., 1998). Although absence
of the entire muscle or one of its heads (Greig et al.,
1952; Rodriguez-Niedenfuhr et al., 2003) and varia-
tions of the insertion seem to be uncommon (Greig
et al., 1952; Reina-de la Torre et al., 1994), supernum-
erary heads of the biceps brachii are relatively fre-
quent (Greig et al., 1952; Kosugi et al., 1992; Asvat
et al., 1993; Nakatani et al., 1998; Rodriguez-Nieden-
fuhr et al., 2003).
Variations in the course and distribution of the
musculocutaneous nerve have been reported previ-
ously (Schafer et al., 1909; Bergman et al., 1988; Saeed
and Rufai, 2003). Although a communicating branch
from the musculocutaneous nerve to the median nerve
in the arm is common (Le Minor, 1990; Eglseder and
Goldman, 1997; Venieratos and Anagnostopoulou,
1998; Choi et al., 2002), a branch in the opposite
direction or complete absence of the musculocutane-
ous nerve, with its muscular branches arising from the
median nerve or lateral cord of the brachial plexus,
are less frequent (Schafer et al., 1909; Nakatani et al.,
1997; Gumusburun and Adiguzel, 2000).
CASE REPORT
During routine dissection of the upper limbs of a
79-year-old male embalmed cadaver, a unilateral
*Correspondence to: Dr. Marwan F. Abu-Hijleh, MD, PhD,
Associate Professor,Department
Medicine and Medical Sciences, Arabian Gulf University, PO
Box 22979, Manama, Kingdom of Bahrain.
E-mail: marwanah@ agu.edu.bh
ofAnatomy, College of
Received 31 October 2004; Accepted 4 November 2004
Published online in Wiley InterScience (www.interscience.wiley.com).
DOI 10.1002/ca.20100
V V
C2005 Wiley-Liss, Inc.
Clinical Anatomy 18:376–379 (2005)

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three-headed biceps brachii was discovered in the
right arm. The supernumerary head (Fig. 1) was a
flat muscular belly (1.5 cm wide ? 9.5 cm long) that
originated from the antero-medial surface of the
humerus between the insertion of the coracobrachia-
lis and the origin of the brachialis. The belly contin-
ued infero-medial to the bulk of the biceps brachii
and anterior to the brachialis muscle and lay lateral
to the brachial artery and median nerve. It inserted
into the proximal part of the common biceps tendon
(Fig. 1). The nerve supply to this third head was
from a branch of an aberrant musculocutaneous
nerve and the blood supply was from a branch of the
brachial artery. Careful dissection under 2? magnifi-
cation to identify the nerve supply to this accessory
bicipital head showed a duplicated musculocutane-
ous nerve (Fig. 1). The proximal musculocutaneous
nerve followed a normal course only as far as the
biceps brachii where it terminated. It originated
from the lateral cord of brachial plexus and pierced
coracobrachialis and, after supplying it, terminated as
branches to both normal heads of the biceps brachii
muscle. The nerve was thus purely muscular.
The distal aberrant musculocutaneous nerve arose
from the median nerve in the lower third of the arm
(at a distance of about 23.5 cm from the coracoid
process and 11 cm from the origin of the median
nerve). It crossed laterally over the brachial artery
and passed between and supplied the supernumerary
bicipital head and the brachialis muscle before
emerging lateral to the bicipital tendon as the lateral
cutaneous nerve of the forearm (Fig. 1). Cords and
other terminal branches from the brachial plexus
were found to have normal origins, courses, and dis-
Fig. 1.
(B) of the dissected right axilla, arm and the cubital fossa. It demon-
strates the presence of a supernumerary head of biceps brachii (*) asso-
ciated with a duplicated musculocutaneous nerve (2,6). Abbreviations:
1, lateral cord of brachial plexus; 2, proximal musculocutaneous
nerve; 3, lateral root of median nerve; 4, medial root of median nerve;
5, median nerve; 6, distal musculocutaneous nerve; 7, axillary artery;
Photograph (A) and corresponding schematic drawing
8, brachial artery; 9, lateral cutaneous nerve of forearm; 10, coraco-
brachialis, attached to the coracoid process (star, shown only in the
prosection photograph for orientation); 11, biceps brachii (displaced
laterally); 12, conjoined bicipital tendon; 13, brachialis; 14, pectoralis
major (reflected and displaced laterally); 15, subscapularis; 16, ulnar
nerve (shown only in the drawing, in the prosection photograph it is
concealed by the median nerve).
377Variant Biceps Brachii and Musculocutaneous Nerve

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tributions. No additional muscular, neural, or vascu-
lar anomalies were found in the remainder of the
right upper limb or in the left upper limb of the
same cadaver.
DISCUSSION
The most frequent variation of the biceps brachii
muscle is in the number of muscle heads with a
prevalence range of 9.1–22.9% (Greig et al., 1952;
Bergman et al., 1988; Kosugi et al., 1992; Nakatani
et al., 1998; Kopuz et al., 1999; Rodriguez-Nieden-
fuhr et al., 2003). Although supernumerary bicipital
heads have been described as part of either a three-,
four-, five- or seven-headed biceps brachii, the
three-headed variant represents the most common
type that has been reported with a prevalence rang-
ing from 7.5–18.3% and with no clear racial or gen-
der differences (Greig et al., 1952; Kosugi et al.,
1992; Asvat et al., 1993; Nakatani et al., 1998; Neto
et al., 1998; Kopuz et al., 1999; Rodriguez-Nieden-
fuhr et al., 2003). Bilateral occurrence of supernum-
erary heads in the biceps brachii muscles is rela-
tively rare (Greig et al., 1952; Kosugi et al., 1992;
Nakatani et al., 1998).
Recently, Rodriguez-Niedenfuhr et al. (2003) clas-
sified the supernumerary bicipital heads based on
their origin and location. Taking into account all
studies and cases reported previously, they defined
three different types: superior, infero-medial, and
infero-lateral humeral heads. They observed the
presence of a third head in 23 of 175 (13.1%) cadav-
ers or in 27 of 350 (7.7%) arms. In 26 arms, the
supernumerary head was represented by the infero-
medial humeral head and in one arm by an infero-
lateral humeral head. In the present case, the super-
numerary bicipital head corresponds to the infero-
medial type. It originated from the antero-medial
surface of the humerus distal to the insertion of the
coracobrachialis, passed infero-medial to the main
biceps brachii and anterior to the brachialis muscle,
and inserted into the medial side of the common
biceps tendon. The development of the third head
may have influenced the course or branching pattern
of the variant musculocutaneous nerve, or vice versa,
and could explain the coexistence of such a neuro-
muscular anomaly.
The most frequent variation of the musculocuta-
neous nerve is the presence of a communicating
branch from the nerve to the median nerve (Le
Minor, 1990; Eglseder and Goldman, 1997; Veniera-
tos and Anagnostopoulou, 1998; Choi et al., 2002). A
branch in the opposite direction is less common
(Schafer et al., 1909; Bergman et al., 1988; Nakatani
et al., 1997). Very occasionally, the musculocutaneous
nerve fails to separate from the median nerve, and
the latter therefore gives off the branches that should
arise from the musculocutaneous. In a similar fashion,
the musculocutaneous has been reported to go only
to the muscles of the arm, whereas the lateral cutane-
ous nerve of the forearm arose from the median
(Schafer et al., 1909; Kosugi et al., 1992). Kosugi
et al. (1992) studied the branching pattern of the
musculocutaneous nerve and found variations in 75
of 546 limbs (13.5%). They divided the variations
into five groups according to the manner of communi-
cation with the median nerve: in Group I there were
no communications (32 of 75 limbs); in Group II
there was a communicating branch from the musculo-
cutaneous nerve to the median nerve (24 of 75
limbs); in Group III a branch ran from the median
nerve to the musculocutaneous nerve (12 of 75
limbs); in Group IV the above two communications
were present (5 of 75 limbs); in Group V there were
various other patterns (2 of 75 limbs). In the present
study, the musculocutaneous nerve seemed to be
duplicated; the proximal division (purely muscular)
had a normal origin from the lateral cord of the bra-
chial plexus and pierced the coracobrachialis muscle,
but the more distal aberrant division (muscular and
cutaneous) arose from the median nerve in the lower
arm and terminated as the definitive lateral cutaneous
nerve of the forearm. The course and distribution of
the duplicated musculocutaneous nerve seen in this
case, and the manner of connection of its distal divi-
sion with the median nerve, did not correspond with
any of those described in detail by previous authors.
Awareness of anatomic, neurological, and muscu-
lar variations of the types reported in the present
case can be helpful in explaining unusual clinical
signs and symptoms. For example, the very close
relationship of the variant distal musculocutaneous
nerve to the brachial artery (it crossed the artery
after leaving the median nerve) may result in arterial
compression (Saeed and Rufai, 2003) or the natural
beating of the artery could cause irritative neurologic
symptoms in certain positions and movements of the
arm or shoulder. Variant nerves having an abnormal
origin, course, and distribution may be more prone
to accidental injuries and entrapment neuropathies
(Roberts, 1992). Injury to the segment of the median
nerve in the mid-arm containing the more distal
anomalous musculocutaneous nerve may cause para-
lysis of the supernumerary head of biceps brachii
and brachialis muscles and anesthesia on the lateral
aspect of the forearm, in addition to motor and sen-
sory deficits that would have been expected from
such a lesion of the median nerve. Lack of aware-
378Abu-Hijleh

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ness of such variations in the median and musculo-
cutaneous nerves might thus complicate surgical
repair of the nerves. Variations of the heads of the
biceps brachii also have clinical importance as they
may cause compression of neurovascular structures
or confuse a surgeon during surgical procedures
(Warner et al., 1992).
REFERENCES
Abu-Hijleh MF. 1993. Extensor pollicis tertius: an additional
muscle to the thumb. Plastic Reconstr Surg 92:340–343.
Asvat R, Candler P, Sarmiento EE. 1993. High incidence of
the third head of biceps brachii in South African popula-
tions. J Anat 182:101–104.
Bergman RA, Thompson SA, Afifi AK, Saadeh FA. 1988.
Compendium of human anatomic variations. Baltimore:
Urban & Schwarzenberg. p 139–142.
Choi D, Rodriguez-Niedenfuhr M, Vazquez T, Parkin I,
Sanudo JR. 2002. Patterns of connection between the
musculocutaneous and median nerves in the axilla and
arm. Clin Anat 15:11–17.
Eglseder WA, Goldman M. 1997. Anatomic variations of the mus-
culocutaneous nerve in the arm. Am J Orthop 26:777–780.
Greig HW, Anson BJ, Budinger JM. 1952. Variations in the
form and attachments of the biceps brachii muscle. Quart
Bull Northwestern Univ Med Sch 26:241–244.
Gumusburun E, Adiguzel E. 2000. A variation of the brachial
plexus characterized by the absence of the musculocutane-
ous nerve: a case report. Surg Radiol Anat 22:63–65.
Kopuz C, Sancak B, Ozbenli S. 1999. On the incidence of
third head of biceps brachii in Turkish neonates and
adults. Kaibogaku Zasshi 74:301–305.
Kosugi K, Shibata S, Yamashita H. 1992. Supernumerary
head of biceps brachii and branching pattern of the mus-
culocutaneous nerve in Japanese. Surg Radiol Anat 14:
175–185.
Le Minor JM. 1990. A rare variation of the median and mus-
culocutaneous nerves in man. Arch Anat Histol Embryol
73:33–42.
Nakatani T, Tanaka S, Mizukami S. 1997. Absence of the mus-
culocutaneous nerve with innervation of coracobrachialis,
biceps brachii, brachialis and the lateral border of the fore-
arm by branches from the lateral cord of the brachial plexus.
J Anat 191:459–460.
Nakatani T, Tanaka S, Mizukami S. 1998. Bilateral four-
headed biceps brachii muscles: the median nerve and bra-
chial artery passing through a tunnel formed by a muscle
slip from the accessory head. Clin Anat 11:209–212.
Neto HS, Camilli JA, Andrade JCT, Filho JM, Marques MJ.
1998. On the incidence of the biceps brachii third head in
Brazilian whites and blacks. Ann Anat 180:69–71.
Reina-de la Torre F, Nebot-Cegarra J, Pe ´rez-Berruezo J.
1994. Biceps brachii muscle attached to the extensor carpi
radialis brevis muscle: an unreported anatomical variation
in humans. Anat Anz 176:319–321.
Roberts WH. 1992. Anomalous course of the median nerve
medial to the trochlea and anterior to the medial epicon-
dyle of the humerus. Anat Anz 174:309–311.
Rodriguez-Niedenfuhr M, Vazquez T, Choi D, Parkin I,
Sanudo JR. 2003. Supernumerary humeral heads of the
biceps brachii muscle revisited. Clin Anat 16:197–203.
Saeed M, Rufai AA. 2003. Median and musculocutaneous nerves:
variant formation and distribution. Clin Anat 16: 453–457.
Schafer EL, Symington J, Bryce TH. 1909. Spinal nerves. In:
Quain’s elements of anatomy. Vol. III. Part II. 11th Ed.
New York: Longmans, Green & Co. p 74–81.
Venieratos D, Anagnostopoulou S. 1998. Classification of
communicationsbetween
median nerves. Clin Anat 11:327–331.
Warner JJP, Paletta GA, Warren RF. 1992. Accessory head of
the biceps brachii: case report demonstrating clinical rele-
vance. Clin Orthop Rel Res 280:179–181.
the musculocutaneousand
379Variant Biceps Brachii and Musculocutaneous Nerve