Download Case report Unusual looping pattern of ansa cervicalis: case report

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Anatomy
Case report
Unusual looping pattern of ansa cervicalis: case report
Introduction
The course and location of ansa cervicalis of the neck often vary. Because
of its closeness with the major vessels and nerves of the neck, any variation in its pattern is of great clinical
and surgical importance. This paper
reports a case of an unusual looping
pattern of ansa cervicalis.
Case report
We report here an unusual looping
pattern of ansa cervicalis. The inferior root of ansa cervicalis, instead of
joining the superior root as a single
nerve, had both the C2 and C3 components of it joined to the superior
root separately without uniting each
other. Due to this, two loops of AC
were formed superior and inferior.
Conclusion
Since the branches of ansa cervicalis
are often chosen for nerve–muscle
transplantation in the treatment of
paralysed larynx, and some of the
branches arise from the loop of the
AC, an abnormal looping pattern may
hinder such surgical procedures.
Therefore, it is essential to the surgeons to be familiar with its unusual
variations.
Introduction
Ansa cervicalis (AC) is a thin nerve
loop of cervical plexus, formed in
the side of the neck by the union of
superior and inferior roots. Its superior root is the continuation of
the descending branch of the hypoglossal nerve conveying the fibres of
the first cervical nerve. It descends
over the internal carotid artery. The
* Corresponding Author
E-mail: [email protected]
Department of Anatomy, Melaka Manipal
Medical College (Manipal campus), Manipal
University, Manipal, Karnataka, India
inferior root of AC is derived from
the union of ventral rami of C2 and
C3 spinal nerves. Superior root
courses downwards, winds around
the internal jugular vein and joins
with the inferior root in front of the
common carotid artery. AC supplies
all the infrahyoid muscles, except
­thyrohyoid1,2.
The formation of the lower root
(descendens cervicalis) varies greatly when compared with that of the
upper root owing to the various cervical root contributions possible in
its formation2. Though the variation
in the formation and distribution of
AC is not uncommon, unusual pattern of AC is seldom reported. This
paper reports a case of an unusual
looping pattern of AC in the neck.
Case report
During routine dissection for the undergraduate medical students, we
came across a variation in AC. AC in
the left side of the neck presented
a double loop pattern. There were
two separate components of inferior
roots of AC, one from C2 and another
from C3 ventral rami. The component
from C2 joined with the superior root
of AC and formed a smaller superior
loop, while nerve components from
the C3 root joined with AC at a lower level and formed a larger inferior
loop (Figure 1 and Figure 2). Both the
loops appeared to be Y-shaped and
a combined apex of AC descended
downwards to supply the infrahyoid
muscles. AC, in this case, was present
lateral to the internal jugular vein.
Discussion
Variation in ansa cervicalis has been
encountered earlier. AC frequently
shows variation in its origin and
distribution. Jyothi et al.3 reported a
variation in which the superior root
of AC received nerve fibres from hypoglossal and vagus nerves. Babu4
reported the absence of the inferior
root of AC. Studies have reported incidences of variant origin of both its
superior and inferior roots5,6. Contribution by the spinal accessory nerve
plexus to the formation of AC was reported by Khaki et al.7. A case with bilateral absence of AC, which was replaced by a vagocervical plexus, has
been reported by Abu et al.8. In this
case, the infrahyoid muscles were
supplied by the branches arising directly from the C2 and C3 ventral
rami. The nerve to the thyrohyoid
may arise as a branch of the ramus
descendens hypoglossi. The phrenic
nerve may also receive contribution
from the descendens hypoglossi, as
reported by Ramesh et al.9. Banneka
Figure 1: Dissection of left side of the
neck region showing the superior
loop (SL) and inferior loop (IL) of
ansa cervicalis, sternocleidomastoid
muscle (SCM), superior belly
of omohyoid muscle (SBO) and
submandibular gland (SMG).
Licensee OA Publishing London 2013. Creative Commons Attribution License (CC-BY)
For citation purposes: Ravindra SS, Kumar N, Nayak SB, Mohandas Rao KG, Jyothsna P, Anitha G. Unusual looping pattern
of ansa cervicalis: Case report. OA Case Reports 2013 Sep 10;2(9):81.
Competing interests: none declared. Conflict of interests: none declared.
All authors contributed to conception and design, manuscript preparation, read and approved the final manuscript.
All authors abide by the Association for Medical Ethics (AME) ethical rules of disclosure.
Abstract
SS Ravindra, N Kumar*, SB Nayak, KGM Rao, P Jyothsna, G Anitha
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Figure 2: Closer view of the dissection
showing superior root (SR), C2 and
C3 components of inferior root of
unusual ansa cervicalis, common
carotid artery (CCA), internal jugular
vein (IJV), sternocleidomastoid
muscle (SCM) and hypoglossal nerve
(HN).
reported that in 75% of the cases, AC
is present on the lateral side of the
internal jugular vein, i.e., lateral type,
in such cases; the inferior root nerve
components formed a common trunk
which then joined the superior root.
In the medial type of AC, 74.8% of
the nerve components of the inferior
root joined the superior root independently10. In the present case, the
AC is of lateral type and had separate nerve components of C2 and C3
forming two separate inferior roots,
which join with the superior root of
AC forming double loops.
AC is useful in the treatment of
hemiatrophy of the tongue after fa-
cial–hypoglossal
anastomosis11,12,
and is also considered to be the nerve
of choice in nerve–muscle transplantation in treating paralysed larynx5,13.
It is suggested that the branch of AC
supplying sternothyroid muscle can
safely be transplanted in the place
of the recurrent laryngeal nerve as it
lies very close to the larynx14. Since
this branch usually derives from the
looped part of AC, existence of unusual looping patterns or duplex loop
as encountered in the present case
may mislead such surgical approaches. Further, iatrogenic injuries to the
AC may happen during surgical procedures such as in thyroplasty, arytenoid adduction, Teflon injection, and
nerve–muscle pedicle implantation6.
In order to avoid these injuries, it is
important for surgeons to understand the course and morphological
variations of AC15.
Conclusion
Prior knowledge of variant looping
pattern of AC is handy for surgeons
who perform nerve reconstructive
surgery. Surgeons should also be
aware of AC relations with carotid
artery and internal jugular vein to
avoid injury to these vessels during
surgical procedures of the neck.
References
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practical anatomy: vol.III: Head and neck
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2. Susan S. Gray’s Anatomy: The anatomical basis of clinical practice. 39th
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3. Jyothi SR, Dakshayani KR. Variation in the formation of ansa cervica-
lis on right side. Anatomica Karnataka.
2013;7(1):81–3.
4. Babu PB. Variant inferior root of ansa cervicalis. Int J Morphol. 2011;29(1):240–3.
5. Loukas M, Thorsell A, Tubbs RS, Kapos
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cervicalis as a variant of spinal accessory
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8. Abu-Hijleh MF. Bilateral absence of
ansa cervicalis replaced by vagocervical
plexus: case report and literature review.
Ann Anat. 2005 Apr;187(2):121–5.
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formation of double ansa cervicalis. Neuroanatomy. 2007 Mar;6:26–7.
10. Banneheka S. Morphological study of
the ansa cervicalis and the phrenic nerve.
Anat Sci Int. 2008;83(1):31–44.
11. Natsugoe S, Okumura H, Matsumoto
M, Ishigami S, Owaki T, Nakano S, et al.
Reconstruction of recurrent laryngeal
nerve with involvement by metastatic
node in esophageal cancer. Ann Thorac
Surg. 2005 Jun;79(6):1886–9.
12. Crumley RL, Izdebski K, McMicken
B. Nerve transfer versus Teflon injection
for vocal cord paralysis: A comparison.
Laryngoscope. 1998 Nov;98(11):1200–4.
13. Chhetri DK, Berke GS. Ansa cervicalis
nerve: review of the topographic anatomy and morphology. Laryngoscope. 1997
Oct;107(10):1366–72.
14. Vacher C, Caix P. Anatomy of the hypoglossal nerve and the hypoglossal ansa
cervicalis. Rev Stomatol Chir Maxillofac.
2004 Jun;105(3):160–4.
15. Loukas M, Thorsell A, Tubbs RS, Kapos T, Louis RG Jr, Vulis M, et al. The
ansa cervicalis revisited. Folia Morphol
(Warsz). 2007 May; 66(2):120–5.
Licensee OA Publishing London 2013. Creative Commons Attribution License (CC-BY)
For citation purposes: Ravindra SS, Kumar N, Nayak SB, Rao KGM, Jyothsna P, Anitha G. Unusual looping pattern of ansa
cervicalis: Case report. OA Case Reports 2013 Sep 10;2(9):81.
Competing interests: none declared. Conflict of interests: none declared.
All authors contributed to conception and design, manuscript preparation, read and approved the final manuscript.
All authors abide by the Association for Medical Ethics (AME) ethical rules of disclosure.
Case report