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Clinical Anatomy 17:667– 671 (2004)
CASE REPORT
Triplication of the Lesser Occipital Nerve
C. MADHAVI
AND
S.J. HOLLA*
Department of Anatomy, Christian Medical College, Tamil Nadu, India
Triplication of the lesser occipital nerve (LON) was observed bilaterally in an adult male
cadaver during routine prosection of the posterior triangle. The three LONs were studied to
determine the clinical importance of this variation. The origin of one LON was from a nerve
to the trapezius that had a common origin with the trunk of the supraclavicular nerve (C3,4)
from the cervical plexus. Such a common origin of a LON may explain the pain referred to
the shoulder and arm that is experienced by some patients with cervicogenic headache.
Another LON ran across the roof of the posterior triangle, passed through the trapezius and
was closely related to the point of exit of the greater occipital nerve (GON) from the
trapezius. This LON supplied the nape of the neck, back of the scalp and the auricle. The
anomalous course taken by this LON through the trapezius may be an explanation for
cervicogenic headache precipitated by neck movement. The close relationship of this variant
LON to the exit of the GON from the trapezius seems to be relevant to the management of
cervicogenic headache. The authors suggest that the reason for the complete pain relief
experienced by some patients with cervicogenic headache by anesthetic blockade of the GON
may be because both the GON and LON are blocked simultaneously due to their proximity
in these patients. Clin. Anat. 17:667– 671, 2004. © 2004 Wiley-Liss, Inc.
Key words: anomalous course; cervicogenic headache; anesthetic blockade; cervical segments C2– 4
INTRODUCTION
The LON normally has a variable origin either
from the 2nd or 2nd and 3rd cervical ventral rami. The
LON then curves around the accessory nerve and
ascends along the posterior border of the sternocleidomastoid, and pierces the deep fascia near the cranium to supply the skin over the scalp and the auricle.
The GON is the medial branch of the second cervical
dorsal ramus.
Whether the LON is involved in cervicogenic
headache is controversial. Cervicogenic headache is
the term used by Sjaastad et al. (1983) to describe a
distinct type of headache of cervical origin with unclear etiology. They studied a group of patients who
could provoke headaches by certain head and neck
movements. They defined cervicogenic headache as a
unilateral headache of moderate intensity, with relatively rare and long-lasting attacks. During the attacks
the patients usually have stiffness and pain in the
neck, neck movements are restricted and associated
with crepitation. In some patients there may be ipsilateral shoulder, arm, and hand pain. Most patients are
able to provoke attacks by certain acts, e.g., move©
2004 Wiley-Liss, Inc.
ments of the neck, coughing, sneezing, and bowel
movements, and also by pressure over the C2 root,
over the GON, and over the transverse process of
C4-C5 on the symptomatic side. Headaches are associated with ipsilateral phenomena such as blurring and
reduced vision, slight lacrimation, conjunctival injection, runny nose, and erythema of the forehead or
temporal region. Sometimes patients complain of dizziness, difficulty in swallowing, nausea, loss of appetite and occasionally even vomiting during attacks.
The pain is mainly in the temporal, frontal, and ocular
areas, with pain sometimes in the face. The mean age
of onset is 29 years and there is a female preponderance. There may be a previous history of neck trauma.
Fredriksen et al. (1987) further defined the clinical
manifestations of cervicogenic headache. Typically at*Correspondence to: Dr. Sunil J. Holla, Department of Anatomy,
Christian Medical College, Vellore 632 002, Tamil Nadu, India.
E-mail: [email protected]
Received 1 May 2003; Revised 4 September 2003
Published online in Wiley InterScience (www.interscience.wiley.
com). DOI 10.1002/ca.10252
668
Madhavi and Holla
tacks last for 1–3 days with a pain-free interval of 1– 4
weeks and the pain involved the neck and the nape of
the neck. In most patients the pain was constantly
boring and in none of the patients did the pain have a
typical radiating character. Most patients experienced
phonophobia and a general feeling of irritability with
the attack and did not seem to experience much relief
with pain medication such as non-steroidal anti-inflammatory agents and ergotamine. There was no significant past history or family history of migraine in
most patients. Various structures in the neck were
implicated as possibly being involved in the etiology
of cervicogenic headache such as C1, C2, or C3 root
fibers, the occipital nerves, the uncovertebral joints,
and the vertebral artery.
Hogan and Abram (1997) mentioned that there is a
lack of a pathophysiologic understanding of cervicogenic headache and the typical lack of sensory deficit
in the area of distribution of the GON does not support a neuropathic mechanism. Alternately, it is possible that pain radiating in the distribution of the
GON represents converging deep somatic input from
the lateral atlanto-axial joint, which is innervated by
the C2 anterior ramus, or from irritation of suboccipital
muscles and periosteum, which has been shown to
produce ascending headache. The role of the LON in
cervicogenic headache has not been emphasized in
the aforementioned three articles that deal with cervicogenic headache.
In the context of local anesthetic blockade of the
GON and LON, Sjaastad et al. (1986) were of the
opinion that even though compression of the GON as
it passes through the trapezius may be of pathogenetic
significance, the primary fault might be lower in the
neck, where there may be some anatomic misalignment. They suggested certain theoretically possible
causes of cervicogenic headache such as cervical spondylosis, uncovertebral arthritis, and vascular malformations along the C2/C3 roots. It has been considered
as a matter of debate, however, whether entrapment
of the GON in the pertinent muscles might cause
headache (Becser et al., 1998).
The GON has been implicated as one of the structures involved in cervicogenic headache because anesthetic blockade of the GON relieved the pain in
many patients with cervicogenic headache (Sjaastad et
al., 1983). The LON also has been implicated in
cervicogenic headache (Raffaelli et al., 1987; Lucas et
al., 1994).
This study describes an anomalous lesser occipital
nerve. The anatomical features observed in this case
might explain the simultaneous involvement of both
the GON and the LON in cervicogenic headache.
Fig. 1. Posterolateral view of head and neck showing triplication
of the lesser occipital nerve (LON). A, great auricular nerve; Ac,
Accessory nerve; E, external jugular vein; G, greater occipital nerve
(GON); S, supraclavicular nerve; ST, sternocleidomastoid; T, cervical
nerve to trapezius; TR, trapezius; I, LON-I; II, LON-II. Arrowheads:
LON-III.
CASE REPORT
During routine prosection of the head and neck for
teaching first year MBBS students an anomaly of the
LON was observed bilaterally in an adult male cadaver. Careful dissection of the posterior triangle
showed three nerves, referred to as the LON I, II, and
III that supplied the area that is normally innervated
by the LON (Fig. 1). At the middle of the posterior
border of the sternocleidomastoid various nerves were
seen to emerge and run in different directions. The
spinal accessory nerve was found to run parallel to the
levator scapulae from the posterior border of the sternocleidomastoid to the anterior border of the trapezius. The great auricular nerve hooked around the
posterior border of the sternocleidomastoid 1 cm below the accessory nerve. Midway between these two
nerves, a slender nerve (LON-I) hooked around the
Triplication of Lesser Occipital Nerve
posterior border of the sternocleidomastoid, coursed
upwards superficial to this muscle and the mastoid
process, and crossed the superior nuchal line. It was
distributed to the retroauricular and posterolateral aspects of the occiput.
At the posterior border of the sternocleidomastoid,
about 3 cm below the exit of the accessory nerve, a
nerve emerged that ended by forming the supraclavicular nerve trunk and a branch to the trapezius. The
branch to the trapezius gave rise to a slender branch
(LON-II) that ascended along the posterior border of
the sternocleidomastoid lying parallel to LON-I. This
nerve also was distributed to the retroauricular and
posterolateral aspects of the occiput. It passed over
the mastoid process but did not extend beyond the
superior nuchal line. It had a slender communication
with LON-I.
The LON-III, thicker than the other two LONs,
emerged at the posterior border of the sternocleidomastoid superior to the accessory nerve and running a
sinuous course across the posterior triangle the LONIII passed deep to the trapezius (Fig. 1). The LONIII then ascended superomedially for 2 cm, passing
deep to the lateral-most fascicles of the trapezius and
pierced this muscle in a fascial cleft 3 cm below the
superior nuchal line and 3.5 cm lateral to the midline.
The GON and the occipital artery also pierced the
trapezius in the same fascial cleft at a point 2 cm
superior to the exit of the LON-III from the trapezius
and 3.5 cm lateral to the midline. After piercing the
trapezius the LON-III ran superolaterally superficial
to the lateral fascicles of the trapezius on the subocciput and divided into two branches below the superior nuchal line. The lateral branch arched forward and
was distributed to the upper third of the cranial surface of the auricle. The medial branch ran superior to
the lateral branch and was distributed to the occiput.
The LON-III was distributed to the nape of the neck,
occiput, and the upper third of the cranial surface of
the auricle. Its area of innervation partly overlapped
that of the GON in the scalp. The GON was normal
and was distributed to the medial half of both the
subocciput and occiput.
DISCUSSION
Normally a single LON supplies the posterolateral
aspect of the neck and scalp and the cranial surface of
the upper part of the auricle. Duplication of the LON
has been reported, where the lateral nerve supplied
the retroauricular region, whereas the medial nerve
supplied the adjacent scalp (Romanes, 1987; Lucas et
al., 1994; Berry et al., 1995; Becser et al., 1998).
669
Triplication of the LON has not been reported. In
the present case, there were three distinct LONs.
Two of these (LON-I and II) were slender nerves
following the normal course in relation to the sternocleidomastoid muscle and supplying the retroauricular
and posterolateral aspect of the occiput. The LON-II
had a common origin with the cervical nerve to trapezius and the supraclavicular nerve trunk; both of
which came from ventral rami. This common origin
may result in a contribution of C3 fibers to the LONII. The shoulder and arm pain felt by some patients
with cervicogenic headache (Sjaastad et al., 1983)
might have resulted from the presence of a common
origin for the LON, supraclavicular nerves and cervical nerves to trapezius, as in the present case. The
explanation for this referred pain may be altered central processing of nociceptor information at the level
of the second order neurons as highlighted in a similar
situation by Kinney et al. (2003).
The LON-III and the GON pierced the same fibrous tissue that separated the lateral fascicles of the
trapezius from the rest of the muscle (Fig. 1). The
complete relief of pain experienced in patients with
cervicogenic headache by anesthetic blockade of the
GON (Sjaastad et al., 1986) may have been due to the
presence of a LON close to the GON (as in the
present case) that was also blocked. Patients who had
incomplete pain relief might have had a LON outside
the site of the block. Reasons for the inefficacy of local
blocks of the GON have been described, and it has
been reported that variations and communications
with other nerves could have an impact on the efficacy
and extent of LON blockade (Becser et al., 1998).
Pantaloni and Sullivan (2000) reported that in 5 of 19
cadaver dissections the LON supplied the superior
two-thirds of the ear (rather than the superior onethird that is usually described), and highlighted the
importance of this variation in facial rejuvenation surgery. Sjaastad et al. (1986) carried out more than 40
diagnostic anesthetic blockades of the GON in patients with suspected cervicogenic headache, and reported incomplete pain relief in some cases. Austad
(2000) surgically treated about 300 patients with occipital neuritis and described the location for occipital
block as a horizontal band approximately 2 cm long
over the insertion of the trapezius and centered approximately 4 cm from the midline. He noted that in
30 – 40% of his patients the greater occipital artery
seemed to significantly compress the GON and about
30% of his patients had perineural lymph nodes that
seemed to be causing extraneural compression at or
near the exit of the GON from the trapezius. He
carried out decompression of the GON at the point
where the nerve passed through the trapezius. He
670
Madhavi and Holla
reported that approximately one-third of his patients
dramatically improved after surgery for occipital neuritis. Hunter and Mayfield (1949) suggested the vulnerability of the anterior and posterior primary rami of
C2 to trauma between the atlas and axis and this has
been emphasized recently (Kinney et al., 2003). Kerr
and Olafson (1961) suggested that the convergence of
trigeminal and cervical dorsal root afferents to the
same area of the upper cervical spinal segments might
be a basis for spread of hemicranial pain from cervical
to trigeminal areas. Becser et al. (1998) mentioned
that anatomic variants in the periphery combined with
such mechanisms as compression, stretch, trauma or
inflammation may be important in the pathogenesis of
cervicogenic headache, and that the combination of
various factors may be necessary for pain production,
at least in some cases.
Hogan and Abram (1997) have emphasized that
there are various limitations and interpretations of
nerve blocks. They mentioned that because all the
proposed pathophysiologies of cervicogenic headache
are unproved, the meaning of various blockade responses do not rest on a solid mechanistic base. In
addition, the therapeutic plan is not well defined after
a favorable response to test injections, and the ability
of GON blockade to identify patients with disease is
hampered by an inexact definition of cervicogenic
headache and no means of confirmation. They also
stated that most studies, as well as the definition of
the condition, come from a single group of authors.
The position of emergence of the LON and the
GON in the fibrous tissue partition between the lateral muscle fascicles and the rest of the trapezius
might make it vulnerable to compression and stretching. Relief by surgical release of clinical manifestations of nerve compression by a tendon have been
reported (Spinner et al., 1996). It is controversial
whether there is clinical evidence of the involvement
of the LON in cervicogenic headache (Raffaelli et al.,
1987; Lucas et al., 1994). If the LON is involved, it
may be due to entrapment neuropathy of the LON as
it passed through the trapezius. Because dermatomes
of adjacent spinal segments overlap markedly (Berry
et al., 1995), the involvement of the GON (C2) may
manifest in the of cutaneous area innervated by the
LON (C2,3). Lucas et al. (1994) noted that the area
described for the dermatome of C2 comprises the
region supplied by the GON, and the dermatome of
C3 occupies areas innervated by the LON, great auricular nerve and the transverse cervical nerve.
Fredriksen et al. (1987) noted that the characteristic
pain of an attack of cervicogenic headache could be
precipitated by firm manual pressure directed to four
“trigger” points: midway between the external occip-
ital protuberance and the mastoid process; C2 area,
that is behind and just below the mastoid process, and
the transverse processes of C4 and C5. Lucas et al.
(1994) have pointed out that the first two of these
points are sites that are anatomically occupied by the
LON. The anatomical peculiarities of the LON observed in the present case, such as its anteroposterior
course across the posterior triangle and the manner of
exit from the trapezius may be an explanation for the
precipitation of cervicogenic headache by neck movement in some patients.
Basmajian and Slonecker (1989) refer to the part of
the posterior triangle superior to the accessory nerve
as the “carefree part,” where there is no important
structure in the fascial roof. Lucas et al. (1994) have
reported an anomalous course taken by the LON in 6
of 16 dissections, in the region where the nerve ascended to the occipital region lying between the posterior border of the sternocleidomastoid and the lateral border of the trapezius. In the present case the
thickest of the three LONs, the LON-III, stretched
anteroposteriorly across the roof of the posterior triangle extending from the posterior border of the sternocleidomastoid to the lateral border of the trapezius
(Fig. 1). These cases indicate that the superior part of
the posterior triangle is not always a “carefree part.”
Awareness of variations in the course of the LON can
help to prevent inadvertent injury to it during surgery
of this region.
Considering the apparent involvement of the
LON-II and III in cervicogenic headache, awareness
of the possible presence of triplication of the LON
may be of value to physicians and surgeons practicing
interventional pain medicine.
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