raniocervical junction is the area comprising
the inferior portion of the occipital bone that
surrounds the foramen magnum and the first 2
cervical vertebrae, atlas and axis. Due to its
complicated embryonic development, this area is
easily susceptible to
developmental variants and anomalies, producing a
wide spectrum of symptom.1 Clinical syndromes
develop as a result of mechanical disturbance of
movement or of deformities of the cervical cord
accompanying these developmental anomalies and
the variants of skeletal elements. The bone
deformity itself may be sufficient to cause pressure
on the upper cervical cord and the vertebral artery
during movements of the head and neck. In some
skeletal and neural
situations (such as, transient vertebra basilar
insufficiency, Barre-Lieou syndrome and chronic
upper cervical syndrome) a developmental variant
of the atlas is a significant factor.2-5 Due to the
clinical significance, a variation of the first
vertebrae, retroarticular canal, was examined in
several populations.3,5-9 Recently, a review by
Prescher10 also reported the osseous variations in the
The present study was undertaken to investigate
several varieties or deformities of the atlas vertebra
from skeletal specimens of the Eastern Anatolian
people. The purpose of the present study was to
determine the frequencies of the varieties of the first
From the Department of Anatomy (Kavakli, Kus), School of Medicine, Firat University, Elazig, Department of Anatomy (Aydinlioglu, Erdem),
Department of Neurology (Anlar), School of Medicine, Yuzuncu Yil University, Van, Department of Anatomy (Yesilyurt, Diyarbakırlı), School of
Medicine, Atatürk University, Erzurum, Turkey.
Received 11th August 2003. Accepted for publication in final form 29th October 2003.
Address correspondence and reprint request to: Dr. Ahmet Kavakli, Fırat University, Department of Anatomy, School of Medicine, 23119 Elazıg,
Turkey. Tel. +90 (424) 2370000. Fax . +90 (424) 2379138. E-mail: firstname.lastname@example.org
Variants and deformities of atlas vertebrae in
Eastern Anatolian people
Ahmet Kavaklı, MD PhD, Atıf Aydınlıoglu, MD PhD, Hakkı Yesilyurt, MD PhD, Ilter Kus, PhD,
Semih Diyarbakırlı, PhD, Saadet Erdem, MSc, Ömer Anlar, MD.
developmental anomalies of the atlas may produce
clinical symptoms by compressing on the vertebral
artery, particularly during extreme rotational movements
of the cervical spine. The aim of the present study was to
investigate several varieties and deformities of the atlas
vertebra from the skeletal specimens of Eastern Anatolian
At the craniocervical junction,
period, 2000 through to 2002 in the Department of
Anatomy, Firat, Yuzuncu Yil and Ataturk University,
Turkey. Developmental anomalies and the variants of the
first vertebrae were investigated on 86 atlas.
This study was carried out over a 3-year
Ponticulus posterior was observed with a low
frequency on right as 2.3%. The bilateral localization was
10.5% and the left-side localization was 9.3%. Ponticulus
lateralis showed an equal localization as 1.2% on the
right, 1.2% on the left and 1.2% bilateral. In the present
study, a complete subdivision of the joint surface was
observed in 11 atlases
infratransversarius atlantis with a frequency between
1.2-7%, arthrotic formation and corona atlantis
peridentals in 8 cases (9.3%) were also found.
might be peculiar to the population living in this area.
The low frequency for fonticulus posterior
Saudi Med J 2004; Vol. 25 (3): 322-325
Variations of atlas ... Kavakli et al
www.smj.org.sa Saudi Med J 2004; Vol. 25 (3) 323
localization of 3.5% on the right, 1.2% on the left
and 7% bilateral (Table 1).
Arthritic deformities. (Figures 3 & 4). In our
study, an arthritic formation at the arcus anterior
atlantis was found in 8 cases with a frequency of
9.3% (Table 1).
vertebrae: ponticulus posterior and ponticulus
description, a wide groove for vertebral artery and
suboccipital nerve on the superior aspect of the
posterior arch of the atlas vertebra crosses behind
each lateral mass. In some cases it is partly or
wholly made of a foramen by bone arching back
from the superior surface of the lateral mass.11 This
bony bridge was first reported by MacAlister.6 It
was variously described as ponticulus posterior or
posticus, Kimmerle’s variant, retroarticular canal,
foramen retro-articular superior, retro condylar
vertebral artery ring, posterior atlantoid foramen,
foramen arcual and atlas bridging.2-5,8,10,12,13 The
ponticulus posterior was observed with a low
frequency on the right (2.3%) (Table 1). The
percentage of the bilateral and left side localization
(Figure 1) showed no difference with those of the
American population, which was reported to be
between 9-15%.3,5,6,9 Its incidence in the Indian
population was found as 11.4%14 while in the South
African population, it was reported with complete
occurrence as 11.7% on the right and 24.6% on the
left.4 Our study presented with partial posterior
bridge formation with 9.3% and complete formation
with 12.8% (Table 1). Taitz and Nathan5 found
partial formation as 25.9% and complete formation
bridge, which extends from the upper edge of the
massa lateralis to fuse with the posterior root of the
transverse process.5,10 The frequency of the lateral
Bridge formations of the atlas
Represents the lateral
cervical vertebra in the mentioned population,
which have not been documented in the literature.
The clinical symptoms and disturbances caused by
the anomalies of the atlas were also reviewed.
3-year period from 2000 through to 2002, in the
Department of Anatomy, Firat, Yuzuncu Yil and
Ataturk University, Turkey. The present study is
based on the examination of 86 complete and
undamaged adult atlas vertebrae. Most of them were
the course materials obtained from cadavers for our
medical students. The others were from a collection
of vertebrae available in our departments. Our
materials were of undetermined age and gender.
Special attention was directed to the bridge
formation and arthritic changes of the atlas, which
are responsible for clinical symptoms.
This study was carried out over a
as the shape variations and arthritic formations
Bony bridges. (Figure 1) In the present study,
ponticulus posterior was observed with a frequency
of 2.3% on the right. The percentage of bilateral
localization was 10.5%
localization was found with 9.3%. Partial posterior
bridge formation was found with 9.3% and
complete formation with 12%. The lateral bony
bridge, ponticulus lateralis represented an equal
localization with frequencies of 1.2% on the right,
1.2% on the left and 1.2% bilateral. One case
showed both posterior and lateral bridges (Table 1).
Facies articularis superior atlantis bipartite.
(Figure 2) Eleven atlases (12.8%) presented with a
complete subdivision of the joint surface was found
in our study (Table 1). No incomplete subdivision
Processus infratransversarius atlantis. (Figure 3)
This variation was observed with a frequency and
The results are summarized in Table 1
and the left-sided
Table 1 - Variations and arthrotic changes of atlas found in the present study (N=86).
Facies articularis superior atlantis bipartita
Processus infratransversarius atlantis
Corona atlantis peridentalis
Variations of atlas ... Kavakli et al
Variations of atlas ... Kavakli et al
324 Saudi Med J 2004; Vol. 25 (3)www.smj.org.sa
materials of the dorsal arch and the lateral
extensions of the proatlas and to belong to the
manifestations of the occipital vertebra.10
The clinical significance of bridge formation has
been discussed in reference to their possible effect
on normal vertebral artery function due to the
ponticulus formations that can be identified on the
conventional lateral and a.-p. radiographs.3,10,18 This
formation can cause compression of the vertebral
artery, particularly during extreme rotational
movements of the cervical spine. This may play a
role in reduction of vertebral artery blood flow,
leading to symptoms
insufficiency.3,4,7 A correlation between migraine
cervicale and the presence of a ponticulus posterior
was reported. In such cases, resection of the
ponticulus may be indicated, which results in
decompression of the vertebral artery and the
The superior articular surface of the
bridge in our study generally resembles to that of
the previous studies. In the literature, this variation
is reported with a percentage between 1.8-3.8,5,10,15
which agrees with our findings. Our study also
presented an equal localization for this formation,
namely 1.2% on the right, 1.2% on the left and 1.2%
bilateral. Our observations showed a ratio of 2:1 for
complete and incomplete formation, similar to Taitz
and Nathan5 finding. In our study, one atlas (1.2%)
showed both posterior and lateral bridges (Table 1),
which accords with the literature.5,10 The origin of
atlas bridging has been debated in the literature. The
opinion of ancient authors was that the posterior
bridge is a direct homologue of the superior oblique
process of other mammals.6,16 Familial nature of
atlas bridging proposed by Selby et al17 and an
acquired ossification of ligaments occurring with
aging5,8 was not the same with the study of Lamberty
and Zivanovic,3 that
posteriores have been seen in fetuses and children.
Recently, atlas bridging is supposed to develop from
Figure 1 - A bony arch bridging the sulcus arteriae vertebralis
(arrows) behind the massa lateralis atlantis, namely,
ponticulus posterior. A complete bridge over the foramen
processus transversi of the atlas, ponticulus lateralis
Figure 2 - Superior articular facet of atlas vertebra showing
subdivision into 2 parts, facies articularis superior atlantis
bipartite, with bilateral localisation (asterisk).
Figure 3 - A bony extension in the caudal direction, emerging from
the transverse process of the atlas (such as, processus
infratransversarius atlantis) (arrows) and arthrotic
formation of the atlas at the arcus anterior atlantis
Figure 4 - A bony element at the arcus anterior atlantis, corona
atlantis peridentalis or "coulisse of the atlas" (asterisk).
Variations of atlas ... Kavakli et al Download full-text
www.smj.org.saSaudi Med J 2004; Vol. 25 (3) 325
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artery ring of the atlas and its significance. Acta Anat
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retroarticular canal of the atlas vertebra. Acta Anat (Basel)
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cervical vertebra. Radiology 1959; 72: 850-854.
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the atlas for the vertebral artery. Acta Radiol Diagn
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10. Prescher A. The craniocervical junction in man, the osseous
variations, their significance and differential diagnosis.
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11. Williams PL, Warwick R, Dyson M, Bannister LH. Grays
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seventeen. Anat Rec 1963; 145: 449-454.
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variants: Atlas bridging and clinoid bridging. Am J Phys
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osseux de l’artére vertébrale de l’atlas. Acta Anat (Basel)
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(UK): Butterworth Heinemann; 1972. p. 93.
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20. Ganguly DN, Singh-Roy KK. A study on the
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21. Kattan KR. Two features of the atlas vertebra simulating
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atlas is concave and elongated, joint with the
corresponding occipital condyle. Sometimes the
articular surface is divided into 2-facet.11 In the
present study, a complete subdivision of the joint
surface was observed in 11 atlases (12.8%) (Table 1)
(Figure 2). Prescher10 found this variation in 28 out
of 200 atlases (14%): 7.5% on the right, 2% on the
left, 4.5% bilateral. In the literature, the frequency
of the bipartite superior joint surface was reported
between 5.5-33%.10,19 That this variation develops
from 2 sources, namely, the proatlas and C1
segment, may explain its origin.10,18,20
symptoms and disturbances caused by facies
articularis superior bipartita atlantis have not been
reported. However, it may be mistaken for fractures
Processus infratransversarius atlantis.
a bony extension emerging from the transverse
process in caudal direction.10 In the present study,
this structure was observed in different localization
with a frequency of 1.2-7% in variable lengths
(Figure 3). Clinically, this variation may represent
symptomatic disturbances at the craniocervical
junction.22 Patients with symptomatic variations of
the craniocervical junction often complain of pain in
the neck region or at the back of the head or they
suffer from vertigo or disturbances in balance.
Principal mechanisms of symptoms are mechanical
compression of nervous and vascular structures,
marked instability or in contrast, elevated rigidity.23
Corona atlantis peridentalis.
arthritic formation, corona atlantis peridentalis or
"coulisse of the atlas" termed by Prescher,10 at the
arcus anterior atlantis was found in 8 cases (9.3%),
corresponding to the "coulisse of the dens" (Figure 3
& 4). Lombardi24 reported that these formations
might be partly attributed to the occipital vertebra.
He also observed that the patients in his series were
free of any physical disturbances attributable to the
In conclusion, the findings from our study
generally agree with those of the previous. The only
difference was that ponticulus posterior was
observed with a low frequency on the right, only
perhaps encountered by chance. It might even be
peculiar to the population living in the area. Our
results for processus infratransversarius atlantis,
arthrotic formation and corona atlantis peridentalis,
will also be compared with those of further works
for our literature survey failed to find any data
concerning them in other populations.
In the present study,
Assoc. Prof. Hassan Boynukara who made the necessary
correction of the English grammar.
The authors would like to thank