Spontaneous atlanto-axial dislocation and trisomy 21: causal factors and management
Fah Bouaré1,&, Mohamed Lmejjati1, Davis Mpando1
1Department of Neurosurgery, Mohammed VI Hospital, Cadi Ayyad University, Marrakesh, Morocco
Fah Bouaré, Department of Neurosurgery, Mohammed VI Hospital, Cadi Ayyad University, Marrakesh, Morocco
Spontaneous atlanto-axial (C1-C2) dislocation is an atlanto-axial instability,
found in 10 to 30% of trisomy 21 patients, the majority of whom is asymptomatic.
We report a case of a 21 years-old woman, with trisomy 21, admitted in
our department presenting a spinal cord compression syndrome with right
hemiparesis associated with a cervicalgia evolving for 3 months of admission
Standard cervical radiography showed a C1-C2 dislocation with posterior
displacement of the odontoid process. A cervical computerized tomography
revealed a C1-C2
dislocation with significant recoil of the odontoid process. A cervical
magnetic resonance imaging (MRI) confirmed the bulbo-medullar junction
compression on the dislocation.
The surgical treatment consisted of a cervico-occipital fixation. The laxity
of the transverse ligament is one of the main causes of C1-C2 dislocation;
hypoplasia, malformation or complete absence of the odontoid process; are
also predisposing factors. It must be early detected. The treatment of
choice is surgical also by arthrodesis of C1 to C4 + graft and enlargement
of the occipital foramen or occipito-cervical arthrodesis by synthetic graft
and Cotrel-Dubousset system or occipito-C4 arthrodesis + laminectomy of C1
and enlargement of the occipital foramen.
Spontaneous atlanto-axial (C1-C2) dislocation is an atlanto-axial
instability found in 10 to 30% of trisomic 21 patients, most of whom is
asymptomatic [1, 2]. Only 1-2% of people with downs develop symptoms .
The aim of this work is to specify the etiological factors and the surgical
treatment of spontaneous C1-C2 dislocation in trisomy 21.
Patient and observation
A 21-years-old woman with a trisomy 21, admitted in our department
with a spinal cord compression syndrome made of cervical spinal
syndrome and right hemiparesis evolving for 3 months without context
of trauma. Standard
cervical radiography (Figure
1) showed a C1-C2 dislocation with posterior displacement of the
odontoid process. A cervical tomodensitometry (CT) in axial section
of the bony window (Figure
confirmed the dislocation C1-C2 with a significant recoil of the
odontoid process. A cervical magnetic resonance imaging (MRI) (Figure
3) was made, which found C1-C2 dislocation with compression of the
bulbo-medullary junction. A surgical decision was made regarding
the neurological repercussions of dislocation. The goal of the
surgical treatment was to reduce, decompress and fix by a posterior
approach. The patient was in prone position, the head on the Mayfield
and an occipito-cervical incision from the external occipital protuberance
to C4 was performed. Under X-ray, we put a Vertex type material
(medtronic) which allowed the placement of 2 occipital screws and
4 hooks on all laminae of C2 and C3. Postoperative radiography was performed
The clinical evolution was marked by a slight recovery of muscle
strengths on the right hemi-body and an infection of the area of the operative
incision which was treated by application of antiseptics, healing products
and oral antibiotics.
As anatomic review, the C2 odontoid process or the dens, visible
on the Figure 5,
has many attachment ligaments on C1 and occiput. Among these ligaments
we can see the transverse ligament on the Figure
6 . The C1-C2 dislocation or instability
in trisomy 21 may be present in the neonatal period .
The laxity of the transverse ligament is one of its the main causes;
hypoplasia, malformation or complete absence of the odontoid process
is also predisposing
factors . Screening is done by careful clinical examination
(looking for signs of spinal cord compression) and standard radiography
with the flexion and hyper-extension of the neck. This screening is recommended
twice, between the age of 5 and 10 and at the age of 15 .
The dislocation can lead to spinal cord compression and should
be investigated by dynamic radiographies in case of trisomy 21 .
Its signs may be: torticollis, spastic hemiparesis, quadriparesis, anal
incontinence, neurogenic bladder, paresthesia; or ataxia, disturbances of
Imaging (CT scan, MRI) can be used to diagnose, in addition to C1-C2 dislocation, odontoid bone dysplasia and cervical spinal cord compression associated with signs of myelomalacia [7
Surgical treatment by posterior approach may consist of an arthrodesis of C1
to C4 + graft and enlargement of the occipital foramen or occipito-cervical arthrodesis
by synthetic graft and Cotrel-dubousset system or occipito-C4 arthrodesis + laminectomy
of C1 and enlargement of the occipital foramen [7
]. The choice of occipito-cervical fixation by the vertex type material (medtronic) is that it allows a reduction with decompression and effective stabilization of the reduction. The predominant risk is a spinal cord compression during hyper-extension of the neck, especially during intubation preparation [5
Its surgical treatment allows a favorable evolution except for completely deficit
Spontaneous atlanto-axoid dislocation in the trisomic patient 21 may be congenital, related to transverse ligament laxity, hypoplasia, malformation, or complete absence of the odontoid process. Its screening must be done carefully, clinically and radiologically. It must be early diagnosed and the treatment of choice is surgery.
The authors declare no competing interests.
Each author contributed to the writing of this manuscript, either
by the correction, the reading, or the translation into English. All authors
have read and agreed to the final manuscript.
Figure 1: cervical spine X-ray showing C1-C2 dislocation with posterior displacement of the odontoid process
Figure 2: cervical CT in axial section bone window showing C1-C2 dislocation with significant recoil of the odontoid process
Figure 3: cervical spinal MRI showing C1-C2 dislocation with compression of the bulbo-medullary junction
Figure 4: post-operative X-Ray after occipito-cervical fixation
Figure 5: view of the C2 odontoid process
Figure 6: view of the different ligaments attaching the C2 odontoid process to C1 and occiput
- Davidson MA. Primary care for children and adolescents with Down syndrome. Pediatr Clin North Am. 2008 Oct;55(5):1099-111, xi. PubMed | Google Scholar
- Chaanine A, Hugonenq C, Lena G, Mancini J. Les complications neurologiques liées à la trisomie 21. Arch Pediatr. 2008 Apr;15(4):388-96. PubMed | Google Scholar
- Jonathan Hobbs, Edwin Ramos. Craniovertebral Junction. In: Ali A. Baaj, Praveen V. Mummaneni, Juan S. Uribe, Alexander R. Vaccaro, Mark S. Greenberg. Handbook of
spine surgery. Second edition. New York: Thieme Medical Publishers; 2016. p 34-41.
- Lefvre Y, Rigal J, Mariey R, Durbec-Vinay A. Anomalies rachidiennes diagnostiquées en période néonatale - Conduite à tenir. Archives de Pédiatrie. 2012;19(6S1):H241-H242. Google Scholar
- Neurologic sequelae secondary to atlantoaxial instability in Down syndrome - Implications in otolaryngologic surgery. Arch Otolaryngol Head Neck Surg. 1994;120(2):159-65. PubMed | Google
- Cullen S, O'Connell E, Blake NS, Ward OC. Atlantoaxial instability in Down’s syndrome: clinical and radiological screening. Ir Med J. 1989 Jun;82(2):64-5. PubMed | Google Scholar
- Alvarez N, Kao A, Schneck MJ, Talavera F. Atlantoaxial instability in Down syndrome. 2011, June 7. Medscape reference. Accessed on January 05 2019