|Year : 2012 | Volume
| Issue : 2 | Page : 99-101
Spinabifida of atlas
K Padmalatha1, BS Prakash2, N Balachandra3, Y Mamatha4
1 Assistant Professor of Anatomy, ESIC Medical College, Rajajinagar, Bengaluru, India
2 Associate professor, Dr. B R Ambedkar Medical College, K G Halli, Bengaluru, India
3 Assistant Professor of Anatomy, Dr. B R Ambedkar Medical College, K G Halli, Bengaluru, India
4 Assistant Professor of Anatomy, Hassan Institute of Medical Sciences, Hassan, Karnataka, India
|Date of Web Publication||23-Jan-2020|
Assistant Professor of Anatomy, ESIC Medical College & PGIMSR, Rajaji Nagar, Bengaluru - 560 010
Source of Support: None, Conflict of Interest: None
During the routine osteology demonstration for the first year MBBS students, the authors came across the presence of incomplete posterior arch in one of the atlas. Congenital clefts and other developmental anomalies of the atlas are rarely encountered. They are incidental findings discovered while investigating the cervical spine following trauma. Differentiation of developmental variants of the atlas from the Burst fracture of Jefferson is essential to prevent unnecessary medical intervention. Posterior midline cleft of atlas/ rachischisis/spinabifida occulta are well recognized and attributed to the defect /absent development of cartilaginous preformation of the arch and not to the disturbance of the ossification.
Keywords: Atlas, Spinabifida, Midline cleft
|How to cite this article:|
Padmalatha K, Prakash B S, Balachandra N, Mamatha Y. Spinabifida of atlas. Natl J Clin Anat 2012;1:99-101
| Introduction|| |
Cervical vertebra anomalies are classified into two main categories, posterior arch deficiencies and fusions. Posterior arch deficiencies include spinabifida and Dehiscence. Fusions include fusion, Block fusion, assimilation and occipitalization. Congenital anomalies of the posterior arch of atlas are rare. They range from partial clefts to total agenesis of posterior arch of atlas. Congenital clefts and other malformations of atlas are incidental findings which are identified while investigating the cervical spine following trauma.
| Case Report|| |
During the routine osteology demonstration for the first year MBBS students at Dr. B. R. Ambedkar Medical College, Bengaluru, the authors came across the presence of incomplete posterior arch in one of the atlas, with the tapering ends. [Figure 1] and [Figure 2].
|Figure 2: Inferior surface of atlas.|
A- Anterior arch; P- Posterior arch; The gap in the posterior arch of atlas measured 0.65mm.
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| Discussion|| |
Atlas usually ossifies in three centres, one appears for centrum during 8th week, one centre each for lateral mass/neural arch during 7th week. At birth, the anterior arch is fibrocartilaginous and separate centre appears at the end of first year and unites with the lateral masses between 6th & 8th year. The centre for posterior arch appears during second year and they unite between third and fourth year.
The defects of posterior arch of atlas are commonly believed to be due to a local mesenchymal defect leading to lack of chondrification.
Posterior midline clefts of atlas are attributed to the defective development of cartilaginous preformation of arch & NOT due to the disturbance of ossification.
The basic defect in agenesis of posterior arch of atlas is the lack of a cartilage template on which the ossification process builds. [Figure 3].
|Figure 3: Classification of posterior arch defects of the atlas (reproduced from Currarino et al)|
A. Failure of posterior midline fusion of the two hemiarches. Sometimes a small separate ossicle is seen within the gap; B. Unilateral cleft, ranging from a small gap to a complete absence of the hemiarch and posterior tubercle; C. Bilateral clefts of the lateral aspects of the arches with preservation of the most dorsal part of the arch ; D. Complete absence of the posterior arch with a persistent isolated tubercle. This anomaly is conceivably a more extensive form of bilateral clefts. The lateral parts of the posterior arch are absent except for the posterior tubercle; E. Absence of the entire posterior arch including the Tubercle.
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High incidence of both anterior and posterior spinabifida Atlas is associated with certain diseases such as mucopolysaccharidiasis, Down’s syndrome and Morquio’s syndrome.
Clinical implications of posterior arch defects of atlas include acute neurologic deficits such as transient quadriparesis, paraparesis, Lhermitt’s sign, chronic neck pain & headache.
Cervical vertebra anomalies are usually associated with cleft Hp, cleft palate, the common pathogenesis most probably relates to simultaneous embryogenesis of both structures.
Congenital anomaly of posterior arch of atlas leads to cervical canal stenosis and that may cause cervical myelopathy.
| Conclusions|| |
Defects of the posterior arch of atlas are very rare. The basic defect is due to local mesenchymal defect leading to lack of a cartilage template and not due to disturbance in ossification. Congenital clefts and other malformations of atlas are incidental findings which are identified while investigating the cervical spine following trauma.
The authors express heartfelt thanks to Non teaching staff and students of Dr. B R Ambedkar Medical College, KG Halli, Bengaluru for their support.
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[Figure 1], [Figure 2], [Figure 3]