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NEUROIMAGE
Year : 2015  |  Volume : 63  |  Issue : 5  |  Page : 805-806

Ponticulus posticus: An anatomical curiosity with clinical implications


1 Department of Neurosurgery, National Neurosciences Centre, Peerless Hospital, Kolkata, West Bengal, India
2 Department of Radiology, Peerless Hospital, Kolkata, West Bengal, India

Date of Web Publication6-Oct-2015

Correspondence Address:
Dr. Prasad Krishnan
Department of Neurosurgery, National Neurosciences Centre, Peerless Hospital Campus, Second Floor, 360 Panchasayar, Garia - 700 094, Kolkata, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.166555

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How to cite this article:
Krishnan P, Kartikueyan R, Patel SM, Das S. Ponticulus posticus: An anatomical curiosity with clinical implications. Neurol India 2015;63:805-6

How to cite this URL:
Krishnan P, Kartikueyan R, Patel SM, Das S. Ponticulus posticus: An anatomical curiosity with clinical implications. Neurol India [serial online] 2015 [cited 2019 Oct 19];63:805-6. Available from: http://www.neurologyindia.com/text.asp?2015/63/5/805/166555


A 64-year-old man underwent an X-ray cervical spine to rule out injuries following a road traffic accident. A foramen superior to the posterior arch of the  Atlas More Details was an incidental finding observed [Figure 1]. Computed tomography scans [Figure 2] revealed a completely formed foramen on the right side and an incompletely formed ring on the left side.
Figure 1: Lateral skiagram of craniovertebral junction showing a foramen above C1 posterior arch and parasagittal computed tomography section showing the fully formed canal behind C1 lateral mass that encloses the vertebral artery

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Figure 2: Three-dimensional reconstruction of computed tomography scan of craniovertebral junction (oblique lateral and superior views) showing the fully formed canal on the right side and a partially formed bridge on the left side as well

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Ossification of the lateral part of the posterior atlanto-occipital membrane tends to enclose the vertebral artery in a foramen bounded anteriorly by the C1 articular facet, inferiorly by the groove for the vertebral artery on the superior surface of the posterior C1 arch and posterosuperiorly by the ossified membrane itself. This is variously called the ponticulus posticus (latin for the small posterior bridge), arcuate foramen, retroarticular/retrocondylar foramen, Kimmerle's anomaly, foramen sagittal or retrocondylar vertebral canal ring. A cadaveric study has described its incidence as 13.8% in the Indian population[1] while the literature meta-analysis places it at 16.7%.[2]

The presence of this foramen has been associated with chronic tension-type headaches, and sensorineural hearing loss[3] and shoulder as well as arm pain, neck pain, and vertigo.[4] It has also been implicated as a cause of vertebral artery dissection and stroke in children due to tethering of the vertebral artery within it.[5] It has been described in other primates and Schilling et al., state that it may have a functional significance in protecting the tortuous vertebral artery in an area of high mobility.[6] Its surgical importance lies in that it may mislead the surgeon into believing that the posterior arch of C1 is unduly thick and may thus result in damage to the vertebral artery while a screw is being passed into the lateral mass of C1 during C1–C2 fixation.[2],[7] However, the foramen can easily be identified on preoperative X-rays or parasagittal CT slices, and careful examination of the imaging is essential to avoid this pitfall.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Krishnamurthy A, Nayak SR, Khan S, Prabhu LV, Ramanathan LA, Ganesh Kumar C, et al. Arcuate foramen of atlas: Incidence, phylogenetic and clinical significance. Rom J Morphol Embryol 2007;48:263-6.  Back to cited text no. 1
    
2.
Elliott RE, Tanweer O. The prevalence of the ponticulus posticus (arcuate foramen) and its importance in the Goel-Harms procedure: Meta-analysis and review of the literature. World Neurosurg 2014;82:e335-43.  Back to cited text no. 2
    
3.
Koutsouraki E, Avdelidi E, Michmizos D, Kapsali SE, Costa V, Baloyannis S. Kimmerle's anomaly as a possible causative factor of chronic tension-type headaches and neurosensory hearing loss: Case report and literature review. Int J Neurosci 2010;120:236-9.  Back to cited text no. 3
    
4.
Cakmak O, Gurdal E, Ekinci G, Yildiz E, Cavdar S. Arcuate foramen and its clinical significance. Saudi Med J 2005;26:1409-13.  Back to cited text no. 4
    
5.
Cushing KE, Ramesh V, Gardner-Medwin D, Todd NV, Gholkar A, Baxter P, et al. Tethering of the vertebral artery in the congenital arcuate foramen of the atlas vertebra: A possible cause of vertebral artery dissection in children. Dev Med Child Neurol 2001;43:491-6.  Back to cited text no. 5
    
6.
Schilling J, Schilling A, Galdames IS. Ponticulus posticus on the posterior arch of atlas: Prevalence analysis in asymptomatic patients. Int J Morphol 2010;28:317-22.  Back to cited text no. 6
    
7.
Huang MJ, Glaser JA. Complete arcuate foramen precluding C1 lateral mass screw fixation in a patient with rheumatoid arthritis: Case report. Iowa Orthop J 2003;23:96-9.  Back to cited text no. 7
    


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