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|Year : 2015 | Volume
| Issue : 5 | Page : 805-806
Ponticulus posticus: An anatomical curiosity with clinical implications
Prasad Krishnan1, Rajaraman Kartikueyan1, Sachinkumar Maheshbhai Patel1, Sayan Das2
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 Publication||6-Oct-2015|
Dr. Prasad Krishnan
Department of Neurosurgery, National Neurosciences Centre, Peerless Hospital Campus, Second Floor, 360 Panchasayar, Garia - 700 094, Kolkata, West Bengal
Source of Support: None, Conflict of Interest: None
|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
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 while the literature meta-analysis places it at 16.7%.
The presence of this foramen has been associated with chronic tension-type headaches, and sensorineural hearing loss and shoulder as well as arm pain, neck pain, and vertigo. 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. 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. 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., 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.
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[Figure 1], [Figure 2]