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How to revise a failed C1–C2 fusion
Published in Gregory D. Schroeder, Ali A. Baaj, Alexander R. Vaccaro, Revision Spine Surgery, 2019
Nizar Moayeri, Michael G. Fehlings
CT angiography is important in planning a C1–C2 fusion revision, especially when the anatomy is altered or anatomic variations involving the VA between C1 and C2 are present. In particular, V3 segment anomalies, which occur in up to 10% of the population, should be carefully studied. These include the persistent intersegmental artery, in which the VA courses abnormally below the C1 arch after leaving the transverse foramen of the C2 and enters the spinal canal without passing through the C1 transverse foramen; a VA fenestrated at the atlas level; and the posterior inferior cerebellar artery, originating from the VA between C1 and C2 and entering the spinal canal from the caudal side of C1. In addition, the presence of a dominant VA must be noted to avoid introducing any extra risks during screw placement. The presence of a high-riding VA (i.e., one that is more cranial than usual and medially located in the body of C2) occurs in up to 23% of patients and may increase the risk of vertebral artery injury (VAI).
Vascular Anatomy
Published in Swati Goyal, Neuroradiology, 2020
These are persistent embryonic circulatory channels between the caudal carotid artery and the vertebrobasilar arteries (embryonic paired longitudinal neural arteries), which fail to regress: The persistent trigeminal artery (PTA).The persistent hypoglossal artery (PHA) courses through the enlarged hypoglossal canal, parallels the 12th cranial nerve, and connects the cervical ICA with the basilar artery. It does not pass through the foramen magnum and may cause glossopharyngeal neuralgia.The persistent dorsal ophthalmic artery arises from the supraclinoid ICA, and traverses through the superior orbital fissure to the orbit instead of the optic canal.The persistent primitive olfactory artery normally regresses to the recurrent artery of Heubner. If it persists, it is associated with absent ACom artery and aneurysms.The persistent otic artery (POA).The proatlantal intersegmental artery (PIA) originates from the ICA/ECA and joins the vertebral artery at the C2–4 level, and passes through the foramen magnum.
Paracondylar process combined with persistent first intersegmental vertebral artery: an anatomic case report and literature review
Published in British Journal of Neurosurgery, 2023
Haigui Yang, Xiaofei Bai, Xiaoli Huan, Tingzhong Wang
The PFIA comes from the failed obliteration of the first intersegmental artery. Embryologically, the vertebrobasilar artery develops slower than the carotid artery. When the vertebrobasilar artery has not formed, there are only 2 longitudinal neural arteries (LNAs) dorsal to the carotid artery. At this stage, the LNAs are plexuses rather than real arteries. The carotid artery supplies the LNAs through the presegmental and intersegmental arteries from the anterior circulation to the posterior circulation. After the formation of posterior communicating artery, all the presegmental arteries including primitive trigeminal artery, primitive otic artery, and primitive hypoglossal artery obliterate. Then, both upper LNAs anastomose into a basilar artery. Simultaneously, the lower LNA (segmental plexuses) anastomose to form a VA. Once the vertebrobasilar artery has formed, all the anterior-posterior intersegmental arteries obliterate to maintain a mature down-up blood flow in the vertebrobasilar artery.9 However, the order of the segmental plexuses anastomosis is from down to up. It means that the first intersegmental artery is the last one which obliterates. Genetic, hemodynamic, and environmental factors may cause the failure of its obliteration, which results in a PFIA.6 Occipitalized atlas is caused by the failure of embryonic sclerotome resegmentation which also occurs at similar embryonic stages when LNA segmental plexuses anastomosis progresses. That could explain why PFIA is usually associated with an osseous anomaly such as occipitalized atlas or Klippel-Feil syndrome.7
Intra-operative vagal neuromonitoring predicts non-recurrent laryngeal nerves: technical notes and review of the recent literature
Published in Acta Chirurgica Belgica, 2021
S. Van Slycke, K. Van Den Heede, K. Magamadov, J.-P. Gillardin, H. Vermeersch, N. Brusselaers
It is generally acknowledged that the absence of a normal RLN results from an embryologic error in the development of the sixth primitive aortic arch. The laryngeal nerve originates from the vagal nerve caudally of the sixth arch. Due to a normal regression of the fifth and sixth aortic arch, the laryngeal nerve stays caudal to the structures that develop from the fourth arch, i.e. the subclavian artery on the right side and the definitive main aortic arch on the left side. During their descent into the thorax, these arterial structures elongate the inferior laryngeal nerves and this explains their recurrent course. Due to the absence of the fourth arch, the inferior laryngeal nerve arises higher in the cervical region. In terms of the developmental anomaly, involution of the fourth vascular arch, along with the dorsal aorta, leaves the seventh intersegmental artery attached to the descending aorta. This persistent seventh intersegmental artery assumes a retro-esophageal position as it proceeds out of the thorax into the right arm and becomes the lusorian artery in the adult [7].
Surgical considerations in posterior C1-2 instrumentation in the presence of vertebral artery anomalies: case illustration and review of literature
Published in British Journal of Neurosurgery, 2019
Lee A. Tan, Manish K. Kasliwal, Carter S. Gerard, Vincent C. Traynelis, Ricardo B.V. Fontes
The vertebral artery develops from plexiform anastomoses among the embryonic cervical intersegmental arteries around 5–6 weeks of gestation. The seven intersegmental arteries enlarge and become the subclavian arteries and the VAs arise from the enlarging seven cervical intersegmental arteries and supply the caudal end of the longitudinal neural arteries that develop into the basilar artery. If the first intersegmental artery persists without sufficient growth of the normal VA branch, then the VA takes an anomalous course and enters the spinal canal inferior to the C1 posterior arch after emerging from the C2 transverse foramen, then ascends under the C1 posterior arch and enters the dura without passing through the C1 transverse foramen, becoming the PFIA. When the VA develops but the first intersegmental arterty fails to regress, then a FVA would form. Low-lying PICA and HRVA may be present as natural variations of normal anatomy. With respect to PP, it has been suggested that the arcuate foramen is commonly present in early primates and may be a ruminant of evolution.