·LogIn/LogOut

·Fulltext PDF(104K) Free

·Abstract download TXT | XML

·Articles in CMJ by YI Zhi-qiang LI Liang

·Articles in PubMed by YI ZQ LI L

·Put into my bookshelf

·Email to Friend

·Email to author

·Visit:658

·Download:305

·Advanced Search

·Related Articles

·Change font size:

·Cannot read some characters

Usually the vertebral artery (VA) arises from the first part of the subclavian artery and enters the transverse foramen of the C-6 vertebra (first segment) and then ascends through the transverse foramen from C-6 to the atlas (second segment). In its third segment, the artery emerges on the superior surface of the atlas and curves horizontally over the lateral and posterior surfaces of the superior articular process of C-1 and then passes medially in front of the posterior atlanto-occipital membrane. In its fourth segment, the artery pierces the dura mater and arachnoid between the occipital bone and atlas then enters the cranial cavity through the foramen magnum. To identify and preserve the VA is vital in the surgery of the craniaocervical and cervical region. However, the variations of the VA complicate the procedures of VA identification. It is valuable to know the course of VA preoperatively. Some anatomical variations of the VA occur due to its abnormal development process.^1,2 The variation of the VA not passing through the transverse foramen is relatively rare and, to our knowledge, only eight similar cases have been reported in the literature before the year 2008. In five cases, this anatomical anomaly was discovered by angiography,^1,3-5 whereas two other examples were found at autopsy.^6,7 With 3-D computed tomography angiography (CTA) being commonly used, more of this kind of VA anomaly has been reported in recent years.^8-10

We describe a case of anomalous VA not passing through the transverse foramen found incidentally when we treated a patient with meningioma of the right sphenoid ridge.

A 64-year-old man presented with headaches for 3 months. Neurological examination found no abnormality. Head MRI showed a meningioma of the right sphenoid ridge. CT, MRI, digital subtraction angiography (DSA) revealed no abnormity other than the signs associated with the meningioma. We used the Destroscope Virtual Reality System (Volume Interaction Pte Ltd, software: RadioDexter^TM 1.0, Singapore) to optimize the preoperative plan. The data of CTA (1-mm thin slice scan) in DICOM were imported to the system for reconstruction and a 3-dimentional (3-D) stereotactic image was obtained. During this procedure we found an anomalous VA. The right VA does not pass through the transverse foramen of the atlas, but instead passes the posterior arch of the atlas (Figure 1). We reviewed the DSA and found that the course of the right VA is different from that of the left and reconfirmed that the right VA is thinner than the left (Figure 2). But no definite signs of the abnormal relation between VA and the transverse foramen of atlas were demonstrated. The patient was reexamined and no symptoms or signs were detected such as occipitocervical neuralgia, dizziness, vertigo, tinnitus, etc. The meningioma was totally resected and the patient was discharged uneventfully. No events related to the VA anomaly were seen in the follow-up period of 15 months. 】

view in a new window

Figure 1. The right anomalous VA and the meningioma of sphenoid ridge in posterior-anterior view and lateral view. A: The white arrow indicates the right VA passes inferior the posterior arch of atlas, not passing through the transverse foramen of the atlas; the black arrow indicates the meningioma of sphenoid ridge. B: The black arrow indicates the meningioma of sphenoid ridge; the white arrow indicates the empty transverse foramen of the atlas through which the VA does not pass. Figure 2. DSA image of the left and right VAs. A: Left VA. The black arrow shows where the VA pass through the transverse foramen of C-1; the white arrow shows where the VA pass through the transverse foramen of C-2. B: Right VA. The black arrow shows where the VA pass through the posterior arch of C-1; the white arrow shows where the VA pass through the transverse foramen of C-2. Figure 3. The right VA (white arrow) is significantly thinner than the left one (black arrow). Figure 4. The distance between the tubercle of atlas and the point where the VA pass the posterior arch of atlas (white arrow) is 12.95 mm.

DISCUSSION

The VA is a hemodynamic pathway resulting from the development of anastomoses between the segmental arteries of the cervical sclerotomes.^1,2 If portrait anastomoses failed to form between the C-1 segmental arteries and C-2 segmental arteries, the latter takes the place of the former, and the VA emerges inferior of the C-1 posterior arch in the adult.² With 3D-CTA being more commonly used, more of this kind of VA anomaly is being reported. Hong et al⁸ reported that in 1013 Korean patients who underwent CT angiography, 39 cases (3.8%) with unilateral persistent first intersegmental artery were detected, in which the VA courses below the C-1 arch after exiting the transverse foramen of the axis, and subsequently enters the spinal canal without passing through the C-1 transverse foramen; 8 cases (0.8%) with bilateral persistent first intersegmental artery.

In 140 cases with CTA examination Yamaguchi et al⁹ reported five of 280 VAs (1.8%) passed beneath the posterior arch of the atlas without going through the transverse foramen. In the series of Duan et al,¹⁰ four cases out of 68 cases evaluated with 3-D CTA examination were found with the VA anomaly of not passing through the transverse foramen of the atlas. Therefore the anomalous VA not passing through the transverse foramen of the atlas artery could be more common than expected. The literature has reported that this kind of VA anomaly may be associated with Klippel-Feil syndrome.^3,4 In this case, no other malformation was found. The right VA, from the origin to the end is significantly thinner than the left one (Figure 3). According to literature, the left VA is larger than the right in 42% to 51% of people, and the right is larger the left in 32% to 41%.^11,12 Hong et al⁸ reported in their study of 1013 cases that the incidences of a right- and left-dominant VA were 9.8% and 22.3%, respectively. It is essential to identify and preserve VA in the operations of craniocervical junction and cervical region; such as far lateral approach, cervical posterior approach, cervical anterolateral approach, etc.^13-15 Usually, we regard 15 mm from the tubercle of atlas toward lateral direction as a safe distance when resecting the posterior arch of the atlas during surgery using the posterior occipital midline approach. However, in this patient, the distance between the tubercle of atlas and the point where the VA passes the posterior arch of atlas is 12.95 mm that unquestionably make the VA potentially vulnerable (Figure 4). Although only a small percentage of patients demonstrated this kind of anomaly, there exists the possibility for inadvertent intraoperative VA injury if surgeons fail to recognize these types of variations. The VA not passing through the transverse foramen of the atlas may be related to some diseases. Sharma et al³ reported a symptomatic congenitally anomalous ecstatic VA not passing through the transverse foramen of the atlas, but instead piercing the dura mater below the posterior arch of the C-1 in the atlantoaxial (C1-2) interlaminar space. The ecstatic VA resulted in occipital neuralgia due to vascular compression of the C-2. Vincentelli et al⁵ reported a case of an abnormal loop of the VA compressing both the cervicomedullary junction and the accessory nerve which resulted in spasmodic torticollis. Both the two cases were cured by microvascular decompression. In this case, there were no symptoms or signs related to the VA anomaly, and no events related to the VA anomaly happened in the follow-up period of 15 months. The patient is still under follow-up now. A dense venous plexus with multiple anastomoses around the VA may potentially obscure the operative view and increase the risk of VA damage. Surgeons should consider the possibility of this VA variation when operating in the region of the craniocervical junction and seek the causes for occipital neuralgia, spasmodic torticollis and other symptoms caused by an occupying-lesion in the C-1 adjacent region. The 3D-CTA, which gains an advantage over DSA in its noninvasiveness and by showing the vessel and bone simultaneously, facilitates the identification of an abnormal relation between the VA and bone structures. Additionally, CTA is less invasive and able to be performed in a much shorter time than catheter or MR angiography. In our case, we used the Destroscope Virtual Reality System to observe and measure the VA anomaly. The VR system not only has the advantage of 3D-CTA but also is extraordinarily useful in making a detailed preoperative plan to avoid VA damage by providing us with a 3-D volumetric object, which can be viewed stereoscopically and cropped, cut, drilled and measured from any angle.

1. Lasjanias P, Braun JP, Hasso AN, Moret J, Manelfe C. True and false fenestration of the vertebral artery. J Neuroradiol 1980; 7: 157-166.

2. Padget DH. The development of the vertebral arteries in the human embryo. Contrib Embryo 1948; 32: 205-262.

3. Sharma RR, Parekh HC, Prabhu S, Gurusinghe NT, Bertolis G. Compression of the C-2 root by a rare anomalous ectatic vertebral artery. Case report. J Neurosurg 1993; 78: 669-672.

4. Tokuda K, Myasaka K, Abe H. Anomalous atlantoaxial portions of vertebral and posterior inferior cerebellar arteries. Neuroradiology 1985; 27: 410-413.

5. Vincentelli F, Caruso G, Rabehanta PB, Rey M. Surgical treatment of a rare congenital anomaly of the vertebral artery: case report and review of the literature. Neurosurgery 1991; 28: 416-420.

6. Abe K. A rare abnormal case of the vertebral artery showing no passing through the foramen transversarium of the atlas. Acta Anat Nippon 1968; 43: 393-394.

7. Takahashi K. A case of the vertebral artery, not passing through the foramen transversarium of the atlas. Sapporo Igaku Zasshi (Japan) 1963; 24: 250-252.

8. Hong JT, Lee SW, Son BC, Sung JH, Yang SH, Kim IS, et al. Analysis of anatomical variations of bone and vascular structures around the posterior atlantal arch using three-dimensional computed tomography angiography. J Neurosurg Spine 2008; 8: 230-236.

9. Yamaguchi S, Eguchi K, Kiura Y, Takeda M, Kurisu K. Posterolateral protrusion of the vertebral artery over the posterior arch of the atlas: quantitative anatomical study using three-dimensional computed tomography angiography. J Neurosurg Spine 2008; 9: 167-174.

10. Duan SY, Lü SM, Ye F, Lin QC, Chen LB. Three-dimensional CT angiography study on the relations between the vertebral artery and atlantoaxial joint. Chin Med J 2009; 122: 917-920.

11. Fisher CM, Gore I, Okabe N. Atherosclerosis of the carotid and vertebral arteries－extracranial and intracranial. J Neuropathol Exp Neurol 1965; 24: 455-476.

12. Thevenet A, Ruotolo C. Surgical repair of vertebral artery stenosis. J Cardiovasc Surg 1984; 25: 101-110.

13. Civelek E, Kiris T, Hepgul K, Canbolat A, Ersoy G, Cansever T. Anterolateral approach to the cervical spine: major anatomical structures and landmarks. J Neurosurg Spine 2007; 7: 669-678.

14. Rocha R, Safavi-Abbasi S, Reis C, Theodore N, Bambakidis N, de Oliveira E, et al. Working area, safety zones, and angles of approach for posterior C-1 lateral mass screw placement: a quantitative anatomical and morphometric evaluation. J Neurosurg Spine 2007; 6: 247-254.

15. Wong CW, Poon WS. Far lateral approach with intraoperative ultrasound Doppler identification of the vertebral artery. Clin Neurol Neurosurg 1999; 101: 264-267.