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ORIGINAL ARTICLE
Year : 2022 | Volume
: 70
| Issue : 8 | Page : 144-148
Vision Loss Following Vertebral Artery Injury during Surgery for Atlantoaxial Instability
Atul Goel1, Sagar Bhambere2, Abhidha Shah2, Hardik Darji2, Chandrima Biswas2, Akshay Hawaldar2
1 Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel; Department of Neurosurgery , Lilavati Hospital and Research Centre, Bandra (E), Mumbai, Maharashtra, India
2 Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai, Maharashtra, India
Correspondence Address:
Atul Goel
Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai - 400 012, Maharashtra
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/0028-3886.360938
Background: A number of complications following surgery aimed at atlantoaxial fixation have been reported. However, there is no report in the literature describing visual loss following vertebral artery injury.
Objective: Vision loss as a complication of vertebral artery injury during surgery for atlantoaxial fixation is reported.
Material and Methods: This is a report of two patients who were operated for atlantoaxial instability by the Goel technique of atlantoaxial fixation. During surgery, there was an injury to the vertebral artery and the artery had to be sacrificed.
Results: Both patients suffered severe visual loss following surgery. One patient had a partial visual recovery that started within few days of surgery while the other patient remained completely blind.
Conclusions: Although rare, visual loss can be a complication of vertebral artery sacrifice during surgery for atlantoaxial stabilization.
Keywords: Atlantoaxial instability, Goel technique, Magerl technique, vertebral artery
Key Message: Two adult male patients underwent surgery for craniovertebral junction stabilization. Both these patients had intraoperative vertebral artery injury needing arterial sacrifice. Despite the improvement in limb function, both patients developed severe visual deficits. Investigations revealed large occipital lobe infarcts.
Lateral mass screw insertion techniques have become increasingly popular for atlantoaxial stabilization. Magerl's technique involves transarticular screw insertion and the Goel technique involves independent screw insertion in the lateral masses of the Atlas More Details and axis.[1],[2],[3] The varied and intimate relationship of the vertebral artery to the pedicle-superior facet of the axis makes it susceptible to injury during C2 screw insertion. Several authors have alluded to the possibility of vertebral artery injury during such surgery.[14] We report our experience with two cases wherein vertebral artery injury resulted in severe visual loss. Our literature search did not isolate reports of such disabling complications following vertebral artery injury during atlantoaxial stabilization surgery.
Case 1
A 35-year-old male patient presented with complaints of neck pain and progressively increasing stiffness and weakness of all four limbs for about 9 months. When admitted, he had difficulty in walking, was unable to hold objects properly in his hand, and was also unable to take his hands above his shoulder to carry out overhead activities. On examination, he had spastic grade 3–4/5 quadriparesis. Investigations revealed the presence of os odontoideum, basilar invagination with assimilation of atlas. Ossification of the posterior longitudinal ligament from the posterior aspect of the body of C2 extended to the C3 vertebral body. Magnetic resonance imaging (MRI) showed severe cord compression with external syringomyelia and external syringobulbia [Figure 1]. The joints were vertically aligned and the vertebral artery was “high-riding” on both sides.
Figure 1: Images of a 35-year-old male patient (Case 1). (a) T2-weighted magnetic resonance imaging (MRI) showing a complex craniovertebral junction anomaly and severe compression of the craniocervical cord. (b) Computed tomography (CT) scan showing Os odontoideum, assimilation of the atlas, and ossification of the posterior longitudinal ligament. (c) CT scan cut passing through the facets showing a vertical alignment of the facets. High-riding vertebral artery can be seen. (d) 3-D CT scan showing the large vertebral artery groove in relationship to the pedicle of C2 on the left side. (e) Postoperative CT scan showing satisfactory craniovertebral junction realignment. (f) CT scan showing the metal implant. (g) CT scan of the head showing bilateral occipital lobe infarctsSurgical technique
The patient was operated on by the techniques described by us earlier and summarized here.[2],[3],[4] The patient was placed in a prone position after applying cervical traction with the head end of the operation table elevated by about 30°. The traction assisted in stabilizing the head and helped in keeping the head and face away from the headrest and avoided their direct pressure contact. The atlantoaxial joint was exposed bilaterally with significant difficulty due to its rostral location and alignment. The joints were opened widely, the articular cartilage was denuded and bone graft harvested from the iliac crest was stuffed in the joint space. While making a guide hole for inserting a C2 pedicle-facet screw, the vertebral artery was damaged and resulted in significant blood loss. Completion of screw insertion in the site controlled the bleeding. The rest of the surgical procedure was then completed on both sides. The patient was reversed and extubated. In the immediate postoperative period, the patient improved in his stiffness in all four limbs and power in his left-sided limbs. However, he complained of inability to see anything around him. On examination, he was found to have very little perception of light on the right side and no perception of light on the left side. The pupils were bilaterally equal and reacting to light. After about 5 h of surgery, he complained of complete blindness. An emergent computed tomography (CT) of the brain showed bilateral posterior cerebral artery territory infarcts. CT of the craniovertebral junction showed satisfactory bone realignment [Figure 1]. An ophthalmological evaluation did not show any abnormality of the fundus or the visual apparatus. The patient was diagnosed to have cortical blindness. The patient did not improve in his vision in the next several days. His stiffness and power in the limbs were significantly recovered, but he became dependant due to his blindness. At a follow-up of 3 years, he continued to remain blind.
Case 2
A 33-year-old male patient presented with complaints of progressively increasing weakness and stiffness in all four limbs, tingling paresthesias, neck pain, and restricted neck movements for 2 years. On neurological examination, he had spastic quadriparesis of grade 4/5. He was able to carry out his routine activities only with difficulty. He also had a short neck. CT scan of the craniovertebral junction showed group A basilar invagination, assimilation of atlas, atlantoaxial dislocation, and type 1 atlantoaxial facetal instability. MRI revealed cord compression opposite the odontoid process. A 3-D printed model showed the vertebral artery to have an anomalous course on the right side.[5] It was running on the posterior aspect of the lateral mass of the C1 vertebra [Figure 2]. The patient was operated and the basic surgical steps of the procedure have been elaborated above. The atlantoaxial articulation was exposed with difficulty amid considerable venous bleeding. The joints were opened, the articular cartilage denuded, and bone graft harvested from the iliac crest was inserted into the joint cavity. Left-sided C1 lateral mass and C2 pedicle screw insertion were completed uneventfully. On the right side, the anomalous vertebral artery was protected appropriately in the region of the C1 lateral mass and a C1 lateral mass screw insertion was performed uneventfully. However, while dissecting in the region of the lateral gutter, the vertebral artery was accidentally lacerated. Attempts were made to identify the site of arterial injury and to suture the rent. However, considerable venous bleeding in the region made these attempts futile. The artery was then sacrificed by coagulation. The rest of the procedure was completed and the patient reversed and extubated. In the immediate postoperative period, the patient improved in his stiffness and tingling in all four limbs and also had improvement in his bilateral hand grip. However, he complained of difficulty in seeing objects from both his eyes, with the left eye being worse than the right. On examination, he only had a perception of light in both eyes. CT brain and spine was performed on an emergent basis and it showed bilateral posterior cerebral artery infarcts more on the right cerebral hemisphere. CT of the craniovertebral junction showed a good craniovertebral realignment [Figure 2]. An ophthalmological evaluation was performed, which did not show any other abnormality. Pupils were bilaterally equal and reacting to light. The patient was diagnosed to have cortical blindness. Over the next 2 days, the patient's vision started recovering. He initially started seeing vague shapes and then over the next few days, he was able to count fingers at 3–4 feet in the right eye and 6 feet in the left eye. His symptoms of stiffness, weakness, and tingling had remarkably improved. Over the next few months, there was a gradual improvement in his vision. At the last follow-up, at the end of 2 years, his vision had returned to 6/6 in the left eye and 6/9 in the right eye and his neurological symptoms had completely recovered. He was back to his daily routine life.
Figure 2: Images of a 33-year-old male patient (Case 2). (a) MRI showing the craniovertebral junction anomaly. (b) CT scan with the head in flexed position showing atlantoaxial dislocation. Posterior assimilation of the atlas can be seen. (c) CT scan with the head in an extended position does not show any reduction of the dislocation. (d) CT scan cut along the facets showing the instability. (e) 3-D model showing the anomalous course of the vertebral artery posterior to the facet of the atlas on the right side. (f) Postoperative CT scan showing reduction of the dislocation. (g) CT scan showing the implant. (h) CT scan of the head showing bilateral occipital lobe infarcts Discussion 
The vertebral artery has a serpentine and “dynamic” course in the craniovertebral region that facilitates stretch-free circumferential neck movements.[6],[7],[15] After a near-vertical course in relation to bones of C6 to C2 vertebrae, the vertebral artery loops medially toward the undersurface of the pedicle and facet of axis bone. This loop can be “high-riding” and can make a deep groove in the pedicle/facet of the axis.[16] The vertebral artery then loops laterally outside the C2 transverse foramina and travels rostrally toward the vertebral artery foramen in the C1 transverse process. The possibility of vertebral artery injury during C2 pedicle-facet screw insertion and dissection in the region of the lateral gutter has been alluded to on several occasions. The presence of high riding of vertebral artery makes insertion of C2 screw particularly challenging.[17]
A 3-D understanding of the course of the artery in general and in the case for surgery in question has to be evaluated before surgery.[8],[9] In this respect, 3-D models can be a useful modality of investigation.[5] It is clear that to deploy the screw safely and strongly, the surgical exposure of the region should be wide and the instrumentation should be done under direct surgical vision. The medial surface of the pedicle of C2 should be appropriately visualized before screw insertion. Neuronavigation is of help in identifying the correct site of screw insertion and its trajectory. The screw insertion has to be sharply medial and directed toward the anterior tubercle of the C1 for Magerl transarticular fixation and toward the vertebral body of C2 for the Goel technique of interarticular fixation.
Such high riding of vertebral artery makes insertion of C2 screw a surgical challenge.
Lateral mass screw fixation techniques are currently a popular surgical method for atlantoaxial stabilization. A number of techniques have been advocated to safeguard the artery during the surgical procedure. We recently advocated mobilization of the vertebral artery loop laterally or inferiorly after careful drilling of the bone over the dome of the artery to facilitate screw insertion.[10] We also identified the possibility of insertion of the C2 screw in the inferior facet of the axis bone.[11] The use of laminar or spinolaminar screws has been identified to be a useful option to avoid the course of the vertebral artery.[12]
In case the vessel is injured during the making of the screw guiding drill hole, blood gushes out of the hole made. At this time, it is most appropriate to rapidly complete the screw insertion process. In a vast majority of cases, this will stop the bleeding. In case the bleeding continues from the hole made, it is best to forcefully pack Surgicel into the hole. Bone wax can also be used to block the blood gushing out of the hole. Essentially, the procedure will sacrifice the blood vessel. In both our cases, the screw insertion process was completed to achieve fixation and to control bleeding.
The other site of possible injury to the vertebral artery is during its course lateral to the C1-C2 articulation and over the arch of the atlas. Anomalous course of the artery in this region can make it susceptible to injury (Case 2). In cases where the artery is injured in this segment, an attempt must be made to suture the arterial rent. However, extensive venous bleeding in the vicinity makes the procedure of suturing difficult. Retraction of the two cut ends of the artery also makes the procedure of suturing a formidable technical issue.
The issue of blindness in prone surgical positions has been alluded to on several occasions. Apart from other possible causes of blindness, direct and prolonged pressure on the eyeball and resultant retinal ischemia can be a cause for such devastating complications. In this respect, the position of “floating head” as described by us for surgery is relevant. Our 35-year experience with more than 2,500 cases of selective atlantoaxial joint fixation surgery with our experience with injury to vertebral artery it appears that quick sacrifice of the vertebral artery in the C2 is associated with a “small” risk (maybe <5%) of related vascular ischemia. Even bilateral vertebral artery injury is frequently tolerated well. The clinical outcome following vertebral artery injury during surgery and arterial sacrifice is unpredictable and depends on several factors, more importantly on the adequacy of flow from other cranial arteries. Cross-flow from anterior circulation through posterior communicating arteries is crucial. Apart from direct vertebral artery laceration, arterial manipulation and dissection result in vascular occlusion or thromboembolism. Younger patients seem to tolerate the vertebral artery sacrifice better.[13] In majority of instances, there is no arterial sacrifice-related symptom. While larger cerebellar infarcts can result in ataxia, a relatively small infarct may be clinically insignificant. Larger posterior cerebral artery territory infarct can lead to unilateral or bilateral blindness as in our cases. Extensive posterior circulation infarct can lead to sudden death. Such large infarcts that lead to an acute neurological worsening usually occur between 6–10 h after the surgical procedure. Vascular infarct-related clinical events might occur within 48 h of surgery. The recovery of vision in our second case is probably related to its supply from both vertebral arteries through a common basilar artery conduit. The author has never identified a delayed vascular event related to vertebral artery injury. Some surgeons have indicated the need for angiography to rule out pseudoaneurysms. Such a procedure was not done in our series. Prediction of outcome of visual loss following vascular insult is not possible.
ConclusionsThe surgeons dealing with lateral mass fixation techniques for atlantoaxial instability should be aware of the possibility of visual deterioration following vertebral artery injury during surgery.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initial s will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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