C1 dome-like laminotomy and posterior C1-C2 polyaxial screw-rod fixation for a patient with cervical myelopathy due to a retro-odontoid pseudotumor.

A 49-year-old man presented with progressive cervical myelopathy caused by a retro-odontoid mass, with associated developmental canal stenosis at C1, and C1-C2 instability. Surgery was scheduled for a dome-like laminotomy at C1, posterior C1-C2 fixation using C1 lateral mass screws and C2 pedicle screws, and structural bone grafting between C1 and C2. Prior to surgery, we produced a 3-dimensional full-scale model of the patient's cervical spine and performed a simulation of the scheduled surgery. Through the simulation, we accurately evaluated the laminotomy sites and the screw insertion points. During the actual surgery, all procedures were successful. After surgery, the patient's neurological deficits markedly improved. Successful C1-C2 fusion, adequate decompression of the spinal cord, and spontaneous regression of the retro-odontoid mass were achieved by this procedure without any apparent restriction in neck movement.

Anomalous vertebral arteries in the extra- and intraosseous regions of the craniovertebral junction visualized by 3-dimensional computed tomographic angiography: analysis of 100 consecutive surgical cases and review of the literature.

STUDY DESIGN: Consecutive case series and literature review. OBJECTIVE: To describe the utility of 3-dimensional computed tomographic angiography (3D CTA) for evaluating vertebral artery (VA) anomalies before surgery. SUMMARY OF BACKGROUND DATA: Recent advances in instrumentation surgery at the craniovertebral junction (CVJ) enable us to perform rigid internal fixation. However, the risk of VA injury as a complication of the surgery has become a major problem. Thus, the importance of preoperative evaluation of the VA course has been emphasized. METHODS: Cases of 100 consecutive patients who underwent CVJ instrumentation surgery since July 1998 were analyzed. Occipitocervical/thoracic or C1-C2 posterior fusion was performed for atlantoaxial subluxation (AAS) in 59 patients and cervical fixation including C2 was required for middle-to-lower cervical lesions in 41 patients. Twenty-seven patients with AAS had a congenital skeletal anomaly (CSA) at the CVJ including os odontoideum and occipitalization of C1 (AAS-CSA[+] group). Anomalous VAs at the extra- and intraosseous regions were evaluated by 3D CTA. RESULTS: No neurovascular injury occurred during surgery. Abnormal courses of the VA at the extraosseous region were detected in 10 cases: 2 had fenestration and 8 had a persistent first intersegmental artery. All 10 cases were in the AAS-CSA(+) group. A high-riding VA was detected in 31 cases. Fourteen out of the 31 cases were in the AAS-CSA(+) group, indicating 51.9% of the AAS-CSA(+) group had high-riding VA. In the AAS-CSA(+) group, a C1-C2 transarticular screw and C2 pedicle screw were actually inserted in 58% and 31% of the planned insertions, respectively. CONCLUSION: The present findings suggest that the frequency of an abnormal VA at the extra- and intraosseous regions is increased when patients have AAS and CSA at the CVJ. Using preoperative 3D CTA, we can precisely identify anomalous VAs and thereby reduce the risk of their intraoperative injury.

Abnormal course of the vertebral artery at the craniovertebral junction in patients with Down syndrome visualized by three-dimensional CT angiography.

INTRODUCTION: We determined the incidence of vertebral artery (VA) anomalies at the craniovertebral junction (CVJ) in patients with Down syndrome, and characterized the VA anomalies. METHODS: The course of the VA in 46 consecutive patients who were due to undergo posterior arthrodesis surgery at the CVJ were evaluated by three-dimensional CT angiography (3DCTA). Included were five patients with Down syndrome who suffered from myelopathy due to atlantoaxial subluxation. All five patients with Down syndrome also had a simultaneous congenital skeletal anomaly, either os odontoideum or ossiculum terminale. RESULTS: Of the five patients with Down syndrome, three had VA anomalies at the CVJ, two had fenestration and one had a persistent first intersegmental artery. Of the other 41 patients without Down syndrome, five had VA anomalies at the CVJ. The incidence of VA anomalies at the CVJ was much higher in patients with Down syndrome than in those without Down syndrome. CONCLUSION: In planning surgery in patients with Down syndrome with symptomatic atlantoaxial subluxation and a congenital skeletal anomaly at the CVJ, we should consider the possible presence of VA anomalies. Preoperative 3DCTA allows us to precisely identify an anomalous VA and evaluate the possible risk of intraoperative VA injury in advance.

Anomalous vertebral artery at the extraosseous and intraosseous regions of the craniovertebral junction: analysis by three-dimensional computed tomography angiography.

STUDY DESIGN: This study examined the extraosseous and intraosseous anomalies of vertebral arteries in patients who underwent surgery of the craniovertebral junction. OBJECTIVES: To describe the usefulness of three-dimensional computed tomography angiography for evaluating vertebral artery anomalies before surgery. SUMMARY OF BACKGROUND DATA: Previous studies using catheter angiograms have identified anomalous courses of the vertebral artery at the craniovertebral junction. Studies using computed tomography reconstruction also showed deviation of the vertebral artery groove at the C2 isthmus, demonstrating a risk of vertebral artery injury for C1-C2 transarticular screw placement. These analyses provided us with useful information for identifying anomalies of the vertebral artery, but they could not visualize the artery and its circumferential osseous tissue simultaneously, nor could they analyze the reciprocal anatomy of both tissues. METHODS: Thirty-one consecutive patients who submitted to surgery at the craniovertebral junction were evaluated before surgery by three-dimensional computed tomography angiography. Eleven of the patients had congenital osseous anomalies at the craniovertebral junction including os odontoideum and ossiculum terminale. Anomalous vertebral arteries at the extraosseous region were visualized by three-dimensional reconstruction images, and the intraosseous deviation of the vertebral artery at the C2 isthmus was evaluated by multiplanar reconstruction images. RESULTS: Extraosseous and/or intraosseous vertebral artery anomalies were detected in 9 cases. Eight of the 9 cases had osseous anomalies at the craniovertebral junction. Abnormal courses of the vertebral artery at the extraosseous region were detected in 4 cases: 2 had fenestration and 2 had persistent first intersegmental artery. Asymmetry of bilateral vertebral arteries was found in 5 cases: the right was dominant in 3 cases and the left in 2 cases. A high-riding vertebral artery at the C2 isthmus was detected in 5 cases. Based on these findings, we modified our surgical approach and the screw placement; consequently, no vertebral artery injury occurred. CONCLUSIONS: In patients having osseous anomalies at the craniovertebral junction, the frequency of vertebral artery anomalies at the extraosseous and intraosseous regions is increased. With preoperative three-dimensional computed tomography angiography, we can precisely identify the anomalous vertebral artery and reduce the risk of intraoperative injury to the vertebral artery, in advance.

Fenestration of vertebral artery at the craniovertebral junction in Down syndrome: a case report.

STUDY DESIGN: Case report of a Down syndrome patient with right vertebral artery fenestration and abnormalities of the craniovertebral junction. OBJECTIVES: Describe the utility of 3-dimensional computed tomography angiography for evaluating vertebral artery anomalies before surgery. SUMMARY OF BACKGROUND DATA: Previous reviews evaluating catheter angiograms identified various anomalies of vertebral artery at the craniovertebral junction. The frequency of vertebral artery anomalies is increased in patients having osseous anomalies at the craniovertebral junction. Down syndrome is associated with a high incidence of bone abnormalities at the craniovertebral junction, but there have been no published reports of vertebral artery anomalies per se at the craniovertebral junction. METHODS: A 16-year-old woman with trisomy 21 presented with gait abnormalities and myelopathy in association with bone abnormalities at the craniovertebral junction, including hypoplastic odontoid and ossiculum terminale. Computed tomography angiography showed that right vertebral artery bifurcated after exiting the C2 transverse foramen with one branch passing through the C1 transverse foramen, whereas the other turned posteromedially and entered the spinal canal between C1 and C2. RESULTS: Occipito-C2 posterior fusion was performed with a rod and screw system. Intraoperatively, the course of the anomalous right vertebral artery was identified by Doppler angiography, and the surgical approach was modified to allow safe pedicle screw insertion while avoiding vertebral artery injury. After surgery, myelopathy resolved within 3 months. CONCLUSIONS: Before corrective surgery of craniovertebral junction anomalies in patients with Down syndrome, the possibility of vertebral artery anomalies associated with abnormal craniovertebral junction anatomy should be considered. With preoperative 3-dimensional computed tomography angiography, we can precisely identify the anomalous vertebral artery and modify the surgical approach to reduce the possible risk of intraoperative vertebral artery injury in advance.