Aberrant left brachiocephalic vein is a contraindication for anterior cervicothoracic approach

Abstract

Aberrant left brachiocephalic vein is a rare condition. Its occurrence in patients requiring anterior cervicothoracic approach for severe kyphoscoliosis has not been described. A 16-year-old male with neurofibromatosis and severe upper thoracic kyphoscoliosis presented to us with curve progression. Halo gravity traction was attempted but failed to achieve significant correction. Subsequently, he underwent halo-pelvic traction and later Posterior Spinal Fusion (PSF) from C2 to T10. Second-stage anterior cervicothoracic approach with anterior fibula strut grafting was planned; however, preoperative computed tomography angiography revealed an aberrant left brachiocephalic vein with an anomalous retrotracheal and retroesophageal course, directly anterior to the T5/T6 vertebrae (planned anchor site for fibula strut graft) before draining into superior vena cava. Therefore, surgery was abandoned due to the risks associated with this anomaly. Aberrant left brachiocephalic vein is rare, the presence of which could be a contraindication for anterior cervicothoracic approach. Assessment of the anterior neurovascular structures is crucial in preoperative planning.

Introduction

The left brachiocephalic vein is formed by the confluence of the left subclavian and the left internal jugular vein behind the sternoclavicular joint. The left brachiocephalic vein is longer and travels a more horizontal course to cross the mediastinum to join the right brachiocephalic vein to drain into the superior vena cava. An aberrant brachiocephalic vein was described by Kershner more than 100 years ago. ¹ The pathogenesis of such aberrancy remains unknown; the most accepted mechanism is the interruption of the upper and ventral anastomosis between the right and the left precardinal veins. Abnormal development of aortic arch and pulmonary artery reduces the direct pressure onto the inferior dorsal portion of the upper transverse capillary plexus leading to the formation of aberrant left brachiocephalic vein. ^2,3 Isolated aberrant left brachiocephalic vein has no clinical significance. However, it is crucial to diagnose it prior to anterior cervicothoracic approach for the placement of a fibula strut graft in severe kyphoscoliosis cases in the upper thoracic region to avoid disastrous complications. ⁴

To our knowledge, the occurrence of retrotracheal and retroesophageal left brachiocephalic vein has not been previously described in a patient who requires anterior cervicothoracic approach for severe upper thoracic kyphoscoliosis surgery. Therefore, we describe a rare case of an aberrant left brachiocephalic vein in a neurofibromatosis patient with severe upper thoracic kyphoscoliosis.

Case presentation

A 16-year-old boy with neurofibromatosis type 1 presented to our institution with severe hunching over the upper back (Figure 1(a) and (b)). Whole spine radiograph and computed tomography (CT) revealed a severe angular kyphoscoliotic deformity with scoliotic Cobb angle of 74° (T1–T5) and kyphotic Cobb angle of 81° (T2–T7), which had progressed to 89° and 124°, respectively, over a period of 2 years (Figure 2(a) to (d)).

Figure 1.

Clinical photographs from the (a) front and (b) back showed severe upper thoracic kyphoscoliosis. (c) and (d) Clinical photographs showed correction of scoliosis with halo-pelvic traction prior to the posterior correction surgery. (e) and (f) Clinical photographs are shown at 1 year postoperatively.

Figure 2.

Preoperative (a) posteroanterior and (b) lateral standing radiographs of the spine showed severe right upper thoracic kyphoscoliosis. (c) and (d) Three-dimensional (3D) computed tomography (CT) scan of the spine showed the severity of the structural abnormality preoperatively. Postoperative (e) posteroanterior and (f) lateral standing radiographs revealed correction of the scoliotic curve of 40.4% and kyphosis of 44.3% with posterior spinal instrumentation and halo-pelvic traction. (g) and (h) Standing radiographs after removal of halo-pelvic frame are shown.

Initially, he was managed with halo gravity traction with incremental traction weight up to 20 kg for 6 weeks. However, there was no significant improvement in the curve magnitude. Therefore, halo gravity traction was abandoned upon parents’ request.

Within the next 3 months, the patient developed thoracic myelopathy with bilateral lower limb paraparesis. Halo gravity traction was reapplied and subsequently converted to a halo-pelvic traction with gradual distraction of the construct (Figure 1(c) and (d)). The patient regained near-normal neurological function after 6 months of immobilization and rehabilitation with the halo-pelvic device. Later, he underwent Posterior Spinal Fusion (PSF) with autologous bone grafting (local and fibula bone grafts) from C2 to T10 vertebral levels (Figures 1(e) and (f) and 2(e) to (h)).

A second-staged anterior spinal fusion using a fibula strut graft was planned. However, preoperative CT angiography revealed an aberrant retrotracheal and retroesophageal left brachiocephalic vein coursing anterior to T5 and T6 vertebrae corresponding to the anchor site for the fibula strut graft. A CT venography was requested to assess the anastomosis of the vein, but there was no anterior branch of the left brachiocephalic vein seen (Figure 3(a) to (e)). Cardiothoracic opinion was sought, and preservation and mobilization of the aberrant left brachiocephalic vein was not feasible. The option of ligation of the brachiocephalic vein and its associated risks was discussed with the parents. A decision was undertaken not to proceed with the second stage of the surgery.

Figure 3.

(a to c) Axial views of contiguous CTA displayed unusual course of left brachiocephalic vein crossing midline behind the trachea and esophagus and above aortic arch before draining into superior vena cava (white arrows). Diagrams illustrated the normal anatomy of (d) the left brachiocephalic vein and (e) the pattern of the anomalous retrotracheal and retroesophageal left brachiocephalic vein. CTA: computed tomography angiography.

At 1-year postoperatively, the patient regained normal daily activities with full neurological recovery and no radiological evidence of rod breakage.

Discussion

In a case of severe upper thoracic kyphoscoliosis, posterior approach alone is insufficient neither to resist the forces acting on it nor to resist the curve progression. ⁵ Posterior instrumented fusion alone in dystrophic severe kyphoscoliosis is associated with a high failure rate of 63%. Even combined anterior and posterior instrumented spinal fusion has a 33% failure rate. ⁶ Under such circumstances, an anterior cervicothoracic approach is necessary to prevent risks of implant failure of the PSF. This approach is difficult as the operative field is narrow with bony obstructions by manubrium, clavicle, and ribs and the risk of injury to many anatomical structures: great vessels, esophagus, trachea, recurrent laryngeal nerve, thoracic duct, and sympathetic ganglions. ⁷ Often caudal access is limited by the amount of retraction of the left brachiocephalic vein; its anatomy is often variable. Teng et al. described the left brachiocephalic vein crossing anterior to T3 in 51% of cadavers and 37% anterior to T2 vertebra. ⁸ Aberrancy in the distribution of the left brachiocephalic vein is rare: it accounts for only 0.06–0.37% in the general population and 0.2–1% among congenital heart disease population. ² However, the presence of such anomaly could be a contraindication for anterior cervicothoracic approach especially in this case, where the vessel was located at the anchor site for the fibula strut graft.

Takada et al. had described four major patterns to classify aberrant left brachiocephalic veins. ⁹ However, the description did not include a retrotracheal aberrant left brachiocephalic vein, which was later described by Yigit et al. ¹⁰ Neurovascular structural assessment must be performed routinely prior to surgery to prevent a disastrous bleeding complication intraoperatively. Ligation of the left brachiocephalic vein after injury of the vein also carries possible complications, such as left upper limb swelling and neurological symptoms. ¹¹

Conclusion

Retrotracheal and retroesophageal aberrant left brachiocephalic vein is rare, and it is a contraindication for anterior cervicothoracic approach for severe kyphoscoliosis surgery. Therefore, preoperative assessment of the anterior neurovascular structures is mandatory prior to anterior cervicothoracic approach.