Giant aneurysmal bone cyst of cervical spine: Surgical management and circumferential spinal fusion in a 13-year-old girl.

Aneurysmal bone cysts (ABCs) of the cervical spine are rare occurrences accounting for about 2% of all cases. Having a propensity to develop in the pediatric population, it generally involves the posterior elements with occasional extension to the facets and body of one vertebral level. Surgical treatment of high cervical ABC in pediatric patients is challenging. Where as complete tumor resection should be attempted for the best chance for cure, spinal fusion should be added to correct the defects created by resection to minimize the risk of postoperative instability. This paper presents a multi-level giant expansile ABC of the high cervical spine involving all three spinal columns in a 13-year-old girl and discuss the surgical management. Surgical treatment in this patient included complete tumor excision and circumferential fusion in two stages without any neurovascular injury. The safety and efficacy of this method, especially in the pediatric population is discussed in view of pertinent literature.

Introduction

Aneurysmal bone cyst (ABC) is a benign, nonneoplastic, expansile lytic lesion of the bone characterized by multiple blood-filled cavities.[1] They usually arise from long bones, but about 12-30% of cases involve the spine.[23] The lumbar spine is the most frequent site; followed by the thoracic spine, with cysts typically involving the posterior elements. Only 2% of ABCs are encountered in the cervical spine and generally involve the lamina, pedicles, spinous processes and occasionally extend to the facets and vertebral body.[4] Total excision is usually associated with a good outcome, but may be difficult to achieve at the cervical spine due to close proximity of neurovascular structures and resultant instability.[1]

In 1942, Jaffe and Lichtenstein[5] coined the name “aneurismal bone cysts” when they described a lesion that appeared to be a blood-filled cavity with a “blow out” radiographic appearance analogous to a saccular aneurysm. The expansile osteolytic capita with thin cortices, showing a bubbly appearance on radiology, gives the lesion its name of ABC.[6] Fusion and stabilization with instrumentation have often been avoided in children due to concerns over instability following future spine growth. We report the clinical, radiological, and therapeutic aspects of a giant ABC of the high cervical spine in a child that was operated on by anteroposterior approaches. The evolution of the case and the current treatment options are discussed.

Case Report

A 13-year-old girl was admitted to our hospital with complaints of dull aching neck pain radiating to the shoulders and progressive quadriparesis with bladder and bowel involvement for 2 months. She had difficulty in respiration due to decreased chest expansion. On examination, the child had a 4 × 5 cm bony, tender, immobile swelling on the left posterior triangle of the neck. Neurological examination revealed spastic quadriplegia and symmetric hypoesthesia involving C2 dermatome and below. Power in all the four limbs was 0/5 with exaggeration of all deep tendon reflexes.

Cervical spine X-ray showed destruction of the C3 vertebral body and its posterior elements [Figure 1]. Computed tomography (CT) of cervical spine showed near total destruction of body and posterior elements of C3 vertebra with partial destruction of body and posterior elements predominantly on the left side of C2 and C4 vertebrae [Figure 2]. Magnetic resonance imaging (MRI) of the cervical spine revealed grossly compressed and collapsed C3 vertebral body with ballooning of the posterior arch due to a mass of T1-weighted image (T1-wi), T2-wi mixed signal intensity and heterogeneous contrast enhancement extending from C2 to C5 [Figure 3].

Figure 1

X-ray cervical spine showing destruction of the C3 vertebral body and its posterior elements

Figure 2

Computed tomography of cervical spine with three-dimensional reconstruction showing destruction of body and posterior elements of C3 vertebra with partial destruction of body and posterior elements predominantly on the left side of C2 and C4 vertebrae

Figure 3

Magnetic resonance imaging of the cervical spine demonstrating grossly compressed and collapsed C3 vertebral body with ballooning of the posterior arch due to a mass extending from C2 to C5. The mass is showing mixed signal intensity in T1-weighted image (T1-wi), T2-wi and has heterogeneous contrast enhancement

The patient underwent two-staged surgery with intention of excision and 360° fusion. In stage 1 with the anterior approach, C3 corpectomy was carried out using high speed drill. Bone was soft, vascular and honey combed, which crumpled easily. Anterior interbody fusion with titanium graft placement and cervical plating from C2 to T4 was completed. The primary procedure was followed by stage 2 surgery after 3 days with the planned posterior approach. Intraoperatively, an expansile pinkish moderately vascular firm friable tumor measuring 6 × 6 cm was encountered. The lesion had destroyed whole of the C3 body and posterior elements and had involved C2 lamina, pedicle and facets. Gross total tumor excision was performed avoiding injury to the left vertebral artery (VA) and cord decompression achieved. Posterior fixation was accomplished by occipitocervical fusion using instrumentation (screws in occiput and C4, C5 lateral mass fixed with occipital plate, and rod). Histopathological examination confirmed the diagnosis of ABC [Figure 4]. There was no neurological deterioration in the postoperative period. The patient was uneventfully mobilized with a soft neck-collar for 4 weeks. Follow-up X-rays show circumferential spinal fusion [Figure 5] and improvement in power in all four limbs (2/5).

Figure 4

Photomicrograph showing scattered osteoclastic giant cells and foci of calcification in the background of cellular area comprising of round ovoid to spindloid cells

Figure 5

Postoperative X-ray at 3 month follow-up showing circumferential fusion

Discussion

Aneurysmal bone cyst is an expansile, tumor-like, osteolytic lesion consisting of a highly vascular honeycomb of blood-filled cavities separated by connective tissue septa, surrounded by a thin cortical bone shell that may expand, which frequently affects the pediatric population.[7] Although it is viewed as a benign lesion, it is aggressive in its ability to destroy and expand bony tissue. Although they most commonly occur around the knee, about 12-30% of cases involve the spine.[23] ABC usually arises in the posterior elements of a vertebra and spreads into pedicles, body and can expand to the spinal canal resulting in pathological fractures and neurological deficits. It is generally characterized by progressive growth.

Most patients present symptoms of ill-defined somatic pain, stiffness, and swelling. On an average, symptoms persist for 12 months before definitive diagnosis.[8] Pathological fracture or partial vertebral body collapse are common findings; rarely is complete collapse seen.[9] Most of these cases are small lesions and only one segment of the column is affected.[10]

Preoperative radiologic evaluation with MRI and CT scan is useful in planning the surgical management.[2] CT imaging, particularly the three-dimensional reconstruction is helpful for assessing pedicle and vertebral body integrity preinstrumentation.[11] The finding of multilocular cysts with fluid-fluid interfaces on T2-wi is highly suggestive of ABC.[11] Inside the tumor, there are multiple cysts, commonly with fluid levels and varying signal intensity in T1- and T2-wi. These signal differences are caused by different oxidation levels of blood and blood breakdown products in the cyst fluid.[12] Identification of feeding vessels can be helpful in preoperative embolization, which is required in selective cases to minimize intraoperative blood loss.[11] However, the success of these therapeutic procedures depends on the tumor's size and the degree of osseous destruction. For larger tumors, in which there are numerous supply vessels to embolize, complete devascularization of the tumor is often impossible as it was in our case.

The treatment of ABC remains controversial. The options include intralesional curettage and bone grafting, complete excision, arterial embolization, radiation, intralesional injections with calcitonin and steroids and combination of these.[2713] Surgical resection is frequently considered the treatment of choice. The high rate of cure relates to the degree of excision.[127] Total excision of the lesion must include entire cyst walls and spongy tissues that are lined with hypervascular membrane because of its reactive expansion. However, total excision may not be achieved in a single stage in lesions, involving the cranio-vertebral junction. Skeletonizing the VA that is generally encased by the lesion is an essential part of the procedure to protect them bilaterally. Iatrogenic instability after the operation is another issue that must be considered, and as the facets are usually involved, reconstruction and stabilization of the spine needs to be planned preoperatively.[14] In cases of spinal cord involvement, decompression is recommended to be pursued rapidly, with the greatest possible tumor removal. Children have the highest incidence of postlaminectomy kyphosis of about 37% because of wedging of the anterior vertebral bodies caused by compression of the cartilaginous end plates.[15] These deformities progress during the adolescent growth phase, rather than spontaneously correcting; hence, instrumentation must be considered. Radiotherapy is usually used as an adjunct to surgery. However, it entails the danger of radiation induced myelopathy and spinal deformity, especially in young patients.[1]

In this case, circumferential and multilevel involvement of the cervical vertebra required complete surgical resection and 360° instrumented fusion, avoiding postoperative radiation because of the young age of the patient. The two-stage operation was planned due to a high probability of intraoperative bleeding. This approach was selected to maintain sagittal spinal alignment, provide stability and to protect VAs bilaterally.

Conclusion

Surgery of benign ABCs constitutes a feasible means of reducing the compression of neural structures despite a risk of intraoperative bleeding. Complete resection of ABCs is associated with an excellent prognosis for cure. Careful preoperative instrumentation planning is important for management of postresection spinal instability. Circumferential fusion is required in extensive tumors with involvement of both body and posterior elements.