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Abstract
Aneurysmal bone cysts (ABCs) are primary bone tumours that rarely occur in the spine and generally affect one vertebral level in adolescents. Here, we present an unusual case of a multilevel thoracolumbar ABC, which presented a unique surgical challenge due to its infiltrative and destructive nature. A teenage male presented with back pain, paresthesias and a mildly spastic gait. MRI of the thoracolumbar spine revealed an expansive, multicystic mass extending from the left T12–L1 vertebral bodies into adjacent musculature. The patient underwent a two-stage surgical approach with decompression of the spinal cord and instrumentation to stabilise the vertebral column. The first stage involved posterior decompression, laminectomy and facetectomies, followed by pedicle-based instrumentation from T10 to L3. This was followed by a vertebrectomy and anterior stabilisation with an expansile cage from T11 to L2. A gross total resection was achieved with the patient maintaining full neurological function.
- Neuroimaging
- Neurological injury
- Spinal cord
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Background
Aneurysmal bone cysts (ABCs) are rare benign primary bone tumours that most commonly occur in individuals under the age of 20.1 Approximately 12%–30% of ABCs occur in the spine, usually affecting a single vertebral level in the lumbar spine and, rarely, the cervical region.2 Despite being benign in nature, the destructive nature of ABC’s poses a risk to the stability of the spinal column. Resulting spinal cord compression can lead to devastating neurological injury.3 Their proximity to the spinal cord and destructive and infiltrative nature pose a surgical challenge.4 Here, we present an unusual case of a large multilevel ABC in a teenage male and the successful surgical treatment with a two-stage approach.
Case presentation
A previously healthy man in his teens presented to our clinic with a 6-month history of worsening lumbago, paresthesia in his feet and left groin region, and difficulty walking due to the pain. On physical exam, he had no pain on palpation in the thoracolumbar region and no apparent motor or sensory deficits. He had a mildly spastic gait, but no clonus was evident.
Investigations
An MRI of the thoracolumbar region demonstrated an expansile multicystic mass centred over the left T12–L1 neural exit foramina extending both laterally into the adjacent musculature and centrally into the T12–L1 vertebral bodies (figures 1 and 2). The mass extended from the posterior elements of the vertebral bodies anteriorly, causing severe central spinal canal stenosis (figures 1 and 2). Given the degree of invasion and concern for cord compression, the patient underwent urgent surgical intervention.
Volume rendering technique of a normal spine CT showing (A) lateral three-dimensional (3D) view of normal anatomy of a healthy spine, showcasing labelled vertebrae, vertebral body (VB), neural foramen (NF) and the spinous process (SP) (B) a 3D transverse view (C) magnified depiction of the posterolateral view of the lumbar spine showing anatomical landmarks, including the superior articular process (SAP), inferior articular process (IAP), transverse process (TP), lamina and the spinous process (D) axial CT showing normal anatomy of a thoracic vertebrae showing VB, TP, SP, pedicles (P), lamina (L) and the spinal canal (SC).
(A) Sagittal T2-weighted MRI of the thoracolumbar spine showing expansile aneurysmal bone cyst (ABC) spanning T12–L1. (C) Sagittal T2-weighted CT of the thoracolumbar spine showing expansile ABC. Axial images showing (C) T12 and (D) L1 cross-sections.
Treatment
As ABCs usually involve only one vertebral level, this case presented a surgical challenge due to the extent of the lesion, degree of invasion, bone destruction and concern for substantial blood loss. Surgical resection and stabilisation were done as a two-stage approach with intraoperative neuromonitoring. The first stage allowed for decompression of the spinal cord and debulking of the ABC with T11 and L2 laminectomies and facetectomies. A right-sided laminectomy was performed at the T12 and L1 levels, but not on the left due to the presence of the vascular heterogeneous tumour. Neurosurgery then performed a left-sided laminectomy at the L2 level to define normal dura. Following this L2 laminectomy, the tumour was visualised and then separated and resected from the left paraspinal muscles and the dura in a caudal to cranial fashion up to the T11 level. An extensive vertebrectomy was then performed at the T12 and L1 levels, which removed all remaining visible tumour. Residual tumour in the epidural space laterally at T12 and L1 and the muscle was also removed. Following resection, instrumentation and fusion of T10–T11, L1–L3 on the right and of T10–11 and L2–L3 on the left was performed.
Two weeks after the first surgery, the patient underwent a lateral approach for vertebrectomy and anterior stabilisation. The patient was positioned in the right lateral decubitus position. With the assistance of thoracic surgery, a lateral thoracotomy was performed for an anterior retroperitoneal approach to expose the T12 and L1 vertebral bodies and their adjacent discs. Discectomies were then performed at the T11–L2 disc spaces. Partial corpectomies of T12 and L1 were done. Vertebrectomies of T12 and L1 were subsequently performed. An expandable cage was then sized, placed and expanded that bridged the T11 to the L2 levels and allowed for arthrodesis across those three segments. An anterolateral plate was then selected, and screws were fixed into the vertebral bodies of T11 and L2 for anterolateral fixation (figure 3A,B). Thoracic surgery then closed the incision completing the second stage at this point.
(A) Stage 1 postoperation changes and (B) Stage 2 postoperation image. (C) Microscopic examination of H&E slides at low power shows bony fragments disrupted by large multiloculated, blood-filled cystic spaces with collagenous cyst walls. (D) On higher power examination, the cyst walls demonstrate plump spindle cells with mild atypia and scattered multinucleated osteoclast-like giant cells. Mitoses are infrequent. USP6 rearrangement studies by fluorescence in situ hybridization (FISH) are positive for USP6 rearrangement, confirming the histopathological diagnosis.
Histopathological examination of the tissue showed a multiloculated solid and cystic mass involving and destroying the bone, characterised by multiple large blood-filled cystic spaces with collagenous cyst walls containing plump spindled cells with mild atypia and scattered multinucleated osteoclast-like giant cells. Mitoses were infrequent, and necrosis was not identified. Fluorescent in situ hybridisation studies were positive for USP6 rearrangement, confirming the histological diagnosis of primary ABC (figure 3C,D).
Outcome and follow-up
The patient recovered well following both surgical stages. After the second stage, the patient experienced some transient left lower extremity weakness specifically in the tibialis anterior and extensor hallucis longus (4/5). At discharge, however, the patient had full strength in all muscle groups in the lower extremities. Approximately 12 months postoperation, a follow-up was conducted via a phone call. The patient reported the absence of new symptoms or pain, with the only concern being reduced mobility attributed to the fusion. The patient declined further imaging and in-office follow-up but has no return of symptoms. One month after surgery, the X-ray of the thoracolumbar spine showed that the hardware was intact and stable in the spine.
Discussion
The majority of ABCs affect paediatric individuals often in adolescence.1 ABCs of the spine, especially multilevel ABCs, are very rare with most affecting the thoracolumbar region and, rarely the cervical regions.2 ABCs while benign, are often locally aggressive, destructive and have a high rate of recurrence making them difficult to treat.3 In general treatment of ABCs aims to fully eliminate the tumour, decompress the spinal cord and restore stability to the spine. While surgery is the most common treatment, embolisation, radiation and incisional curettage are other treatment options.5 There have only been five cases published in the literature on multilevel ABCs2 6–9 (table 1). In four of the five cases, patients were paediatric or adolescents presenting with motor neuron deficiencies. Although it is stated that ABCs rarely affect the cervical region, this may not be the case in multilevel ABCs. In our literature search, four of the five cases stated that the cervical region was affected suggesting a distinct pathology of multilevel ABCs compared with single-level ones. Our case was unique compared with other multilevel ABCs as it affected the thoracolumbar region and presented with milder symptoms, which suggests a more chronic and less aggressive progression.
Current multilevel aneurysmal bone cyst (ABC) case studies broken down by age, sex, spine level, treatment type, approach and outcomes
Given our patient’s overall health, youth and potential for recovery, we opted for surgical resection and instrumented fusion for the best outcome. In the majority of reported multilevel ABC cases, a two-stage approach involving both anterior and posterior methods was employed, leading to complete recovery or restored functionality. In our case, a timely two-stage surgical intervention resulted in minimal morbidity with complete ABC resection, spine stabilisation and preservation of neurological function.
While we were able to achieve complete resection and stabilisation, the extensive surgical approach required vigilance to avoid major complications. For one, the ABC had invaded the spinal canal and was in close proximity to the spinal cord and exiting nerve roots. Resection of the ABC required care to avoid injury to the spinal cord which could result in devastating neurological damage. Furthermore, while the lateral approach allowed for optimal access to the ABC for full resection, involvement of thoracic surgery was critical in minimising risk to adjacent structures such as the great vessels (aorta and superior vena vaca) that course anteriorly to the vertebral bodies, the peritoneum and retroperitoneal structures including the kidney. Finally, resection of ABCs can result in significant blood loss. Ensuring that haemoglobin levels are normal preoperatively and having red blood cells on hold for intraoperative transfusion can help avoid complications related to blood loss. The large fusion construct, while it enabled an extensive resection of the ABC, also carries the risk of adjacent segment disease, hardware failure and pseudoarthrosis, which may require future operations. After much thought regarding the risk and benefits of this surgical approach, our team opted to proceed with the two-stage procedure to provide the best chance at preventing recurrence while providing the necessary stabilisation of the spine and preserving neurological function.
Learning points
Rare case of a multilevel ABC (T12–L1) in a teenage male.
Two-stage surgical approach involving posterior decompression, laminectomy, facetectomies, pedicle-based instrumentation, vertebrectomy and anterior stabilisation using an expandable cage.
Surgery was tolerated well by the young patient maintaining neurological stability.
Interdisciplinary team combining the expertise of neurosurgeons, orthopaedic surgeons and thoracic surgeons.
Ethics statements
Patient consent for publication
Footnotes
Contributors The following authors were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content: RG, AR, ED, ES and KM. The following authors gave final approval of the manuscript: RG, AR, ED, ES and KM.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.