Keywords
aneurysmal bone cysts - thoracic spine - arthrodesis - spinal cord
Palavras-chave
cistos ósseos aneurismáticos - coluna torácica - artrodese - medula espinhal
Introduction
Aneurysmal bone cysts (ABC) are benign, hypervascular, osteolytic lesions that can
cause local destruction, primarily occurring in the metaphysis of long bones and along
the spine.[1]
[2] They were first described in 1942 by Jaffe and Lichtenstein, and subsequently became
known as Jaffe-Lichtenstein Disease.[3]
ABCs are more common in women, with an incidence of 1.4 per 100,000 people and a prevalence
of 75 to 90% in individuals under 20 years old (1.05 to 1.26 per 100,000).[1] They predominantly affect the pediatric population, with peak incidence occurring
in the second decade of life.[4] ABCs account for 1.4% of bone tumors, compromising approximately 10 to 30% of cases.
Common sites include the femur, tibia, pelvis, and, less occasionally, the bones of
the hands and feet.[3]
[4] Of those affecting the spine, 70% are found in the lumbar region, and 2% are in
the cervical segment.[5]
ABCs can be classified as primary or secondary. Primary ABCs, which represent about
70% of cases, are considered neoplastic lesions associated with specific genetic translocation.
Secondary ABCs, constituting the remaining 30%, develop due to pre-existing bone lesions,
such as hemorrhagic degeneration in giant cell tumors, osteoblastoma, and chondroblastoma.[2]
[5]
Patients with spinal ABCs typically present localized pain, as well as neurological
deficits depending on the level of spinal involvement. The most common neurological
symptoms include changes in sensation, motor strength, and gait. In severe cases,
patients may present with plegia.[6] The clinical presentation is influenced by the location and extent of spinal cord
or nerve root involvement and the degree of local bone destruction.[7]
[8]
In the present study, the authors describe two cases of ABC which were properly treated
by surgical management, with tumor resection and reconstruction of the spine.
Cases Descriptions
Case 1
History and Examination
A 16-year-old girl presented with acute paraplegia (ASIA A), sensory level at the
T12 level, and neurogenic bladder, following an incident where she experienced a jolt
while riding as a passenger on a motorcycle. She was initially admitted to the local
hospital and subsequently transferred to a specialized neurosurgical facility.
A comptograph tomography (CT) scan of the spine revealed a collapsed T11 vertebral
body, along with an osteolytic lesion involving T10 and T11, accompanied by a kyphotic
deformity of the thoracic spine and grade III spondylolisthesis of T11 on T12 ([Figs. 1] and [2]). Magnetic resonance image (MRI) findings showed a heterogeneous, multiloculated
mass with thematic content. The mass demonstrated intense septal contrast enhancement,
highly suggestive of an aneurysmal bone cyst ([Figs. 3] and [4]). Due to the extent of neurological impairment, the lesion was classified as Enneking
stage 3.
Fig. 1 CT of the spine showing a kyphotic deformity of the thoracic spine and grade III
spondylolysis of T11 on T12.
Fig. 2 CT of the spine showing a T11 body collapse.
Figs. 3 and 4 MRI show an anomalous, heterogeneous, multiloculated, multiseptated tissue formation,
of an inflatable aspect, markedly filled with hematogenic content, characterized by
areas by in which liquid-liquid level formation is defined, with intense septal contrast,
suggesting ABC enhancement.
Operation
Preoperative embolization was initially proposed but it could not be performed due
to the absence of a favorable arterial pedicle. Consequently, the patient underwent
complete tumor resection, including total T11 and partial T10 corpectomy. This was
followed by anterior spinal reconstruction using a body cage combined with bone graft,
and posterior stabilization from T7 to T12 with pedicle screws ([Figs. 5] and [6]). Histopathological evaluation revealed a fibrous bone lesion rich in giant cells
with hemorrhagic areas but without significant atypia. Together with the radiological
findings, this confirmed the diagnosis of ABC.
Figs. 5 and 6 CT showing total T11 and partial T10 corpectomy, associated with reconstruction of
the previous spine with body cage and posterior stabilization from T7 to T12 with
pedicle screws.
Postoperative Course
In the immediate postoperative period, the patient evolved without worsening the existing
deficit, but still with paraplegia. One week after surgery, the patient began a neurological
rehabilitation program. On postoperative day 21, the patient developed a wound infection,
which was treated with surgical debridement and intravenous antibiotics (ceftazidime,
vancomycin, and meropenem). Around the same time, she experienced extensive thrombosis
in the femoro-popliteal-fibular axis, which was managed with full anticoagulation
and a vena cava filter. After three months of daily neurological rehabilitation, the
patient showed progressive improvement in muscle strength, which began distally in
the lower limbs and gradually advanced. At her five-month postoperative follow-up,
the patient exhibited a motor strength grade of 4/5 in the lower limbs, with some
asymmetry, being slightly weaker on the left side. She was able to walk with the aid
of a walker and had regained normal sphincter control. Sensory deficits had almost
fully resolved. MRI at 6 months follow-up showed no recurrences.
Case 2
History and Examination
The second patient was an 8-year-old boy who was presented for a neurosurgical evaluation
with a seven-month history of lumbago accompanied by sciatica. He reported noticing
difficulty walking due to the left leg weakness that had developed three months prior.
On physical examination, the patient presented with a muscle strength of 4/5 in the
left iliopsoas and, with normal deep tendon reflex. He also exhibited hypoesthesia
in the anterior aspect of the left thigh.
A CT scan revealed an osteolytic lesion involving the left posterior element and vertebral
body of L3 ([Figs. 7] and [8]). MRI showed a tumor with a low sign on T1-weighted images and a high sign on T2-weighted
images. The lesion had multiple internal septations with enhancement and fluid-fluid
levels ([Fig. 9]).
Figs. 7 and 8 CT scan showing an osteolytic lesion involving the left posterior element and vertebral
body of L3.
Fig. 9 MRI showing a high sign, with multiple internal septations with enhancement and fluid-fluid
levels on T2-weighted.
Operation
At first, the patient underwent a percutaneous transpedicular vertebral body biopsy
on the left side, which revealed a multiloculated cystic lesion with calcifications,
without cytological atypia. The patient continued to experience focal neurological
deficit. Considering his neurological deficits, a complete tumor resection, including
an L3 corpectomy, followed by anterior spine reconstruction with a body cage and bone
graft was performed. The posterior spine was stabilized with pedicular screws from
L2 to L4 on the left and right sides.
Postoperative Course
In the postoperative period, the patient demonstrated an improvement in their condition
without a worsening of the existing deficit. Physical therapy began three days after
surgery, and the patient was discharged on postoperative day five. At a follow-up
visit 15 days post-surgery, the patient showed full recovery of muscle strength in
the left iliopsoas and quadriceps (5/5), such that the patient was walking without
support and without pain complaints. In 1-month follow-up, all sensory deficits had
been resolved. MRI at 6 months follow-up showed no recurrences.
Discussion
Aneurysmal bone cysts (ABC) are benign, hypervascularized, osteolytic lesions that
are locally destructive and predominantly arise in the metaphysis of the long bones
and spine.[1]
[2] Clinically, they manifest with pain, which may or may not be accompanied by neurological
deficits due to vertebral body fractures or spinal cord and/or root compression. The
severity of symptoms depends on the degree of associated spinal cord injury.[6]
[9]
In 1986, Enneking classified ABC into three stages of evolution. In the first stage,
the lesions are benign, latent, and asymptomatic. In the second stage, they become
active and present clinically with pain. The final stage represents aggressive lesions
that are often associated with neurological impairment, as seen in the present cases.[10]
Radiological diagnosis of ABC is primarily done through CT and MRI. CT typically reveals
an expansive, lytic lesion with thin septa and cortices, suggestive of a cystic lesion.
MRI, the preferred modality for detecting neurological compression, epidural extension,
and internal septations, frequently demonstrates the “fluid-fluid” pattern, which
can be critical for planning surgical resection.[9]
[11]
[12] These imaging findings are consistent with those observed in our reports.
The definitive diagnosis of ABC is achieved through histopathological analysis, which
reveals circumscribed cystic lesions filled with blood and separated by fibrous septa.
These septa contain soft fibroblasts, osteoclast-like giant cells, and reactive bone
tissue surrounded by osteoblasts. In about 30% of cases, this bone tissue takes on
a basophilic hue, referred to as “blue bone”. In cases of pathological fractures,
tissue necrosis is more commonly seen.[6]
[8]
[13] In our reports, histopathological analysis was crucial for confirming the diagnosis,
aligning with current literature findings.
The differential diagnosis includes other bone tumors, with hemorrhagic cystic alterations,
such as osteosarcoma and chondroblastoma. However, the most important differential
diagnosis is telangiectatic osteosarcoma, due to its image similarities and macroscopic
appearance. Telangiectatic osteosarcoma can be distinguished from ABC through histological
examination, which reveals the presence of malignant cells, absent in ABC.[13]
The choice of treatment for ABCs depends on the clinical manifestations and stage
of the lesion.[6] Surgical intervention is often necessary due to the risk of significant bleeding,
structural instability from fractures, and the potential for neurological compression.[7] The primary objective of surgical intervention is the complete resection of the
cyst. This is because partial resections have been observed to have a recurrence probability
of approximately 70%. In such cases, spinal reconstruction and stabilization may also
be required.[4]
[14]
In both cases we present, complete resection of the lesion was performed alongside
spinal stabilization using pedicular screws and reconstruction of the anterior spine
with a body cage. This allowed for adequate decompression of the neural structures,
restoration of spinal stability, and prevention of further complications.
Selective arterial embolization (SAE) has emerged as a therapeutic option, either
as a standalone treatment or as an adjunct to surgery. SAW involves the embolization
of the ABCs blood supply, with a reported cure of approximately 80%. However, its
use is limited in cases of myelopathy or spinal instability. In this procedure, the
aneurysmal bone cyst is embolizing.[2]
[13] In thoracolumbar lesions, embolization carries the risk of compromising the Adamkiewicz
artery, while in cervical lesions, the vertebral arteries are a concern.[10]
[13] In our first case, embolization was attempted but was unsuccessful.
Common postoperative complications include pulmonary infections, cerebrospinal fluid
leaks, surgical wound infections, thromboembolic events, and release or failure of
instrumentation.[15] In our first case, the patient developed deep vein thrombosis, which was treated
with anticoagulation and a vena cava filter, as well as a surgical wound infection
requiring surgical debridement and antibiotic therapy. The second one presented no
postoperative complications.
The prognosis in ABC cases is influenced by factors such as the degree of resection,
preoperative neurological impairment, and the location of the lesion. A complete resection
generally improves outcomes, particularly in patients without severe preoperative
neurological deficits.[9]
[14]
[16]
[17]
Conclusion
In cases of severe clinical manifestations, such as acute paraplegia, prompt and appropriate
treatment, compromising tumor resection, spinal decompression, spinal reconstruction,
and postoperative rehabilitation, can result in substantial neurological recovery.
In cases where profound neurological impairments are present, appropriate surgical
and rehabilitation can result in a complete resolution of deficits.
