Keywords

Introduction

In pediatric neurosurgical practice spinal tumours occur considerably less frequently than intracranial tumours, accounting for only 5–10% of pediatric CNS tumours. Moreover, spinal tumours are much less common in children compared with adults. Approximately one third of spinal tumours in childhood are extradural , the remainder being intramedullary or intradural but extramedullary. Intramedullary and intradural extramedullary tumours are dealt with elsewhere in this book.

The term vertebral tumours is used here to encompass those tumours that arise in the extradural space and the paraspinal regions, as well as from the bony and cartilaginous elements of the spine. A variety of tumour types, both benign and malignant, may be encountered in these locations though both the age of the patient and the anatomical site of origin will aid in refining the differential diagnosis in individual cases.

The management of spinal column tumours is guided by:

  1. 1.

    Biology of the tumour

  2. 2.

    Neurological status of the patient

  3. 3.

    Spinal deformity or instability

Tumours of extradural origin are more likely to be malignant than intradural tumours. Furthermore, spinal column tumours may be part of a more systemic malignant disease and in such cases surgery alone is unlikely to be curative. It is therefore imperative that these cases be managed by a multidisciplinary neuro-oncology team to ensure that the timing, objectives, and extent of surgery are agreed and appropriate.

Severe neurological deterioration mandating emergency intervention is rare in pediatric spinal column tumours; there is usually time to permit appropriate investigations and planning of intervention.

Vertebral collapse with deformity or instability will mean that spinal stabilization will have to be considered as part of the surgical strategy in many cases. Even if there is no evidence of deformity or instability at the outset, late postsurgical deformity is a significant risk following laminectomy or laminoplasty, particularly in a growing child, and these risks need to be factored into the clinical decision-making process (Guzey et al. 2008; Joaquim et al. 2012).

In this chapter, the clinical presentation and investigative modalities of vertebral column tumours are discussed. The principle malignant and benign spinal column tumours are then reviewed followed by an overview of surgical strategy and complications.

Clinical Presentation

Unfortunately, as vertebral tumours are rare in childhood and as the presenting symptoms, particularly back pain, are frequently nonspecific, diagnosis is often delayed. In a series of 28 paravertebral malignant tumours of childhood, 11 patients had advanced disease at the time of diagnosis and 16 had radiological evidence of spinal cord compression. Late referral and delayed diagnosis were cited as major causes of morbidity and mortality (Gunes et al. 2009).

Pain

Spinal pain is present in at least two thirds of cases of spinal tumour at the time of diagnosis. The onset of pain may be acute, due to pathological fracture or vertebral collapse, or insidious, due to tumour infiltration of bone or progressive neural compression. The pain associated with spinal tumours is frequently poorly localized; it may have been present for many months prior to diagnosis, commonly dismissed as “growing pain” or non-specific musculoskeletal pain (Grattan-Smith et al. 2000). Constant pain or pain of increasing intensity, pain that wakes the child at night, or that is associated with radicular spread or sensory impairment should be deemed “red flag” symptoms that warrant prompt investigation (Garg and Dormans 2005; Sciubba et al. 2008).

Weakness

Along with pain, weakness is one of the commonest findings in children with spinal tumour and is present in two thirds of children at the time of presentation. In the infant and young child, weakness can be easily overlooked until the late stages of spinal cord compression. In an older child a limp, fatigability, a tendency to tripping, or falls may be the manifestations of lower limb weakness. Examination findings are typically those of upper motor neuron type with hyperreflexia; however, in children (in contrast to adults) good motor function may be preserved, even in the face of severe radiological evidence of neural compression.

Mass

Extension of a spinal or paraspinal mass into the adjacent soft tissue can result in a palpable mass in a thin child. A soft tissue mass in association with a bone tumour is suggestive of malignancy and is present in one third of vertebral malignancies (Gunes et al. 2009).

Spinal Deformity

Scoliosis is present in approximately one quarter of cases at initial diagnosis. Rapid curve progression, atypical or left sided curves should prompt the search for an underlying spinal lesion or spinal cord anomaly. When present, tumours tend to occur on the concavity, at the apex of the deformity. Spinal deformity occurs either as a response to local pain and muscle spasm, for example, in osteoid osteoma, or may be secondary to bone destruction and mechanical instability. This is in contrast to the scoliotic deformity associated with intramedullary spinal cord tumours, which is essentially neurogenic in origin. Torticollis or limitation of neck movements may herald the presence of a tumour involving the upper cervical vertebrae or craniovertebral junction.

Sphincter Disturbance

This is an unusual presenting symptom in childhood but one that is easily overlooked, particularly in the younger child or infant. Tumours of the lumbosacral region, such as neuroblastoma or sarcoma, are more likely to present in this way as a result of cauda equina compression. A history of urinary infection or frank incontinence is sometimes present and examination findings can include an enlarged bladder, incomplete bladder emptying, or fecal soiling. Disturbances of rectal continence are less common than those of urinary continence; neurogenic sphincter disturbance almost always affects the bladder first. The exception to this rule is sacral tumours with pre-sacral extension where direct, mechanical impairment of rectal emptying can occur.

Systemic Signs

Constitutional symptoms such as weight loss, poor appetite, and malaise when present suggest a malignancy or systemic disease such as tuberculosis.

Investigations

The following objectives need to be considered when selecting the most appropriate imaging modalities with which to evaluate spinal tumours:

  1. 1.

    Establish the site and extent of the lesion, and its effect on the neuraxis (spinal cord and nerve roots)

  2. 2.

    Evaluate the extent of bone involvement

  3. 3.

    Evaluate spinal deformity

  4. 4.

    Assess spinal stability

  5. 5.

    Refine the differential diagnosis

The most commonly required investigations are as follows.

Spinal MRI

The whole spine should be imaged with and without contrast. MRI provides the best modality to assess the effect of the lesion on the neuraxis (Bloomer et al. 2006). It is important to be aware of lesions that might masquerade as tumour, in particular spinal tuberculosis which, will not infrequently present with vertebral body involvement and an associated soft tissue mass, features that can be difficult to distinguish from those of malignant vertebral column tumour (Fig. 1).

Fig. 1
figure 1

Sagittal T2 MRI scan showing tuberculosis of the thoracic spine mimicking vertebral tumour

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Spinal CT

High-resolution CT scan (using a bone window algorithm) of the involved vertebral levels is used where detailed bony information is required, for example, in assessing extent of bone involvement or suitability for instrumental fixation. CT-guided biopsy of the lesion can be useful in cases of suspected malignancy.

Plain X-Rays

Plain X-rays will typically have been performed in the initial investigation of a child with a vertebral column tumour. Abnormalities including pathological fracture, deformity, and loss of a pedicle (“winking owl” sign) are present in over two thirds of cases (Guzey et al. 2008), but sensitivity is poor compared to other modalities, and normal X-rays should not preclude the pursuit of a more detailed search in a child with worrisome symptoms. While of limited help in providing diagnostic information, plain X-rays do have a role in assessing spinal deformity or in cases of suspected instability, for example, flexion/extension X-rays in cervical lesions.

Additional Investigations

There are some investigations that are specific to the workup of certain tumour types, for example, MiBG scan is a nuclear medicine scan that is useful in the staging of neuroblastoma. Bone marrow biopsy will also be required in the staging and typing of neuroblastoma and lymphoma, and skeletal survey is necessary in suspected Langerhans cell histiocytosis to assess for multifocality. Spinal angiography, with a view to embolization, is being increasingly used not only for diagnosis but in the definitive treatment or preoperative management of lesions such as hemangioma of bone, in an attempt to reduce operative blood loss (Griessenauer et al. 2016).

Tumour types principles of management

There is a broad range of tumour types that can affect the pediatric spinal column; however, these are rare tumours, accounting for less than 1% of childhood tumours and so will be encountered relatively infrequently in the majority of pediatric neurosurgical practices.

Management of spinal column tumours will typically require a multidisciplinary approach, both in establishing an accurate histological diagnosis and then determining an appropriate treatment regime. To reiterate, the three factors that need to be borne in mind throughout this process comprise: the specific histological diagnosis and its natural history, the neurological status of the patient, and finally the effect of the pathology or the (surgical) treatment on integrity of the spinal column.

Pathological Diagnosis

The treatment of malignant spinal column tumours such as sarcomas will be dependent upon an accurate pathological diagnosis; this will usually need to be established before commencing chemotherapy or embarking upon definitive surgery. The mode of initial biopsy (image guided vs. open) may have a significant effect on outcome, and this should be ideally undertaken in the specialist centers where the definitive treatment will be undertaken.

Neurological Status

Preservation of neurological function , in particular motor function and continence, should remain a goal at all stages in treatment. It is relatively rare for children to require emergency surgery for spinal column tumours; therefore, there is usually time for radiological and oncological discussion to take place such that interventions are appropriate and timely. For example, in an infant with lower limb weakness due to neuroblastoma, optimal neurological outcome with reduced treatment related morbidity might be better achieved by urgent chemotherapy rather than decompressive surgery.

Spinal Integrity

Spinal deformity with or without instability may be present at the time of diagnosis; the management of this has to be factored into the treatment plan. Moreover, multiple level laminectomy or laminotomy may produce or exacerbate preexisting deformity resulting in late morbidity and the need for additional surgery.

Establishing a differential diagnosis

Some of the more common tumour pathologies to affect the pediatric spinal column are discussed individually below. However, at the time of presentation, it is helpful to try and refine a differential diagnosis; the age of the patient and the apparent site of origin of the tumour can help in achieving this.

Age

The distribution of tumour types varies through childhood , for example, neuroblastoma would be rare in a teenager, and osteosarcoma would be exceptional in an infant. (Figure 2 provides a rough guide to the age related distribution of spinal column tumours.)

Fig. 2
figure 2

Distribution of vertebral tumours according to age at presentation

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Anatomical Site of Origin

Spinal column tumours show a predilection for certain patterns of growth and this can be of help in refining the differential diagnosis. Spinal column tumours can be considered to originate either in the vertebral body, the neural arch or in the paraspinal tissues with secondary spinal invasion. While there are exceptions, Fig. 3 illustrates the distribution of tumour types according to their typical site of origin.

Fig. 3
figure 3

Distribution of vertebral tumours according to anatomical location

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Malignant Vertebral Tumours in Children

Malignant tumours of the spinal column present with spinal pain (this may have a radicular component), painful scoliosis, gait disturbance, or limb weakness. Bladder (or rarely bowel) incontinence is seen in lumbosacral malignancies when the conus or cauda equina are involved, though these are unusual presenting features in tumours originating higher in the spinal column. Systemic features such as weight loss, lethargy, and night sweats may be present, particularly in lymphoma and Ewing sarcoma.

Malignant tumours of the spinal column require multidisciplinary approach. Accurate pathological diagnosis can be difficult but is an essential prerequisite to treatment. CT-guided biopsy or open biopsy will usually be required in the first instance, though in cases presenting with spinal compression, tumour tissue will be obtained at the time of the decompression procedure. Given the propensity for hematogenous spread, staging investigations including chest CT scan, abdominal ultrasound, and bone marrow aspiration are required.

Surgery should be considered as an adjunctive therapy in the management of malignant tumours of the spinal column. Neoadjuvant and adjuvant chemotherapy have improved the prognosis for many malignant tumours, largely due to their ability to shrink tumours and reduce tumour vascularity, thus optimizing the chances of gross total resection.

Neuroblastoma (NB)

Spinal NB is predominantly a tumour of infancy and younger children. The histogenesis of NB is uncertain; these tumours are thought to originate in neural crest derived peripheral nerve progenitors. Spinal NB commonly occurs along the sympathetic chain (and adrenal gland), and so is typically centered on the paravertebral region with secondary extension through the intervertebral foramina into the intraspinal compartment (Fig. 4). The cells of origin are involved in catecholamine secretion; this feature is exploited in the diagnosis and workup, as metabolites from the catecholamine synthesis pathway are excreted via the kidney and can be detected in the urine. The metabolic activity of these tumours is also utilized in staging the disease; the radionuclide MiBG is taken up by NB and will permit identification of metastatic disease (Fig. 5).

Fig. 4
figure 4

Infant neuroblastoma. Sagittal T2 weighted image showing extensive intraspinal extension of neuroblastoma

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Fig. 5
figure 5

Metastastic neuroblastoma. (a) MiBG radio nucleotide scan demonstrating multiple hot (dark) spots due to widespread metastases. (b) SPECT CT scan combining MiBG scan with low dose spinal CT to improve anatomical delineation of tumour (Images courtesy of Dr. Lorenzo Biassoni, Department of Nuclear Medicine, Great Ormond Street)

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Some of these tumours show a phenomenon of maturation toward more favorable pathology, either on treatment or spontaneously, and so a spectrum of tumours ranging from malignant neuroblastoma, through ganglioneuroblastoma, to the more benign ganglioneuroma is recognized in pediatric practice.

The oncological outcome for neuroblastoma has been known to be dependent on a number of factors, in particular cytogenetic profile. This has allowed treatment to be stratified according to risk factors identified by the International Neuroblastoma Risk Group (INRG) as of particular prognostic significance. These factors include tumour stage, histology, MYCN oncogene status, chromosome 11 status, and degree of DNA ploidy (Cohn et al. 2009).

Between 5% and 10% of cases of neuroblastoma present with symptoms of extradural spinal compression (De Bernardi et al. 2005), moreover as many as half of these cases will be aged less than 1 year. Motor weakness (85%), pain (40%), and sphincter impairment manifesting as urinary dribbling, incomplete voiding, or retention of urine (20%) are among the most frequently recorded symptoms. Delayed presentation is common, and this is considered a major factor in determining functional outcome (De Bernardi et al. 2014; Katzenstein et al. 2001).

The mainstay of treatment for NB is chemotherapy. The role of surgery in the treatment of extradural compression is controversial; studies have failed to show clinical benefit in terms of neurological recovery in cases treated by initial laminectomy, compared with chemotherapy alone. Furthermore, the morbidity associated with spinal decompression is significant, between 30% and 60% of laminectomy patients developing late spinal deformity (Hoover et al. 1999; Katzenstein et al. 2001), compared with less than 5–12% of patients treated medically (Sandberg et al. 2003).

Surgical decompression is therefore reserved for cases presenting with severe deficit or rapidly evolving neurology, or for those whose neurological exam progresses during chemotherapy. For children who present with neurological symptoms, who are selected for initial medical rather than surgical treatment, chemotherapy should be started urgently and it is imperative that the neurological status is closely monitored in the early stages of medical treatment. Tumour swelling with neurological deterioration may occur and should prompt a reconsideration of surgical decompression.

It is not known whether aspects of surgical treatment, such as osteoblastic laminoplasty or postsurgical orthotic bracing, reduce the risk of late scoliosis.

Overall, 5 year survival for childhood neuroblastoma is approximately 70%. In one large review, children presenting with symptomatic spinal cord compression had similar event free survival (71% vs. 61%), compared with those who did not have spinal involvement. Furthermore, overall survival was better in the spinal compression group (85% vs. 71%), though this was thought to be influenced by younger age and a higher incidence of localized, better biology tumours (De Bernardi et al. 2005).

Ewing’s Sarcoma (EWS)/Peripheral PNET

Ewing’s sarcoma (EWS) is a tumour of older children and teenagers, approximately 75% of cases present between the ages of 5 and 15 years. Moreover, EWS is the most common primary malignant spinal bone tumour in this age group. Approximately 10% of cases of EWS involve the spine; however, in contrast with OS, there is a predilection for the lumbosacral region (Kim et al. 2012). Metastatic spread is present in up to half of cases at the time of presentation (Sciubba et al. 2008). Histologically these are “small round blue cell” tumours and are considered to be part of the PNET spectrum; they share certain cytogenetic changes seen in medulloblastoma.

On MRI, EWS appears as an area of lytic bone destruction with an associated mass lesion that will commonly extend into the paravertebral region and produce a palpable mass (Fig. 6). These tumours are centered on the vertebral body rather than neural arch, typically respecting the intervertebral disc (in contrast to infection).

Fig. 6
figure 6

Post-contrast axial (a) and sagittal (b) MRI scans of sacral Ewing sarcoma. There is destruction of the vertebra, and a soft tissue mass that involves the sacral spinal canal. Extension of the mass into the posterior paravertebral muscles is shown. A mass could be palpated on clinical examination

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As with OS, accurate tissue diagnosis is essential. CT-guided needle biopsy is generally recommended over open biopsy as the latter has been suggested to carry an increased risk of local recurrence (Yamazaki et al. 2009). Once the diagnosis is established, neoadjuvant chemotherapy is the initial treatment of choice, followed by resection, usually necessitating vertebral reconstruction with instrumented fixation. Wide en bloc excision should be aimed for where possible, as it appears this offers greater potential for local disease control (Sewell et al. 2015). Surgery will commonly require a combination of anterior and posterior approaches (Mattei et al. 2015) with the aim of radical resection with margins; however, while this is occasionally feasible in the mobile spine, it is frequently not feasible in the lumbosacral region. Surgical morbidity is significant; in a recent systematic review, surgical complications ranged from 13% to 56% and mortality from 0% to 7.7% (Yamazaki et al. 2009). These procedures are therefore best managed in a multidisciplinary team with neurosurgical and spinal orthopedic expertise.

Radiation therapy is used for postsurgical residual disease. While more aggressive surgical interventions have improved outcomes for young patients, with small volume, localized disease, unfortunately overall survival remains poor with 5 and 10 year survival rates of 42% and 32%, respectively (Bacci et al. 2009).

Osteogenic Sarcoma (OS)

Overall this is the most common primary bone neoplasm in children and typically presents around the time of puberty. However, spinal involvement (either as primary lesion or site of metastasis) is seen in only 5% of cases (Kim et al. 2012), and thus presentation to the pediatric neurosurgeon will be less common than for EWS. The thoracic and lumbar regions are the most commonly affected, and in as many as 10% of cases there will be metastatic spread at the time of diagnosis. Spinal involvement portends a worse prognosis compared with OS of long bones.

Imaging typically reveals bone destruction and an associated soft tissue mass demonstrating variable degrees of mineralization (Fig. 7). Tissue diagnosis is established by open or CT-guided biopsy. Neoadjuvant chemotherapy is used to reduce tumour volume, followed by maximal surgical resection of the involved field. The 5 year survival rate for all OS is poor, approximately 18%.

Fig. 7
figure 7

Osteosarcoma , sagittal T2 (a) and axial T1 (b) MRI scan of thoracic bone lesion with extension into the spinal canal. There is a soft tissue mass based on the vertebral body. Osteosarcoma was confirmed on biopsy

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Chordoma

Chordoma is a rare tumour of presumed notochordal origin with a predilection for the craniovertebral junction and the sacrum; together these two sites comprise over two thirds of cases. Sacral chordomas tend to have poor histology and worse outcomes; however, this location is distinctly rare in children. Only 5% of chordomas occur in the pediatric age group, and 85% of these occur at the craniocervical junction. The radiological features are of local bone destruction with associated soft tissue mass. Craniocervical lesions are typically centered on the clivus (Fig. 8). The mass will commonly have a honeycomb appearance on MR, and is high signal on T2 with intermediate to low signal on T1 (Fig. 9). Enhancement is quite heterogeneous, and areas of intratumoural hemorrhage are common.

Fig. 8
figure 8

Post-contrast sagittal T1 weighted MRI scan of clival chordoma. There is soft tissue mass, based on the clivus with local erosion of bone. The lesion demonstrates heterogeneous enhancement

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Fig. 9
figure 9

Axial T2 weighted MRI of chordoma involving the spinal canal and prevertebral space. There is local bone destruction and the lesion has a multicystic, honeycomb appearance commonly seen in chordoma

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The histological features are those of a lobulated lesion, pockets of cells are separated by fibrous septa; the cells have foamy, vacuolated cytoplasm and are termed physaliphorous cells. Immunohistochemical techniques are required to distinguish chordoma from chondrosarcoma which may also occur in the same location, the latter has a more favorable prognosis. Traditional histological subtypes of chordoma include classical, chondroid, and dedifferentiated. The latter has a more aggressive natural history. There is now increasing recognition that the expression patterns of a number of biomarkers are useful in determining the prognosis for chordoma (Tauziède-Espariat et al. 2016). This may be of future benefit in stratifying treatment for childhood chordoma in an attempt to reduce treatment related toxicity.

Most studies concur that gross total en bloc resection provides the best long-term survival (Choi et al. 2010) for chordoma. Unfortunately, this is usually only feasible for small volume, localized tumours (<30 mls). Chordoma is only moderately radiosensitive; however, proton beam therapy has increased the dose of radiotherapy that can be safely delivered to residual or recurrent tumours (Hug and Slater 2000; Hug et al. 2002). There is a high rate of local recurrence and 5 year survival is approximately 60%. Young children (less than 5 years) are more likely to have immature, poor biology tumours and are also more likely to have early metastatic disease; this group has a particularly poor prognosis.

Lymphoma

Spinal involvement in lymphoma is rare and usually occurs late in the course of the disease. Most lymphomas that involve the spine in childhood are B cell lymphomas of the non-Hodgkin type and tend to occur in the adolescent age group. Spinal lymphoma characteristically spreads along nerve roots and through the intervertebral foramina. Pathological fractures are present in up to one quarter of patients. Chemotherapy is the mainstay of treatment; surgery is reserved for cases of spinal disease refractory to primary treatment or for clinical symptoms or signs of spinal cord compression.

Benign Vertebral Tumours in Children

Within the spectrum of benign spinal tumours there are those that can be considered benign, with favorable natural history (e.g., Langerhans cell histiocytosis and osteoid osteoma) and those that are histologically benign but have a tendency toward a locally aggressive natural history (e.g., aneurysmal bone cyst, giant cell tumour of bone) (Harrop et al. 2009).

Aneurysmal Bone Cyst (ABC)

This benign but locally aggressive lesion can occur in isolation or in conjunction with another pathology such as fibrous dysplasia or giant cell tumour of bone. Long bones, such as the femur, tibia, and humerus, are well recognized sites for ABC in children; the vertebral column location accounts for up to 20% of cases. ABCs are usually limited to a single vertebral level, and any level of the spine can be affected, including the sacrum, though in the mobile spine the distribution was found to be lumbar (40%), thoracic (30%), and cervical (30%) in one large literature review (Cottalorda et al. 2004). ABC is a lesion of young people, 80% of cases present before the age of 20 and the second decade has the highest incidence (Leithner et al. 1999). ABCs more usually originate in the posterior elements; nonetheless, extension to the vertebral body is not infrequent (Garg et al. 2005; Sebaaly et al. 2015). These lesions characteristically consist of well-demarcated cysts, frequently containing chocolate colored fluid, reflecting the tendency for intermittent intralesional hemorrhage. The cyst wall comprises a thin shell of reactive bone; this tends to expand the vertebra, producing the hallmark “soap bubble” appearance on CT or MRI (Fig. 10). Radiological features are usually diagnostic, and therefore preliminary biopsy is rarely necessary.

Fig. 10
figure 10

T2 weighted (noncontrast) MRI scans of an aneurysmal bone cyst of L4 vertebra. (a) Sagittal, (b) axial. The anterior and posterior vertebral elements are expanded by the multicystic lesion. Fluid levels are seen within the cysts representing areas of repeated hemorrhage

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Localized pain is the commonest presenting symptom, though neurological symptoms secondary to nerve root or spinal cord compression can occur due to local expansion of the lesion, or as a result of pathological fracture (Zenonos et al. 2012). Neck pain with torticollis is common in cervical lesions.

Treatment options for ABC have been controversial. The majority of published evidence suggests that complete surgical resection is associated with the lowest risk of recurrence. However, this may be difficult to achieve in large lesions, those in less accessible regions of the spine and where there is significant risk to neurovascular structures, such nerve roots and the vertebral artery. Where there is evidence of spinal or nerve root compression, urgent surgical decompression either by means of marginal resection or extensive curettage should be performed to decompress neural structures as the primary aim. Simultaneous vertebral reconstruction using a combination of prosthetic cages, bone grafts, and internal fixation techniques will often be required.

Given the propensity to intraoperative hemorrhage, selective arterial embolization (SAE) has been advocated in the preoperative workup of spinal ABC. However, in spite of the name, these lesions are not inevitably vascular at surgery (in contrast with hemangioma of bone), and some authors have suggested that preoperative embolization should not be considered a requirement prior to surgery (Zenonos et al. 2012). Given the difficulty of predicting vascularity, if access to interventional neuroradiology is readily available, then angiography should be considered advisable, with a view to proceeding to embolization, once the risks and benefits have been evaluated.

Curettage alone is associated with a high rate of local recurrence (Sebaaly et al. 2015); however, in a small series of eight patients, Garg et al. reported no recurrences when extensive curettage was combined with high speed blur, electrocautery, and bone grafting (Garg et al. 2005). The mode of removal, curettage versus en bloc resection, seems less important that the extent of resection and gross total resection should, wherever possible, be the goal of surgery.

Where there is existing deformity or instability, or where this is a likely consequence of the extent of bone removal, then instrumented spinal reconstruction will be indicated; this is required in at least 80% of cases (Zenonos et al. 2012). As the majority of lesions originate in the posterior elements and will be amenable to a posterior approach, then a single stage resection, with posterior fixation alone, will suffice. Where the vertebral body has collapsed, or when part of the body has had to be resected in order to achieve complete removal, there will be a risk of kyphotic deformity and so anterior instrumented fixation will be indicated. Anterior fixation is required in up to half of cervical, instrumented cases.

Postsurgical surveillance is required as there is a significant risk of local recurrence particularly in partially resected lesions (Novais et al. 2011).

While selective arterial embolization (SAE) has hitherto been used as an adjunct to surgery, recent evidence suggests that this modality should be considered as a primary definitive treatment for ABC in the absence of instability or neurological compromise. Serial SAE was successfully used in seven pediatric and adult patients, with radiological evidence of regression and recalcification of bone at follow-up (Amendola et al. 2012). Dubois et al. have reported success in 17 children with spinal ABC treated by percutaneous instillation of alcohol and histoacryl glue after a follow-up period of mean follow-up of 57 months (Dubois et al. 2003). Success in this series was defined as residual cyst size <20% of the primary lesion, therefore longer follow-up will be required to evaluate the durability of this treatment.

Radiotherapy has also been used in the treatment of ABC; however in children, due to the potentially hazardous late effects, radiotherapy is generally reserved for instances where primary treatment has failed (Burch et al. 2008).

Osteoid Osteoma/Osteoblastoma

The distinction between these two entities is essentially a matter of size; their pathological appearances are indistinguishable. Small lesions, <2 cm are termed osteoid osteoma (Fig. 11), while the larger version is referred to as osteoblastoma (Fig. 12). The clinical presentation is with local spinal pain; the pain will characteristically respond to nonsteroidal anti-inflammatory drugs. Neurological deficits are more commonly seen with osteoblastoma, and osteoblastoma tends to have a higher rate of recurrence, again this reflects larger size and the implications that this has for complete resection. Radiologically there is often a central nidus of dense bone, frequently with sclerosis of the surrounding bone resulting in a lucent halo around the lesion (this finding is more consistent in osteoid osteoma) (Zileli et al. 2003). These lesions appear as “hot spots” on radionuclide scanning. Complete surgical resection is the principle treatment modality and can be considered curative.

Fig. 11
figure 11

Axial cervical CT scan showing osteoid osteoma. The lesion is localized to the left hemilamina with expansion of the cortical bone rather than destruction in keeping with a benign pathology

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Fig. 12
figure 12

Osteoblastoma. Axial CT scan showing an expansile, bone based lesion arising in the lateral mass and lamina of a cervical vertebra

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While surgery continues to be the mainstay of treatment for larger lesions, there is a trend to consider minimally invasive techniques for smaller lesions (Atesok et al. 2011). There are now large series reporting the efficacy of CT-guided radiofrequency ablation for osteoid osteoma, including in children. While most reports relate to extra spinal lesions, the success of the technique (both in terms of pain control and deformity) has been repeated in spinal lesions. Clearly the benefit of such a minimally invasive procedure, avoiding potentially destabilizing surgery, needs to be weighed against the risk of thermal injury to adjacent neural structures (Vanderschueren et al. 2009).

Osteochondroma

These are benign tumours arising typically in long bones at the site of the epiphysis; here they appear as cartilage capped, exophytic outgrowths. On plain X-rays or on CT, these tumours can be seen to emerge from the surface of bone, indeed the continuity between the cortex and medullary canal of the bone of origin with that of the bony outgrowth is pathognomonic of osteochondroma. These tumours tend to occur in the second decade and are more frequently seen in males. While the majority are solitary, multiple lesions can occur in the setting of an autosomal dominant condition, hereditary multiple exostosis (HME). HME has been demonstrated to be associated with mutations in the EXT1 and EXT2 genes. Most osteochondromas are extra spinal in location, with no more than 5% of cases affecting the vertebral column (Sinelnikov and Kale 2014). In cases of vertebral osteochondroma the cervical region is the most common location, with a predilection for the posterior arch rather than vertebral body. Pain, neurological deficit due to compromise of the spinal canal or nerve root foramen, and deformity due to mechanical effects on the growing spine are all recognized modes of presentation. Complete surgical excision is the mainstay of treatment. Incidentally found lesions, with classical radiological appearance, can be safely observed.

Langerhans Cell Histiocytosis (LCH)

The term “histiocyte” encompasses two important components of the immune-regulatory system, namely the monocyte/macrophage series and the Langerhans cell series. Langerhans cells are dendritic cells; they have a particular role in antigen presentation and thus are a cornerstone of the immune system. They can undergo neoplastic transformation resulting in distinct clinical entities of variable malignancy.

LCH may occur as an isolated bone lesion (unifocal LCH) or with multiple bony lesions (multifocal unisystem LCH). A more malignant form, with widespread extraosseous tissue involvement, is recognized (multifocal multisystem LCH). This classification of Langerhans cell disorders replaces the older terminology of eosinophilic granuloma (histiocytosis X), Hand-Schuller-Christian disease, and Letter-Siwe disease to describe these three entities (Favara et al. 1997).

LCH is a disorder of the young; there is a peak incidence of the first decade of life. In children, 80% of cases are unifocal, the skull being a common site; multifocality is more common in children that have presented with a spinal lesion The spine is involved in up to 25% of cases, with the cervical region being the most commonly affected (Garg et al. 2004). The classical spinal appearance of LCH is vertebra plana, a symmetrical collapse of the vertebral body (Fig. 13). Vertebra plana is, however, neither specific (other lesions such as sarcoma and aneurysmal bone cyst can also produce this appearance) nor sensitive (in one series only 3 of 18 cases had typical vertebra plana) for LCH (Peng et al. 2009). There is often an associated soft lesion, and this can cause neural compression though frank spinal cord compression is rare; pain rather than neurological compromise is the most common presentation (Garg et al. 2004; Peng et al. 2009).

Fig. 13
figure 13

Sagittal reformatted CT scan illustrating histiocytosis of the third cervical vertebra. There is loss of height of the vertebral body due to tumour involvement; the appearances is known as known vertebra plana

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Given the unreliability of radiological criteria, a tissue diagnosis should be sought in the majority of cases, and this can commonly be achieved by CT-guided needle biopsy. Once the diagnosis is confirmed, skeletal survey, chest X-ray, and abdominal ultrasound are recommended in the search for evidence of systemic lesions.

Solitary lesions, with minimal symptoms, may be observed in the first instance as spontaneous regression is well documented. While this policy is reasonable for sites such as the skull vault, in more “eloquent” sites, such as the cervical spine, the threshold to intervene should be lower. Though even in the cervical spine the natural history can be extremely benign, in a meta-analysis by Bertram et al., they concluded that most cases could be successfully treated with immobilization, pain relief, and surveillance (Bertram et al. 2002). Treatment is indicated for symptomatic cases, multifocal lesions, or in instances of extension into the spinal canal. Various treatment options have been advocated including chemotherapy, radiotherapy, and surgery, either alone or in combination (Sadashiva et al. 2016). Medical therapies have been shown to be effective and are the preferred first-line treatment (Bezdjian et al. 2015; Peng et al. 2009). Treatment consists of steroids, bisphosphonates, and chemotherapy, with a bracing regime to control spinal deformity. The role of surgery is limited to rare instances of spinal compression or cases of progressive spinal deformity.

In spite of a variety of treatment modalities the long-term prognosis for spinal LCH is extremely favorable.

Hemangioma

Vertebral hemangioma is the most common benign vertebral tumour. Typically these lesions, appearing as discrete areas of high T2 signal change within a vertebral body, are found incidentally on MRI scans. Such hemangiomas have an extremely indolent natural history and no treatment or follow-up is indicated. However, in some circumstances spinal hemangioma can present as a locally infiltrative lesion, with extension into the paraspinal tissues and spinal canal resulting in spinal cord compression.

Symptomatic vertebral hemangioma is rare in childhood, but when they do occur symptoms are often severe and rapidly progressive. Lesions have a predilection for thoracic and lumbar spine (Acosta et al. 2008; Singh et al. 2015) and although usually limited to a single level can be multiple in about one third of cases. The histological appearances are of a proliferative capillary or venous structure, classified as capillary, cavernous, or mixed, depending on the relative proportions of the vessels.

MRI is necessary to delineate the extraosseous extent of the lesion, particularly intraspinal extension. On CT scan these lesions have a characteristic pattern of vertical trabeculation (Fig. 14).

Fig. 14
figure 14

Vertebral hemangioma. (a) Sagittal T2 weighted MRI scan showing intrinsic bone lesion at T12. (b) Axial T2 imaging confirms intraspinal extension with compression of the thecal sac. (c) CT scan with sagittal reconstruction demonstrating vertebral trabeculation within the vertebral body, characteristic of hemangioma of bone

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These are highly vascular tumours, where surgical intervention is required (usually due to pain or radiculo-myelopathy), preoperative angiography, proceeding to selective arterial embolization, should definitely be considered. Following embolization radical surgical excision combined with instrumented spinal fixation is performed.

An alternative approach has been described by Singh et al., who reported seven children treated by means of intraoperative transpedicular injection of absolute alcohol, performed under image guidance, then proceeding to laminectomy to decompress the theca and thence limited posterior instrumented fixation (Singh et al. 2015).

Successful treatment has also been described using vertebroplasty with acrylic cement; however, reports are largely limited to adult patients presenting with bone pain. This mode of treatment is generally contraindicated in the presence of spinal cord compression (Acosta et al. 2008). Propranolol, shown to be effective in promoting regression of cutaneous hemangioma in infants, has also been reported to be effective in controlling pain symptoms with vertebral body hemangioma, though this has not led to radiological regression of the lesion (Uzunaslan et al. 2013). Currently, propranolol would not be regarded as proven therapy in the management of childhood vertebral hemangioma; moreover, the presence of spinal or nerve root compression would be a relative contraindication in children.

Giant Cell Tumour of Bone

Giant cell tumours of bone are extremely rare spinal tumours in pediatric practice, rather they are much more a condition of adulthood. These tumours occur typically in long bones; when they do occur in the spine there is a predilection for the sacrum. Giant cell tumours are locally aggressive neoplasms with a strong propensity for local recurrence. Where possible, wide en bloc resection is the goal, though the sacral location, common for this pathology may preclude this. In selected circumstances, SAE and local radiotherapy may be considered (Sobti et al. 2016).

Treatment Considerations

In children with vertebral column tumours, management strategies are formulated according to:

  1. 1.

    Grade and stage of the tumour

  2. 2.

    The role of surgery in relation to other oncological modalities

  3. 3.

    The need to preserve neurological function

  4. 4.

    The perceived effect of the tumour, or surgical treatment on spinal stability and deformity

A wide range of therapeutic strategies is available for vertebral column tumours in children. Since many of the diseases have excellent long-term prognosis, and given the potential for long term treatment related morbidity, the importance of a comprehensive multidisciplinary approach to these pathologies cannot be overstated. For some malignant tumours, neoadjuvant treatment with chemotherapy or radiotherapy can optimize the chances of successful surgical resection. Indeed, in cases of spinal neuroblastoma, spinal surgery maybe avoided altogether, without compromising outcome. Additionally, embolization can significantly reduce the vascularity of tumours such as hemangioma, thus reducing operative risk and facilitating radical surgical resection. The role of more novel techniques that might obviate the need for major surgical interventions or reconstructions, including radiofrequency ablation and therapeutic selective arterial embolization, is likely to increase in the future but needs to be better defined in the pediatric population.

Surgical Planning

Once the need for surgery has been established, detailed review of multiple imaging modalities and planes is essential to preoperative planning. The use of 3D imaging software or even 3D printed models is beginning to be used in some centers. The following techniques of tumour resection are recognized, again, the choice of surgical approach will be guided according by the principles of neurological preservation, tumour pathology, and implications for spinal integrity (Chi et al. 2008).

En Bloc Resection

For primary malignant tumours of bone a complete oncological resection, preserving all tumour margins, should be pursued where possible. Such resections should also be considered for locally aggressive benign tumours, such as chordoma and giant cell tumour. These are however complex procedures, requiring extensive exposures and reconstructive instrumentation. While most experience is in adults these techniques are being increasingly applied to selected pediatric cases.

Determining the extent of resection, the surgical approach and the implications for spinal reconstruction can be aided by the use of a reproducible and validated approach to tumour staging such as the WBB system (Boriani et al. 1997). Using this method the vertebra is divided into radial segments and a series of concentric zones from intradural to extraspinal. This system is then used to define the most appropriate technique of en bloc resection. Broadly speaking three types of en bloc resection are described:

Vertebrectomy

En bloc excision of the vertebral body and posterior elements is achieved either via separate anterior and posterior approaches or via a single posterior approach.

Sagittal Resection

For tumours that are lateralized within the vertebral bodies or posterior elements, a segmental resection may be performed, comprising part of the vertebral body and any involved ipsilateral pedicle or hemilamina.

Posterior Arch Resection

An en bloc removal of the entire lamina and spinous process is appropriate in circumstances where the pedicles are not involved.

Intralesional Resection

Many benign lesions are amenable to less extensive surgery and can be satisfactorily treated by an intralesional approach using piecemeal resection or curettage; however, complete removal should remain the goal given the propensity for local recurrence for lesions such as ABC or osteoblastoma.

Complications and Their Prevention

Spinal tumour surgery, particularly major tumour resections, carries significant risks, many of which can be anticipated and measures can be taken to minimize them.

Neurological

The spinal cord may be compromised at the time of presentation due to direct compression from the lesion or vertebral collapse; moreover, the spinal cord will remain vulnerable during tumour surgery. Perioperative steroid treatment is commenced prior to surgery. Intraoperative neurophysiological monitoring (motor evoked potentials, somatosensory evoked potentials) is generally recommended for all but the most minor of cases.

Vascular

Major blood loss should be anticipated; cross-matched blood and clotting factors are ordered preoperatively. Preoperative SAE should be considered in particular circumstances such as spinal hemangioma.

Deformity

The integrity of the spinal column may be compromised by tumour involvement or by surgical intervention. There is little doubt that the risk of postsurgical deformity is much greater in children compared with adults. Multiple level laminectomy, young age, and spinal deformity at the time of presentation have each been associated with an increased risk of late postsurgical deformity. It is perhaps worth noting that most published pediatric series relate to surgery for intramedullary spinal cord tumours (IMSCT) rather than primary tumours of the vertebral column, and the two are not entirely comparable. In IMSCT, the bone integrity is usually normal though the number of levels involved in the surgical exposure tends to be greater. Moreover, the mechanism of deformity is more likely to involve neuromuscular weakness in addition to mechanical factors. Most pediatric neurosurgeons would advocate laminoplasty over laminectomy, and while some series have reported reduced rates of deformity with laminoplasty, this has not been observed by others (McGirt et al. 2010). By contrast, in vertebral tumours the bone is, by definition, abnormal; disease is usually localized to one or two segments and mechanical rather than neurogenic factors govern the risk of late deformity.

For vertebral column tumours where there is preexisting deformity or where there is a perceived high risk for postsurgical deformity or instability, for example, where there is both anterior and posterior column involvement, then spinal instrumentation will need to be performed concomitantly with the tumour resection. Young age does not necessarily preclude the use of spinal instrumentation.

If there is no deformity at the time of presentation, then these patients can be followed expectantly, with clinical review and serial spinal X-rays to monitor for the emergence of delayed deformity. A customized spinal brace may reduce the rate of postsurgical deformity in children considered at increased risk. It is important to note that radiotherapy to spinal column tumours, even in the absence of a surgical intervention, appears to increase the risk of spinal deformity (Mayfield et al. 1981); therefore, nonoperated children with spinal tumours should also be afforded a similar level of surveillance for the possibility of late deformity.

Conclusions

Spinal pain is the commonest presenting symptom of spinal column tumours. Red flag symptoms include pain that is constant, nocturnal pain, pain with a radicular distribution, and pain associated with abnormal neurological examination.

The spectrum of spinal column neoplasms in children is different compared with adults. The age of the patient and position of the tumour within the vertebra are valuable in refining the differential diagnosis.

A soft tissue mass, associated with a bone tumour, is suggestive of malignancy. Malignant spinal column tumours are rarely treated with surgery alone; these tumours require a coordinated multidisciplinary neuro-oncology approach.

The potential for spinal deformity should be incorporated into neurosurgical management plan. Risk factors for progressive spinal deformity include: young age, scoliosis at the time of presentation, involvement of the vertebral body and posterior elements and multiple level laminectomies.

Tumours of the spinal column in childhood are rare, the pathology is diverse, and therefore these tumours are best managed in a multidisciplinary team to ensure that the management plan appropriately accounts for the histology of the lesion, the neurological status of the child, and the effect of the tumour (or its treatment) on spinal deformity or instability.