Spinal Deformity due to Tumors
9 Spinal Deformity due to Tumors
There is a wide variety of tumors, tumor-like processes, and cysts that can give rise to a deformity of the growing spine (▶ Fig. 9.1), either by the physical presence of the lesion, or as a result of the necessary treatment in dealing with it. A number of different effects can thereby by produced, which include loss of physical support to the spine, paralysis, and the asymmetric growth effect of radiation therapy, and these effects are frequently present in combination. It is helpful in describing these effects to consider these tumors according to their site. Spinal tumors can be intradural or extradural, the former being the initial management province of the neurosurgeon, while the latter more frequently present to the orthopaedic surgeon. Importantly, quite a different range of pathological tumor types are encountered in children from that found in adults.
Spinal cord tumors in children can be extradural or intradural and if intradural can be either intramedullary or extramedullary (▶ Fig. 9.1). Nowadays in major hospitals there are “spinal teams” comprising both orthopaedic and neurosurgical spine surgeons which markedly helps to look after these combined cases.
Fig. 9.1 Different categories of spinal cord tumors. (a) Extradural tumor lying outside the thecal sac but within the bony confines of the spinal canal. (b) Intradural extramedullary tumor lying within the thecal sac but outside the spinal cord. (c) Intramedullary tumor entirely in the substance of the spinal cord, causing cord widening. Reproduced with permission by Pediatric Spine, Ed S Weinstein, 2nd Ed, Lippincott PA 2001, Fig 1, p. 710.
9.1 Intradural Tumors
9.1.1 Clinical Features
When spinal cord dysfunction in the child occurs in a subacute or chronic manner, it is most often due to tumor. 1 While meningiomas and neurofibromas are common in adults they are rare in children, in whom the most common intradural spinal neoplasms are gliomas, including astrocytomas and ependymomas (▶ Table 9.1). Neuroblastomas are the second most common neoplasm, but the most common cause of spinal cord compression in the infant. 1 Then come lymphomas, which can be of the Hodgkin’s variety, or the non-Hodgkin’s lymphosarcoma (lymphocytic or lymphoblastic lymphoma) or reticulum cell sarcoma (histiocytic variety of lymphoma). Developmental lesions such as teratomas and cysts account for most of the remainder.
Reticulum cell sarcomas
Tachdjian and Matson have written the most informative orthopaedic article on the subject of intraspinal tumors in children, which should be compulsory reading for all learning spine surgeons. 1 They reported on 30 years’ experience in Boston. Spinal intradural tumors were found to be one-fifth as common as intracranial neoplasms. As regards intraspinal tumors, boys were affected twice as commonly as girls, and 50% occurred in the first 4 years of life. Slightly more lesions were benign than malignant, and intramedullary gliomas were the most common, followed by neuroblastomas, and then a collection of developmental tumors, the latter usually encountered in the very young. Lymphosarcomas were found in children of all ages. These tumors occurred throughout the length of the spine, but the thoracic and cervical regions were relatively overrepresented. Limp and leg weakness were the chief presenting features in more than 50% of cases (▶ Table 9.2). Back pain was present in one-third and torticollis in one-fifth. The most important physical findings in order of frequency were pathological reflexes, spastic paralysis, flaccid paralysis, a sensory level, a scoliosis in one-third, and muscle spasm. Tachdjian and Matson also found an incredibly high rate of wrong initial diagnosis, with these tumors commonly masquerading as poliomyelitis, brachial plexus lesions, muscular dystrophy, and postural torticollis. Repeat clinical examination was very important (▶ Table 9.3).
Fraser et al, while reporting on only 15 intradural tumors, again found limp, with limb weakness and back pain, to be the common presenting features, but also noted a sphincter disturbance in one-fifth. 2 Of those children presenting under the age of 6 years, 75% of lesions were malignant, whereas this figure was only 30% for those presenting after the age of 6 years. They also stressed a worrying delay between clinical presentation and diagnosis of spinal tumor. In the infant who has not yet walked the diagnosis is not easy and Balakrishnan et al reported a case of constipation until it was realized that the infant girl was, in fact, paralyzed. 3
When back pain is the predominant presenting feature it tends to be characteristic. It is continuous, not episodic as with mechanical problems, and steadily worsens with time. It is increased by walking and any jolting increases the severity of the pain. In the older child and adolescent inactivity characteristically increases the pain, such that patients tend to “pace the room” at night in an effort to achieve symptomatic relief. 4 Tumors involving the cord tend to have upper motor neuron features and a gradually progressing sensory disturbance, while those involving the cauda equina have a predominance of lower motor neuron features with painless leg wasting. With intramedullary lesions there is the characteristic suspended disassociated sensory loss with a reduction in pain and temperature but normal appreciation of touch, and this physical sign is common also in syringomyelia. This is caused by dilatation of the central canal by tumor/syrinx causing an interruption of the pain and temperature fibers crossing in the anterior commissure. The vertebral column signs of reduced straight-leg raising, reduced lumbar lordosis, a scoliosis—usually of the nonstructural variety—and local tenderness are all variable and not necessarily present. The scoliosis associated with spinal tumors is atypical and quite different from an idiopathic curve (▶ Fig. 9.2). They may be in the “wrong” direction (e.g., left thoracic). They can be very stiff with muscle spasm, and can be very painful (constant pain worse at night). These are all red flags that should ring alarm bells in the mind of the clinician.
Fig. 9.2 This boy had an intradural astrocytoma and it can be seen that he stands stiffly with muscle spasm and his scoliosis is left-sided—all red flags. (a) Back view erect. (b) Forward bending views of a 10-year-old boy who presented with a mild and stiff idiopathic type deformity but left-sided with not much rotation and with pathological reflexes in association with an intradural astrocytoma. (c) PA myelogram of this boy’s spine showing a typical intramedullary tumor (▶ Fig. 9.1c) and a mild scoliosis.
Plain radiographs may reveal an increased interpedicular distance which, if more than 3 mm bigger than the adjacent vertebra, is very suggestive of tumor. There is also scalloping of the vertebral margins and pedicular flattening (▶ Fig. 9.3). Foraminal widening occurs with neurofibromas. Magnetic resonance imaging (MRI) has become the imaging modality of choice, has largely replaced computed tomography (CT) myelography (which, however, may be required for the patient who cannot undergo or tolerate MRI), and has revolutionized diagnosis and assessment of spinal cord tumors as well as management and follow-up. Then MRI with gadolinium enhancement aids both identification and vascularity as well as likely pathology. 5 On MRI there tends to be a smooth, curved margin to any filling defect or block and the extent of this may be considerable. If the intradural tumor is intramedullary, then there is expansion of the cord with gradual obliteration of the surrounding subarachnoid space, allowing a thin layer of dye to surround the cord (▶ Fig. 9.1). However, if the tumor is extramedullary, there is widening of the subarachnoid space due to cord displacement, and a concave filling defect. 6 Multiple filling defects are sometimes seen in metastases from medulloblastomas of the central nervous system which have seeded via the cerebrospinal fluid. MRI provides more information about the extent of the tumor and if a vascular tumor is expected then spinal MR angiography may be helpful in assessing the tumor vascularity.
Fig. 9.3 PA myelotomography showing the pedicular flattening (arrows) typical of an intradural tumor with a mild nonstructural scoliosis.
9.1.3 Treatment of Intramedullary Tumors
Laminectomy, with tumor excision, even if subtotal for those that are malignant, has always been the treatment of choice. 1– 6 Indeed, operation is always necessary unless there are proven metastases elsewhere. Microsurgical techniques are essential and a wide and deep laminectomy, often with removal of the pedicles, may be required. 6 It is increasingly common to respect the integrity of the spinal column and not remove the entirety of the facet joints bilaterally and then use an ultrasonic aspirator to debulk the tumor. 7 Many malignant tumors cannot be totally removed by surgery and, if the lesion is in the region of the conus, then sphincter preservation implies incomplete excision. Clearly as much tumor as possible should be removed and this may require a surgical revisit. Whereas radiotherapy or chemotherapy was routinely prescribed postoperatively 8 this is now less commonly indicated and it would appear that the host’s body defense mechanisms come into play to minimize the deleterious effect of residual tumor. Nonetheless, particularly with the ependymoma, the prognosis is not appreciably reduced by incomplete excision. Of Tachdjian and Matson’s 115 cases, 47 died up to 8 years from treatment, but 24 developed full neurological function postoperatively. The 5-year survival from malignant astrocytomas is of the order of 60%.
If the facet joints have to be removed in the cervical or thoracic regions then a local angular kyphosis commonly develops. Nevertheless, even if the integrity of the facet joints is preserved, a progressive gentle kyphosis can occur postoperatively. As a consequence, strategies to prevent these postoperative and essentially iatrogenic deformities have developed. Instead of doing a laminectomy to gain entrance to the canal the technique of laminoplasty is now more commonly been used. There are various techniques for this including osteotomizing the lateral edge of the lamina on each side and removing the roof of the canal and then reattaching this after the tumor has been removed. A popular alternative is the hinge laminoplasty whereby the laminar osteotomy is only carried out on one side but the other side is tenderized to provide a hinge whereby the spinal canal is hinged open with closure of the hinge at the end of tumor removal. It seems that none of these particular posterior column preservation techniques are immune to the development of a significant postoperative spinal deformity whereas a concomitant spinal fusion procedure posterolaterally with instrumentation protects the great majority of cases from postoperative progressive deformity. 9, 10 Particular risk factors for progressive deformity after resection of intramedullary spinal tumors are an age of less than 13 years, a preoperative scoliotic deformity, an increasing number of resections, a tumor-associated syrinx, and surgery spanning the thoracolumbar junction. That was the conclusion of a review of 161 consecutive cases. 11 To this can be added the removal of more than four laminae. We have considerable experience of spinal cord tumors in children in the neurosurgical department in Leeds with whom we work closely in a number of areas. ▶ Fig. 9.4 is an 8-year-old with an intradural intramedullary glioma who presented with a rather mild but painful thoracic scoliosis. The lesion was resected using a laminoplasty approach and a syringoperitoneal shunt inserted to drain the syrinx. This was followed by chemotherapy and radiotherapy to the residual tumor. The scoliosis progressed and so initially growing rod instrumentation was inserted and after several lengthening procedures, the spine was definitively instrumented and fused.
Fig. 9.4 (a) Sagittal T1 MRI slice showing extensive intradural glioma in the thoracic spine. (b) After resection, radiotherapy and chemotherapy there was an increase in the amount of thoracic kyphosis. (c) After surgery and despite laminoplasty, a scoliosis also developed. (d) Because there was a lot of growth to go special instrumentation was in the form of growing dual rods. (e) At the end of growth this was exchanged for definitive metalwork and fusion. (With thanks to Mr. Atul Tyagi, Leeds Teaching Hospitals NHS Trust.)
It is useful at this stage to review the condition of syringomyelia, as this intradural problem has some similarities with intradural neoplasms, and both can present with a spinal deformity by similar neurological mechanisms. Syringomyelia is a chronic slowly progressive degeneration of the spinal cord and medulla with cavitation and gliosis within the substance of the cord. 12 This pathological cavitation was first termed syringomyelia by Ollivier in 1827, 13 but Duchenne is attributed with the first clinical description although he called the condition progressive muscular atrophy. 14 It was not until 1882, when Schultze correlated the pathology of syringomyelia with the clinical picture, that the true nature of the syndrome became obvious. 15
It is important to understand Chiari malformations. Types I and II account for nearly all clinical cases. A Chiari I malformation refers to the descent of the cerebellar tonsils below the plane of the foramen magnum. However, the cerebellar tonsils can be a few millimeters below the foramen magnum as a normal variant referred to as cerebellar ectopia. In Chiari I the volume of the posterior fossa can be too small for its contents although a tethered cord can also produce the same foramen magnum cerebrospinal fluid (CSF) blockage. Chiari II malformations are all associated with a myelomeningocele. 16
Williams refers to two pathological types of syringomyelia: the communicating and the noncommunicating varieties. 17, 18 In the former there is a communication between the cavity and the posterior fossa, while in the latter fluid has another origin, usually tumor or traumatic paralysis. The orthopaedic features of syringomyelia are also commonly encountered in diastematomyelia and myelomeningocele which has suggested a common origin, 12, 19, 20 although spina bifida occulta does not occur in syringomyelia any more commonly than in normal people. 20
Classically there is sensory dissociation with pain and temperature sensation involved but not touch, at the level of the lesion, and weakness and wasting of the muscles of the involved segments. Altered pain and temperature sensation is attributed to the central location of the cavitation in the cord such that the decussating pain and temperature fibers are involved while interference with the local medial nuclear cells, which innervate the trunk muscles, gives rise to the characteristic muscle wasting, particularly of the scapular region.
The most common presenting symptom is pain, felt in the head, neck, trunk, or limbs, which is particularly increased by straining. A history of birth injury or a family history of spina bifida are both important. The cervical spine is the area most often affected, but these cystic lesions may extend up to the medulla and down to the lumbosacral area. In advanced cases the characteristic dissociated sensory loss combined with loss of tendon reflexes makes recognition easy but diagnosis in the earlier stages depends upon a combination of clinical, radiographic, and operative findings. In this respect MRI demonstrates the dilatation while CSF protein determination reveals a moderately elevated level. Plain spinal radiographs may show interpedicular widening and erosion of both neural arches and vertebral bodies locally. Williams has determined that at the C5 level if the size of the canal exceeds that of the vertebral body by 6 mm in the adult then pathological dilatation is present. 17
Hydrocephalus can be detected in 15% of patients and basilar impression in 55%, with the Klippel-Feil syndrome and spina bifida often being associated. 21 The presence of cervical ribs is also more common and indeed may be associated with signs of peripheral nerve involvement in the upper limb before the true nature of the underlying syringomyelia is discovered. 22 Other limb abnormalities include intrinsic muscle wasting and clawing of the hands, pes cavus, and Charcot’s joints, which have been observed in 25% of patients with syringomyelia, 80% of which involve the upper extremity. 23
9.2.1 Spinal Deformity in Association with Intradural Neoplasms and Syringomyelia
The high prevalence rate of spinal deformities in association with intradural problems is well known. 1– 3, 19, 20, 24, 25 In many of these reports the issue is clouded by the performance of some sort of surgical intervention, often diagnostic laminectomy, so that there is an iatrogenic component to the deformity. Nonetheless, there is plenty of evidence that the virgin intradural condition commonly presents in the form of a spinal deformity (▶ Fig. 9.2). Tachdjian and Matson, reporting on 115 intraspinal tumors in children, noted at presentation that 27% had a scoliosis, 15% had a kyphosis, 18% had a torticollis, and that these were often combined. 1, 26 There was clearly some confusion between kyphosis and lordosis, as lateral views of the patient and not the deformity were obtained, but it would appear that about 50% of such children do present with a spinal deformity.
They reported on an 11-year-old girl, allegedly presenting with a progressive scoliosis of 5 years’ duration, but inspection of the anteroposterior radiograph shows a very mild thoracolumbar curve with little, if any, rotation, and thus the term progressive scoliosis is scarcely applicable. It is also clear that true progressive structural scoliosis is uncommon in association with intraspinal tumors, but the situation, as will be seen, is quite different after these tumors have been dealt with therapeutically. There are several mechanisms by which these mild nonstructural curves can develop. Tachdjian and Matson reported that two-thirds of their patients had either spastic or flaccid paralysis and a quarter had paravertebral muscle spasm, 1 and thus asymmetric muscle action is one mechanism and this is shared with syringomyelia.
Approximately 45% of cases of syringomyelia have a spinal deformity of clinical significance, but if the threshold is lowered to a Cobb angle in excess of 5 degrees then 70% of patients can be shown to have a scoliosis 20 (seven times the normal prevalence rate). This is rather akin to the situation derived from scoliosis screening where the more thorough the search, the higher the prevalence rate of the condition being sought. Indeed, Perret reported that there was always a scoliosis in association with syringomyelia. 27 While the essential lesion of syringomyelia is thought to be overdistension of the embryonic neural tube (hydrocephalomyelia), with associated atresia of the fourth ventricle, the mechanism of production of a scoliosis is thought to be the same as that occurring in poliomyelitis with the lower motor neuron incriminated. As Alexander and Season showed, involvement on the sensory side leads to anterior horn cell chromatolysis, further implicating the efferent pathway. 28 Pincott et al have produced some recent evidence that involvement on the sensory side alone is sufficient to produce a scoliosis, 29 but only of the nonstructural variety. A mild scoliosis is thus a frequent and early finding in syringomyelia and will eventually occur in all cases.
If the diagnosis of syringomyelia is made in the immature individual then as many as 90% will have a scoliosis, whereas only about 50% of mature patients have a spinal deformity. 12, 30 These mild curves have a Cobb angle of less than 25 degrees. The great majority are in the thoracic region, the remainder being thoracolumbar, and there is a good correlation between the site of the cord lesion, and thus the level of neurological involvement, and the site of the deformity. 25
9.2.2 Management of the Scoliosis Associated with Intradural Neoplasms and Syringomyelia
There is necessarily a considerable difference in management, according to whether the underlying problem is a neoplasm or syringomyelia. In the former situation it is extirpation of the growth that is the essential treatment consideration, whereas in syringomyelia there may be a real need to correct the rare severe structural curve. If that is the situation, there is one serious problem and that is the high incidence of paraplegia associated with corrective surgery in syringomyelia scoliosis. This is due to the altered tension on the spinal cord in which there is a significant lesion, which has already rendered local neurological function extremely precarious. Huebert and Mackinnon’s two operated cases became paraplegic and died albeit following old-fashioned posterior Harrington distraction instrumentation. 12 MRI would therefore be essential in these cases in order to determine the exact extent of the cavitation and any associated cord tether (▶ Fig. 9.4). Moreover, consultation with an experienced radiologist and neurosurgeon is important in estimating the extent of the underlying lesion before embarking upon spinal surgery. As there is such a high risk of causing neurological damage, then the spine must be shortened at the same time as being straightened, and so anterior and posterior surgery is required. For the moderate deformity this can be achieved by way of anterior multiple diskectomy, followed by posterior transpedicular instrumentation, as with the idiopathic curve. For the more severe deformity, however, the only safe procedure would appear to be wedge resection, thus ensuring that the deformity has been really shortened. 31
9.2.3 Deformities Associated with the Treatment of Intradural Tumors
The necessary management of intradural malignant neoplasms of childhood unfortunately produces a high prevalence rate of subsequent serious spinal deformity because of the destabilizing effect that laminectomy has on the growing spine. Loss of posterior column support is a serious matter at any age, but the tendency to produce a progressive deformity is magnified during the growth period. Over the past 20 years orthopaedic surgeons have increasingly focused on these problem, but neurosurgeons have been aware of the harmful effects of laminectomy for much longer. In the 1950s Ingraham and Matson warned against laminectomy producing a deformity, particularly when the posterior bone removal was extensive. 32 They noted increased lordosis occurring in the cervical and lumbar regions (▶ Fig. 9.5) and increasing kyphoses in the thoracic region. However, the center of gravity of the body passes in front of the entire spine, just coming in contact with the anterior border of L4, and thus loss of posterior support tends to produce a progressive kyphosis anywhere in the spine. They also noted that the thoracic kyphosis could be asymmetrical thus producing a mild scoliotic component. This coronal plane asymmetry was also noted by Haft et al in 10 out of 17 children who survived following the treatment of spinal tumors. 33 Experienced neurosurgeons repeated the warnings and reported serious spinal deformities in more than 80% of children who underwent laminectomies while stressing the need for orthopaedic assistance. 34, 35
Fig. 9.5 Post-laminectomy lumbar hyperlordosis. (a) PA radiograph 4 years after extensive lumbar laminectomy for intradural tumor removal at age 15. (b) Lateral radiograph showing the development of a hyperlordosis with growth.