Spinal tumours

These have been divided into:

tumour of the vertebral column;

  intraspinal tumours.

Tumours of the vertebral column

Between 90 and 95 per cent of spinal tumours are secondary tumours, and occur mostly in older individuals. Although almost any tumour can metastasise to bone

the six most common are:

  thyroid;

breast;

  lung;

GI tract;

renal;

  prostate.

The most common among these are breast, lung and prostate. Pain is the commonest cause of presentation and only 10 per cent of individuals present with neurological symptoms alone. Patients may present with pain in the spine itself due to collapse or instability of the spine, or with radicular pain in the distribution of a nerve root. Features of pain which should alert the clinician are night pain and uncontrollable pain which is not relieved by rest. Patients will usually have a history of weight loss and may have a history of previous tumour.

Careful examination of patients presenting with spinal pain may pick up the primary site of the tumour, although in many cases the primary site is not evident.

Plain radiographs of the site of the pain may show vertebral collapse, loss of a pedicle on the AP radiograph, loss of bone substance or occasionally sclerosis of bone (prostate). Bone scans may show turnouts, although they are unreliable in myeloma and plasmacytoma. An MRI scan is the most sensitive and reliable way of diagnosing spinal tumours, and allows assessment of the size and invasiveness of the tumour. CT scans can also be used for better definition of bone and bone destruction. Myelography is seldom required now unless MRI scans are impossible (e.g. pacemaker) or difficult technically (e.g. previous metallic implant).

Primary bone tumours do occur in the spine. The most common are:

  benign:

     haemangioma (10 per cent of autopsies),

     osteoid osteoma,

     osteoblastoma,

     aneurysmal bone cyst,

   giant cell tumour;

 

malignant:

     myeloma,

     lymphoma.

 Biopsy is indicated in most cases either to confirm the diagnosis or to make the diagnosis. In the terminal patient with a known primary diagnosis biopsy is sometimes not necessary. Diagnosis of the tumour allows planning of appropriate treatment. For example, some turnouts are radiosensitive (e.g. lymphoma), whereas others are relatively radioresistant (e.g. lung secondaries).

Three types of biopsy are possible: excisional, incisional and needle biopsy. Occasionally a posteriorly sited tumour will be suitable for excisional biopsy but this is unusual. In most cases a needle biopsy will provide enough material for a diagnosis to be made histologically, but in more complex lesions where there is a subtle differential diagnosis incisional biopsy is probably best. Frozen section can be used so that the whole procedure can be done under one anaesthetic, as long as appropriate staging of the tumour has been carried out beforehand. The needle biopsy should be sited so that the entry point can be excised at the time of definitive surgery.

Excision of the tumour is most commonly carried out for benign tumours in younger individuals where there is a real possibility of cure and where recurrence is possible, for example giant cell tumour. This may require simultaneous anterior and posterior en bloc excision of the affected vertebra with a cuff of normal tissue, and then reconstruction of the spine. Osteoid osteoma, in contrast, on the other hand usually requires simple excision of the affected part of the vertebra.

Total excision of malignant tumours may be carried out where the tumour is an isolated tumour and cure of the patient is possible (e.g. some plasmacytomas), but in many cases the tumour cannot be cured either because there is widespread infiltration of the tumour, the tumour has metastasised, or most commonly because the tumour is a distant metastasis of a primary tumour and cure is not possible. In these cases decompression of the neurological structures and stabilisation of the spine are most appropriate.

Intraspinal tumours

‘Lumps’ within the spinal canal can he classified anatomically or pathologically. Anatomically they may be intradural or extradural. Pathologically they may he benign or malignant (primary or secondary). Thus a combined classification can be devised (see Table 33.4).

Occurring in one per 100 000 of the population, men­ingiomas are the commonest intradural lesion accounting for 23 per cent of those visualised, whilst metastatic tumour forms the commonest extradural lesion.

Presenting features

Pain. Usually localised to the anatomical location of the tumour, the pain is progressive over weeks or months, although it may fluctuate in intensity. Characteristically the pain is nocturnal and will often wake the patient at 3 a.m. to 4 a.m. causing them to get up, walk around and maybe try to sleep in a chair. Local tenderness may be present but this is more common with extraspinal tumours.

Radicular signs. Owing to the root irritation this may result in pain in a radicular distribution with associated pins and needles in the corresponding dermatomal area.

Clearly if the root involved is cervical or lumbar in origin the symptoms may mimic cervical brachalgia or sciatica. If the tumour is in the thoracic region the pain will radiate around the chest wall in a dermatomal distribution. Clinical examination may reveal signs of a radiculopathy — indicated by a lower motor neuron lesion of the affected nerves.

Spinal cord/cauda equina signs. Here the signs and symptoms are dependent upon the level of the tumour. If it is above the L1/L2 junction leading to compression of the spinal cord, the patient will develop a progressive spastic paraparesis/quadriparesis with an ascending sensory level, although there may be suspended. Pain due to pressure on the spinal cored is rare. The patient will usually present with a progressive loss of function with pins and needles in the feet (and hands) with, on examination, signs of an upper motor neuron lesion with increased tone, pyramidal distribution weakness, brisk reflexes and extensor plantar responses. Although there is an ascending sensory level, perianal and pericoccygeal sensation may be spared.

Cauda equina compression (below L1/L2 junction) results in symptoms and signs of a lower motor neuron lesion with radicular pain, dermatomal sensory loss and myotomal loss of power. The reflexes will be reduced with normal or absent plantar responses. Pericoccygeal sensory loss should specifically be examined for, having also made enquiry for changes in bladder, bowel and sexual function. A lack of awareness of the bladder filling, an inability to distinguish the passage of flatus or faeces, and in men erectile dysfunction, all indicate neurological compromise. It should be noted that the neurological picture may be incomplete in the early stages of compression. For example a Brown-Séquard syndrome or contralateral pain and temperature loss with equilateral loss of light touch is occasionally found.

Investigations

Magnetic resonance imaging. With and without gadolinium enhancement, this now forms an investigation of choice. Careful clinical examination with a knowledge of spinal cord anatomy will direct where the imaging is done. A differential diagnosis, according to the classification seen in Table 33.4, can then be made. It should be noted that some tumours can spread throughout the CSF pathways including into the brain, and thus whole neuraxis imaging may be required (Fig. 33.29a and b).

Plain X-rays/CT scan. When dealing with extradural malig­nant disease the anatomy of the surrounding bone is vital when considering the stability of the spine. This clearly influences the management options. Plain films may show enlargement of the intervertebral canal with a dumb-bell neurofibroma, or scalloping of the vertebral body. In the absence of MRI a CT myelography will provide details of the level of disease, but not the extent, and some information about the relationship to the cord, but not the internal features. CT scan is particularly helpful, however, in performing CT-guided biopsies for extradural tumours (Fig. 33.30a and b).

Other investigations. It should be noted that intraspinal tumours may form part of a systemic disease, for example metastatic tumour, and thus general examination with chest X-ray and routine laboratory tests should always be done.

  Only after a careful history and examination have been performed with review of the radiology and other tests can the course of management be decided. In principle, symptomatic intraspinal tumours should he excised as completely as possible using micro-neurosurgical techniques and, further­more, this may have to he done urgently if there is progressive neurological dysfunction.

 The aims of treatment are:

1.       relief of pain;

2.       to achieve a histological diagnosis;

3.       excision of benign tumours;

4.       prevention of further neurological deterioration.

 Pain relief. Decompression of the spine with removal of the tumour will usually provide immediate pain relief, even if this is incomplete. Radiotherapy of malignant tumours will provide some pain relief but nor immediately. Clearly, the patient will suffer postoperative pain, but the severe noc­turnal, often interscapular pain will immediately be relieved once the dura is decompressed and the tumour removed.

Achieve histological diagnosis. Clearly this is important when deciding whether further adjunctive therapy will be required. For extradural tumours when surgery is not feasible, a CT-guided needle biopsy can be carried our with a good chance of achieving a histological diagnosis and minimal risk of morbidity.

Excision of benign tumours. Irrespective of whether the tumour is inside or outside the spinal cord, surgery represents the mainstay of treatment using micro-neurosurgical techniques. Careful definition of the anatomy, debulking of tumour, teasing it away from the surrounding tissues will allow removal with minimum risk of morbidity.

Prevention of further deterioration. Decompression of the spinal cord or cauda equina with either malignant or benign disease will prevent further deterioration and may allow some neurological improvement.

Surgical technique

Patients and their families should be carefully consented prior to operation. A back marker will help with localisation, although advances in technology using the optical tracking systems will nor only allow help with location but also help to define the extent of the dissection, especially with intramedullary disease.

A posterior or dorsal approach is usual via a midline inci­sion through a laminectomy. The full cephal-ocaudal extent of the tumour should be exposed and, ii extradural, the dural tissue above and below should be identified to allow gentle excision of the tumour.

Care should be taken to keep the dura intact if at all possible and to avoid injury to the emerging spinal nerves. Surrounding the extradural tumour is often a plexus of veins that will bleed quite profusely as the tumour is decompressed. These should be controlled using bipolar coagulation. The lateral extension of a neurofibroma will often require a second approach at a later stage.

It an intradural tumour is the dura should be opened above and below the tumour and, if required, the dural opening should be done using the microscope. Retaining sutures will retract the dura and all dissection thereafter should be carried out using micro-instruments with the help of a microscope. Excision of a neurofibroma will require isolation of the root of origin and its subsequent division. Meningiomas require careful debulking and excision of their origin, whilst keeping the arachnoid planes intact to preserve and protect the spinal cord itself. Care should he taken to avoid any additional compression or distortion of the spinal cord.

If an intramedullary tumour is visible on the surface of the cord then this can be used as a portal of entry to the tumour. If not, a midline myelotomy can he used with tiny pial retraction sutures. This will then allow access to the tumour itself.

For ependymoma or haemangioblastoma a plane intersection can usually be identified, which will allow the tumour to be gently teased away using any cystic component of the tumour to assist with that dissection. Astrocytomas, however, may not have such a well-defined plane and their removal, therefore, is more difficult.

For tumours within the cauda equina, again careful definition of the anatomy — especially the arachnoid planes —is vital. To fully excise a cauda equina ependymoma requires division of the filum terminale. Beware of the sacral roots, which are often closely attached.

Dural closure follows careful haemostasis. This should be watertight to prevent postoperative CSF leakage. Spinal cord monitoring should be carried our where possible.

Spinal artereovenous malformations

First successfully operated on in 1914 by Ellsburg, the classification of these rare lesions has changed as understanding of the aetiology and anatomy has developed.

The revised classification of spinal vascular malformations is as follows.

Dural AV fistulas. This represents a low-flow shunt in the dural sleeve supplied by a dural branch of intervertebral artery. Drainage to superficial intradural veins produces local venous hypertension with venous congestion and an associated myelopathy.

Intradural AVM’s. (a) Juvenile — fed by multiple feeders, these high flow lesions may involve the vertebral column. (b) The glomus type — this has a rightly packed nidus usually supplied by one vessel. It may be associated with the arterial aneurysm.

Intradural. This is a direct fistula between the intradural spinal artery and vein. It is defined by an absence of the nidus and associated with haemorrhage from aneurysm or venous varix.

Cavernous angiomas. These are angiographically occult, with normal vascular anatomy. They appear as small black­berry-like lesions, with low flow and are demarcated on MRI scan.

Management

This is usually with progressive symptoms with an ascending myelopathy; it may occasionally present with subarachnoid haemorrhage.

Diagnosis

Depends upon a high index of suspicion, often with the identification of a draining vein on MRI scan. Confirmation should be via the spinal angiography (Fig. 33.31).

Treatment

The aim is to eradicate the fistula and the nidus without compromising the blood supply to the spinal cord. Depending on the vascular anatomy and the type of lesion, this can be achieved either by intravascular therapy, using particle embolisation, or by surgical exposure of the lesion with identification and closure of the fistula (Fig. 33.32).