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:
—
haemangioma (10 per cent of autopsies),
—
osteoid osteoma,
—
osteoblastoma,
—
aneurysmal bone cyst,
—
giant cell tumour;
• malignant:
—
myeloma,
—
lymphoma.
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
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,
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.
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.
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
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).