Diagnostic Forum: Malignant spinal cord compression
Malignant spinal cord compression (MSCC) and/or cauda equina compression are caused by pressure from a tumour. The most common cause is haematological spread of cancer to vertebral bodies, which subsequently collapse (in lytic metastases) or may expand to cause compression in sclerotic metastases.
The next most common cause is growth of tumour between the vertebral bodies or along the vertebral foramina and (rarely) by leptomeningeal metastases, for example, where the metastatic deposit is with the meninges, or drop metastases, such as enlarging metastatic deposits within the spinal cord per se.
The thoracic vertebrae are the most common site for MSCC. About 5-10 per cent of patients with cancer go on to develop it.1,2 MSCC and cauda equina compression are oncological emergencies because pre-treatment neurological status is the most powerful predictor of functional outcome. In rapidly progressing cord compression, hours can make a difference.3
The ability to walk can be maintained in about 80 per cent of patients who can walk at presentation and initiation of treatment.4 Functional outcome also depends on response to treatment. Delays in initiation of treatment usually result in irreversible weakness and loss of sensation below the level of compression.
A high index of suspicion is required for any patient with malignancy, but especially patients with multiple myeloma or cancers that frequently metastasise to bone, such as prostate, breast, lung, thyroid and renal cell cancers.
To understand a patient's signs and symptoms, it is helpful to recall that the spinal cord ends around the L1/L2 disc space and from this level, forms a sheaf of nerve roots (the cauda equina). Therefore on the whole, compression above L2 will cause predominantly upper motor neurone signs and below L2, lower motor neurone signs (see Box 1), so symptoms and signs will depend on the level(s) of compression.
Symptoms suggestive of MSCC are pain, sensation, weakness and bladder/bowel symptoms (see box 2). In the majority of cases, pain precedes other neurological symptoms. It can present as back pain of sudden onset, exacerbated by movement, coughing or straining, with significant changes in the characteristics of the pain. Dermatomal neuropathic pain often presents as a band-like pain around the trunk. The band often signifies the level of compression, for example, band-like pain around the level of the xiphisternum often signifies compression at the level of the eighth thoracic vertebra (T8). L'Hermitte's sign is described when patients might state they have a shooting, electric type pain that radiates down their spine and into their legs when they flex their neck.
There are dermatomal changes in sensation. This often presents as band-like tingling or burning around the trunk. The patient might also complain of altered sensation below the level of compression. Patients frequently talk about their legs being in cotton wool or suddenly having 'heavy legs'.
The weakness is described as paralysis (partial/complete) below the level of compression. Bladder/bowel symptoms, including urinary retention, hesitancy or urinary/faecal incontinence, are usually late symptoms.