Spinal metastases is a vague term which can be variably taken to refer to metastatic disease to any of the following:
see Vertebral metastases.
Intradural extramedullary metastases (5%)
Metastases to the spine are a common source of severe pain in cancer patients. The secondary effects of spinal metastases include pain, bone fractures, hypercalcemia, and neurological deficits. As the disease progresses, pain severity can increase until it becomes refractory to medical treatments and leads to a decreased quality of life for patients. A key obstacle in the study of pain-induced spinal cancer is the lack of reliable and reproducible spine cancer animal models 1).
The Spine Oncology Study Group Outcome Questionnaire (SOSGOQ) includes all domains relevant for measurement of function and disability and its content validity is confirmed by linkage with the International Classification of Function and Disability ICF. This questionnaire has superior content capacity to measure disease burden of patients with spine metastases 2).
A study proposes a scoring methodology -after reversing 4 inversely scored items- for the SOSGOQ and demonstrates that the questionnaire is a valid tool for the assessment of quality of life in patients with metastatic spine disease. The SOSG-OQ is superior to the EQ-5D in terms of coverage and internal consistency, but consists of more questions 3).
Choi et al. recommend the use of the EQ-5D measure in research for assessment of patient-centered outcomes and calculation of cost effectiveness of surgery for spinal metastases. Routine use of the measure in clinical practice is also encouraged, because it is a simple and quick method to assess overall clinical outcome 4).
There are three ways in which metastatic tumors can reach the epidural space. The most common way in approximately 85% of patients, the tumor reaches the spinal cord by the indirect route of an initial hematogenous metastasis to the vertebral body and the metastasis grows in the bone and then spreads into the epidural space, eventually causing secondary compression of the spinal cord 5).
The less common way is invasion of a paravertebral tumor directly into the spinal canal through an intervertebral foramen, which compresses the spinal cord. This process causes about 15% of MESCC and is commonly associated with lymphomas, Ewing's sarcoma, and neuroblastomas. However, least common mode of metastasis described is the direct hematogenous spread to spinal epidural space, dura, or spinal cord 6).
Spinal metastases may present in a myriad of ways, most commonly back pain with or without neurology.
Apart from chronic and increasing pain, spinal metastases lead to neurological deficits due to destruction of the vertebral body and subsequent epidural growth expansion.
Back pain is the earliest and most common symptom of spinal epidural metastasis. Back pain is present in more than 95% of patients at diagnosis 8).
Spinal epidural metastasis associated back pain can takes several forms. Localized pain to the region of the spine affected by the metastases is usually the first symptom; typically, the pain progressively increases in intensity over time. This pain is caused when the bone marrow metastasis extends to stretch the periosteum or invades soft tissues. Radicular pain due to compression or invasion of the nerve roots is commonly present in patients who develop MESCC. The pain is frequently unilateral with cervical or lumbosacral spine involvement or bilateral with thoracic spine involvement. Mechanical back pain is associated with spinal instability caused by vertebral body collapse and is relatively uncommon; it is made worse by movement and partially relieved by rest 9).
Magnetic resonance imaging is the most sensitive imaging modality for the detection of spinal metastases, but plain x-rays, computed tomography, and 18F positron emission tomography play a role in diagnosis and management.
Early diagnosis is of the utmost importance to prevent neurological deficit due to spinal cord compression. Magnetic resonance imaging (MRI) has become the final tool in that diagnostic process. However, access to MRI is still limited, requiring cost-effective use. It is generally acknowledged that patients with systemic cancer who present with a radiculopathy or myelopathy should undergo an MRI. However, the diagnostic policy in patients with systemic cancer who present with recently developed back pain is still a matter of debate.
Selection of patients with cancer with back pain at risk of SEM was not possible with the standard neurological checkup. After intake by the neurologist, the next step should be MRI of the whole spine 10).
MRI proved superior in detecting bone and epidural involvement by tumor and was valuable in clinical decision making. In addition, MRI provided better visualization of paravertebral soft tissue involvement by tumor. MRI is recommended as the initial study in patients with suspected metastatic spinal disease 11).
It provides excellent visualization of soft tissue involvement, bone marrow replacement, ligament involvement, degree of canal compromise, cord edema, and cord compression. The overall accuracy of MRI is 95% (sensitivity 93%, specificity 97%) 12)
Not very specific.
see Winking owl sign
Plain x-rays are quite good at evaluating bony metastases, but not good at evaluating the spinal cord and surrounding soft tissues. Metastatic epidural spinal cord compression most commonly occurs at the site of vertebral involvement on plain x-ray, especially where there is evidence of vertebral collapse. Most common findings on x-rays include pedicle erosion, paravertebral soft shadow, vertebral collapse, and pathologic fracture or dislocation 14).
In 1990, x-rays were found to have a 10% to 17% false negative rate 17).
The rate of missed metastatic epidural spinal cord compression is unacceptable.
An unusual presentation of isolated atypical chest pain preceding metastatic cord compression, secondary to penile carcinoma. Spinal metastasis from penile carcinoma is rare with few cases reported. This unusual presentation highlights the need for a heightened level of clinical suspicion for spinal metastases as a possible cause for chest pain in any patients with a history of carcinoma. The case is discussed with reference to the literature 18).