Identifying serious causes of back pain: Cancer, infection, fracture
ABSTRACTMost patients with back pain have a benign condition, but tumors, infections, and fractures must be considered during an initial evaluation because overlooking them can have serious consequences. This article discusses the presentation and diagnostic strategies of these serious causes of back pain.
KEY POINTS
- A primary tumor or metastasis to the spine tends to cause unremitting back pain that worsens at night and is accompanied by systemic disease and abnormal laboratory findings.
- Infection typically causes focal pain, an elevated erythrocyte sedimentation rate (the most sensitive laboratory test) and C-reactive protein level, and sometimes neurologic signs and symptoms.
- Fractures cause focal pain and should be suspected especially in older white women and patients who take corticosteroids or who have ankylosing spondylitis.
- Plain radiography can help detect fractures, but magnetic resonance imaging is needed to evaluate spinal tumors, soft tissue infections, and epidural abscesses, and to further evaluate neural compression due to fractures.
History, physical examination
Patients may present with a history of trauma with associated back pain or a neurologic deficit. In osteoporotic patients, the trauma may have been minimal, eg, a sneeze, a fall from a chair, or a slip and fall in the home. Pain tends to be worse when standing erect and occasionally when lying flat.
The patient is commonly visibly uncomfortable and may be limited to a wheelchair or stoop forward when standing. The spine may show an absence of the midline crease or an exaggerated thoracic kyphosis. Pain is typically reproduced by deep pressure over the spinous process at the involved level. Compression fractures rarely cause neurologic deficits but should always be considered.
Fractures commonly occur in the thoracolumbar region but may be anywhere in the spine. Fractures in the upper thoracic spine may indicate an underlying malignant tumor, and a thorough search for a possible primary lesion should always be carried out for fractures in this location.
Laboratory testing
Routine laboratory evaluation and thyroid function tests should be done, as well as a 24-hour urine specimen for collagen breakdown products, calcium, phosphate, and creatinine levels. Serum and urine protein electrophoresis should be performed if myeloma is suspected. A white blood-cell count, erythrocyte sedimentation rate, and C-reactive protein level help determine if an underlying infection caused the fracture.
MRI needed if plain films reveal fracture or are equivocal
Anteroposterior and lateral roentgenograms should be taken first; they typically show osteopenia. A fracture in the vertebral body is characterized by loss of height and by wedging. Osseous fragments can occasionally be seen in the spinal canal.
Sagittal short tau inversion recovery sequences, which use specifically timed pulse sequences to suppress fat signals, show high-intensity signal changes in areas of edema from acute or healing fractures. They provide a sensitive but nonspecific marker of abnormality.
Dual energy x-ray absorptiometry helps determine the extent of osteoporosis.
Bone scans should only be used for patients with suspected metastatic disease.
Patients with ankylosing spondylitis need thorough workup
Ankylosing spondylitis predisposes to serious spinal injury. Even after only minor trauma, patients with ankylosing spondylitis and acute, severe back pain should be thoroughly evaluated for fracture with CT and MRI of the entire spine. Plain radiography should not be relied on for these patients because of the risk of misinterpretation, delayed diagnosis, and poorer outcomes.52,53
NEUROLOGIC COMPROMISE—A RED FLAG
Cauda equina compression classically presents with back pain, bilateral sciatica, saddle anesthesia, and lower extremity weakness progressing to paraplegia, but in practice these symptoms are variably present and diagnosing the condition often requires a high degree of suspicion. Hyporeflexia is typically a sign of cauda equina compression, while hyperreflexia, clonus, and the Babinski sign suggest spinal cord compression, requiring an evaluation of the cervical and thoracic spine. Cauda equina compression typically involves urinary retention; in contrast, cord compression typically causes incontinence.55
If either cauda equina or spinal cord compression is detected during an initial examination, an immediate more extensive evaluation is warranted. MRI is the study of choice.
Spinal epidural hematoma
Spinal epidural hematoma is a rare but dramatic cause of paralysis in elderly patients. In most cases, there is no antecedent trauma. Lawton et al,56 in a series of 30 patients treated surgically for spinal epidural hematoma, found that 73% resulted from spine surgery, epidural catheterization, or anticoagulation therapy. Other possible causes of epidural hematoma include vascular malformations, angiomas, aneurysms, hypertension, and aspirin therapy.57
The same study56 found that the time from the first symptom to maximal neurologic deficit ranged from a few minutes to 4 days, with the average interval being nearly 13 hours.
Although painless onset has been reported,58 spinal epidural hematoma typically presents with acute pain at the level of the lesion, which is often rapidly followed by paraplegia or quadriplegia, depending on the location of the hemorrhage. Sometimes the onset of pain is preceded by a sudden increase of venous pressure from coughing, sneezing, or straining at stool. Urinary retention often develops at an early stage.
Most lesions occur in the thoracic region and extend into the cervicothoracic or the thoracolumbar area. The pain distribution may be radicular, mimicking a ruptured intervertebral disk.
Evaluation should be with MRI. Acute hemorrhage is characterized by a marked decrease in signal intensity on T2-weighted images. Subacute hematoma has increased signal intensity on both T1- and T2-weighted images.56
Early recognition, MRI confirmation, and treatment should be accomplished as soon as possible.56 Recovery depends on the severity of the neurologic deficit and the duration of symptoms before treatment. Lawton et al56 found that patients taken to surgery within 12 hours had better neurologic outcomes than patients with identical preoperative neurologic status whose surgery was delayed beyond 12 hours. Surgery should not be withheld because of advanced age or poor health: in 10 reported cases in which surgery was delayed, all patients died.59
