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.
MRI findings: Pyogenic vs tuberculous spondylitis
MRI can help differentiate pyogenic vertebral osteomyelitis from tubercular disease, although findings may be similar (eg, both conditions have a high signal on T2-weighted images).32 Jung et al,33 in a retrospective study of 52 patients with spondylitis, found that compared with patients with pyogenic infections, patients with tuberculous spondylitis had a significantly higher incidence of a well-defined paraspinal abnormal signal on MRI, a thin and smooth abscess wall, a paraspinal or intraosseous abscess, subligamentous spread to three or more vertebral levels, involvement of multiple vertebral bodies, thoracic spine involvement, and a hyperintense signal on T2-weighted images. Other MRI features characteristically seen in patients with tuberculous spinal disease are anterior corner destruction, a relative preservation of the intervertebral disk, and large soft-tissue abscesses with calcifications.34
Prompt diagnosis and aggressive treatment needed
Pigrau et al35 found that spinal osteomyelitis is highly associated with endocarditis: among 606 patients with infectious endocarditis, 28 (4.6%) had pyogenic vertebral osteomyelitis, and among 91 patients with pyogenic vertebral osteomyelitis, 28 (30.8%) had infectious endocarditis.
McHenry et al36 retrospectively studied outcomes of 253 patients with vertebral osteomyelitis after a median of 6.5 years (range 2 days to 38 years): 11% died, more than one-third of survivors had residual disability, and 14% had a relapse. Surgery resulted in recovery or improvement in 86 (79%) of 109 patients. Independent risk factors for adverse outcome (death or incomplete recovery) were neurologic compromise, increased time to diagnosis, and having a hospital-acquired infection (P = .004). Relapse commonly developed in patients with severe vertebral destruction and abscesses, which appeared some time after surgical drainage or debridement. Recurrent bacteremia, paravertebral abscesses, and chronically draining sinuses were independently associated with relapse (P = .001). MRI, done in 110 patients, was often performed late in the course of infection and did not significantly affect outcome. The authors stressed that an optimal outcome of vertebral osteomyelitis requires heightened awareness, early diagnosis, prompt identification of pathogens, reversal of complications, and prolonged antimicrobial therapy.
Epidural abscess may also be present
Epidural abscess occurs in 10% of spine infections. About half of patients with an epidural abscess are misdiagnosed on their initial evaluation.37,38 Patients initially complain of local spine pain, followed by radicular pain, weakness, and finally paralysis. Between 12% and 30% of patients report a history of trauma, even as minor as a fall, preceding the infection.38,39
Radiologic findings are frequently equivocal, and MRI is preferred; gadolinium enhancement further increases sensitivity.39,40 Spinal canal abscesses usually appear hypointense on T1-weighted images and hyperintense on T2-weighted images, with ring enhancement surrounding the abscess area in contrast studies.41 MRI may give negative findings in the early stages of a spinal canal infection and so may need to be repeated.41 MRI may not help distinguish an epidural from a subdural abscess. However, primary spinal epidural abscesses without concomitant vertebral osteomyelitis are rare; therefore, the finding of associated vertebral osteomyelitis makes a spinal epidural abscess more likely.
FRACTURES
Fractures of the spine can be asymptomatic and may have no preceding trauma. They can be due to osteoporosis, malignancy, infection, or metabolic disorders such as renal osteodystrophy or hyperparathyroidism. Fractures in normal bone are almost always associated with trauma. Any suspicion of infection or malignancy should be investigated.
Corticosteroids increase risk
Any patient with back pain who is receiving corticosteroid therapy should be considered as having a compression fracture until proven otherwise.3 De Vries et al42 found that in a database of nearly 200,000 patients receiving glucocorticoids, risk increased substantially with increasing cumulative exposure. Those who intermittently received high doses (= 15 mg/day) and those who had no or little previous exposure to corticosteroids (cumulative exposure = 1 g) had only a slightly increased risk of osteoporotic fracture, and their risk of fracture of the hip and femur was not increased. In contrast, patients who received a daily dose of at least 30 mg and whose cumulative exposure was more than 5 g had a relative risk of osteoporotic vertebral fracture of 14.42 (95% confidence interval 8.29–25.08).
Osteoporotic compression fractures are common in the elderly
Osteoporosis involves reduced bone density, disrupted trabecular architecture, and increased susceptibility to fractures. About 700,000 vertebral body compression fractures occur in the United States each year43: about 10% result in hospitalization, involving an average stay of 8 days.44 Osteoporotic compression fractures are highly associated with age older than 65, female sex, and European descent.45,46 The estimated lifetime risk of a clinically evident vertebral fracture after age 50 years is 16% among postmenopausal white women and 5% among white men.47
A single osteoporotic vertebral compression fracture increases the risk of subsequent fractures by a factor of five, and up to 20% of patients with a vertebral compression fracture are likely to have another one within the same year if osteoporosis remains untreated.48 Population studies suggest that the death rate among patients who have osteoporotic vertebral compression fractures increases with the number of involved vertebrae.43
Unfortunately, osteoporotic vertebral compression fractures are not always easily amenable to treatment: up to 30% of patients who are symptomatic and seek treatment do not respond adequately to nonsurgical methods.49,50 However, new minimally invasive interventions such as vertebral augmentation make timely evaluation clinically relevant.
