A 54-year-old man comes to the office due to worsening low back pain. The pain started 3 weeks ago and is worse at night but continues through the day. It does not improve with rest or over-the-counter ibuprofen. The patient has no other symptoms. Medical history is notable for non–small cell carcinoma of the lung treated with surgical resection a year ago. At that time, preoperative positron emission tomography scanning did not reveal evidence of metastasis. The patient has smoked a pack of cigarettes a day for 30 years and quit a year ago. Vital signs are within normal limits. Examination shows local spinal tenderness at the L4-L5 level. Muscle strength is 5/5, and deep tendon reflexes are within normal limits. Sensory examination shows no abnormalities. What is the most likely cause of this patient's back pain?
Causes of low back pain | ||
Condition | Clinical clues | |
Musculoskeletal | Mechanical |
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Radiculopathy |
| |
Spinal stenosis |
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Compression fracture |
| |
Malignancy | Metastatic cancer |
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Infectious | Osteomyelitis, discitis, abscess |
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Vertebral metastasis should be suspected in a patient with back pain and a current or recent history of malignancy. Characteristic features include pain that is progressive, worse at night, unrelieved by rest, and associated with focal vertebral tenderness. Acute neurologic deficits (eg, cauda equina syndrome), unexpected weight loss, and hypercalcemia may also occur. Bony metastases are much more common than primary bone tumors; the most common tumors that metastasize to bone include prostate, breast, kidney, thyroid, and non–small cell lung cancer, as well as non-Hodgkin lymphoma.
This patient with a history of non–small cell lung cancer has back pain that is worse at night and focal vertebral tenderness on examination. Although his initial positron emission tomography scan was negative a year ago, his history of high-risk malignancy and the characteristics of his pain make metastatic bone disease the most likely diagnosis.
(Choice A) Disc herniation typically presents with mechanical back pain (ie, worse with activity, better with rest) or lumbosacral radiculopathy (ie, back pain radiating below the knee, decreased sensation in a dermatomal distribution, positive straight-leg raising test). Progressive pain for 3 weeks without radicular symptoms is very uncommon because most herniations are posterolateral where they can cause nerve root compression.
(Choice B) Lumbar muscle strain is the most common cause of low back pain; however, muscle strains are usually worsened with activity, alleviated by rest, and associated with paraspinal tenderness (not focal vertebral tenderness). Progressively worse nocturnal pain is not common.
(Choice C) Spinal stenosis most commonly occurs in elderly patients with advanced degenerative changes in the spine. It typically presents with chronic back pain that radiates to the posterior thighs or calves, is worse with spinal extension, and is relieved with spinal flexion. Focal spinal tenderness is not common.
(Choice E) Osteoporotic compression fracture can cause midline spinal tenderness. However, osteoporosis is uncommon in men, particularly those age <65. Compression (pathologic) fracture in this patient, if present, is more likely to be due to metastatic deposits, and pain can be present at rest.
Educational objective:
Vertebral metastasis should be suspected in patients with back pain who have a history of cancer, pain worse at night and unrelieved with rest, and focal vertebral tenderness. Other features may include neurologic deficits, unexpected weight loss, and hypercalcemia. The most common cancers associated with vertebral metastasis include prostate, breast, kidney, thyroid, and non–small cell lung cancer, as well as non-Hodgkin lymphoma.