Review Question - QID 107169

This patient has acute radicular lower extremity pain, with positive straight leg raise test and intact sensation. This presentation is suggestive of acute disc herniation as the cause of her pain.

Lower back pain is extremely common in adults. While most back pain results from benign causes, there are certain red-flag findings, which raise concern for more serious etiologies. Red-flag findings include infectious signs, history of injection drug use, trauma, bowel or bladder continence changes, or family history of abdominal aortic aneurysm. The most common overall cause of low back pain is a muscle strain. Common degenerative disorders include lumbar spinal stenosis, lumbar disc herniation, and discogenic back pain.

Gregory et al. review acute lumbar back pain. The straight-leg-test is the most sensitive physical exam maneuver for lumbar disc herniation. It can be performed supine or seated. When supine, when hip flexion from 30-70 degrees reproduces the patient's radicular pain the test is considered positive. Note that when pain is ipsilateral to the raised leg, the sensitivity is high and the specificity is low for diagnosing a herniated disc. In contrast, when the pain is contralateral to the raised leg, sensitivity is decreased but specificity is increased.

Sabnis et al. discuss the management of disc herniation. Studies have shown that, in the majority of cases, pain substantially reduces within 4 weeks following an acute disc herniation. Conservative measures include rest, physical therapy, and sometimes injections of corticosteroids into the epidural space. In some refractory cases, surgery to remove the offending disc may be helpful.

Illustration A depicts the typical MRI appearance of a herniated lumbar disc (see circle).

Incorrect Answers:
Answer 2: Osteomyelitis is a comparatively rare cause of back pain and typically presents with fever. It is more likely in an injection drug user.
Answer 3: Cauda equina syndrome is a surgical emergency. Patients typically present with saddle anesthesia and loss of bowel/bladder control.
Answer 4: The pain in spinal stenosis is usually relieved by sitting or spinal flexion, in contrast to disc herniation. Spinal stenosis pain is also less acute and dramatic in onset.
Answer 5: Ankylosing spondylitis causes back pain, usually in men under 40, who present with chronic pain that is worse in the morning and improved with activity.