Internal Medicine Low Back Pain Case File
Eugene C. Toy, MD, Gabriel M. Aisenberg, MD
Case 32
A 45-year-old woman presents with low back pain and requests an x-ray. She states she works cleaning homes and has had this pain off and on for several years; however, for the past 2 days it is worse than it has ever been. It started after she vigorously vacuumed a rug; the pain is primarily on the right lower side, radiates down her posterior right thigh to her knee, but is not associated with any numbness or tingling. It is relieved by lying flat on her back with her legs slightly elevated and lessened somewhat when she takes ibuprofen 400 mg. Upon examination, she is a well-appearing, moderately obese woman. She has difficulty maneuvering onto the examination table because of pain; the rest of her examination is fairly normal. The only abnormality you note is a positive straight leg raise test, with raising the right leg eliciting more pain than the left. Her strength, sensation, and deep tendon reflexes in all extremities are normal.
▶ What is the most likely diagnosis?
▶ What is your next step in management?
ANSWERS TO CASE 32:
Low Back Pain
Summary: A 45-year-old woman presents with
- Acute worsening of chronic low back pain
- Pain radiating down her right leg
- Positive straight leg raise test, with raising the right leg eliciting more pain than the left
- Obesity
- Normal physical examination
Most likely diagnosis: Musculoskeletal low back pain, possible sciatica without neurologic deficits.
Next step: Encourage continuation of usual activity, avoiding twisting motions or heavy lifting. Using nonsteroidal anti-inflammatory drugs (NSAIDs) on a scheduled basis is helpful; you can also recommend muscle relaxants, although these drugs may cause sleepiness. Massage or physical therapy might be helpful. Follow up in 4 weeks. Long-term advice includes weight loss and back-strengthening exercises.
ANALYSIS
Objectives
- Describe the history and physical examination findings that help to distinguish benign musculoskeletal low back pain from more serious causes of low back pain. (EPA 1, 2)
- List the treatment options and their effectiveness in low back pain. (EPA 4)
- Describe the indications for laboratory and imaging tests in evaluating low back pain. (EPA 3)
Considerations
This 45-year-old patient with chronic back pain has an acute exacerbation with pain radiating down her leg, which may indicate possible sciatic nerve compression. She has no other neurologic abnormalities, such as sensory deficits, motor weakness, or “red flag” symptoms of more serious etiologies of back pain, which if present would demand a more urgent evaluation. Thus, this individual has a good prognosis for recovery with conservative therapy, perhaps with time being the most important factor. If she does not improve after 4 to 6 weeks, imaging studies can be considered.
APPROACH TO:
Low Back Pain
DEFINITIONS
CAUDA EQUINA SYNDROME: Lower back pain, saddle anesthesia, and bowel or bladder dysfunction with possible lower extremity weakness and loss of reflexes caused by compression of multiple sacral nerve roots. Cauda equina syndrome is a surgical emergency.
HERNIATED DISK (NUCLEUS PULPOSUS): Condition in which the annulus fibrosus (outer layer) of the vertebral disk is torn, which allows the nucleus portion to herniate and compress the nerve fibers adjacent, leading to paresthesia, dysesthesia, and sometimes weakness.
SCIATICA: Pain in the distribution of the sciatic nerve, made up by the roots of the lumbar nerves L4 and L5, and the sacral nerves S1, S2, and S3; it can present with or without motor or sensory deficits.
SPINAL STENOSIS: Narrowing of the spinal canal, nerve root, or intervertebral foramina due to spondylosis and degenerative disk disease. Symptoms include back pain with numbness or tingling of the legs, which increases with activity and is better with sitting, lying down, or leaning forward.
SPONDYLOLISTHESIS: Anterior displacement of a vertebra on the one beneath it, which can cause symptoms and signs of spinal stenosis.
SPONDYLOSIS: Osteoarthritic spine disease, typically affecting cervical and lumbosacral spine, seen radiographically as disk space narrowing and arthritic changes of the facet joints.
CLINICAL APPROACH
Epidemiology
Low back pain is experienced by two-thirds of all adults at some point in their lives. There are approximately 20 million annual ambulatory visits because of low back pain. This complaint is most common in adults in their working years, usually affecting patients between 30 and 60 years, with a prevalence of 80%. Although it is common in workers required to perform lifting and twisting, it is also a common complaint in those who sit or stand for prolonged periods. Low back pain is a recurrent symptom that tends to be mild in younger patients, often resolving within 2 weeks, but it can be more severe and prolonged as the patient ages. It is one of the most common reasons for young adults to seek medical care, second only to upper respiratory infections, and millions of health care dollars are expended on this problem each year.
Pathophysiology
In evaluating patients with low back pain, the clinician needs to exclude potentially serious conditions, such as malignancy, infection, inflammatory back pain (eg, ankylosing spondyloarthritis), and dangerous neurologic processes, such as spinal cord compression or cauda equina syndrome. Individuals without these conditions are initially managed with conservative therapy. Nearly all patients recover spontaneously within 4 to 6 weeks, but a small percentage develops chronic mechanical low back pain. If patients do not improve within 4 weeks with conservative management, another etiology of the back pain might be present, and further evaluation may be necessary, especially in patients with localized pain, nocturnal pain, or sciatica.
The potential causes of back pain are numerous (Table 32–1). Pain can emanate from the bones, ligaments, muscles, or nerves. Rarely, it can be a result of referred pain from a visceral organ or other structure. Back pain with radiation down the back of the leg suggests sciatic nerve root compression, generally caused by a herniated intervertebral disk at the L4–L5 or L5–S1 level. Patients typically report aching pain in the buttock and paresthesias radiating into the posterior thigh and calf or lateral foreleg. When pain radiates below the knee as opposed to just the posterior thigh, it is more likely to indicate a true radiculopathy than radiation only to the posterior thigh. A history of persistent leg numbness or weakness further increases the likelihood of neurologic involvement.
Most cases of back pain are idiopathic, referred to as nonspecific low back pain, and usually of musculoskeletal origin. In patients with back pain < 4 weeks’ duration and no associated symptoms, imaging studies and other diagnostic tests are generally not beneficial. Studies have shown that the history and physical examination can help separate the majority of patients with simple and self-limited musculoskeletal back pain from the minority with more serious underlying causes. Most patients with low back pain have nonserious causes, and the pain will resolve with rest; however, some conditions can be life threatening. Searching for “red flag” symptoms can help the clinician use diagnostic tests in a more judicious manner. Major red flag symptoms include weight loss, fever, young age, constant pain, neurologic symptoms, history of cancer, injection drug use, and nonmechanical pain. The following section discusses clinical examples of nonmechanical back pain.
In patients with systemic symptoms who have pain at night or pain that is not relieved by lying in a supine position, malignancy should be considered. Primary cancers that commonly metastasize to the spine include lung, breast, prostate, lymphoma, and gastrointestinal tumors and melanoma. Multiple myeloma affects the skeleton diffusely; the spinal compromise frequently manifests as back pain.
Ankylosing spondyloarthritis usually presents in young patients (age < 45); the back pain improves with activity and can awaken the patient from sleep. Characteristic x-ray findings include sacroiliitis and “bamboo spine.”
Diskitis, spinal osteomyelitis, and sometimes epidural abscesses present with fever, constant back pain, and history of intravenous drug use or intravascular catheters (hemodialysis patients). Rapid workup with blood cultures, spinal magnetic resonance imaging (MRI), and rapid initiation of antibiotics are indicated. Some cases require surgery. Table 32–2 describes the recommended workup for some concerning causes of low back pain.
Clinical Presentation
When the patient has worrisome symptoms or signs, the most effective initial evaluation includes plain anteroposterior and lateral radiographs of the involved area of the spine, a sedimentation rate test, and a complete blood count (CBC). More advanced imaging, such as MRI, should be reserved for those patients for whom surgery is being considered (concerning neurologic symptoms, without surgical contraindications). Imaging studies often have abnormal findings, even in patients without low back pain, making it difficult to correlate symptoms with imaging findings.
During the physical examination, palpable point tenderness over the spinous processes may indicate a destructive lesion of the spine itself; in contrast, those with musculoskeletal back pain most often have tenderness in the muscular paraspinal area. Strength, sensation, and reflexes should be assessed, especially in those with complaints of radicular or radiating pain. Straight leg raise testing, in which the examiner holds the patient’s ankle and passively elevates the patient’s leg to 45 degrees, is helpful if it elicits pain in the lower back, suggesting nerve root compression. However, it is not a very sensitive or specific test. The Patrick maneuver, also known as a flexion abduction external rotation (FABER) test, can help distinguish pain emanating from the sacroiliac joint. In this test, the patient externally rotates the hip, flexes the knee, and crosses the knee of the other leg with the ankle (like a number 4) while the examiner simultaneously presses down on the flexed knee and the opposite side of the pelvis. Pain produced anteriorly on the flexed side suggests a hip disorder, while contralateral posterior pain suggests sacroiliac pathology.
Treatment
In treating idiopathic low back pain, various modalities have been shown to be equally effective in the long run. Randomized, controlled trials have shown that encouraging the patient to continue his or her usual activity is superior to recommendations for bed rest. Therefore, patients without disability and without evidence of nerve root compression probably can maintain judicious activity. Bed rest probably is appropriate only for individuals with severe pain or neurologic deficits.
Nonsteroidal anti-inflammatory medications (on a scheduled rather than on an as-needed basis), nonaspirin analgesics, and muscle relaxants may help in the acute phase. Because most cases of disk herniation with radiculopathy resolve spontaneously within 4 to 6 weeks without surgery, conservative measures are the initial regimen recommended for these patients as well. Narcotic analgesics may be an option in cases of very severe pain; however, because idiopathic low back pain is often a chronic problem, prolonged narcotic use beyond the initial phase is highly discouraged. Chiropractic therapy, physical therapy, massage therapy, and acupuncture have been studied in trials of varying quality, with results comparable to traditional approaches. Referral to a surgeon may be considered for those patients with radicular pain, with or without neuropathy, that does not resolve with 4 to 6 weeks of conservative management.
Patients with concerning clinical features, such as a history of malignancy, fever, or examination findings suggestive of spinal cord compression or cauda equina syndrome, should be referred for urgent imaging, either MRI or computed tomography of the spine, to evaluate for conditions such as vertebral metastases, vertebral osteomyelitis, or spinal epidural abscesses that require urgent treatment.
CASE CORRELATION
- See also Case 31 (Osteoarthritis/Degenerative Joint Disease), Case 33 (Acute Monoarticular Arthritis—Gout), and Case 34 (Rheumatoid Arthritis).
COMPREHENSION QUESTIONS
32.1 A 35-year-old woman presents with 1 week of lower back pain. Her history and examination are without red flag symptoms and completely normal. Her blood pressure is 120/70 mm Hg, heart rate is 90 beats per minute, and temperature is 98 °F. Her body mass index (BMI) is 36 kg/m2. The physical examination is normal, and the straight leg raise test is negative. Neurologic examination of the lower extremities does not show any deficits. Which of the following is the best next step for this patient?
A. Regular doses of ibuprofen and activity as tolerated
B. Six weeks of bed rest
C. MRI of the lumbar spine
D. Plain film x-ray of the lumbosacral spine
32.2 A 28-year-old woman from Nigeria presents with a 6-month history of persistent lower lumbar back pain, associated with a low-grade fever and night sweats. She denies any extremity weakness or human immunodeficiency virus (HIV) risk factors. Her examination is normal except for point tenderness over the spinous processes of L4–L5. Which of the following is the most likely diagnosis?
A. Staphylococcus aureus osteomyelitis
B. Tuberculous osteomyelitis
C. Given her age, idiopathic low back pain
D. Metastatic breast cancer
E. Multiple myeloma
32.3 A 70-year-old woman presents with a 4-week history of low back pain, generalized weakness, and a 15-lb weight loss over the last 2 months. Her medical history is unremarkable, and her examination is normal except that she has generalized weakness with strength rated as 4/5 in all extremities. Initial laboratory tests reveal an erythrocyte sedimentation rate (ESR) of 80 mm/h (normal < 35), hemoglobin of 10 g/dL, creatinine level 1.8 mg/dL (nl 0.5-1.3), and calcium level 11.2 mg/dL (normal 8.5–10.5). Which of the following is the most likely diagnosis?
A. Osteoporosis with compression fractures
B. Renal failure with osteodystrophy
C. Multiple myeloma
D. Lumbar strain
E. Osteomyelitis
32.4 A 45-year-old man presents to the office for lower back pain of 2 weeks’ duration related to a motor vehicle collision. After the collision, he did not initially seek medical care and took acetaminophen over the counter. However, for the past day, he has complained of decreased sensation in his buttock area, problems voiding (urine dribbling), and inability to achieve an erection. On examination, he has decreased anal sphincter tone and decreased ankle reflexes bilaterally. Which of the following is the next best step in management?
A. Bed rest and follow-up in 4 to 6 weeks
B. Plain film x-ray of lumbosacral spine
C. Determination of sedimentation rate and CBC
D. Immediate referral for advanced imaging and surgical evaluation
ANSWERS
32.1 A. This is a patient who has no red flag signs of back pain and class 2 obesity (severe obesity with BMI 35-39.9 kg/m2). Regular (scheduled) doses of NSAIDs and resuming activity as normal (as tolerated) are the recommended therapy. Bed rest (answer B) has not been shown to improve outcomes in idiopathic low back pain compared to encouraging mild-to-moderate activity, and it increases the risk of deep venous thrombosis. Imaging (answers C and D) is not necessary with uncomplicated back pain.
32.2 B. The patient’s country of origin, the chronic and slowly progressive nature of the pain in association with fever, and night sweats are highly suggestive of tuberculous osteomyelitis of the spine or Pott disease. Bacterial osteomyelitis (answer A) presents more acutely, often with high, spiking fevers. Metastatic breast cancer (answer D) and multiple myeloma (answer E) are extremely rare in this age group. The fevers, night sweats, and persistent and progressive nature of her back pain make a musculoskeletal cause (answer C) unlikely.
32.3 C. This patient likely has multiple myeloma. She has many “red flag” symptoms in her presentation: her age, new-onset pain, and history of weight loss. The markedly elevated ESR suggests an inflammatory condition or situation with high levels of proteins (in this case, immunoglobulins). The elevated calcium level and mild renal failure are also suggestive of multiple myeloma. Plain radiographs of the axial and appendicular skeleton may illustrate the lytic bone lesions often seen in this disease. Because the lesions are purely osteolytic, serum levels of alkaline phosphatase are normal, and bone scans do not detect them. Osteoporosis and compression fractures (answer A) are common in postmenopausal women but they are either asymptomatic or lead to some localized pain of the spine; the other red flags such as fever, trauma, urinary dysfunction, and saddle anesthesia are not present. Answer B (renal failure with osteodystrophy) can occur due to secondary hyperparathyroidism; this occurs due to decreased levels of vitamin D and, thus, decreased calcium absorption. The elevated ESR and weight loss do not occur with this condition; also, this patient’s creatinine level of 1.8 mg/dL is not high enough to suggest this etiology. Answer D (lumbar strain) is not associated with an elevated ESR or weigh loss; also, the patient should recall the injury. Answer E (osteomyelitis) usually manifests as fever and can elevate the ESR, but usually there is point tenderness at the site of infection.
32.4 D. Most patients with lower back pain have self-limited symptoms and improve with conservative measures. However, some red flag conditions are important to monitor. This patient, for instance, has bladder and buttocks sensory dysfunction and erectile dysfunction, which are highly suggestive of cauda equina syndrome. Immediate assessment by MRI or myelography and prompt surgical decompression should be accomplished to avoid long-term nerve denervation and incontinence/lower extremity weakness. Answers A (bed rest and follow-up in 4-6 weeks), B (x-ray of lumbosacral spine), and C (sedimentation rate and CBC) all delay treatment.
CLINICAL PEARLS
▶ Acute low back pain, even with sciatic nerve involvement, resolves within 4 to 6 weeks in 90% of patients.
▶ Analgesics, such as NSAIDs or acetaminophen, muscle relaxants, and attempts at maintaining some level of activity are helpful in managing acute low back pain; bed rest does not help.
▶ Pain that interferes with sleep, significant unintentional weight loss, or fever suggests an infectious or neoplastic cause of back pain.
▶ Imaging studies, such as MRI, are useful only if surgery is being considered (persistent pain and neurologic symptoms after 4-6 weeks of conservative care in patients with herniated disks) or if neoplastic, inflammatory, or infectious causes of back pain are being considered.
▶ Signs for cauda equina syndrome are a clinical emergency and require immediate referral to surgery for decompression.
REFERENCES
Deyo RA, Weinstein JN. Low back pain. N Engl J Med. 2001;344:363-370.
Engstrom JW, Deyo RA. Back and neck pain. In: Kasper DL, Fauci AS, Hauser SL, et al, eds. Harrison’s Principles of Internal Medicine. 19th ed. New York, NY: McGraw Hill; 2015:111-123.
Jarvik JG, Deyo RA. Diagnostic evaluation of low back pain with emphasis on imaging. Ann Intern Med. 2002;137:586-597.
Maher C, Underwood M, Buchbinder R. Non-specific low back pain. Lancet. 2017;389:736-747.
Staal JB, Hlobil H, Twisk JW, et al. Graded activity for low back pain in occupational health care: a randomized, controlled trial. Ann Intern Med. 2004;140:77-84.
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