Differential diagnosis of low-back pain: A review

Differential diagnosis of low-back pain: A review

Herzog, James

As our profession continues its progress toward the new millennium, we will continue to face challenges that must be overcome if we are to take our rightful places in the everchanging health care arena. Health care is rapidly becoming an outcome-based delivery system: only those treatments proven to be scientifically based and costeffective will survive. To meet the challenges ahead, our approach to diagnosing and treating low-back pain (LBP) must be compatible with these highly specific criteria.

Proper management of LBP requires a logical and well-reasoned approach. We must determine the precise diagnosis of a lesion and know its nature, site, location, and level. Positive outcomes are based on sound clinical findings, proper diagnosis, and a wellthought-out and effective treatment plan.

Some fundamental principles of diagnosis should be applied when any patient comes to one of our offices with musculoskeletal complaints. Of course, the importance of taking a comprehensive patient history cannot be overstated. This should include several questions about the chief complaint. We should inquire about onset of pain, whether any recent injuries have occurred (including their anatomic site and timing), and whether there is any radiation of pain.

When the chief complaint is LBP, the review of systems should include questions about any visceral distress or complaints, vascular history, trauma history, and any related or unrelated past medical problems that the patient may have had. Any history of cancer or surgery should be thoroughly investigated. Family history, social history, and occupational history are also important elements in a thorough patient work-up.

Next, we must perform a complete examination of the area of chief complaint. If a patient presents with LBP, with or without lower-extremity radiculopathy, we need to examine the lumbar spine, hip and pelvis, and knee for pathology, to determine whether problems in any of these areas are contributing to the chief complaint.

Our examination should also be comprehensive. Patients should be examined in the sitting, standing, and lying positions. Ranges of motion should be documented, as well as the presence of any muscle spasms, muscle atrophy, or weakness. A complete neurological examination is necessary as well, and should include testing of motor strength, reflexes, and sensory deficits.1,2

When a patient complains of LBP, formulate an initial working diagnosis and treatment plan prior to beginninq treatment. The clinical history, along with the physical examination and appropriate radiology studies such as MRIs, x-rays, and CT scans, frequently makes it easier to pinpoint the anatomic lesion or the source of the pain. These studies may prompt you to change your initial diagnosis, or corroborate your first diagnostic impression. Either way, it is important to try to specify the etiology of the chief complaint as accurately as possible. In most cases, failure to do a thorough exam or order appropriate tests or investigations at the onset of treatment is the reason why the correct diagnosis is missed.,

Because of the complexity of LBP, pain can arise from many sources. Pathologies of bone, muscle, disc, connective tissue, nerves, and the spinal cord and brain account for a substantial proportion of causes of LBP. But bear in mind that not all back pain is mechanical in origin. The differential diagnosis of a patient with LBP should typically include:

Lumbar disc herniation

Peripheral neuropathies

Cauda equina syndrome

Fracture

Spinal cord tumor

Vascular disease

Primary or metastatic carcinoma

Rheumatoid disorders

Infection

Mechanical origin1,2

Visceral disease

Most of the patients we see are suffering from some form of mechanical dysfunction. However, it is very important that we be able to determine quickly which patients we may not be able to help the ones who should be referred to other specialties.

In identifying the etiology of a patient’s complaints, we should be aware of several “red flags,” which dictate a need for further investigation. These basic principles cover all musculoskeletal complaints; however, here we focus specifically on the lumbar spine.

Each differential-diagnosis category cited above can be broken down further; each comprises one subset of the many conditions, diseases, and syndromes that contribute to LBP. Some we will decide to treat; others, we will not. Regardless, we are still responsible, as physicians, for ruling out certain groups of conditions that we should not treat and, instead, refer to other specialists.

Conditions considered in the differential diagnosis of any patient with LBP include:

Destructive lesion

Neurologic spinal lesions

Rheumatologic lesions

Neurologic compressive lesion

Psychosocial disturbances.

Destructive Lesions

It is imperative that the chiropractor rule out the presence of any destructive lesions. Destructive spinal lesions typically include spinal infections, spinal fractures, primary spinal tumors, metastatic spinal tumors, osteoporosis, and aortic aneurysms.

Spinal infection is perhaps the most under-diagnosed etiology in LBP.2 A patient whose history includes any recent infection should prompt further investigation. Infections that may spread to the bone or discs of the lumbar spine and cause back pain will typically include kidney infections, urinary tract infections, pelvic inflammatory disease, and skin tuberculosis. Certain groups are at particularly high risk for these kinds of infections: IV drug users, AIDS patients, and those with a diminished immune response from an autoimmune syndrome or corticosteroid use.1,2,5 Of course any patient who has recently had an invasive procedure, such as surgery, is more likely to have an infection.

Certain symptoms-notably, fevers, night sweats, and recent weight loss should make any physician suspect infection, or worse. Bear in mind, too, that a spinal infection may be present despite a normal body temperature and a normal white blood cell count.5 Signs of infections in this sort of case include an elevated erythrocyte sedimentation rate and, in most instances, spinous tenderness on percussion.

The possibility of spinal fracture should be considered too in ruling out the broad category of destructive lesions. Any history of major trauma (or minor trauma in the elderly), past or present history of cancer, or osteoporosis should be considered an immediate red flag indicating that a fracture may be present.

In addition, primary spinal tumors should be considered and clearly ruled out as another type of destructive lesion that causes back pain. Typically, these patients report severe and progressive pain, which commonly occurs during the night. There may be a slow and progressive neurological loss as well; however, in some patients, this pathology is not apparent until the physical exam, as an incidental finding.

Multiple myeloma is the most common primary bone cancer in adults.2 The principal indicator of this condition is Bence Jones protein in the urine. There may also be abnormal results in serum-protein electrophoresis (an inverse alpha:gamma ratio).3 Also, young adults who describe back pain that becomes worse at night, but is relieved by taking aspirin, may have an osteoid osteoma. To check for this condition, look for visible bone loss on x-ray studies.

Metastatic spinal tumors constitute another category of pathologies that can cause destruction of bone in the lumbar spine and most certainly initiate LBP Patients with any history of breast, prostate, lung, thyroid, or GI cancer are prime candidates. Again, any unexplained weight loss or other non-spinal symptom may be a clue to this diagnosis.

One piece of evidence useful in differentiating metastatic bone disease from degenerative joint disease (DJD) is that the pain associated with DJD is typically relieved by rest, while metastatic bone pain is not.2

Osteoporosis primarily affects people over 65. This condition, in which bone mass is lost, is usually seen in postmenopausal women and women who have had a hysterectomy, and in individuals who have used oral steroids for many years. Advanced osteoporosis in the lumbar spine will predispose the patient to compression fractures, which must be considered in diagnosing the cause of back pain.

Abdominal aortic aneurysm is another condition that may precipitate a destructive bone lesion in the lumbar spine, as the dilatated artery wall comes to rest against the bodies of the lumbar vertebrae. Pulsating LBP may be a clue. Abdominal palpation and auscultation are helpful; however, x-ray and MRI studies are usually necessary to confirm the diagnosis.

Neurologic Spinal Lesions

There are several types of neurologic spinal lesions that should be considered when a patient with LBP comes to your office. Some of these conditions are well within the scope of our treatment. Others, however, should be referred out. These conditions include cauda equina syndrome, myelopathies, intracranial lesions, radiculopathy, and peripheral neuropathies.

Cauda equina syndrome is a condition that requires immediate medical attention-surgical decompression-if it presents in your office. The symptoms may include bilateral leg pain, numbness, and/or weakness, as well as bowel and bladder incontinence. Saddle anesthesia around the anus and buttocks should arouse suspicion that cauda equina is present. This condition may be due to spinal stenosis, a spinal cord lesion, a very large posterior disc herniation, an inflammatory reaction, or a combination of all of these pathologies.

Patients who show an unsteady or ataxic gait may have myelopathies or central nervous system lesions. Bladder urgency and urge incontinence are additional symptoms of these conditions. There may be paraparetic sensory loss; some other dissociative sensory or motor loss may be observed. We need to be aware of any central neurologic symptoms that also suggest the presence of the CNS lesion. A complete neurological work-up is mandatory if a lesion of this type is suspected. Radiculopathy and peripheral entrapment neuropathies are commonly seen in the practice setting. Usually, these conditions respond very favorably to chiropractic. Patients with radiculopathy usually present with either leg or arm pain; weakness and numbness in the extremities are common complaints as well. For diagnosing radiculopathy in the lumbar spine, straight leg raising is the easiest test; it should be positive if this condition is present. Other root tension signs include the bowstring sign and the sitting root test. Electrodiagnostic imaging such as EMG and NCM and radiographic imaging, including MRI or CT, are often helpful in pinpointing the location of a patient’s lesion.

When peripheral entrapment neuropathies are present, the patient’s history typically reveals a progressive ascending weakness of the affected extremity. We frequently see numbness and tingling of the feet. Focal weakness may be noted, and pain may be present in the distal region of the extremity. An entrapment or peripheral neuropathy is usually diagnosed using electrodiagnostic studies, in addition to motor sensory and reflex examination. Tinel’s test, when positive, is a good indicator of a peripheral neuropathy.

Rheumatoid Disorder

The rheumatoid disorders constitute another category of conditions frequently overlooked by chiropractic and medical physicians alike. Some of these conditions are in fact more prevalent than one might at first assume. The ones most likely to be seen by doctors of chiropractic are ankylosing spondylitis (AS), rheumatoid arthritis, Reiter’s syndrome, psoriatic arthritis, systemic lupus erthythematosus (SLE), and gout. In these disorders, patients usually report insidious and progressive pain. Peripheral joint involvement, strongly suggestive of a systemic origin, is usually reported as well. Laboratory examination should include a CBC and SMAC series, as well as a sedimentation rate and rheumatoid screen. HLA tagging may be useful in differentiating AS from psoriatic arthritis.3 X-rays and bone scans may provide important clues, too. Like any other type of condition, further investigation and basic care must precede treatment of these rheumatoid conditions. Neurologic Compressive Lesions

Neurologic compressive lesions, as a group, are extremely common in chiropractic practice today. Patients with these conditions generally respond well to the conservative care that we offer. Sometimes, though, patients with these types of lesions will need referrals to orthopedic surgeons and neurosurgeons. The compressive lesions we see quite frequently are disc herniations, central spinal stenosis, lateral recess stenosis, and spondylolisthesis.

In most cases, lumbar disc herniation is a slowly progressive degenerative process. The distribution of pain in the body is similar to that of sciatica. The physical findings are predictable; i.e., a unilateral L3/LA disc herniation generally involves compression of the LiA nerve root, a unilateral LA/L5 disc herniation compresses the L5 nerve root, and a unilateral L5/S1 disc herniation compresses the S1 nerve root. Sensory deficits follow the typical dermatomal pattern, and muscle strength is weaker in the muscle groups innervated by the corresponding nerve. Disc herniations are considered medical emergencies only if progressive neurological deficits are observed or if cauda equina syndrome is present.

Spinal stenosis is another condition frequently seen in everyday practice. This occurs when there is a narrowing of the spinal canal or foramina. This narrowing can cause compression of the dural sac and nerve roots.1-4 Stenosis of the spine can be divided into two groups: congenital and acquired. Congenital stenosis is prevalent in conditions such as dwarfism, Hurler’s syndrome, and other achondroplastic diseases. Acquired spinal stenosis is more common, however. This condition is, in most cases, a consequence of degenerative joint disease that has been present for many years. Iatrogenic causes, such as laminectomy procedures, will typically produce some degree of spinal stenosis over time.

Pain with this condition is generally confined to the lower back and buttocks, but it may also radiate to the legs. The patient may complain of a burning sensation in the buttocks and posterior thighs. The onset of pain is usually insidious rather than acute. Pain typically increases with walking and is relieved by rest. The patient may also feel better when he or she bends at the waist, because the diameter of the spinal canal is increased with flexion and decreased with extension. That is why a patient with spinal stenosis feels worse with hyperextension.

Vascular disease, such as the peripheral vascular disorders, may be difficult to differentiate from spinal stenosis because the symptoms are similar. Both vascular and neurogenic pain will be relieved by rest. However, neurogenic pain is not induced quickly by exercise as long as the spine is flexed (as in riding a bike), whereas vascular pain comes on quickly with exercise, regardless of the position of the spine.

Spondylolisthesis is another condition commonly encountered in the chiropractic setting. Rarely is this a medical emergency, unless the indicative signs and symptoms are present, such as progressive neurological deficit, cauda equina syndrome, or unremitting leg pain. This condition affects women more than men and most commonly occurs at LA/L5. Flexion and extension stress films are usually taken in cases of spondylolisthesis, to determine whether there is any lumbar instability present.

Psychosocial Disturbances

Patients who present with psychosocial complicating factors that cause, or exacerbate, back pain will generally benefit from psychological counseling, biofeedback, and stress reduction therapy. In general the patients who fall into this category are those with poor work environments, poor home or social environments, depression or anxiety, disputes about workers , compensation or other pending litigation, or those who have inadequate coping skills.

What Chiropractic Can Accomplish

There are many other causes of LBP that are successfully treated and managed in the chiropractic office. The nociceptive lesions included are those that affect the discs, facet joints, sacroiliac joints, bones and periosteum, muscles (muscle spasms), and other related soft tissues. Mechanical pain syndromes, such as muscular pain, postural anomalies, and joint restriction, are also successfully treated by our profession. Hyperalgesic neuromuscular disorders such as regional pain syndromes, fibromyalgia, and myofascial pain are common as well, and they also respond favorably to conservative therapy.

As we already know, most musculoskeletal complaints are benign and will respond to manipulative treatment. We must make careful observations, however, so we do not miss other potentially serious conditions. Knowledge and appropriate clinical decisionmaking are the key elements in making these diagnoses, and having the ability to identify these other conditions clearly benefits our patients.

Health care, it seems, is ruled these days far more by cost than by quality. Nevertheless, we must remember that we owe it to our patients, to our profession, and to ourselves to be as thorough as possible in evaluating any patient with LBP.

Reference

1. Brown DE, Neumann RD. Orthopedic Secrets. Hanley and Be/fun, 1995, pp.185-192.

2. Kirkald y-Willis WH, Burton CV. Managing Low-Back Pain, 3rd Ed. Churchill Livingstone, 1992, pp. 105,

137-147, 203-212, ?25-241.

3. Ravel R. Clinical Laboratory Medicine, 5th ed. Year Book Medical Publishers, 1989, pp. 369-379, 585-586.

4 Alvarez JA, Hardy RH Jr. “Lumbar spine stenosis: A common causeof back and leg pain. ” Am Fam Physician, 1998; 57:1825-1834.

5. Prendergast H, Jerrard D, O’Connell J. ‘Atypical presentations of epidural obscess in intravenois drug abusers.” Am J Emerg Med, 1997; 5:158-160.

JAMES HERZOG, DC, DABCO, is a1tLt who board-certified chiropractic orthopedist who maintains a private practice in Freehold and Trenton, NJ. He is co-founder of Chiropractic Orthopedic Associates, a practice and consulting firm, and writes and lectures on orthopedics for the chiropractic and legal professions.

Copyright American Chiropractic Association Sep 1998

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