Diagnosis

There are numerous well-documented approaches to LBP diagnosis and management. All patients presenting with LBP should be thoroughly examined. Although most are candidates for electrodiagnostic and imaging studies, the "hands-on" examination may reveal information that would otherwise be missed. All patients require palpation of the spine and muscles, with determination of whether tender or trigger (tender plus spastic response) points are present in lumbar musculature (often neglected is the quadratus lumborum muscle, a major source of tender points in conditions such as fibromyalgia and in somatic presentations). A dolorimetric examination in which a simple device (dolorimeter) is used to deliver measured amounts of pressure (up to 10 kg/cm2) is valuable in evaluation of tender points and may provide evidence of pain pathology (e.g., hyperalgesia or hyperpathia). Tenderness on palpation of the lower extremity may be due to referred pain, and tenderness at the level of an involved intervertebral disk is also common (44).

Another often-neglected examination technique is the establishment of the range of motion of the affected spine. Range of flexion, extension, lateral bending, and rotation should be documented. We recommend the Schober test as a simple and quick method of measurement of range of flexion of the spine. In this test, one point is marked midway between the two posterior sacroiliac spines, and the second and third points are marked 5 cm (2 inches) below and 10 cm (4 inches) above the initial mark. The distance between the three points is measured (surprisingly, it is rarely exactly 15 cm!). The distance is remeasured upon the patient's flexing of the spine and may be remea-sured several times, for example, after the patient lies down and relaxes the muscles for several minutes. The change between erect and flexed measurements of less than 4 cm (1.6 inches) is indicative of restricted range of flexion (44).

Although time-consuming, dermatomal sensory examination may be needed in cases of lumbar radiculopathy that are not clear-cut and may contribute to an improved choice of locations for needle EMG and other diagnostic studies. Hyperesthesia is common, but, since this is a subjective presentation, its value in diagnosis is controversial (44).

Examination must include bilateral testing of reflexes, with any sign of asymmetry carefully noted. Provocative maneuvers, such as straight leg raising, may provide evidence of increased dural tension, indicating underlying nerve root pathology. They are also somewhat patient-dependent, but common consensus is that the straight leg raising test is only considered positive if pain occurs when the leg is elevated 30 to 70 degrees and when pain travels down below the knee, as nerve root tension is negligible if the leg is elevated less than 30 degrees, while painful presentation above 70 degrees is most likely related to muscular pain in the hamstrings or gluteal muscles (44).

Computed tomography scan of the lumbar spine provides superior anatomical imaging of the osseous structures of the spine and good resolution for disk herniation. However, its sensitivity for detecting disk herniations when used with myelography is inferior to that of MRI, especially the T2-weighted images, which may show areas of intervertebral disk degeneration (showing as darker areas due to loss of hydration). Results of CT and MRI should not be overinterpreted, as many healthy subjects show sometimes dramatic changes in disk anatomy, especially as they age. In a sobering study, Jensen and colleagues (45) found that out of 98 asymptomatic people, 64% of subjects without any back pain had a bulge, protrusion, or extrusion of the intervertebral disk at one level, and 38% had an disk abnormality at more than one level.

Electrodiagnostic studies, including NCS, needle EMG, and somatosen-sory evoked potentials (SSEPs), should be considered for all patients with LBP: to clarify the diagnosis in patients with limb pain; to exclude or confirm presence of peripheral neuropathy and motor neuron disease; and, most important, to quantify the extent and acuity of radiculopathies, something that no other diagnostic modality can provide. We usually recommend performing electrodiagnostic studies after 3 to 4 weeks have elapsed from the moment of acute injury; axonal changes may be unnoticeable on studies performed before that time. Diagnostic assessment of the late responses, such as the H-reflex is also a necessity to address the issue of whether proximal nerve or nerve root (or both) are involved, especially at the S1 level. Needle EMG affords a particularly high diagnostic yield, especially if the patient had the onset of symptoms less than 6 to 9 months prior. The SSEP study is indicated in all cases when involvement of the somatosensory pathways is suspected or obviously present during the sensory examination (46).

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