Labs – Serum chemistries, liver function tests, coagulation profiles, and complete blood counts not only may be necessary in the diagnosis of pathology, but are also important to ensure that patients will be able to metabolize drugs a pain medicine practitioner prescribes and safely tolerate invasive interventions that are offered. High rates of over-the-counter acetaminophen and NSAID use in some patients may warrant periodic checks of hepatic and renal function. Urine toxicology can be used to screen for illicit substance abuse and drug diversion.

Imaging – A specific differential diagnosis prior to ordering imaging is always suggested. Indiscriminate test ordering increases the likelihood of false positive findings, resulting in diagnostic confusion.

Plain films – The radiographic approach varies depending on the body region involved and the acuity/chronicity of pain. In chronic neck pain, with or without a history of trauma, an initial 3-view (AP, lateral, open mouth) radiographic series is recommended by the American College of Radiology (Daffner, 2005). Obliques can be ordered at the discretion of the physician. In acute neck pain due to trauma, high speed CT scanning has begun to replace plain films as the initial imaging modality of choice.

Uncomplicated acute low back pain does not warrant imaging studies according to the American College of Radiology (Bradley, 2005) and others. Although plain films are inexpensive and readily available, they can identify many abnormalities not related to symptoms. Abnormalities (e.g., spondylolysis, zygapophysial joint abnormalities, Schmorl’s nodes, and mild scoliosis) can be equally prevalent in symptomatic and asymptomatic patients (Jarvik, 2002). In young females, it also needs to be considered that a single set of plain films of the lumbar spine results in gonadal radiation that is the equivalent of daily chest x-rays for several years (Jarvik, 2002).

Radiographs, as well as other tests, are indicated for back pain in the presence of “red flags” including: recent significant trauma (or milder trauma for age >50), unexplained weight loss, unexplained fever, immunosuppression, history of cancer, IV drug use, prolonged corticosteroid use, osteoporosis, age >70, focal neurologic deficit with progressive or disabling symptoms, or duration greater than 6 weeks (Bradley, 2005). Because pathology due to osteomyelitis or metastases may need to be fairly advanced before detection on plain radiography is likely, suspicion for these pathologic processes usually requires follow up with more advanced imaging modalities.

Standard film sets should include AP and lateral views. Oblique views of the lumbar spine (also known as the “Scottie dog” view) are useful in diagnosing spondylolysis if a pars interarticularis fracture (which corresponds to the “neck” of the Scottie dog) is suspected. Routine oblique views of the lumbar spine, however, are not supported by the literature (Jarvik, 2002). Flexion/extension views may be helpful to rule out unstable spondylolisthesis.

Computed tomography – CT is the imaging modality of choice to examine bony and calcific detail. Examples of indications where CT is superior to MRI include suspected fractures of the posterior elements of the spine and suspected ossification of the posterior longitudinal ligament. The postsurgical spine is also best imaged by CT due to the severe artifacts that can degrade MR images.

CT provides passable, if unexceptional, visualization of the soft tissues, for which modern MRI is generally superior. For instance, CTs are generally less useful in the examination of disc protrusions than MRI. CT also depicts the foraminal and extraforaminal nerve root fairly accurately due to the contrast
provided by the surrounding fat, but is incapable of demonstrating the intrathecal nerve root or spinal cord without myelographic contrast (Jarvik, 2002). Myelography, when combined with CT, can outline the spinal cord, nerve roots and neural foraminae. It is the imaging modality of choice in examining patients with suspected radiculopathy who cannot tolerate MRI. CT myelogram is, in fact, considered by some to be the best test available for examining neuroforaminal anatomy, even superior to MRI, although it is not always clear how it will affect management. Even if it is assumed that the radiculopathy is due to compromise at the neural foramen, management may not change if ongoing conservative care is the appropriate management. Myelography also carries the risk of a potentially fatal anaphylactic reaction to the contrast, as well as the risk of infection and post-lumbar puncture headache.

Magnetic resonance imaging – MRI is the imaging modality of choice in examining the CNS parenchyma, as well as other soft tissues, including the spinal disc elements (annulus fibrosus, nucleus pulposus). Although MRIs do not directly visualize cortical bone, they can be useful in determining the acuity of fractures since the marrow edema and hematoma associated with acute fractures can be visualized.

T1-weighted images illustrate anatomic detail and are well suited for localization of masses and demonstration of mass effect on adjacent structures. T2-weighted images, although less anatomically detailed than T1-weighted images, provide information on many disease processes, such as infection, neoplasm, infarction, and white matter disease. Gadolinium, a paramagnetic contrast agent, has significantly increased the sensitivity and specificity of MRI, and is particularly useful for suspected infection or neoplasm. Enhancing tissues will appear bright on T1-weighted contrast enhanced images. Notably, gadoliniumcontaining contrast agents contain no iodine (i.e., they are safe in patients with iodine contrast allergy) and are not nephrotoxic (i.e., they can be used in patients with renal failure).