Fig. 5.1
Pain severity scales. Various tools have been developed to help patients and clinicians quantify the severity of pain. The following are examples of common pain scales: (a) Wong-Baker FACES Foundation (2015). Wong-Baker FACES® Pain Rating Scale. Retrieved [Date] with permission from http://www.WongBakerFACES.org. (b) numerical pain rating scale, and (c) visual analog scale (Note: for permission please see Wong-Baker FACES pain rating scale: From Wong et al. [9]. Copyrighted by Mosby, Inc. Reprinted with permission, 0–10 numerical pain rating scale: From McCaffery and Pasero [10]. Copyrighted by Mosby, Inc. Reprinted by permission, Visual analog scale and verbal pain intensity scale: From Pain Management: Theory and Practice, edited by RK Portenoy & RM Tanner, copyright 1996 by Oxford University Press, Inc. Used by permission of Oxford University Press)
- 1.
Anatomic location (body part)
- 2.
Severity (0–10 scale; faces; mild, moderate, severe)
- 3.
Verbal descriptors (shooting or burning, dull or achy)
- 4.
Time course (When is it bad? Does it wax and wane throughout the day, week, or month?)
- 5.
Alleviating factors (What makes it better?)
- 6.
Aggravating factors (What makes it worse?)
- 7.
Changes in functional status caused by pain
- 8.
Review of diagnostic workup (previous EMG, MRI, laboratory tests)
- 9.
Review of the previous treatment (previous surgery, medication, and rehabilitation strategies)
Obtaining a past medical history is part of the comprehensive evaluation for pain. Comorbid diseases can be central in defining a differential diagnosis. Patients with a history of many disorders, including diseases such as cancer or diabetes, can develop painful conditions as a result of the disease or its treatment. A complete understanding of the patient’s history thus can be helpful when trying to establish a diagnosis. For example, patients with uncontrolled diabetes may develop peripheral neuropathies that can be quite painful. The practitioner should understand that part of the treatment of the pain is to work with the primary care physician/endocrinologist to get diabetes under control. As part of the comprehensive evaluation, one should understand what treatments have been tried to date and what the outcome has been of previous treatments. Has a patient previously tried medications, injections, physical medicine modalities, or surgical interventions?
The pain practitioner typically takes a history and follows with a focused physical examination that is determined by the history. This helps the physician narrow the differential, or presumptive, diagnosis. This typically involves inspection, palpation, provocative maneuvers, and a neurologic examination. Laboratory workup can be used to help make a diagnosis or determine if it is safe to proceed with a planned course of therapy. In addition, with the use of some pharmacologic agents, specific laboratory testing may help identify complications that can occur with treatment strategies. More commonly, laboratory workup may be used to determine if it is safe to proceed with interventional pain procedures.
The reason to obtain additional studies is to establish a diagnosis and to help guide the therapy. One should only perform the additional studies below as a guide to therapy. Plain X-rays use X-ray radiation to take a picture of the hard and soft tissue in the spine. These can be helpful in arthritic disorders and evaluating other connective tissues. Flexion-extension films of the spine are taken with patients in multiple positions to assess stability of the spine if a fracture (spondylosis) is suspected. This test also helps to determine spinal instability. In addition, by carefully orienting the patient in the correct plane, fractures and foraminal compromise can be identified and correlated with a patient’s symptoms.
Computed tomography uses a series of X-ray-generated images formatted into two-dimensional and now three-dimensional images of both soft and hard tissues. Scans can help identify hard tissue abnormalities, cancer, and spinal pathology. Ultrasound images internal structures by measuring their capacity to transmit and reflect high-frequency sound waves, making them good for evaluating soft tissue abnormalities. Because of the refractive elements of bony structures, they cannot be used to visualize structures deep to the bony tissue. In the soft tissue, patterns of tears and can be seen in muscles, and abnormal activity can be seen in the soft tissue. This highly sensitivity modality is frequently used to evaluate muscle and ligamentous tears as well as soft tissue structures such as cysts.
Magnetic resonance imaging utilizes strong magnetic fields to assess soft tissues. The detailed images allow for detailed evaluation of the internal soft tissue, such as the nervous tissue or herniated disks in the spine. In the spine, there is clearer definition of the spinal cord, surrounding CSF, and extradural structures, such as disks. Moreover architecture of the disks and level of disk dehydration can be assessed by changes in signal intensity in the spine. MRI with and without contrast will help distinguish malignancy and inflammatory or scar tissues from a re-herniation.
EMG, or electromyography, measures electrical activity within muscles. Various patterns of altered activity can indicate both primary muscle pathology and denervation. Electromyography records voltage changes within a muscle by placing a needle into the muscle. Electrical activity is then recorded in the muscle and displayed on an oscilloscope. Various patterns correlate with diseases of the muscle and other pathologic processes. Nerve conduction velocity (NCV) tests help determine if there is damage along the path of specific nerves. Nerve conduction studies measure velocity and amplitude of electrical activity of the nervous tissue. Abnormalities in electrical activity and conduction can indicate pathology of the nervous tissue, and can be used to identify entrapment syndromes, lesions along the course of a nerve or intrinsic problems within a nerve. The pattern of abnormalities identified can help distinguish between radiculopathies, plexopathies, and primary nerve injuries. These patterns can be used to guide therapy.
Radionucleotide bone scanning is used to assess tissue that has high bone turnover, as seen in fractures, metastatic tumor, and infection. Because this technique is relatively sensitive, it can be used to identify subtle lesions that are missed with other techniques. Biopsy to obtain a tissue diagnosis can be helpful with some neurologic and rheumatologic pain states, visceral pain syndromes, as well as with cancer diagnosis.
In an interventional pain, physicians will also perform diagnostic blocks in order to determine if a structure is involved in pain. This involves placing low volumes of local anesthetic around a peripheral nerve. If pain relief follows a local anesthetic block, an ablative procedure is entertained [11]. For example, diagnostic blocks are frequently performed in the spine (medial branch blocks), viscera (celiac plexus block), or peripheral (specific neural structures, i.e., radial nerve) to determine if the structure innervated by that nerve or plexus is the source of the problem [12]. Table 5.1 illustrates the various types of pain and the associated characteristics. If the practitioner is not clear on the diagnosis, it is appropriate to obtain consultation with pain physicians or members of other specialties.
Table 5.1
Types of pain
Types of pain | Characteristics |
|---|---|
Nociceptive pain | Transient, response to noxious stimuli |
Neuropathic pain | Damage or dysfunction of the nervous system |
Inflammatory pain | Response to tissue damage and inflammation |
Postsurgical pain | Transient pain, nociceptive, and inflammatory |
Cancer pain | Associated with malignancy |
Treatment Strategies
All too often practitioners may have not established a diagnosis or have an inaccurate diagnosis before beginning treatment. The treatment strategy chosen should be determined after one has established a presumptive diagnosis and a treatment goal. Broadly speaking, there are several general approaches to treating patients with chronic pain. These include medical approaches, anatomic or surgical approaches, neuromodulatory approaches, psychological approaches, alternative approaches, and interventional approaches. Figure 5.2 illustrates a pain treatment ladder that was adapted from the World Health Organization’s pain treatment.
Fig. 5.2
World Health Organization pain treatment ladder. The WHO pain treatment ladder was originally devised to treat cancer pain (This is an adapted version for treating chronic nonmalignant pain (http://www.who.int/cancer/palliative/painladder/en/#, Krames [14], Stamatos et al. [15])
Generally, the practitioner should consider conservative modalities prior to the more invasive options. One should generally have a clinical matrix in place, understanding the risks of the therapies being recommended, the likelihood of curing or managing the problem, the risks of the proposed therapy for any given patient, and the costs of the therapies over both the short and long term. If a patient presents with back pain, it is crucial to understand the pathology, as well as the patient’s comorbid medical disorders, prior to making decisions on the appropriate treatment strategy. A young patient with new onset neurologic deficit, herniated disk, and classic radicular findings may benefit from a micro-diskectomy early in the treatment algorithm. Alternatively an elderly patient with comorbid medical disorders and back pain may benefit from early treatment with physical therapy, chiropractic care, or medication management. Each treatment strategy is based on the judgment of the practitioner and an understanding of the entire clinical picture for an individual patient.
Medication Management
There are several classes of medications frequently used in the treatment of pain. They can be used for a variety of indications (see Table 5.2). Within each class of medication, there are multiple medications that are commonly used as well as numerous side effects and risks that define the category. The class of medication chosen is determined by the patient’s disorder and side effect profile of the agent(s) chosen. For example, neuropathic pain can be most effectively treated with antiepileptic medications and antidepressant medications. If a patient were to present with chronic burning pain and a comorbid depression, the physician may choose an antidepressant class of medication. Severe lancinating pain is more commonly treated with antiseizure medications (see Table 5.3).
Table 5.2
Common pain medications and their routes of administration
Class of medication | Mechanism of action | Route | Concerns | Notes |
|---|---|---|---|---|
Nonsteroidal anti-inflammatory | Inhibits prostaglandin synthesis | Oral and IV | GI Bleeding/platelet dysfunction Renal dysfunction Cardiovascular risk | Acute chronic and cancer |
Acetaminophen | Central | Oral and IV | Hepatotoxicity in higher doses or chronic use | Hidden in many other combo medications and OTC formulations |
Steroids | Potent anti-inflammatory | Oral IV topical | Bone Immune depression Hyperglycemia associated with GI bleeding Autologous steroid depression | Not a long-term option |
Antiseizure medications | Multiple mechanisms | Oral | Gingivitis, aplastic anemia Drug-drug interactions | Neuropathic pain |
Antidepressant medications | Can alter reuptake of serotonin and norepinephrine | Oral | Serotonin syndrome a rare side effect Anticholinergic effects | Neuropathic pain |
Opiates | Bind opiate receptor | Oral IV, IM, intrathecal | Respiratory depression Endocrine Addiction Constipation Death | Neuropathic Nociceptive pain (Limited) |
Cytokine modulators | Affects TNF-alpha | Oral intravenous | Immune suppression | Rheumatoid arthritis |
Local anesthetics | Blocks Na channels | Topical Epidural and intrathecal | Seizures Tachyphylaxis | Less common oral or IV |
NMDA receptor antagonists | Blocks N-methyl-D-aspartate receptor | Topical Intravenous | Hallucination Sialorrhea | May affect tolerance and |
Alpha-2 agonists | Binds the alpha-2 receptor centrally and peripherally | Topical/intrathecal | Hypotension | Sympathetically maintained pain |
Bisphosphonates | Inhibit pyrophosphate metabolism | Oral Intravenous | Jaw disease | Used in clinical trial for CRPS type 1 osteoporosis |
Table 5.3
Antiseizure medications
Drug | Mechanism of action | Starting dose | Typical daily dose | Primary clinical use | Special considerations |
|---|---|---|---|---|---|
Gabapentin | Binds to voltage-gated calcium channels | 300 mg | 1800–3600 mg | Postherpetic neuralgia (general neuropathic pain) | Start at low dose and slow titration upward |
Pregabalin | Binds to voltage-gated calcium channels | 50 mg | 150–300 mg | Diabetic peripheral neuropathy, fibromyalgia, spinal cord injury | Start at low dose and slow titration upward |
Topiramate | 1. Blocks voltage-gated Na channels
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