Pain is a complex multidimensional symptom. It is determined not only by actual or potential tissue injury and normal and abnormal activity of the nervous system, but also by the patient's personal beliefs, mood, previous painful experiences, psychosocial stressors, coping mechanisms, and motivational factors. Evaluation of a patient with chronic pain should take into consideration all of these factors. Unfortunately, there is no single test or scale that can measure pain comprehensively, reliably, or objectively. A thorough history and physical examination, in combination with other diagnostic tools, are critical in the evaluation of pain patients to identify anatomic and physiologic pain generators. Several visits may be required to elucidate relevant medical and pyschosocial factors. The patient's motivation for the evaluation must be clarified early (i.e., whether there are issues of litigation or disability affecting the patient's pain and whether the patient perceives the potential to control pain as coming from within or without). To do this, it is important to listen well, develop the patient's trust, and not overly structure the interview. Chronic pain patients need validation. Without it, they cannot offer their trust, and trust is vital for treatment compliance and a successful outcome.
Pain assessment is a dynamic process that evolves with the pain management plan. The pain evaluation should be used to localize the source of pain; to determine its quality, pattern, and intensity; to define exacerbating and attenuating factors; and to assess how environmental and behavioral influences affect the pain. Clinicians should always try to make a diagnosis before implementing a treatment plan, recognizing that jumping to a premature conclusion might result in inappropriate treatment or harm to the patient. It is also necessary, at times, to rethink the diagnosis, despite previous and thorough workups. In this chapter, we focus on the history taking and targeted physical examination of a pain patient, pertinent diagnostic testing, pain measurement tools, and models of pain assessment and management.
HISTORY AND PHYSICAL EXAM
DEFINING THE TYPE OF PAIN
Pain should be broadly defined as nociceptive (somatic or visceral), neuropathic, or idiopathic. Toward this end, pain location is of utmost importance to accurate diagnosis. It may be well localized, as in entrapment neuropathy (e.g., carpal tunnel syndrome), widespread and diffuse (e.g., fibromyalgia), or regional (e.g., musculoskeletal pain). Patterns of radiation may help determine the site of pathology, such as in cervical or lumbar radiculopathy. Radicular pain (along a dermatome) implies involvement of a nerve root. Pain may also be referred, as in visceral pain, when it is felt over a particular area of skin that is embryologically associated with but anatomically distant from the source of irritation. Accurate characterization of the pain's location and pathophysiology provides the rationale for treatment. Tables 8-1, 8-2, and 8-3 provide examples of referred pain contrasted with clinical findings associated with nerve root versus peripheral nerve pathology.