How is referred pain differentiated from local pain prior to therapeutic injection?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Answer

Several somatic and peripheral neural blockade procedures are useful for therapeutic and diagnostic purposes. Although the opportunity to block specific nerves can be considered limitless in the hands of an experienced interventionist with appropriate radiographic guidance, only some of the available procedures are mentioned below to highlight their usefulness as potential tools for a neurologist involved in the diagnosis and treatment of pain.

Therapeutic injections for extra-axial soft tissue structures

Therapeutic injections frequently are used as a mode of treatment in general or subspecialty practices, especially orthopedics, physiatry, and rheumatology. Many musculoskeletal disorders respond amenably to injections, including intra-articular and extra-articular tissues of many synovial joints, bursae, muscles, and tendons. Pain from extra-axial articular structures often is managed best by the aforementioned subspecialists.

Understanding a few key principles can help the neurologist determine the structural anatomy of an articular pain syndrome and respond efficiently by specialty referral, especially when certain symptoms indicate a potentially serious etiology. In most cases, patients with generalized arthralgia and arthropathy should be referred to a rheumatologist; therefore, this article concentrates primarily on localized pain disorders. In fact, the neurologist often is asked to differentiate whether pain is localized to a joint or periarticular structures or is referred from diseased neural structures.

Pain referral from joints or other soft tissue structures typically does not assume a myotomal or dermatomal pattern. Pain arising from superficial soft tissue structures that can be identified by palpation often permits more precise localization of the causative tissue or structure. However, pain that is referred from extra-axial joint capsules and other periarticular structures, such as ligaments, tendons, bursae, and muscles, may be more difficult to differentiate. Pain from bone and periosteum is usually well localized and rarely radiates; however, this discrepancy between "soft" and "hard" structures remains unexplained.

The manner in which the pain from symptomatic joints responds to biomechanical stressors is often the key to localization and causation. Pain that is worse when the joint is used suggests a mechanical etiology, especially if improved with rest. Pain in bed at night should bring about concern for a serious underlying etiology and almost always requires investigation. Persistent pain that does not fluctuate despite activity or rest is also worthy of diagnostic inquiry. Psychogenic or operant pain frequently is described as continuous and often more intense and disabling with certain activities, eg, worse at work and better with recreation. Pain and stiffness that are present in the early morning or after inactivity may be a harbinger of inflammatory arthropathy in extra-axial and axial joints. Patients with monoarticular deformity, swelling, stiffness, and warmth should be referred to the appropriate musculoskeletal specialist for evaluation.


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