Pain Medicine is concerned with the study of pain, prevention of pain, and evaluation, treatment, and rehabilitation of persons in pain. Some conditions may have pain and associated symptoms arising from a discrete cause; such as, postoperative pain or pain associated with a malignancy. They may also be conditions in which pain constitutes the primary problem, such as neuropathic pains or headaches.
The evaluation of painful syndromes includes interpretation of historical data; a review of previous laboratory, imaging, and electrodiagnostic studies; assessment of behavioral, social, occupational and vocational issues; and an interview and an examination of the patient by the pain specialist. It may require specialized diagnostic procedures including central and peripheral neural blockade or monitored drug infusions. The special needs of the pediatric and geriatric populations, and patients’ cultural contexts, are considered when formulating a comprehensive treatment plan.
Acute pain is induced by any form of injury (trauma, disease, treatment intervention such as surgery) that results in activation of nerve receptors at the site of local tissue injury. The pain resolves when the underlying mechanism heals or remits.
It is a condition where pain extends beyond the expected period of healing. International Association for study of pain (IASP) definition clearly states, any pain, acute or chronic, regardless of the presence of identifiable tissue damage, is an unpleasant experience, inherently influenced by various cognitive, affective, and environmental factors. Based on this definition, chronic pain should not be assumed as merely functional.
Chronic Back Pain
Chronic low back pain is defined as a chronic pain that has persisted for more than 3 months. (Merskey H, Boduk N. Classification of Chronic Pain. Description of Chronic Pain Syndromes and Definition of Pain Terms. 2ndEdition. Seattle IASP press, 1994).
According to Turk et al (Ref) acute and chronic pain should be conceptualized on two dimensions: Time and physical pathology.
Any case falling above the diagonal line (short duration or high physical pathology e.g., tissue damage ) is acute pain; whereas cases falling below the diagonal line (low physical pathology or long duration) suggest chronic pain. Acute pain resolves when the underlying pathology resolves.
Pain associated with cancer includes pain associated with disease progression as well as treatment example chemotherapy, radiotherapy and surgery that the damage the nervous system. Cancer pain may be acute or chronic. The mechanism of acute and chronic cancer pain is not different than non-cancer pain or sometime called as benign pain such as seen after any form of tissue injury.
McGuirk BE, Bogduk N. Low Back pain. Chapter 72, Bonica’s Management of Pain 4thEdition. Page 1105 – 1122.
Episodic intermittent pain with pain free interval. Examples are Migraine, Sickle cell disease, Trigeminal neuralgia etc. The period of recurrent attacks may last for relatively longer period but each episode does not last long. It may share features of acute and chronic pain. Therefore psychosocial, behavioral, and physical pathology may exist.