ABEM Pain Medicine key terms

The neural process by which tissue-damaging stimuli are detected by peripheral receptors and converted into signals that travel to the spinal cord and brain. It is not identical to the conscious experience of pain.

A peripheral sensory nerve ending that responds to noxious mechanical, thermal, or chemical stimuli. Activation of nociceptors initiates nociceptive signaling, and their sensitization contributes to hyperalgesia after injury.

A thinly myelinated primary afferent that conducts rapidly and carries sharp, well-localized first pain. A-delta fibers terminate mainly in laminae I and V of the dorsal horn.

An unmyelinated primary afferent with slow conduction that signals dull, burning, poorly localized second pain. C fibers are polymodal and release neurotransmitters such as substance P in the dorsal horn.

The gray matter region of the spinal cord where primary afferents synapse and sensory input is modulated before ascending. It contains interneurons and projection neurons organized into laminae.

An ascending pathway carrying pain and temperature information from the dorsal horn to the thalamus. Second-order neurons decussate near their level of origin and travel in the anterolateral cord.

A spinal or brainstem neuron that responds to both innocuous and noxious stimuli, with increasing firing as stimulus intensity rises. These neurons help encode pain intensity and contribute to referred pain patterns.

An activity-dependent increase in central nervous system excitability after repeated noxious input, producing hyperalgesia, allodynia, and expanded receptive fields. It involves NMDA receptor activation, glial signaling, and altered descending inhibition.

A persistent strengthening of synaptic transmission after brief high-frequency stimulation, widely studied in the spinal dorsal horn and hippocampus. In pain circuits it contributes to central sensitization and chronic hyperalgesia.

A midbrain region that coordinates descending pain inhibition through connections to the rostral ventromedial medulla. It receives input from limbic and cortical areas and releases endogenous opioids.

A G-protein-coupled receptor that mediates analgesia, euphoria, respiratory depression, and constipation when activated by endogenous opioids or opioid drugs. It is encoded by the OPRM1 gene.

A neuropeptide released by nociceptive primary afferents in the dorsal horn that promotes neurogenic inflammation and nociceptive transmission. It binds the neurokinin-1 receptor.

Pain caused by a lesion or disease of the somatosensory nervous system, often described as burning, shooting, or electric. Diagnosis requires a plausible neurologic lesion and a compatible distribution.

Pain arising from actual or threatened tissue damage that activates nociceptors, typically aching or sharp and well localized. It is distinguished from neuropathic and nociplastic pain by history and examination.

Pain arising from altered nociception without clear evidence of tissue damage or somatosensory disease. It is common in fibromyalgia and chronic widespread pain and often accompanied by hypersensitivity.

A standardized battery of psychophysical tests measuring detection thresholds, pain thresholds, and temporal summation. It quantifies somatosensory dysfunction but is mainly a research and specialized clinical tool.

A paradigm in which a painful conditioning stimulus reduces the perceived intensity of a test stimulus, reflecting endogenous descending inhibition. Reduced conditioned pain modulation is associated with chronic pain states.

A self-report measure asking patients to rate pain intensity from 0 to 10, where 0 means no pain and 10 means worst imaginable pain. It is simple, validated, and widely used.

A four-item screening tool for neuropathic pain combining symptom interview and bedside sensory examination. A score of four or more out of ten suggests neuropathic pain.

A pharmacologic state in which repeated opioid exposure produces reduced effect, requiring higher doses for equivalent analgesia. It develops at different rates for analgesia, respiratory depression, and constipation.

A paradoxical increase in pain sensitivity during opioid therapy, distinct from tolerance and withdrawal. It may present as widespread pain or pain outside the original site.

The dose of one analgesic that produces approximately the same pain relief as a given dose of another. Equianalgesic tables guide opioid rotation but require adjustment for incomplete cross-tolerance.

A medication whose primary indication is not pain but that relieves pain in certain conditions, such as antidepressants, anticonvulsants, and corticosteroids. Adjuvants are commonly used for neuropathic pain.

A potentially life-threatening toxidrome caused by serotonergic excess, marked by agitation, autonomic instability, clonus, and hyperthermia. Combining opioids such as tramadol with serotonergic drugs increases risk.

A drug class including gabapentin and pregabalin that binds alpha-2-delta subunits of voltage-gated calcium channels. It is used for neuropathic pain and carries risks of sedation and misuse.

A class of older antidepressants, such as amitriptyline and nortriptyline, used at low doses for neuropathic pain. Anticholinergic and cardiac adverse effects require caution in older adults.

An injection of local anesthetic near the medial branch of the dorsal ramus to diagnose facet joint–mediated pain. A positive response supports proceeding to radiofrequency neurotomy.

A procedure using heat generated by alternating current to lesion nociceptive nerves, commonly medial branches or the dorsal root ganglion. It can provide durable pain relief after a positive diagnostic block.

Delivery of corticosteroid, often with local anesthetic, into the epidural space to reduce radicular inflammation and pain. It is used for disc herniation and spinal stenosis but has modest, time-limited benefit.

A neuromodulation therapy in which implanted electrodes deliver electrical pulses to the dorsal columns to reduce chronic neuropathic pain. Evidence supports use in failed back surgery syndrome and complex regional pain syndrome.

An injection of local anesthetic near the cervical sympathetic chain to treat upper extremity complex regional pain syndrome and other sympathetically maintained pain. Complications include Horner syndrome and vascular puncture.

Injection of local anesthetic or saline directly into a palpable taut band to relieve myofascial pain. It is often combined with stretching and physical therapy.

A sequential rehabilitation approach using left/right limb recognition, imagined movement, and mirror therapy to treat chronic pain and cortical reorganization, especially complex regional pain syndrome.

A structured psychological treatment that helps patients identify and modify unhelpful thoughts, emotions, and behaviors related to pain. It improves function and coping in chronic pain.

A psychological approach teaching patients to accept difficult sensations and commit to valued activities rather than fight pain. It is used in multidisciplinary chronic pain programs.

A state-run database tracking controlled substance prescriptions to identify risky patterns such as multiple prescribers or early refills. Clinicians should review it before initiating or continuing opioid therapy.

The process of explaining a procedure's purpose, risks, benefits, and alternatives so a patient can make a voluntary decision. Documentation should reflect the discussion.

Management of blood-thinning medications around interventional pain procedures to balance bleeding risk against thrombotic risk. Guidelines stratify procedures by bleeding risk and specify appropriate drug hold intervals.

Coordinated care combining medical, physical, psychological, and occupational therapies for chronic pain. Programs emphasize functional restoration and self-management rather than solely reducing pain intensity.

External benefits, such as financial compensation or avoidance of work, that may accompany illness behavior. It is a psychosocial factor to assess, not a diagnosis of malingering.