Afferent

Afferent refers to the nerve fibers that carry signals from the body toward the central nervous system (CNS).

In pain medicine, afferent pathways are critical because they transmit sensory information — including touch, temperature and most importantly, pain — from the periphery to the spinal cord and brain.

Different types of afferent fibers carry different qualities of pain: A-delta fibers are thinly myelinated and transmit sharp, fast, well-localized pain, while C fibers are unmyelinated and carry slow, dull, aching pain. These signals enter the spinal cord, where they synapse with second-order neurons that relay the information upward to higher brain centers for processing.
In chronic pain, afferent signaling can become abnormal, either due to nerve injury, ongoing inflammation or central sensitization. This can lead to exaggerated pain responses or pain in the absence of clear tissue injury. Interventions in pain medicine — from drugs that modulate ion channels to procedures like nerve blocks or pulsed radiofrequency (PRF) — often aim to regulate afferent input, reducing excessive or dysfunctional signaling.