Segmental and Brain Stem Mechanisms

Abstract

There are different mechanisms that modify or modulate a pain signal along its pathway. Pain modulation occurs peripherally or centrally at the level of the spinal cord or supraspinal structures. Sensitization of the receptors can lead to hyperalgesia. Peripheral hyperalgesia can be primary or secondary. Sensitization can also occur centrally due to segmental and spinal cord mechanisms leading to facilitation of transmission of the pain signal. Central hypersensitization is commonly referred to as the “Wind-up” phenomenon. Changes in neurochemistry of the dorsal horn due to repetitive stimulation as well as recruitment of non-neuronal cells, such as astrocytes and microglial cells, are believed to play an important role in central sensitization. Inhibition occurs at both spinal and supraspinal levels due to different mechanisms. Gate control theory, concomitant release of inhibitory neurotransmitters, and descending inhibitory pathways are different mechanisms that lead to inhibition.