Itch and neuropathic itch

Abstract

Neuropathic itch is a pathological condition that is due to damage within the nervous system. This type of itch can be severe and unrelenting, which has a very negative impact on quality of life. Neuropathic itch is more common than generally appreciated because most types of neuropathic pain have a neuropathic itch counterpart. Unfortunately, much like neuropathic pain, there is a lack of effective treatments for neuropathic itch. Here, we consider the neural basis of itch and then describe how injuries within these neural circuits can lead to neuropathic itch in both animal models and human disease states.

Figure 1

Neural circuitry and brain regions involved in itch. Different types of neuropathic itch have been found to arise from lesions at different levels of the pathway. Abbrevions: ACC: anterior cingulate cortex; PFC: prefrontal cortex; SI: primary somatosensory cortex; SII: secondary somatosensory cortex; PBn: parabrachial nucleus; PAG: periaqueductal gray; DRG: dorsal root ganglia

Figure 2

Spinal circuits involving B5-I neurons and dynorphin normally limit itch. Loss of this inhibition results in severe neuropathic itch.