When cutaneous nerves pierce through both deep and superficial fascial layers to reach the skin, there is a high potential for entrapment. If entrapment occurs, inflammatory neuropeptides are released, which can cause inflammation and neuropathic pain. Friction injuries can also arise where cutaneous nerves cross over areas of bone, such as the kneecap, which also results in neurogenic inflammation and neuropathic pain. Neurogenic inflammation differs from other forms of inflammation in that it does not respond as well to cortisone injections or other anti-inflammatory drugs such as NSAID’s. Patients are commonly prescribed Lyrica or other neuropathic pain medications, which may or may not be useful.
When the perineural injection solution is injected in an area where cutaneous nerves are trapped, the pressure from the fluid frees the nerve from these adhesions, resulting in an immediate reduction in pressure and therefore inflammation. In addition to this, the 5% dextrose modulates two ion channels that contribute significantly to inflammation and sensation of pain. By modulating these channels, there is a drastic reduction in the number of inflammatory neuropeptides released by the nerve, thereby shutting down neurogenic inflammation. Lastly, as neurogenic inflammation is associated with low levels of glucose surrounding the nerve (known as glucopenia), injecting dextrose to surround the affected nerves can provide the nerve with the dextrose it needs to function correctly.