The persistence of the neurosignature, even after limb amputation, may be the cause of phantom sensations and pain. Phantom pain may arise from abnormal reorganization in the neuromatrix to a pre-existing pain state.Opposition to the neuromatrix theory exists largely because it fails to explain why relief from phantom sensations rarely eliminates phantom pains. It also does not address how sensations can spontaneously end and how some amputees do not experience phantom sensations at all. In addition, a major limitation of the neuromatrix theory is that it too broadly accounts for various aspects of phantom limb perception. It is also likely that it is too difficult to be tested empirically, especially when testing painless phantom sensations. Management
Various methods have been used to treat phantom limb pain. Doctors may prescribe medications to reduce the pain. Some antidepressants or antiepileptics have been shown to have a beneficial effect on reducing phantom limb pain. Often physical methods such as light massage, electrical stimulation, and hot and cold therapy have been used with variable results. There are many different treatment options for phantom limb pain that are actively being researched. Most treatments do not take into account the mechanisms underlying phantom pains, and are therefore ineffective. However, there are a few treatment options that have been shown to alleviate pain in some patients, but these treatment options usually have a success rate less than 30%. It is important to note that this rate of success does not exceed the placebo effect.
Aquagenic urticaria, also known as water allergy and water urticaria, is a rare form of physical urticaria in which hives develop on the skin after contact with water, regardless of its temperature. The condition typically results from contact with water of any type, temperature or additive. Signs and symptoms
The main symptom of aquagenic urticaria is the development of physical hives, which may or may not itch. Itching after contact with water, without the development of physical hives, is known as aquagenic pruritus. Aquadynia is a condition in which pain occurs after contact with water.In severe cases, drinking water can result in swelling of the oral cavity , swelling of the throat  and in extreme cases, anaphylaxis. The hives associated with aquagenic urticaria are typically small (approximately 1–3 mm), red- or skin-colored welts (called wheals) with clearly defined edges. It most commonly develops on the neck, upper trunk and arms, although it can occur anywhere on the body. Once the water source is removed, the rash generally fades within 30 to 60 minutes.Water in all forms, such as tap or sea water, swimming pool water, sweat, tears, and saliva can induce the lesions. Cause
The cause of aquagenic urticaria is not fully understood; however, several mechanisms have been proposed. Interaction between water and a component in or on the skin or sebum has been suggested. This theory suggests that a substance is formed by this interaction, the absorption of which causes perifollicular mast cell degranulation with release of histamine.