Functional Neurological Disorder (FND) : a patient's guide



Complex Regional Pain Syndrome

Complex Regional Pain Syndrome refers to pain in one or more limbs which occurs in a number of different situations, but especially after physical injury. It can also be triggered by other things including minor soft tissue problems like carpal tunnel syndrome.


Complex Regional Pain Syndrome (CRPS) used to be called Reflex Sympathetic Dystrophy, but it is not called this any more because it is now know that it is not just the sympathetic nervous system that is disrupted in this condition.


Here is a typical story

Budapest clinical diagnostic criteria for Complex Regional Pain Syndrome: 


Diagnostic criteria (1–4 must be satisfied):


1. Continuing pain, which is disproportionate to any inciting event



Sensory: reports of hyperesthesia and/or allodynia









There is no other diagnosis that better explains the signs and symptoms




Oedema - Swelling

Sudomotor Activity - Usually refers to colour change or change in blood flow

Allodynia - Describes a painful response to a non-painful stimulus. for example, brushing the skin lightly against bedclothes is painful

Hyperalgesia - Increased sensitivity to stimuli that are normally painful

Complex Regional Pain Article

Andrew's Story


Andrew was a care worker who normally had good health.


He was walking down some steps in icy weather when he slipped and fell. He fractured his wrist. His initial operation to fix his wrist went reasonably well but then there was some infection and he had some bad experience in hospital with pain. Everything took longer to heal than he had expected.


When the plastercast came off his wrist, his hand and wrist felt odd, stiff and weak. He had a lot of pain, there was swelling and redness and the hand was warmer than the other. Initially the doctors and physiotherapists thought this would settle down but it didnt.


After 6 months the symptoms were even worse. Andrew was experiencing constant severe pain. Increasingly he found that even a light touch on the site of his pain was really painful - and produced a horrible electric shock sensation.


He found that he couldnt move his arm properly and tended to hold it in a protected position. He worried that people would bump in to his arm when he went outside. His hand was a little more swollen on that side but when he closed his eyes he felt the hand was much larger than it looked when he had his eyes open. He was embarassed to tell anyone this. His fingers started to curl slightly and he developed a slight tremor in the hand.


Andrew felt confused by what had happened. The doctors said that the fracture and the injuries had all healed yet his pain was worse than ever. He thought he must have damaged some nerves in the hand but nerve conduction studies and a neurological assessment concluded that there was no nerve damage.


After 12 months Andrew still hadnt returned to work and was feeling increasingly frustrated and worried about the situation. He couldnt understand what had happened. He assumed the problem must be to do with damage to the nerves.


When he met the pain management team they explained that although there had been some damage to the wrist this didnt explain how severe the pain was. What had happened is that he had developed a chronic pain syndrome called Complex Regional Pain Syndrome (CRPS).


In CRPS the normal 'volume knobs' in the pain pathways that occur throughout the nervous system become turned up and get stuck at that 'higher volume'. This happens not just in the affected limb but also in the spinal cord and most importantly in the brain.


He learnt that the treatment of CRPS depends on gradually trying to turn down those volume knobs. MEdication can help as can several other types of treatment. The most important way to do that though is to move the hand more with physiotherapy.


Andrew found this a really painful and difficult process. He was given desensitisation exercises and some of his exercises involved using a mirror and learning to recognise hand positions.


He worked hard on his exercises and eventually found that his pain was significantly better. After another 12 months he still had some pain but was able to return to work and could use his hand for most day to day activities. Looking back he was pleased that he had met a team who had been able to explain things in a way that helped him make progress with his rehabilitation


CRPS type 1 has been defined in the following way by the International Association for the Study of Pain (see below for an explanation of some of the jargon)


Some people develop pain in a limb without much in the way of swelling or colour change and there is ongoing debate about whether these patients have CRPS or not. If they don't, then they have something very similar which probably demands similar kinds of treatment


CRPS is a complicated subject hard to do justice to on this page.


Some people reading this will wonder what CRPS is doing on a website for patients with functional symptoms. The reasons for this are discussed in this article.


Popkirov S, Hoeritzauer I, Colvin L, Carson A, Stone J. Complex regional pain syndrome and functional neurological disorders: time for reconciliation. J Neurol Neurosurg Psychiatry. 2018; 0:jnnp-2018-318298.


1. A disabling but genuine neurological condition which occurs in the absence of easily definable structural disease pathology. Most of the physical signs of CRPS have been shown to occur in limbs that are immobilised.


2. Many patients with CRPS have altered sensation (which can't be explained on the basis of disease and has similarities to functional sensory symptoms)


3. Patients with CRPS commonly experience weakness of their limb, often with a dissociative quality. So for example, patients might find that their limb doesn't feel as if it belongs to them as much as it should. When the limb is examined the weakness is clinically indistinugishable from that seen in functional weakness. Occasionally patients with CRPS develop a movement disorder, most commonly a functional dystonia. Functionaldystonia is often assocaited with minor injury too.


4. In some patients one of the most important perpetuating factors in their CRPS may be immobility and avoidance of movement. This is not surprising since CRPS is an intensely painful condition. However, it may be the case that the less someone moves their limb, the more painful it gets, and the less likely they are to move it etc etc.


There is more about this on the pain page and on the physio page


There are undoubted biological changes in patients with CRPS, but then there are too in patients with other functional symptoms and they may have more in common with each other than has been thought.


There are many potential drug treatments and interventions but the mainstay seems to be increasing activity.


Read Hazel's story for an example of how an understaning of FND can help treatment of CRPS