Jun 12 2008
I recently received the following question:
I’ve been listening to The Skeptic’s Guide to the Universe for over a year now. I’ve recently returned to school for nursing and appreciate the NeuroLogica blog, as well. Words can’t describe how much I look forward to them each week. I don’t know where you find the time to keep up with the blog and the podcast!
I’m sure you receive tons of email everyday, but I’m hoping you’ll have an opportunity to respond to my question through one of your outlets. I live in a “new agey” town where “woo” thinking and southern spirituality often result in non-evidence-based approaches to health. A friend of mine suffered a bad leg fracture 1.5 years ago. She has been relatively immobile and has complained about constant pain ever since. This resulted in a roller coaster of doctors and opiates. She was recently diagnosed with Reflex Distrophy Syndrome. I’ve read a bit about this online and am not sure if this disorder is anything beyond a psychogenic pain manifestation, atrophy, or drug-seeking behavior. Of course, I’m not privy to her medical records and may be missing the whole story. I value your medical expertise and would be thrilled if you could weigh in on RDS/CRPS in general.
I can’t thank you, Rebecca, Bob, Evan, and Jay enough for helping me realize that I am not alone. Please keep up the good work! I continue to look forward to your skeptical contributions.
Thanks for the question and the kind words, Alicia. Mostly I cover dubious medical topics on this blog in order to expose them, but occasionally I cover diseases or disorders that are genuine but may seem questionable. That is just one more of the negative consequences of quacks creating fake diagnoses – it makes cautious patients often question the validity or real diagnoses. It adds to the overall confusion making effective health care decision making more difficult.
Reflex Sympathetic Dystrophy (RSD), which is now called Complex Regional Pain Syndrome type I (CRPS), is a real neurological disorder. It is a type of neuropathic pain. It may include sympathetic symptoms (hence the RSD name) and also is typified by being regional (occurring in one limb, for example, rather than all over the body) and is complex in that it often involves symptoms other than just pain (hence the CRPS name). RSD is CRPS type I which means there is no identifiable injury or abnormal nerve as a cause. CRPS type II means that the symptoms can be localized to a specific nerve that has been injured.
Neuropathic pain is a pathological type of pain that originates in the nervous system itself. It is distinguished from nociceptive pain, which is what results from the nervous system doing its job by sensing pain coming from injured or diseased tissue. Nociceptive pain is proportion to the tissue injury and it resolves when the tissue damage heals. Nociceptive pain is therefore protective and represents the nervous system working as it is supposed to.
Neuropathic pain is (as the name implies) a pathological, non-adaptive pain that derives from the nervous system malfunctioning. It is not protective and is typically chronic (lasting beyond any tissue injury that may cause it).
In terms of the character of the pain – some types of pain are non-specific, meaning that they can be nociceptive or neuropathic, including sharp, dull, or achy pain. Pain that is more likely to be neuropathic include burning, tingling, or shooting pain or pain that feels like electricity.
There are a variety of mechanisms of neuropathic pain, including nerve endings firing spontaneously when they are not supposed to, nerve endings firing too easily (with little stimulus), pain signals being amplified as they are conducted from the peripheral nervous system to the central nervous system, or non-painful sensation being wrongly wired into central pain receptors. Damage to pain pathways in the brain (such as in the thalamus) can also cause a purely central form of neuropathic pain.
RSD and CRPS are syndromes of neuropathic pain combined with sympathetic dysregulation, resulting in flushing of the skin, loss of regulation of blood flow to the skin, and edema in the region of pain. The skin may also become thin and shiny, likely due to the chronic poor blood flow regulation.
Treatment for neuropathic pain in general is mostly pharmacological – trying to block the abnormal pain signals at their source or compensate for the poor regulation of pain signals. Some patients with RSD are also helped by sympathetic nerve blocks, which demonstrates, at least in these cases, that sympathetic dysregulation is also driving the pain, not just the skin symptoms.
The challenge with pain syndromes and research is that pain is entirely subjective. It is definitely a real neurological phenomenon, but it does not result directly in anything measurable, only reportable. There are some indirect measures of acute pain – like increased heart rate, but not for chronic pain.
When someone reports having pain, therefore, to some extent we have to take their word for it. This opens the door to two kinds of error in clinical decision making. The first is that we may over-treat pain because the patient is over-reporting their own pain, or they are interpreting as pain symptoms which are really due to anxiety, depression, stress or something else. There is, unfortunately, mixed in patients who are just drug-seeking for one reason or another.
The second kind of error the subjectivity of pain leads to is under-treating, because of the lack of hard physical signs to reassure practitioners they are treating the right thing. I find that the more experience practitiones have with pain treatment the less of a problem this is – because their confidence level is higher. It is mostly a problem for insurance companies who demand objective test results proving someone has a real syndrome – which of course do not exist for many pain syndromes, like migraines and neuropathic pain.
RSD is often less challenging diagnostically because there are specific hard clinical findings – the edema and skin changes. Problems occur, however, with overdiagnosis when people rely upon only the non-specific symptoms (like pain) to make a specific diagnosis (like RSD) even though the specific symptoms are absent.
Over reliance on non-specific symptoms is a common problem in proper diagnosis, and is primarily what leads to the creation of fake medical syndromes (like candida hypersensitivity) or the over diagnosis of uncommon but popular syndromes (like chronic fatigue syndrome). In order to be confident that a diagnosis is real and present you need either specific signs and symptoms or hard laboratory findings for confirmation. If all you have is a collection of vague, common, and non-specific symptoms you cannot reliably invoke a specific diagnosis as an explanation.
In conclusion, RSD is a specific type of neuropathic pain syndrome that is quite real. It is moderately overdiagnosed in my experience, but usually it is misapplied to a real neuropathic pain syndrome that lacks the specific symptoms of RSD. It is not typically applied (at least not by professionals) to psychogenic pain syndromes.
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