Reflex Sympathetic Dystrophy: An Introduction

Originally described by civil war surgeons causalgia remains a baffling medical problem even to this day.

Reflex Sympathetic Dystrophy (RSD) is a fascinating neuropathic pain syndrome usually involving an extremity or part thereof. Originally described by army surgeons during the Civil War it most commonly presented within days of a trivial or relatively mild injury to the shoulder resulting mild nerve damage to the brachial plexus.  This nerve injury is often not appreciable macroscopically.  Instead of doing well these patients complained of burning pain in their arms associated with swelling, warmth and redness. Over time the symptoms would change with the red, warm swollen arm turning into a cold, withered one, which would alternately be pale, white or blue. The arm would become intensely sensitive to touch such that some of the patients were unable to tolerate the weight of clothing on the limb. The syndrome was labeled causalgia although today it is more commonly referred to as complex regional pain syndrome or CRPS.

After 30 years in medicine I have managed to figure out that the more names a syndrome has, the less well it is understood and this appears to be true with RSD. We understand a little more than the civil war surgeons did, but still not much. Firstly we understand that the reason that causalgia had never been described before is that the Civil War was the first major conflict in which large numbers of soldiers were using modern rifles (technically rifled muskets) as opposed to old smooth bore muskets. In a rifled musket spiraling channels are cut into the bore of the musket, which causes the ball (or in modern rifles the bullet) to spin. This spin allows for much higher muzzle velocities without a loss of accuracy. The higher velocity projectiles had much greater kinetic energies and were therefore capable of causing much greater tissue damage. With old smooth bore muskets the balls were traveling slowing enough that they only damaged tissues that they penetrated directly, whereas the new higher velocity projectiles created an expanding cone of shock waves that were capable of damaging tissue at some distance from the path of the bullets. It turns out that all of the cases of causalgia from the Civil War were caused by these new rifled muskets and although the bullets passed through the neck or shoulder of the soldier the shock waves would cause damage to the cervical roots or brachial plexus, which was often not obvious even on direct inspection.

Although relatively few of the cases of CRPS that we see today involve bullet wounds, there is still usually a partial injury to a spinal nerve root or a peripheral nerve. In cases of severe injury nerves totally cease to function resulting in an extremity which is insensate but not painful. However, in cases of partial injury the patient may have altered sensation, often reporting normally innocuous stimuli as painful (allodynia) as well as the vascular changes mentioned above. The exact mechanisms by which these changes occur are at present not understood.

The treatment of RSD remains challenging. In early cases the patient may respond to antiepileptic medication such as gabapentin or a series of sympathetic nerve blocks. When the disease process is well established most forms of therapy are ineffective. Some patients will respond to stimulation. Depending on the location and the severity of the symptoms this might involve a TENS unit or require spinal cord stimulation (SCS).

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