(CRPS 2)

Complex Regional Pain Syndromes type 1 and 2 represent regional pain disorders not limited to the site of injury, with the following features:

1. Pain greater than might be expected from the original injury
2. Altered blood flow, localized edema, skin and hair changes
3. The pain itself may be burning or electrical in nature and is usually non-dermatomal due to hyperalgesia. Allodynia is often present.

The distinction between CRPS 1 and CRPS 2 is made by the specific neural mechanism of injury. CRPS 1 patients have the involvement of the Sympathetic Nervous System, while CRPS 2 patients have involvement of a specific injured Nerve. Both syndromes exhibit pain beyond the distribution of the original injury.

CRPS 2 patients were formerly diagnosed with Causalgia. This was not a descriptive nosology, because it did not reflect the spread of the symptoms beyond the location of the original injury. The current terminology was developed in 1994 by the International Association for the Study of Pain (IASP). Typically CRPS 2 patients are often misdiagnosed with psychogenic pain disorders because of the non-dermatomal nature of their pain and the severe psychological distress it engenders.

The non-dermatomal pattern is due to the pathophysiology of hyperesthesia. This occurs due to sensitization of collateral nerves caused by local sodium channel hyperactivity. Additionally there is sensitization of the Dorsal Horn Nuclei via the displacement of Magnesium, which controls NMDA receptor responsiveness to glutamate, an extremely fast neurotransmitter. This results in wind-up pain and sensitivity of Dorsal Horn ganglia to normally non-Nociceptive touch fibers.

On an anatomical basis, severed axons and damaged axons form new sprouts known as microneuromas. These are hyperexcitable and within minutes to days after injury begin ectopic firing. Intact collateral nerves also develop ectopia and this spreads the area of pain. Normally non-painful touch fibers join in the excessive stimulation, initially creating paresthesias, but with central sensitization, allodynia develops and spreads to non-dermatomal sites.

Mobilization is not particularly helpful with CRPS 2 lesions and usually increases pain and dysfunction. Pain control with anticonvulsants (Gabapentin, Carbemazepine, Lamotrigine, Topramax), Tricyclic Analgesics (Nortriptyline, Desipramine, Amitriptyline), Long Acting Opioids (MS Contin, Oramorph, Kadian, OxyContin, Duragesic, Methadone), Alpha 1 Blockers (Phenoxybenzamine, Terazocin), Alpha 2 agonists (Clonidine), Sodium Channel Blockers (LIdocaine, Mexilletine, Amantadine, Ketamine) and NMDA antagonists (Ketamine, Methadone, Propoxyphene) may help individually or in combination. Selective nerve root blocks, Neuroma blocks and epidural blocks may be helpful. Spinal Cord Stimulators can be quite effective. For particularly unyielding and severe malignant pain, cordotomy, cingulotomy or other neuroablative procedures may be useful.