Here are some of the differences between complex regional pain syndrome I (RSD) and complex regional pain syndrome II (causalgia):

CRPS I

• Sympathetic hyperactivity due to trauma to an extremity, such as a fracture, that doesn’t include direct trauma to a peripheral nerve.
• Usually involves the distal part of the extremity and occurs all around the limb.
• Involves probably the peripheral nervous center and possibly the central nervous syndrome.
• Onset is usually a few weeks after the injury.
• The pain is described as a burning pain made worse by movement or touching the skin.
• Increased temperature of the skin and increased sweating. There is decreased sympathetic variability and increased swelling.
• Later, skin constricts and there is vasoconstriction with a cold extremity.
• Later, there is atrophy of the skin, soft tissue and bone. Hair fails to grow and nails grow slowly.
• X-ray shows atrophy and osteoporosis of bone.
• Persists indefinitely if not treated.
• Sympathetic block and physical therapy seem to help.
• Complications include disuse atrophy, suicide and drug abuse.
• Patients can suffer from depression and social fears.

CRPS II

• Burning pain, hyperpathia or allodynia of an extremity following a direct nerve injury.
• Can simply be symptomatic near the injury but not the extremity all around
• Usually involves the median nerve, the tibial nerve, the ulnar nerve and the sciatic nerve.
• Can occur immediately following the injury or months later.
• Constant burning pain made worse by light touch, movement, change in exercise and stress.
• Atrophy of the appendages, atrophy of bones, joints and muscles.
• Cool, clammy skin that is red in color and sweaty; there is lack of sensation and motor skills in the area innervated by the damaged nerve.
• Sounds or bright lights can trigger burning pain.
• Signs of hyperactivity of the sympathetic nervous system as found by galvanic skin testing and plethysmography.
• Usually, there is no spontaneous remission if not treated but spontaneous remission is possible.
• Sympathetic block done several times along with physical therapy can lead to permanent relief.
• Risk of suicide and drug abuse if left untreated.
• Peripheral and central nervous system involved in an unknown way.
• The nerve damage is usually just partial.

Differential Diagnosis of CRPS-I vs. CRPS-II

CRPS I

Etiology – Any trauma
Localization – Distal extremities
Spread of Symptoms – Obligatory
Spontaneous pain – Common, usually deep
Mechanical Allodynia – Most patients
Autonomic symptoms – Seen distally and spreading
Motor symptoms – Distally and generalized
Sensory symptoms – Distally and generalized

CRPS II

Etiology – Partial nerve lesion
Localization – Along the route of a nerve
Spread of Symptoms – Rare
Spontaneous pain – Obligatory, usually superficial
Mechanical Allodynia – All patients along nerve distribution
Autonomic symptoms – In nerve distribution
Motor symptoms – In nerve distribution
Sensory symptoms – In nerve distribution