This painful response to injury of the shoulder, arm, or leg, is usually the result of an incomplete nerve injury. It consists of protracted pain, characteristically described as “burning,” together with cyanosis or pallor, swelling, coldness, pain on passive motion, osteoporosis, and marked sensitivity of the affected part to tactile stimulation. The condition has been variously described under such terms as Sudeck atrophy, posttraumatic osteoporosis (in which case the bone scan may show increased local uptake of radioactive nuclide), and the related shoulder–hand syndrome. The current term is complex regional pain syndrome. When the pain syndrome occurs in isolation, it is referred to as causalgia. Pharmacologic or surgical sympathectomy appears to relieve the symptoms in some patients. In others with a hypersensitivity of both C-fiber receptors and postganglionic sympathetic fibers, it is not helpful. Chapter 8 discusses this subject further.
Persistent and often incapacitating pain and dysesthesias may follow any type of injury that leads to partial or complete interruption of a nerve, with subsequent neuroma formation or intraneural scarring—fracture, contusion of the limbs, compression from lying on the arm while intoxicated, severing of sensory nerves in the course of surgical operations or biopsy of nerve, or incomplete regeneration after nerve suture. It is stated that the nerves in these cases contain a preponderance of unmyelinated C fibers and a reduced number of A-c fibers; this imbalance is presumably related to the genesis of painful dysesthesias. These cases are best managed by complete excision of the neuromas with end-to-end suture of healthy nerve, but not all cases lend themselves to this procedure.
Another special type of neuroma is the one that forms at the end of a nerve severed at amputation (stump neuroma). Pain from this source is occasionally abolished by relatively simple procedures such as injection of lidocaine, resection of the distal neuroma, proximal neurotomy, or resection of the regional sympathetic ganglia. More common in clinical practice is the mundane, but painful, Morton neuroma, usually found on the plantar nerve between the third and fourth metatarsal bones. Pain on compression of the forefoot is the characteristic Mulder sign.
This rare disorder of the microvasculature produces a burning pain and bright red color change, usually in the toes and forefoot and sometimes in the hands, precipitated by changes in ambient temperature. Since its first description by Weir Mitchell in 1878, many articles have been written about it, and recently the cause of a primary familial form was traced to a mutation in a sodium channel protein. Each patient has a temperature threshold above which symptoms appear and the feet become bright red, warm, and painful. The afflicted patient rarely wears stockings or regular shoes because these tend to bring out the symptoms. The pain is relieved by walking on a cold surface or soaking the feet in ice water and by rest and elevation of the legs. The peripheral pulses are intact, and there are no motor, sensory, or reflex changes. The reviews by Michiels and by Layzer are recommended.
Most cases are idiopathic, some familial and inherited as a dominant trait. There are secondary forms of the disease, the most important one being that associated with essential thrombocythemia (up to 25 percent of patients may have erythromelalgia as the first symptom) but also with other myeloproliferative disorders such as polycythemia vera and with collagen vascular diseases, including thrombotic thrombocytopenic purpura (TTP), during the use of calcium channel blockers and certain dopaminergic agonists such as pergolide and bromocriptine, and with occlusive vascular diseases. Some instances arise as a result of a painful polyneuropathy that predominantly affects the small sensory fibers; more often in these latter conditions, the redness and warmth are constant and the result of damage to sympathetic nerve fibers; see