POST-TRAUMATIC PAIN AND THE CAUSALGIC SYNDROME

Reflex sympathetic dystrophy following nail biopsy

Reflex sympathetic dystrophy following a nail unit biopsy in a patient with long-standing, mycologically negative onychomycosis is reported. The significance of this complication is discussed, and the literature on the condition itself is reviewed. It is suggested that although adverse effects occur as a result of nail biopsy, they are infrequent and therefore should not dissuade the clinician from performing the procedure. Biopsy is necessary in order to establish a more accurate diagnosis of nail disease and thus administer more appropriate and effective therapy.

A hypothesis on the physiological basis for causalgia and related pains

A hypothesis is presented concerning the neuronal mechanisms which subserve the sympathetically maintained pains such as causalgia and reflex sympathetic dystrophy. The hypothesis rests on two assumptions: that a high rate of firing in spinal wide-dynamic-range (WDR) or multireceptive neurons results in painful sensations; and that nociceptor responses associated with trauma can produce long-term sensitization of WDR neurons. The hypothesis states that chronic sympathetically maintained pains are mediated by activity in low-threshold, myelinated mechanoreceptors, that this afferent activity results from sympathetic efferent actions upon the receptors or upon afferent fibers ending in a neuroma and that these afferent fibers evoke sufficient activity in sensitized spinal WDR neurons to produce a painful sensation. This hypothesis is based on known characteristics of these neuronal populations studied in experimental animals and on the observed sensory disturbances reported in patients successfully treated with sympathetic blocks. This hypothesis does not require nerve injury or dystrophic tissue. It explains both the continuous pain and the allodynia that are common to these syndromes and their abolition by sympathetic block. Specific changes are proposed in the diagnosis and treatment of post-traumatic pains.

Acute painful diabetic neuropathy precipitated by strict glycaemic control

A case of acute painful diabetic neuropathy that followed the establishment of strict glycaemic control using continuous subcutaneous insulin infusion is described. Sural nerve biopsy shortly after the onset of the acute painful syndrome showed no evidence of active nerve fibre degeneration; instead, the appearances were those of a chronic neuropathy with prominent regenerative activity. The suggestion is made that adequate diabetic control promoted regeneration and that the pain may have been related to the ectopic generation of impulses in regenerating axon sprouts.

Postsympathectomy pain and changes in sensory neuropeptides: towards an animal model

Postsympathectomy limb pain, postsympathectomy parotid pain, and Raeder's paratrigeminal syndrome are pain states associated with the loss of sympathetic fibres and in particular with postganglionic sympathetic lesions. There is a characteristic interval of about 10 days between surgical sympathectomy and onset of pain. It is proposed that this pain in man is correlated with the delayed rise in sensory neuropeptides seen in rodents after sympathectomy. These chemical changes probably reflect the sprouting of sensory fibres and may result from the greater availability of nerve growth factor after sympathectomy. The balance between the sensory and sympathetic innervations of a peripheral organ may be determined by competition for a limited supply of nerve growth factor.

The use of three-phase radionuclide bone scanning in the diagnosis of reflex sympathetic dystrophy

One hundred forty-five consecutive three-phase radionuclide bone scans were reviewed. One hundred two of these were performed to evaluate pain in the hand. Of these, 23 patients clinically had reflex sympathetic dystrophy (RSD). The hand scans were performed by the three-phase technique. Phase I is a radionuclide angiogram. Phase II is the blood pool or tissue phase. Phase III consists of delayed images obtained 3 to 4 hours after radionuclide injection. Detailed analysis of the 145 three-phase radionuclide bone scans of the hand demonstrated that the diffuse increased tracer uptake in the delayed image (phase III) is diagnostic for RSD, with a sensitivity of 96% and a specificity of 98%. The two early phases (radionuclide angiogram and blood pool) were positive in only 45% and 52% of the RSD patients, respectively. The strictly interpreted delayed radionuclide image is extremely sensitive in the diagnosis of RSD and will facilitate the early diagnosis and subsequent treatment of this syndrome.

Phenoxybenzamine in the treatment of causalgia. Report of 40 cases

Forty consecutive cases of causalgia treated during a 7-year period are presented. The patients ranged in age between 17 and 55 years, and all patients were males who received their nerve injuries from missile or shrapnel wounds. The greater occipital nerve was involved in two cases, median nerve in 10, sciatic nerve in 12, brachial plexus in seven, cauda equina in five, and multiple nerves in four cases. Each patient was treated with phenoxybenzamine, a postsynaptic alpha 1-blocker and presynaptic alpha 2-blocking agent. The drug was given orally in gradually increasing increments until a maximum daily dose of 40 to 120 mg was reached. Duration of treatment was usually 6 to 8 weeks. Total resolution of pain was achieved in all cases. The follow-up period ranged between 6 months and 6 years. Side effects of phenoxybenzamine were minimal and transient, consisting primarily of mild orthostatic hypotension and ejaculatory problems. We conclude that oral phenoxybenzamine is a simple, safe, and effective treatment of causalgia.

Causalgic pain relieved by prolonged procaine amide sympathetic blockade. Case report

Reversible sympathetic blocks diagnostically relieve causalgic pain. At times, repeated blocks may be therapeutic. Causalgic pain of the left hand was successfully treated in a nonsurgical candidate by a continuous infusion of local anesthetic (procaine) into the region of the stellate ganglion. This technique was performed without significant complication and gave relief from the causalgia for extended periods of time. It may provide an effective alternative to surgical sympathectomy in high-risk patients.

Acquired oculomotor synkinesis

Paradoxical patterns of pupillary, lid and eye movement may follow oculomotor nerve palsy or they can develop spontaneously in patients with no known history of oculomotor palsy. The mechanism of this condition, known variously as aberrant regeneration of the third nerve, oculomotor misdirection or acquired oculomotor synkinesis, is not known, although the prevailing opinion has held that it occurs when axons regenerating within an oculomotor nerve become misdirected and innervate muscles for which they were not intended. However, there is evidence against this hypothesis. The authors critically review the various hypotheses and elucidate the controversy concerning the pathogenesis of acquired oculomotor synkinesis.

The treatment of upper extremity reflex sympathetic dystrophy with prolonged continuous stellate ganglion blockade

Twenty-nine consecutively treated patients over a 5-year period with upper extremity reflex sympathetic dystrophy were admitted to Massachusetts General Hospital for prolonged continuous stellate ganglion blockade. Diagnosis was based on the presence of pain, decreased joint motion, trophic changes, and vasomotor disturbances. Selection for blockade was made on the failure to improve with outpatient physical therapy, tranquilizers, and mild analgesics. Treatment consisted of indwelling-catheter injections of bupivacaine hydrochloride every eight hours to the stellate ganglion for an average of 7 days, supplemented with vigorous physical therapy. Improvement during treatment was documented in all but two patients with regard to pain and decreased joint motion and in two-thirds with regard to trophic and vasomotor changes. Long-term follow-up demonstrated a relapse rate of 25%, but marked improvement persisted in the rest and normal status was attained in four of 26 patients at an average of 3 years later.

Nerve pathophysiology and mechanisms of pain in causalgia

In contrast to sensory endings in skin, muscle, etc., afferents in the mid-course of intact nerves are normally incapable of generating impulses upon slow or prolonged depolarization. However, after various types of nerve injury, including complete nerve section and local demyelination, an ectopic pacemaker capability develops. One peculiarity of such abnormal differentiated sites is chemosensitivity to alpha-adrenergic agonists and to sympathetic efferents discharge. Such ectopic chemosensitivity may well be involved in the etiology of paraesthesias and pain in reflex sympathetic dystrophies including causalgia. Specifically, it is proposed that the fundamental cause of these conditions is the development of abnormal electrogenic membrane properties in the region of demyelination and sprout outgrowth. These abnormal properties presumably include the appearance of excess inward current conductances and ectopic alpha-adrenergic receptors. Catecholamines released from sympathetic efferents in the area of injury locally depolarize damaged sensory fibers, and because of the abnormal electrogenic properties of these fibers, an abnormal afferent discharge is generated.

Behavioral test of tolerance for aversive mechanical stimuli in sympathectomized cats

Cats were studied behaviorally to determine their suitability as an animal model for the post-sympathectomy hyperalgesia reported to occur in humans. For this study a device and methodology were developed which allow humane testing of tolerance for intense mechanical stimulation of the hindlegs. Behavioral tolerance was measured quantitatively before and after unilateral sympathectomy. The results from this preliminary study of 6 cats are remarkably similar to those reported for humans; 1 of the 6 cats showed a decreased tolerance on the sympathectomized side which was delayed in onset and of limited duration. The new methodology appears to provide relatively stable, quantitative measures of tolerance for aversive stimulation, and the cat shows promise as an animal model for post-sympathectomy hyperalgesia.

Causalgia: redefinition as a clinical pain syndrome

In this report, the following criteria were used for the diagnosis of causalgia: (a) the presence of continuous, burning pain distal to a site of injury; (b) hyperalgesia and allodynia in the painful area; and (c) a traumatic event occurring proximal in the painful area and within weeks prior to the onset of pain. The McGill pain questionnaire was used to test the selected pain population for homogeneity. The scores were similar among the patients and different from the scores in other pain syndromes. It is concluded that the above criteria are sufficient to make the diagnosis of causalgia. In addition, it appears that a central nervous system abnormality best accounts for the clinical features of causalgia.

The treatment of Sudeck's atrophy in the upper limb by sympathetic blockade

The incidence of Sudeck's atrophy as a sequel to injury in the upper limb has been estimated in relation to casualty attendances in a 3-year period. Seventeen patients were treated at varying intervals after the onset of the condition either by stellate ganglion block or by regional intravenous guanethidine. The results are compared and the advantages of each method are discussed.

Autotomy following peripheral nerve lesions: experimental anaesthesia dolorosa

(1) When hindlimb peripheral nerves are cut across in rats and mice, there is a tendency for the animal to attack the anaesthetic limb. We have called this attack "autotomy". In this paper we describe the time course and degree of autotomy following various types of nerve injury. (2) Four different types of lesion were applied to the sciatic nerve of rats. The most serious autotomy was produced by section of the nerve and encapsulation of its cut end in a polythene tube. Section followed by immediate resuturing also produced serious autotomy. Simple ligation of the nerve end was followed by less autotomy than encapsulation or cut and resuture. A crush lesion caused only minimal attack. (3) Section of the saphenous branch of the femoral nerve produced no autotomy. However, if the saphenous and sciatic nerves were ligated at the same time so that the entire foot became anaesthetic there was a great increase of autotomy over that seen when the sciatic nerve alone was ligated. This increase with the double lesion occurred even if the saphenous nerve was ligated more than 100 days after the sciatic nerve had been cut. (4) Mice showed autotomy very similar to that seen in rats but the onset was somewhat faster. (5) Reasons are given to propose that autotomy is triggered by an abnormal afferent barrage generated in the cut end of the nerve. Autotomy from peripheral nerve lesions is a different phenomenon from that seen after dorsal root section. Autotomy occurs under conditions which produce anaesthesia dolorosa in man. This simple model may be suitable for studies of the prevention of irritations originating from chronic lesions of peripheral nerves.

Painful peripheral states and sympathetic blocks

In various chronic painful states, the sympathetic nerve supply was blocked either by injecting the sympathetic chain and ganglia with local anaesthesia or by the injection of guanethidine during occlusion of the circulation. There was a striking relation between the presence of hyperpathia and the relief of pain by the blocks. The sympathetic block was unlikely to relieve the pain unless hyperpathia accompanied the pain; when hyperpathia was present, a sympathetic block relieved both the constant pain and the hyperpathia. The effectiveness of the guanethidine blocks shows that the pain and the hyperpathia are maintained by the emission of noradrenaline in the periphery. The facts related to the sympathetic system and sensibility are discussed.

Ectopic generation of impulses and cross-talk in spinal nerve roots of "dystrophic" mice

In "dystrophic" mice, many spinal root axons are bare and closely apposed to one another in midroot. The direction of nerve impulse traffic in lubosacral spinal nerve roots was determined by biphasic recording of spontaneous activity. In normal mice, impulse traffic in dorsal and ventral roots is directed toward and away from the spinal cord, respectively. However, in spinal root fibers of dystrophic mice, impulses also originate in midroot and are propagated toward both the spinal cord and the periphery. Impulses originate in midroot as single isolated events, in bursts at frequencies of up to 100 Hz, or as continuous activity persisting for several minutes in single fibers. Ectopically arising activity in some single fibers is consistently associated with transmission of an impulse in another fiber past the site of origin of the ectopically arising impulse. Thus impulses arise in the spinal root axons of dystrophic mice both spontaneously and as a result of cross-talk between single fibers.

Pain mechanisma in causalgia

A study of the clinical features of causalgia and the central neuronal effects of injuries to peripheral nerves suggests that causalgia is the functional expression of the intensity of the retrograde neuronal reaction in which pools of dorsal horn neurones become converted into foci of abnormal activity. These foci initiate a chain reaction along transmission pathways as far centrally as the cortex, causalgia being the terminal effect of this disorderly activity on the sensorium. This is the basis of the 'turbulance hypothesis' introduced to account for the pain.