POST-TRAUMATIC PAIN AND THE CAUSALGIC SYNDROME

George Chance and Frank Holdsworth: Understanding Spinal Instability and the Evolution of Modern Spine Injury Classification Systems

The concept of spinal cord injury has existed since the earliest human civilizations, with the earliest documented cases dating back to 3000 BC under the Egyptian Empire. Howevr, an understanding of this field developed slowly, with real advancements not emerging until the 20th century. Technological advancements including the dawn of modern warfare producing mass human casualties instigated revolutionary advancement in the field of spine injury and its management. Spine surgeons today encounter "Chance" and "Holdsworth" fractures commonly; however, neurosurgical literature has not explored the history of these physicians and their groundbreaking contributions to the modern understanding of spine injury. A literature search using a historical database, Cochrane, Google Scholar, and PubMed was performed. As needed, hospitals and native universities were contacted to add their original contributions to the literature. George Quentin Chance, a Manchester-based British physician, is well known to many as an eminent radiologist of his time who described the eponymous fracture in 1948. Sir Frank Wild Holdsworth (1904-1969), a renowned British orthopedic surgeon who laid a solid foundation for rehabilitation of spinal injuries under the aegis of the Miners' Welfare Commission, described in detail the management of thoraco-lumbar junctional rotational fracture. The work of these 2 men laid the foundation for today's understanding of spinal instability, which is central to modern spine injury classification and management algorithms. This historical vignette will explore the academic legacies of Sir Frank Wild Holdsworth and George Quentin Chance, and the evolution of spinal instability and spine injury classification systems that ensued from their work.

Allergy/hypersensitivity reactions as a predisposing factor to complex regional pain syndrome I in orthopedic patients

Several predisposing conditions have been associated with complex regional pain syndrome I (CRPS I). The purpose of this study was to determine the relationship between a history of allergy/hypersensitivity reactions and CRPS I in orthopedic patients. Orthopedic patients with CRPS I (n=115) who experienced pain relief after a successful sympathetic nerve blockade were identified for study inclusion; a control group (n=115) matched to the CRPS I group by age, sex, and location of injury was also included. All patients in the study had an average age of 42 years. In the CRPS I group, all participants were Caucasian and the majority (80.8%) were women. The skin of patients with CRPS I was described as fair (57.7%), mottled (57.7%), or sensitive (80.8%). Of the patients with CRPS I, 78 (67.8%) reported a statistically significant history of allergies compared with the 39 (33.9%) patients in the control group (P<.0001). Patients with CRPS I who experienced complete pain relief for at least 1 month following a single sympathetic nerve block were asked to answer a questionnaire (n=35), and some then underwent immediate hypersensitivity testing using a skin puncture technique (n=26). Skin hypersensitivity testing yielded an 83.3% positive predictive value with an accuracy of 76.9%. Based on these results, a positive history for allergy/hypersensitivity reactions is a predisposing condition for CRPS I in this subset of orthopedic patients. These hypersensitivity reactions may prove important in gaining a better understanding in the pathophysiology of CRPS I as a regional pain syndrome.

Symptomatic postsurgical traumatic neuromas

HYPOTHESIS

Growing nerve fibers from the stumps of amputated sensory nerves can form traumatic neuromas within inner or middle ear postsurgical fibrosis and may produce symptoms commensurate with the normal function of the nerve involved, that is, balance or pain.

BACKGROUND

Microscopic traumatic neuromas have been identified in postoperative middle and inner ear fibrosis in the temporal bones of patients complaining of intractable pain or imbalance.

METHODS

Postsurgical temporal bones having inner or middle ear traumatic neuromas were reviewed. Of 20 bones with inner ear fibrosis after a variety of neurotologic surgeries, 12 were found to have traumatic neuromas, most from the utricular nerve or lateral canal. Five ears in 4 patients with middle ear fibrosis after chronic ear surgery had traumatic neuromas arising from Jacobson nerve. An additional 58 bones from chronic ear surgery patients with no neuromas served as a control group. Neurofilament immunohistochemistry labeling substantiated the presence of nerve fibers. Clinical symptoms noted from the clinical records were compared between those with and without traumatic neuromas.

RESULTS

Of the 12 patients (75%), 9 with inner ear traumatic neuromas clinically reported constant disequilibrium postsurgery lasting for years. None (0%) without neuromas reported new symptoms postoperatively (p <or= 0.001). All 5 ears with middle ear traumatic neuromas experienced otalgia postsurgery, whereas none of the other 58 patients with no neuroma reported this problem.

CONCLUSION

Postoperative intractable disequilibrium or pain may occur as a result of the formation of traumatic neuromas in scar tissue in the inner or middle ears.

Effect of spinal cord stimulation in Type I complex regional pain syndrome with 2 rare severe cutaneous manifestations

The authors present the case of a 49-year-old female patient with complex regional pain syndrome-Type I (CRPSI) who was suffering from nonhealing wounds and giant bullae, which dramatically improved after spinal cord stimulation (SCS). The scientific literature concerning severe cutaneous manifestations of CRPS-I and their treatment is reviewed. Nonhealing wounds and bullae are rare manifestations of CRPS-I that are extremely difficult to treat. Immediate improvement of both wounds and bullae after SCS, such as in this case, has not been reported previously in literature. Considering the rapidly progressive nature of these severe skin manifestations, immediate treatment, possibly with SCS, is mandatory.

Intravenous Regional Block With Lidocaine for Treatment of Complex Regional Pain Syndrome

OBJECTIVES

The goal of this article is to report the successful treatment of a patient with complex regional pain syndrome (CRPS) type 1 involving the hand with the use of an intravenous regional block.

METHODS

The patient was a 35-year-old woman who developed CRPS during conservative therapy for a metacarpal fracture. An intravenous regional block with lidocaine alone, using a two-tourniquet technique, was delivered 10 times for at least 40 minutes. The first five treatments were given twice a week and the next five were delivered weekly. All affected joints, including the wrist, were manipulated without undue force. Functional physical measurements were assessed, including range of motion and performance of fine and gross motor tasks.

RESULTS

The visual analog scale scores for pain declined from 10 to 0 after treatment. Use of a pen, a pair of chopsticks, and a hammer improved, and edema decreased.

CONCLUSIONS

Intravenous regional block with lidocaine was well tolerated and associated with relief in this case of CRPS type 1.

Severity and duration of hyperalgesia in rat varies with type of nerve lesion

OBJECTIVE

To learn how lesions with differing capacity for nerve regeneration affect the severity and duration of hyperalgesia in an animal model of neuropathic pain.

METHODS

Three groups of rats were studied: 1). L5 nerve root crush (favorable for regeneration); 2). L5 root ligation and section; and 3). sham-operated group. An experimenter who did not know the rats' groups tested the animals for hyperalgesia to mechanical and cold stimuli.

RESULTS

Measures of adverseness of mechanical and cooling stimuli for the crush group and ligation/cut groups were significantly higher than for the sham-operated group (P < 0.001 for both) for the first 30 days after lesioning. By 40 days, the crush group recovered from mechanical hyperalgesia, whereas the ligation/cut group continued to have significant hyperalgesia. At this time, both lesion groups displayed hyperalgesia to the cooling stimulus (P < 0.001), but the hyperalgesia in the ligation/cut group was significantly greater (P < 0.01). No recovery from cooling hyperalgesia was evident during the 54-day period of observation. Histological studies of the sciatic nerve indicated higher numbers of regenerating fibers in the crush group compared with the ligation/cut group.

CONCLUSION

This study demonstrates that axotomy, regardless of how it is induced, produces hyperalgesia to both mechanical and cold stimuli. However, the lesion that favors regeneration is associated with earlier signs of recovery from mechanical hyperalgesia and less severe signs of cooling hyperalgesia. The data support the hypothesis that inputs from the injured afferents play an ongoing role in neuropathic pain from nerve injury. Nerve ligation induces more severe and more sustained behavioral signs of pain than nerve crush.

Sympathectomy for complex regional pain syndrome

BACKGROUND

With the easier and earlier recognition of complex regional pain syndrome (CRPS), a reappraisal of its therapy, particularly the role and timing of sympathectomy, is warranted.

PATIENTS AND METHODS

Over a 9-year period, 42 patients with CRPS type II of the upper extremity were referred for sympathectomy. Patients were categorized according to the duration of the symptoms (group I, <3 months; group II, >3 months). All patients underwent initial medical treatment; stellate ganglion blocks were performed when symptoms persisted beyond 6 weeks. Patients were referred for thoracoscopic sympathectomy on persistence of the pain syndrome. A visual linear analogue scale was used to evaluate outcome of sympathectomy.

RESULTS

Thoracoscopic dorsal sympathectomy was successfully undertaken in 32 patients. In the remaining 10 patients, thoracoscopy was not technically feasible and open sympathectomy was performed. There was an overall improvement in all 42 patients undergoing sympathectomy (P <.001, Wilcoxon signed rank test). The outcome in group I was significantly better than in group II (P <.003, Mann-Whitney U test). The diagnosis of sympathetically mediated pain with stellate blockade did not correlate with clinical outcome. Patients undergoing thoracoscopic sympathectomy had a better outcome than those undergoing open sympathectomy. There were no complications, and the hospital stay was shorter in the thoracoscopic group.

CONCLUSION

Early recognition of CRPS and prompt recourse to surgical sympathectomy is a useful option in the management of CRPS.

Complex Regional Pain Syndrome in the ambulatory surgical care setting

This article provides an historical synopsis from the 17th century to the present regarding the disease process known as Complex Regional Pain Syndrome (CRPS) Type I. An overview of the disease symptoms, plausible theories, and a review of the pain cycle, relief measures, and a case scenario are reported. The focus of pain blockade was chosen because this was the intervention used in this particular case. The author presents the holistic standpoint of the importance of incorporating complementary alternative medical practices (CAMP) to enhance a positive outcome for this client.

OBJECTIVES

-Based on the content of this article, the reader should be able to (1) distinguish the main characteristic between CRPS Type I (reflex sympathetic dystrophy) and CRPS Type II (causalgia); (2) identify symptoms related to CRPS Type I; and (3) identify the stages of CRPS and state potential interventions used in the treatment of CRPS Type I.

Complex regional pain syndrome: a report of two cases recalcitrant to usual treatment protocols

In this report the authors present a review of complex regional pain syndrome and two case reports of complex regional pain syndrome that were recalcitrant to the usual treatments. The first case presented is a middle-aged female who developed signs and symptoms of post-traumatic complex regional pain syndrome. The second case is a woman with a pre-existing history of complex regional pain syndrome whose condition worsened after surgery despite appropriate perioperative precautions. These cases are unique because in both cases an early diagnosis of complex regional pain syndrome was established, yet they were both resistant to the usual treatment protocols.

Uninjured C-fiber nociceptors develop spontaneous activity and alpha-adrenergic sensitivity following L6 spinal nerve ligation in monkey

We investigated whether uninjured cutaneous C-fiber nociceptors in primates develop abnormal responses after partial denervation of the skin. Partial denervation was induced by tightly ligating spinal nerve L6 that innervates the dorsum of the foot. Using an in vitro skin-nerve preparation, we recorded from uninjured single afferent nerve fibers in the superficial peroneal nerve. Recordings were made from 32 C-fiber nociceptors 2-3 wk after ligation and from 29 C-fiber nociceptors in control animals. Phenylephrine, a selective alpha1-adrenergic agonist, and UK14304 (UK), a selective alpha2-adrenergic agonist, were applied to the receptive field for 5 min in increasing concentrations from 0.1 to 100 microM. Nociceptors from in vitro control experiments were not significantly different from nociceptors recorded by us previously in in vivo experiments. In comparison to in vitro control animals, the afferents found in lesioned animals had 1) a significantly higher incidence of spontaneous activity, 2) a significantly higher incidence of response to phenylephrine, and 3) a higher incidence of response to UK. In lesioned animals, the peak response to phenylephrine was significantly greater than to UK, and the mechanical threshold of phenylephrine-sensitive afferents was significantly lower than for phenylephrine-insensitive afferents. Staining with protein gene product 9.5 revealed an approximately 55% reduction in the number of unmyelinated terminals in the epidermis of the lesioned limb compared with the contralateral limb. Thus uninjured cutaneous C-fiber nociceptors that innervate skin partially denervated by ligation of a spinal nerve acquire two abnormal properties: spontaneous activity and alpha-adrenergic sensitivity. These abnormalities in nociceptor function may contribute to neuropathic pain.

Evidence for immune system involvement in reflex sympathetic dystrophy

Skin biopsies from patients with reflex sympathetic dystrophy were immunostained using a variety of antisera. An incidental finding with S100 staining was the presence of numerous Langerhans cells in the epidermis. All patients had significant pain at the time of biopsy, and all had symptoms refractory to treatment. The potential implications of this finding are discussed.

Plasticity of the extracranial facial nerve

Although the expansion properties of peripheral nerves have been a matter of considerable study in recent years, investigations of the plasticity of cranial nerves, including the facial nerve, have been lacking. Clinicians, however, have long recognized the tenacity of facial nerve function in patients with slow-growing benign tumors that enormously distort the nerve. An experimental study was designed to assess whether tissue expansion techniques can be applied to the extracranial portion of the facial nerves of cats. In eight cats the frontozygomatic branch of the facial nerve was expanded by stages in seven sessions over a period of 40 days. The length of the nerve increased an average of 95% without significantly impairing nerve function. Pressure changes in the expander averaged 75 mm Hg during each stage of expansion. Electroneurography was performed after each injection of the expander. Statistical analysis of these data did not show consistent evidence of demyelination or denervation, and all but one cat exhibited a normal blink reflex and had normal electromyographic findings at the end of the experiment. Histologic examination of the expanded nerves, however, did show inflammatory changes, intraneural edema, and occasional demyelination.

Spinal cord stimulation for chronic pain in peripheral neuropathy

BACKGROUND

Spinal cord stimulation (SCS) has been used for the relief of chronic, intractable pain for over 2 decades. Recent technologic improvements in hardware have resulted in improved clinical outcome. We report our experience with epidural spinal cord stimulation for pain control of peripheral neuropathy for the past 15 years.

METHODS

An analysis of our series of 276 patients revealed 30 patients diagnosed with peripheral neuropathy. The mean age of the 16 men and 14 women in the study was 62.4 years. The anatomic sources of pain included thorax, as well as upper and lower limbs. Causes of intractable pain included postherpetic neuralgia, intercostal neuralgia, causalgic pain, diabetic neuropathy, and idiopathic neuropathy.

RESULTS

Nineteen patients reported relief of pain on trial stimulation and had their systems permanently implanted. At an average of 87 months' follow-up, 14 of these patients achieved long-term success in control of chronic pain (47% of all patients included in this study). Six patients reported excellent pain relief (> 75% pain relief), eight described good results (> 50% pain relief), and six had poor pain relief (< 50% pain relief).

CONCLUSION

SCS is an effective therapy for pain syndromes associated with peripheral neuropathy. Causalgic and diabetic neuropathic pain seem to respond relatively well. whereas postherpetic pain and intercostal neuralgia syndromes seem to respond less favorably to the long-term beneficial effects of SCS. This information will be useful in the selection of patients with peripheral neuropathic pain who could be helped by SCS.

"Gamekeeper's thumb" variant, complicated by reflex sympathetic dystropy

A case of gamekeeper's thumb resulting from a motor vehicle accident is presented. This injury was complicated by the onset of reflex sympathetic dystrophy. An overview of the presentation and management of these disorders, which may result in severe disability without prompt recognition and therapy, is submitted for discussion.

Reflex sympathetic dystrophy following arterial blood gas sampling in the intensive care setting

A 54-year-old woman developed signs and symptoms consistent with reflex sympathetic dystrophy in her left upper extremity following arterial puncture. Diagnosis was confirmed by bone scan, and sympathetic blockade with intravenous regional bretylium completely relieved her severe, intractable pain.

Reflex Sympathetic Dystrophy of the Knee

Reflex sympathetic dystrophy (RSD) of the knee frequently does not present with the classic combination of signs and symptoms seen in the upper extremity. Pain out of proportion to the initial injury is the hallmark symptom. Symptom relief by sympathetic block is the current standard for confirmation of the diagnosis. Because invasive diagnostic procedures, such as arthroscopy, are likely to increase symptoms, evaluation with a noninvasive diagnostic modality, such as magnetic resonance imaging, is preferred. Generally, RSD should be treated before surgical intervention to correct any underlying intra-articular pathologic condition. However, surgery may sometimes be necessary before RSD symptoms resolve; in these cases, use of intra- and postoperative continuous epidural block can be successful. The initial treatment of RSD of short duration should be conservative; physical therapy modalities, including exercise and contrast baths, and non-steroidal anti-inflammatory drugs are indicated. In the authors' experience, an indwelling epidural block using bupivacaine for several days followed by use of a narcotic agent, combined with functional rehabilitation, is the most effective management when noninvasive treatment has failed. Surgical sympathectomy can be successful, but should be reserved until repeated lumbar sympathetic block or more than one trial of inpatient epidural block has failed. Early diagnosis and early institution of treatment (prior to 6 months) are the most favorable prognostic indicators in the management of RSD.

The use of thermography in sympathetically maintained pain

This paper reviews the symptomatology, pathophysiology, and treatment of reflex sympathetic dystrophy and sympathetically maintained pain. It is the author's experience that there exists a group of patients who present with chronic, unexplained pain following trauma, but lack the physical findings and positive investigative tests to confirm the diagnosis of reflex sympathetic dystrophy. For these patients, thermography serves as a useful and sensitive test to diagnosis sympathetically maintained pain. This paper presents six case reports in which thermography was used to diagnosis sympathetic dysfunction as the cause of chronic pain.

Reflex sympathetic dystrophy after operative procedures on the lumbar spine

Between July 1987 and April 1991, reflex sympathetic dystrophy developed in eleven patients after a posterior operation on the lumbar spine. The average age of the patients was forty-four years (range, twenty-eight to sixty years). The preoperative diagnosis had been lumbar spondylolisthesis or lumbar instability, associated with degenerative disc disease or with osteoarthrosis of a facet joint. Ten patients had posterior stabilization with bilateral arthrodesis and interpedicular fixation, with use of plates or screws; the remaining patient had a posterior hemilaminotomy of the fourth and fifth lumbar vertebrae, partial discectomy, and foraminal decompression of the fifth lumbar-nerve root. After the operation, all patients had burning pain, vasomotor dysfunction, and dystrophic changes in the lower limb and foot; in four patients, the symptoms were bilateral. The symptoms began four days to twenty weeks after the operation. The patients were followed for nine months to four years. Treatment was most successful in four of six patients who had had at least one nerve-block of the sympathetic lumbar trunk in addition to physiotherapy.

Mechanical hyperalgesias in neuropathic pain patients: dynamic and static subtypes

Two behavioral kinds of mechanical hyperalgesia can be clearly discerned by clinical criteria in patients with neuropathic syndromes, i.e., a dynamic type, elicitable by lightly stroking the symptomatic skin, and a static type, elicitable by steadily applying gentle pressure on it. Of 28 patients studied, 19 had dynamic and 18 had static type mechanical hyperalgesia (9 expressed both types). Experimental compression-ischemia nerve block totally abolished the dynamic hyperalgesia in all patients except in 2, in whom it was markedly diminished. Disappearance of dynamic hyperalgesia occurred contemporaneously with block of myelinated A fibers, as expressed by abolition of the sensations of touch and cold, monitored quantitatively. Static hyperalgesia, however, outlasted A-fiber block in 15 of 18 patients; the phenomenon persisted during the stage when only unmyelinated fibers were available for impulse conduction. It is thus concluded that, at the primary afferent level, dynamic hyperalgesia is mediated by myelinated fibers, whereas static hyperalgesia depends on unmyelinated afferents. These two kinds of hyperalgesia represent discrete pathophysiological entities with distinct clinical connotations.

Psychological aspects of reflex sympathetic dystrophy: a review of the adult and paediatric literature

In 1864, W. Mitchell and colleagues first described the clinical syndrome which came to be known as 'causalgia'. Since that time, the concept of sympathetically related pain has evolved. There is general agreement that profound emotional and behavioural changes can follow these types of pain. Opinions have varied widely on the issue of a psychological etiology. It has often been suggested that certain personality traits predispose one to develop sympathetically related pain syndromes. A review of the literature reveals no valid evidence to substantiate this claim.

Psychophysiological contributions to phantom limbs

Recent studies of amputees reveal a remarkable diversity in the qualities of experiences that define the phantom limb, whether painless or painful. This paper selectively reviews evidence of peripheral, central and psychological processes that trigger or modulate a variety of phantom limb experiences. The data show that pain experienced prior to amputation may persist in the form of a somatosensory memory in the phantom limb. It is suggested that the length and size of the phantom limb may be a perceptual marker of the extent to which sensory input from the amputation stump have re-occupied deprived cortical regions originally subserving the amputated limb. A peripheral mechanism involving a sympathetic-efferent somatic-afferent cycle is presented to explain fluctuations in the intensity of paresthesias referred to the phantom limb. While phantom pain and other sensations are frequently triggered by thoughts and feelings, there is no evidence that the painful or painless phantom limb is a symptom of a psychological disorder. It is concluded that the experience of a phantom limb is determined by a complex interaction of inputs from the periphery and widespread regions of the brain subserving sensory, cognitive, and emotional processes.

Peripheral and central mechanisms of cutaneous hyperalgesia

Hyperalgesia after cutaneous injury can be divided into two phenomena: Primary hyperalgesia occurs at the site of injury and is characterized by hyperalgesia to mechanical and heat stimuli. Secondary hyperalgesia occurs outside the injury site and is characterized by mechanical hyperalgesia only. Hyperalgesia in inflammatory processes corresponds to primary hyperalgesia. Hyperalgesia in referred pain and neuropathic pain resembles secondary hyperalgesia (Table 3). Evidence for the latter would be strengthened if hyperalgesia to cooling stimuli, which is observed in neuropathic pain, was also demonstrated in referred pain and in secondary hyperalgesia. Some of the more likely neural mechanisms to explain primary and secondary hyperalgesia are illustrated in Fig. 8. Primary hyperalgesia to heat stimuli has a counterpart in the sensitization of peripheral nociceptors to heat stimuli (Fig. 8A), leading to similar changes in central neurons. In addition, the enlargement of the mechanical receptive field of primary afferent nociceptors to include the site of injury may account for the primary hyperalgesia to mechanical stimuli (Fig. 8B). In the literature, there are some contradictions with respect to the stimulus modalities to which hyperalgesia and sensitization occur. In spite of the well-documented sensitization of primary afferent nociceptors to heat stimuli, there are few studies on its molecular mechanisms. On the other hand, there is pharmacological evidence for a peripheral mechanism of primary mechanical hyperalgesia, but little direct evidence that nociceptors can be sensitized to mechanical stimuli by injury. This contradiction should spawn further investigations into the mechanical response properties of nociceptors and into the molecular mechanisms of heat sensitization. Secondary hyperalgesia to mechanical stimuli is likely due to the sensitization of central pain signalling neurons (CPSNs). This sensitization could involve only input from nociceptors (Fig. 8C), since mechanical pain thresholds after a cutaneous injury are of the same order as those of nociceptors. Central sensitization could also be the result of enhanced connectivity between low-threshold mechanoreceptors and CPSNs (Fig. 8D). This form of sensitization may account for the pain to light touch associated with neuropathic pain. Receptive field plasticity is a prevalent property of dorsal horn neurons and probably plays a vital role with regard to hyperalgesia. The molecular mechanisms of synaptic plasticity are currently subject to intense experimental investigation and may provide new insights on the mechanisms of pain and hyperalgesia.

Reflex Sympathetic Dystrophy Following Knee Arthroscopy: A Case Report with Electroneuromyographic Analysis

Reflex sympathetic dystrophy (RSD) is a debilitating and recalcitrant condition that has bewildered the medical community for decades. This article briefly reviews the pathophysiology of RSD and describes the clinical presentation and management of patients suffering from RSD. The case study describes the clinical and electrodiagnostic findings of a patient with RSD following arthroscopic surgery on the knee. The medical and physical interventions rendered in this case are described.

Burning pain in an extremity. Breaking the destructive cycle of reflex sympathetic dystrophy

The pathogenesis of reflex sympathetic dystrophy is controversial, but the condition can result from a major or seemingly minor injury to a limb, or even an insult to an organ, such as stroke or myocardial infarction. Onset can be sudden or insidious. The syndrome is characterized primarily by localized, deep, burning pain in a limb--pain that may not follow any logical distribution. Nonpitting edema, skin hyperesthesia, and guarding of the limb usually accompany the pain. If treatment is not instituted, deformity, contracture, and wasting of the limb can eventually occur. With appropriate therapy, the process can be stopped and often reversed. The keys are a high index of suspicion, early diagnosis, and aggressive treatment.

Effects of sympathectomy in a model of causalgiform pain produced by partial sciatic nerve injury in rats

In a previous report we presented a novel behavioral model of neuropathic pain disorders, produced in rat by a unilateral ligation of about half of the sciatic nerve. The model is characterized by rapid onset of behaviors suggesting spontaneous pain and disordered responses to non-noxious and noxious stimuli. These include reduced withdrawal thresholds to repetitive touch in the partially deafferented skin ('touched-evoked hyperesthesia'), touch-evoked allodynia, reduced withdrawal thresholds to noxious thermal stimuli and exaggerated responses to noxious heat and mechanical stimuli ('thermal hyperalgesia'). Some of these disorders are seen at mirror image sites on the hind limb opposite the lesion. These disorder start within hours after partial nerve injury, last many months and are very similar to causalgia in humans following partial nerve injury. Since sympathetic efferent activity is known to aggravate causalgia in humans and sympathectomy is known to relieve it, we studied the effect of changing sympathetic outflow in the rat model. Reversible sympathectomy was carried out using guanethidine injected intraperitoneally in 3 experiments, each at a different time in relation to the partial nerve injury. We found that: (1) sympathectomy performed several months postoperatively alleviated the sensory disorders bilaterally; (2) sympathectomy prior to nerve injury partially prevented the appearance of thermal hyperalgesia but did not affect hyperesthesia to repetitive touch; and (3) sympathectomy at the time of nerve injury aggravated the sensory disorders during the first few days. As maintenance and production of the sensory disorders in this animal model depended on sympathetic nervous outflow, we conclude that the rats were suffering from a syndrome analogous to sympathetically maintained causalgia in man.

Sympathetically-maintained causalgiform disorders in a model for neuropathic pain: a review

Partial nerve injury is the main cause of sympathetically maintained causalgiform pain disorders in humans. We present here an animal model of this condition, produced in rats by a unilateral ligation of about half of the sciatic nerve. Starting hours after the operation and for several months thereafter, the rats developed signs of spontaneous pain, touch-evoked allodynia and hyperesthesia, and mechanical and thermal hyperalgesia in the partially denervated as well as the intact contralateral foot. These disorders were maintained by the sympathetic outflow and disappeared following postoperative sympathectomy. In neonatally capsaicinated rats we found that touch-evoked allodynia and hyperesthesia were mediated by A-fibers whereas thermal hyperalgesia was mediated by C-fibers. These disorders were not due to receptor sensitization of remaining afferent fibers by prostaglandins. We found strain differences and genetic inheritance of these causalgiform disorders which were correlated with the expression of autotomy to hind-paw denervation.

A novel behavioral model of neuropathic pain disorders produced in rats by partial sciatic nerve injury

Partial nerve injury is the main cause of causalgiform pain disorders in humans. We present here a novel animal model of this condition. In rats we unilaterally ligated about half of the sciatic nerve high in the thigh. Within a few hours after the operation, and for several months thereafter, the rats developed guarding behavior of the ipsilateral hind paw and licked it often, suggesting the possibility of spontaneous pain. The plantar surface of the foot was evenly hyperesthetic to non-noxious and noxious stimuli. None of the rats autotomized. There was a sharp decrease in the withdrawal thresholds bilaterally in response to repetitive Von Frey hair stimulation at the plantar side. After a series of such stimuli in the operated side, light touch elicited aversive responses, suggesting allodynia to touch. The withdrawal thresholds to CO2 laser heat pulses were markedly lowered bilaterally. Suprathreshold noxious heat pulses elicited exaggerated responses unilaterally, suggesting thermal hyperalgesia. Pin-prick evoked such exaggerated responses bilaterally (mechanical hyperalgesia). In a companion report, we show that these abnormalities critically depend on the sympathetic outflow. Based on the immediate onset and long-lasting perpetuation of similar symptoms, such as touch-evoked allodynia and hyperalgesia, and the resemblance of the contralateral phenomena to 'mirror image' pains in some humans with causalgia, we suggest that this preparation may serve as a model for syndromes of the causalgiform variety that are triggered by partial nerve injury and maintained by sympathetic activity.

Comparison of sympathetic neurons in orofacial and upper extremity nerves: implications for causalgia

This study compared nerves of the orofacial region with nerves frequently associated with causalgia to determine if there is a significant difference in the proportion of sympathetic neurons within these nerves, which may account for the lower incidence of orofacial causalgia. Three orofacial and two upper extremity nerves were examined. Each nerve was transected and labeled with horseradish peroxidase to identify the cell bodies of neurons contributing axons to the nerve. The study included two trials per nerve, for a total of 10 trials in eight cats. The trigeminal and dorsal root ganglia, containing sensory neurons (SN), and the stellate, middle, and superior cervical ganglia, containing postganglionic sympathetic neurons (PGSN), were sectioned and reacted with tetramethyl benzidine to visualize the labeled neurons. The total number of labeled PGSN and SN were counted and the ratio (PGSN:SN) determined for each of the five nerves. The average PGSN:SN ratio from upper extremity nerves (0.40) is 2 1/2 times greater than the ratio determined for branches of the trigeminal nerve (0.16). The lower proportion of sympathetic neurons within the trigeminal nerves provides an anatomic explanation for the lower incidence of orofacial causalgia consistent with the currently accepted etiology.

Reflex sympathetic dystrophy: a review

Reflex sympathetic dystrophy is a unique traumatic disorder with unusual cutaneous signs. The case of a patient with an uncommon, poorly understood, sharply marginated geometric zone of erythema is reported. Pseudo-Kaposi's sarcoma developed in the same patient in the foot affected by reflex sympathetic dystrophy, an association not previously reported. For effective treatment this disorder must be diagnosed as early as possible. The clinical stages of evolution through which reflex sympathetic dystrophy progresses are described.

Reflex sympathetic dystrophy in central cord syndrome: case report and review of the literature

Reflex sympathetic dystrophy (RSD) has been reported in incomplete spinal cord injury patients, most often occurring unilaterally; however to our knowledge, bilateral RSD has not been reported in patients with a central cord syndrome. We report a case of bilateral RSD in a patient with incomplete cervical myelopathy and the clinical picture of central cord syndrome. Diagnosis of RSD was based upon clinical, roentgenographic and scintigraphic findings. Management of RSD included elevation of forearm and hands, gentle active and passive range of movements of all upper extremity joints and systemic corticosteroids. With treatment, pain subsided, the range of motion of the joints improved and the patient achieved good functional recovery.

Reflex sympathetic imbalance. Response to epidural blockade

Eleven patients (two male, nine female) were treated with epidural sympathetic blockade for reflex sympathetic imbalance, an incomplete manifestation of reflex sympathetic dystrophy. Each had developed severe pain, sensitivity, and disability disproportionate to associated trauma. One patient injured an ankle, and the remaining 10 patients one or both knees (12 knees). Seven patients had undergone previous surgery. All but one had a favorable response to initial blockade. This individual eventually failed treatment despite surgical sympathectomy. Seven have required readministration of a block for clinical relapse. Mean followup was 22 months (range, 10 to 41 months). Five underwent extensive psychological testing. All have required adjunctive forms of therapy including physical therapy, transcutaneous electrical nerve stimulation (TENS), antiinflammatory or other nonnarcotic agents. Recovery is typically prolonged, particularly if the diagnosis is delayed. Close attention to, and therefore prevention of, situations that trigger its recurrence is essential for successful rehabilitation.

Sympathetic facilitation of sustained discharges of polymodal nociceptors

Injection of a compound algogenic substance into a receptive field of the skin induced sustained discharges from single polymodal nociceptors (PMNs) in rats. Stimulation of the sympathetic nerve (SS) innervating the receptive field obviously increased the sustained discharges. Some units were first facilitated and then inhibited. The sympathetic effect could be activated repeatedly and lasted a long time. Injection of norepinephrine (NE, 5 micrograms) into the local artery caused a similar effect. The results indicate that the sympathetic nerve could facilitate sustained discharges of PMN. The possible causes of causalgia and different results of other experiments are discussed in this paper.

Treatment of dysesthesia of the sensory branch of the radial nerve by distal posterior interosseous neurectomy

Complete injuries to the sensory branch of the radial nerve may lead to the development of an area of dysesthesia in the dorsoradial aspect of the hand. However, lesions of the radial nerve proximal to the elbow level, affecting both the sensory branch and the posterior interosseous nerve, will never develop an area of distal dysesthesia. Therefore, it seems likely that the dysesthesia observed in isolated injuries of the sensory branch of the radial nerve is transmitted to the cortical receptors through the intact posterior interosseous nerve. On the basis of the above clinical observations, we have successfully treated 43 patients with radial dysesthesia by division of the distal posterior interosseous nerve. There have been no complications or functional deficits related to this procedure.

Reflex sympathetic dystrophies and algodystrophies: historical and pathogenic considerations

This paper reviews the historical development of the concepts of 'sympathy' of organs and of the sympathetic nervous system. In particular, the afferent function of the sympathetic system is discussed. The attention is focussed on sympathetic reflex dystrophies, known in some European schools as 'algodystrophies'. The pathogenic mechanisms of these affections, especially of causalgia, are discussed, considering the importance of peripheral damage to nerves, lateralisation of pain, 'mirror phenomena', and the relationship between peripheral and central mechanisms of pain.

Treatment of reflex sympathetic dystrophy of the hand with an active "stress loading" program

Reflex sympathetic dystrophy (RSD) is a syndrome characterized by pain out of proportion to injury, vasomotor and trophic changes, stiffness, and decreased function. It is important to separate the active disease process of RSD from its resultant state of contracture and fibrosis. Our treatment program is based on active "stress loading," which consists of active traction and compression exercises that provide stressful stimuli to the extremity without joint motion. Fifty-two patients with RSD were treated during a 3-year period. Their results and long-term follow-up on 41 patients are presented. The "stress loading" program has been used consistently during the past 20 years. The advantages of the program are its effectiveness, simplicity, safety, and noninvasiveness.