Complex Regional Pain Syndromes (Reflex Sympathetic Dystrophy and Causalgia) and Spinal Cord Stimulation

Correlation Between Temperature Rise after Sympathetic Block and Pain Relief in Patients with Complex Regional Pain Syndrome

OBJECTIVE

Determine the correlation between post-sympathetic block pain temperature change, and immediate and intermediate-term pain relief.

DESIGN

Retrospective analysis.

SETTING

Academic setting.

SUBJECTS

79 pts with CRPS who underwent sympathetic block.

METHODS

Pre- and post-block temperatures in the affected extremity, and pain scores immediately (based on 6-hour pain diary) post-block and at the intermediate-term 4-8-week follow-up were recorded. Post-block pain reductions of 30-49% and ≥ 50% were designated as partially sympathetically-maintained pain (SMP) and SMP. A decrease in pain score ≥ 2-points lasting ≥ 4 weeks was considered a positive intermediate-term outcome for sympathetic block.

RESULTS

A weak correlation was found between immediate-term pain relief and the extent of temperature rise for the cohort (R = 0.192, P = 0.043). Greater immediate-term pain reduction was reported among patients who experienced ≥ 7.5° C temperature increase (mean 4.1, 95% CI [3.33, 4.76]) compared to those who experienced < 2° C (2.3, 95% CI [1.36, 3.31]) and ≥ 2° C x < 7.5° C (2.9, 95% CI [1.8; 3.9]; P = 0.036). The correlations between temperature increase and intermediate-term pain score reduction at 4-8 weeks (R = 0.052, P = 0.329), and between immediate and intermediate-term pain relief (R = 0.139, P = 0.119) were not statistically significant.

CONCLUSIONS

A weak correlation was found for those who experienced greater temperature increases post-block to experience greater immediate pain relief. Higher temperature increase cutoffs than are typically used may be necessary to determine whether a patient with CRPS has SMP.

The Evolving Role of High-Frequency Spinal Cord Stimulation as Salvage Therapy in Neurostimulation

BACKGROUND

High-frequency 10-kHz spinal cord stimulation (10-kHz SCS) has shown promise in multicenter prospective trials for the management of chronic back and leg pain. Traditional spinal cord stimulation (t-SCS) has a long history of effectiveness in chronic neuropathic syndromes but not uncommonly can fail to provide long-term relief, leaving a significant group of patients with unsatisfactory outcomes. There is mounting evidence that 10-kHz SCS may offer relief in this subset of patients.

METHODS

The purpose of this retrospective analysis was to report a single-institution long-term experience of 10-kHz SCS in patients who did not get adequate pain relief with prior t-SCS devices. A temporary trial of 10-kHz SCS was carried out for 7 days, and those experiencing an average of 50% reduction in pain intensity underwent implantation. Patients were classified as moderate responders if relief was 31% to 50% and excellent responders if pain relief exceeded 50%.

RESULTS

Thirty-one patients who had experienced failed t-SCS primarily from poor paresthesia coverage underwent a trial of 10-kHz SCS and 29 underwent implantation. Twenty-eight patients were available for analysis, with 57.1% experiencing 30% response and 46.4% experiencing excellent response at a median follow-up of 21.2 (±8.4) months.

CONCLUSIONS

This small single-institution study suggests that a significant proportion of patients with previously failed t-SCS may achieve clinically meaningful and durable pain relief with 10-kHz SCS.

Anti-tumor activity of phenoxybenzamine and its inhibition of histone deacetylases

The principal finding from this study was the recognition that the α-adrenergic antagonist, phenoxybenzamine, possesses histone deacetylase inhibitory activity. Phenoxybenzamine is approved by the United States Food and Drug Administration for the treatment of hypertensive crises associated with tumors of the adrenal medulla, pheochromocytomas. It has several "off label" indications relative to its capacity to relax vascular smooth muscle and smooth muscle of the urogenital tract. The drug also has a long history of apparent efficacy in ameliorating, and perhaps reversing, the severe symptoms of neuropathic pain syndromes. Our interest in this feature of the drug relates to the fact that certain types of neuropathic pain, in particular complex regional pain syndrome, demonstrate a proliferative nature, with the capacity to spread from an injured limb, for example, to a non-injured limb and perhaps to essentially the entire body. Sensory neuronal sprouting in the spinal cord has been observed under conditions where there is a high sensory input from painful stimuli. Searches of gene expression signatures in the BroadBuild02 Molecular Signature Database using their connectivity map software suggested that phenoxybenzamine may have histone deacetylase inhibitory activity. Studies by others have reported inhibitory effects of phenoxybenzamine on growth, invasion and migration of human tumor cell cultures and, in one study, inhibition of tumor expansion in animal experiments. Inhibitory effects on human tumor cell cultures are also reported in the present study. Phenoxybenzamine was also found to have histone deacetylase inhibitory activity; histone deacetylase isoforms 5, 6, and 9 were the most sensitive to inhibition by phenoxybenzamine. The importance of elevated levels of these isoforms as biomarkers of poor prognosis in human malignant disease, and the recognized suppression of tumor growth that may accrue from their inhibition, opens consideration of possible translation of phenoxybenzamine to new clinical applications. This might be facilitated by the fact that phenoxybenzamine is already an approved drug entity. There appears to be no previous report of the activity of phenoxybenzamine as a histone deacetylase inhibitor.

Extrapyramidal signs occurring after sympathetic block for complex regional pain syndrome responding to diphenhydramine: Two case reports

RATIONALE

To present an unusual extrapyramidal motor response occurring after a sympathetic block in CRPS and its successful treatment with diphenhydramine.

PATIENT CONCERNS

Severe pain related to Complex Regional Pain Syndrome type 1 interfering with activities of daily living.

DIAGNOSES

Complex Regional Pain Syndrome type 1.

INTERVENTIONS

We report a video case reports of two patients with a diagnosis of CRPS type-I. Both patients exhibited similar presentation of unusual extrapyramidal motor response of the affected limb following lumbar sympathetic block. Both patients were treated with intravenous diphenhydramine to abort the extrapyramidal motor response.

OUTCOMES

Both patients similarly responded to treatment with intravenous diphenhydramine with abrupt resolution of the motor response.

LESSONS

Sympathetic blockade may interfere with the adaptive autonomic reflex circuits of the motor balance homeostasis in patients with complex regional pain syndrome. Disinhibition of extrapyramidal system may lead to immediate expression of extrapyramidal signs following the sympathetic block. Diphenhydramine, with its anti-histaminic and anticholinergic properties, may be effective in aborting such extrapyramidal signs, and should be considered as a treatment option in similar cases.

Spinal cord stimulation as treatment for complex regional pain syndrome should be considered earlier than last resort therapy

BACKGROUND

Spinal cord stimulation (SCS), by virtue of its historically described up-front costs and level of invasiveness, has been relegated by several complex regional pain syndrome (CRPS) treatment algorithms to a therapy of last resort. Newer information regarding safety, cost, and efficacy leads us to believe that SCS for the treatment of CRPS should be implemented earlier in a treatment algorithm using a more comprehensive approach.

METHODS

We reviewed the literature on pain care algorithmic thinking and applied the safety, appropriateness, fiscal or cost neutrality, and efficacy (S.A.F.E.) principles to establish an appropriate position for SCS in an algorithm of pain care.

RESULTS AND CONCLUSION

Based on literature-contingent considerations of safety, efficacy, cost efficacy, and cost neutrality, we conclude that SCS should not be considered a therapy of last resort for CRPS but rather should be applied earlier (e.g., three months) as soon as more conservative therapies have failed.

Spinal cord stimulation in adolescents with complex regional pain syndrome type I (CRPS-I)

Complex regional pain syndrome type I (CRPS-I) is not uncommon in children, particularly in adolescent girls. Most often, the condition involves a foot and is characterized by spontaneous pain, tactile allodynia and dysautonomic signs. There is usually a history of a minor, local trauma but sometimes no reasonable cause can be identified, and there are no signs of persistent tissue injury giving rise to ongoing nociception. Common analgesics are generally of no benefit, and the standard treatment includes sociopsychological support, physiotherapy, tricyclic antidepressants and antiepileptic drugs, sympathetic blocks (SB), and cognitive-behavioural therapy. For a minority of patients who prove to be resistant to such therapies, spinal cord stimulation (SCS) may be tried. The present study comprises seven girls, 11-14 years of age, presenting with severe, incapacitating and therapy-resistant CRPS-I, who were subjected to SCS. In two of them, percutaneous electrode implantation had to be performed in general anaesthesia. Trial stimulation was performed in all, but one. In two cases, it was not possible to produce paraesthesias that entirely covered the pain area. A pain relieving effect of SCS was usually not reported until after 1-2 weeks of trial stimulation. After another 2-6 weeks, pain alleviation was complete in five of the seven patients, one to eight years after the intervention. In one case, a local infection necessitated the removal of the electrode; nevertheless a few days of trial stimulation produced substantial pain relief that still persists. In four patients, the SCS use was gradually diminished and eventually the device could be removed. The favourable outcome in all seven cases with no or minor remaining symptoms and without severe recurrences illustrates that SCS may also be an efficient treatment in paediatric cases with exceptionally therapy resistant forms of CRPS I.

Spinal cord stimulation in the treatment of complex regional pain syndrome (CRPS) of the lower extremity: a case report

Complex regional pain syndrome (CRPS) is a condition that is often associated with the extremities. This chronic pain syndrome, when localized to the lower extremity, includes peripheral changes such as edema, temperature alterations, limited range of motion, loss of or excessive perspiration, pain out of proportion to any stimulus, and trophic alterations of the skin, hair, and nails. In this report, we describe the case of a patient who developed complex regional pain syndrome following an ankle injury and surgery. This case report highlights treatment options that are available to patients experiencing complex regional pain, including the use of a spinal cord stimulator.

LEVEL OF CLINICAL EVIDENCE

4.

Unravelling the pathophysiology of complex regional pain syndrome: focus on sympathetically maintained pain

1. In diseases such as complex regional pain syndrome (CRPS), where neuropathic pain is the primary concern, traditional pain classifications and lesion descriptors are of limited value. To obtain better treatment outcomes for patients, the underlying pathophysiological mechanisms of neuropathic pain need to be elucidated and analysed so that therapeutic targets can be identified and specific treatments developed. 2. In the present review, we examine the current literature on sympathetically maintained pain (SMP), a subset of neuropathic pain, within the context of CRPS. Evidence from both human and animal studies is presented and discussed in terms of its support for the existence of SMP and the mechanistic information it provides. 3. We discuss three current hypotheses that propose both a site and method for sympathetic-sensory coupling: (i) direct coupling between sympathetic and sensory neurons in the dorsal root ganglion; (ii) chemical coupling between sympathetic and nociceptive neuron terminals in skin; and (iii) the development of a-adrenoceptor-mediated supersensitivity in nociceptive fibres in skin in association with the release of inflammatory mediators. 4. Finally, we propose a new hypothesis that integrates the mechanisms of chemical coupling and a-adrenoceptor-mediated supersensitivity. This hypothesis is based on previously unpublished data from our laboratory showing that a histological substrate suitable for sympathetic-sensory coupling exists in normal subjects. In the diseased state, the nociceptive fibres implicated in this substrate may be activated by both endogenous and exogenous noradrenaline. The mediating a-adrenoceptors may be expressed on the nociceptive fibres or on closely associated support cells.