Appl. Neurophysio!. 42 : 125-134 (1979)
Skin Potential and EMG Changes Induced by Cutaneous Electrical Stimulation II. Subjects with ReHcx Sympathetic Dystrophies
Paolo Procacci, Fabio Francini, Marco Maresca and Massimo Zoppi Cattedra di Terapia Medica Sistematica and Cattedra di Fisiologia Generale, Universität di Firenze, Firenze
Key Words. Skin potential • Electromyography • Reflex sympathetic dystrophy • Skin potential response • Sympathetic nervous system Abstract. In a group of patients suffering from reflex sympathetic dystrophies, the skin potential and EMG responses induced by electrical stimuli applied to the skin were recorded in the four limbs in order to study somato-sympathetic and so mato-motor reflexes. In most patients, the amplitude, delay and shape of the cuta neous responses as well as the pattern of the EMG responses were different from those observed in normal subjects. In particular, it was possible to correlate the pat tern of the cutaneous and muscular responses with the severity of the disease. The cutaneous sensory thresholds to electrical stimuli (tactile, tingling and pain thresh old) showed different values in the dystrophic and in the contralateral limb. In all patients, a block of the sympathetic chain ipsilateral to the dystrophic limb was per formed with local anesthetics. 1 h after the block, the cutaneous responses disap peared not only in the blocked limb but also in the contralateral limb. 48 h after the block, muscular and cutaneous responses as well as sensory thresholds showed a pattern similar to that observed in normal subjects. These findings show that the sympathetic block provides a resetting of the sensory thresholds and reflexes.
Introduction
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Some diseases of the limbs, such as causalgia, Sudeck’s atrophy, posttraumatic osteoporosis and post-traumatic edema, are generally classified under the name of ‘reflex sympathetic dystrophies’ or ‘neurodystrophic syndromes’. Such syndromes have the following common characteristics: (a) the main symptoms are pain, paresthesia, vasomotor disturbances and trophic changes and (b) block of the sympathetic ganglia with local anesthetics induces long-lasting relief of the symptoms.
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The prevalent role of the sympathetic nervous system in the patho genesis of these syndromes was generally accepted after the observation that good results could be obtained with procaine block of the sympa thetic chain. Sympathetic block for the treatment of causalgia was intro duced by Leriche [7] in 1916. Afterwards, many authors [1, 2, 8] extend ed this therapy to other reflex dystrophies. Livingston [S] first proposed a model for the interpretation of the re flex sympathetic dystrophies. A peripheral lesion, often traumatic, acts as a trigger exciting the sensory receptors and the afferent fibers. At the spinal level, this afferent discharge sets up disturbances of an ‘intemuncial pool’ of interneurons. The consequence is an increased activity of the somatic and mainly of the sympathetic efferent pathways which induces modifications of microvascular regulation and of tissue metabolism. The receptors of the trigger point are thus maintained in a state of hyperexcit ability and neighboring receptors are excited. The ‘vicious circle’, periph ery - CNS - periphery, is thus established and maintained. In more recent years, many investigators [3, 5, 6, 9] proposed that this abnormal reflex activity induced and maintained trophic disturbances, pain and other sensory alterations in many diseases classified variously as limb vascular diseases (erythromelalgia, Raynaud’s disease, occlusive ar terial diseases, post-phlebitic syndromes) or some rheumatic diseases (muscular rheumatism with myalgic spots). In a previous report [10] the afferent branch of the vicious circle was investigated in a group of patients with reflex sympathetic dystrophies of the limbs. The cutaneous pain thresholds of the affected and of the con tralateral limb were measured with a thermal algometer in basal condi tions and at different times after a local anesthetic block of the sympa thetic ganglia innervating the affected limb. The basal threshold was sig nificantly different in the two limbs; this difference was not present in normal subjects. After the sympathetic block, damped oscillations of the threshold were observed not only in the blocked limb but also in the con tralateral limb; 48 h after the block, the thresholds of the two limbs did not significantly differ. On the basis of these observations, it was possible to conclude that the cutaneous pain threshold is under the control of the sympathetic nervous system and that the afferent information from one limb controls through central transfer mechanisms the contralateral effer ent sympathetic activity and consequently the cutaneous pain threshold. This control mechanism is altered in neurodystrophic subjects. The sympa thetic block resets the system to a normal steady state.
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In the present research, the efferent sympathetic and motor branches of the vicious circle were investigated and correlated with a detailed anal ysis of the thresholds of various kinds of sensations induced by electrical stimuli in a group of neurodystrophic patients. The sensory thresholds and the reflex cutaneous and muscular responses were investigated before and after a local anesthetic block of the sympathetic ganglia innervating the affected limb. This research follows a similar investigation carried out in a group of normal subjects [4]. Material and Methods The investigation was performed on 20 subjects, 15 males and 5 females, rang ing in age from 33 to 59 years, suffering from the following diseases of the limbs: (a) causalgia, 6 subjects; (b) neurodystrophic syndromes consequent to vascular dis eases (occlusive arterial diseases, 8 subjects; post-phlebitic syndromes, 2 subjects), and (c) painful and paresthesic syndromes (Schultze and Putnam syndromes, shoulder-hand syndrome) with evident dystrophies, 4 subjects. In all subjects, the dystrophy was present or prevalent in one limb. The clinical picture of the disease varied from slight to severe dystrophies. The general procedure was the same as described in the previous paper [4],The sensory thresholds, the cutaneous potentials and the EMG responses were recorded from the same cutaneous and muscular sites. The method used was the same as in normal subjects. The arousing environment was never induced. The stimulating and the recording electrodes were applied to the dystrophic limb in areas not apparently affected by the dystrophy. In every subject, a pharmacological block of the sympathetic chain ipsilateral to the affected limb was induced with 5-10 ml of 0.50°/o bupivacaine (Marcaine®). The blocks were induced at the following levels: (a) stellate ganglion and T2 and T3 thoracic ganglia for the upper limb and (b) lumbar sympathetic ganglia from L2 to L4 for the lower limb. The experimental sessions were (a) 4-5 sessions before the block; (b) 1 session 1 h after the block; and (c) 1 session 48 h after the block, when the action of bupi vacaine had completely vanished.
Results
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In every limb of all subjects the shape of the skin potential responses (SPR) was correlated with the skin potential level (SPL) in the same manner as that reported for the normal subjects [4]. In many patients, the shape of the SPR differed in the various limbs, in that the SPL showed the most negative values in the limbs with the lowest thresholds.
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FO REARM S
Fig. 1. Sensory thresholds in 4 male patients of different groups (I, IIA, IIB, III) with reflex sympathetic dystrophy of the right upper limb, before and after local anesthetic block of the ipsilateral stellate ganglion. A similar pattern was observed in the other patients of the various groups. • = Tactile threshold; ■ = tingling threshold; ▲ = pain threshold; ----= right l i m b s ; ------ = left limbs. Ab scissa: B = Before the block; 1 and 48 h = hours after the block. Ordinate: threshold values in mA.
In the habituated subjects in every experimental session the three fol lowing sensory thresholds in the four limbs were identified: tactile thresh old, tingling threshold and pain threshold.
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Observations before the Block The subjects were divided into three groups according to the charac teristics of the sensory thresholds (fig. 1) and of the cutaneous and mus cular responses.
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s' il S P RL * S P LL EMG r l
sprfa S P LFA
stRL
StRFA
....HijiW ^ IHIlii^lllltWliIttWHWiA’iiRC^MI?!WWIl>?!i?U,r>’i;|)>tKjj
n comparison to the previous alarm reactions: the SPR of the right leg has a regular shape; all responses have greater amplitudes. stLL = Stimulation of the left leg; sîrl = stimulation of the right leg; stRFA = stimulation of the right fo rearm; SPrl = skin potential of the right leg; SPll = skin potential of the left leg; SPr?a = skin potential of the right forearm; SPlfa = skin potential of the left fo rearm; EMG rl = EMG recorded from the right leg (musculus gastrocnemius); * = dystrophic limb; arrow = stimulus; • = SPR; vertical bar = 0.5 mV for EMG responses, 2 mV for SPR. a Responses to the 1st stimulus (alarm reaction), b Re sponses to the 10th stimulus (habituation). Stimulus repeated every 30 sec.
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Group I (3 subjects). The subjects of this group suffered from very slight dystrophies. In this group, SPR, EMG and sensory thresholds did not differ from those observed in normal subjects. Group II (6 subjects). In the subjects of this group, the disease was recent or did not evolve. In the segment of the dystrophy, during the alarm reaction, the amplitude of the SPR was higher in the affected limb (3 sub jects; group IIA) or in the contralateral one (3 subjects; group IIB). The response with lower amplitude showed also an irregular shape. The late
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components of the SPR and of the EMG response were not present (fig. 2a). In these subjects, it was impossible to induce sensitization. In all patients of this group, the sensory threshold of the limbs of one side were lower than those of the contralateral side. The lower thresh olds were observed in the limbs in which during alarm reaction the SPR showed the higher amplitude (fig. 1). In the habituated subjects, when the stimuli were applied to the limb with lower thresholds, the SPR was bilateral. When the stimuli were ap plied to the limb with higher thresholds, the SPR was observed only in the stimulated limb. The EMG did not differ from that of the normal sub jects (fig. 2b). Group III (11 subjects). In these subjects, the stage of the disease was advanced. The preliminary tests did not induce SPR in the four limbs nor EMG responses. The electrical stimulation of the affected or the contralateral limb in duced a SPR of low amplitude, irregular and present only in the stimulat ed limb. In the EMG, all components of the response were absent. When one of the other two limbs was stimulated, the SPR was bilateral and reg ular. Sensitization and irradiation of the SPR to the four limbs was ob served on repeating many times the same pattern of stimulation intervals of 30 sec. During this stage, the SPR of the four limbs showed a regular shape, but the amplitude was lower in the dystrophic limb. In the EMG, the sec ond burst and generalized responses were observed, but the periodic vari ations described in normal subjects were never present. During the ex perimental session, an obvious decrease of the interferential activity was observed (fig. 3). The sensory thresholds were lower in the affected limb than in the contralateral limb. A difference was present also in the other two limbs but with higher thresholds in the limb ipsilateral to the dystrophic process (f'g- !)• After the thresholds were determined, if the trains of pulses were again applied every 50 sec in order to avoid sensitization, the SPR were present only in the stimulated limb.
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Observations 1 h after the Block The SPR disappeared not only in the blocked limb but also in the contralateral limb. In these two limbs, the basal SPL was -20, -30 mV. This value did not change for the whole experimental session. In the
Skin Potentials in Reflex Sympathetic Dystrophies stR L 1st stimulus
s ^ fh_
20th stim ulus
131
stR|_
8th stim ulus
stn_
20th stimulus
—I------------------- -
1sec
|
Fig. 3. Skin potential and EMG traces recorded in a subject suffering from re flex sympathetic dystrophy of the right leg before the sympathetic block; in this sub ject the thresholds of the right leg were lower than of the left leg, the thresholds of the right forearm were higher than of the left forearm (group III). During sensitiza tion the SPL of all limbs increases; the increase is greater in the left leg than in the other limbs. EMG ll = EMG recorded from the left leg (m. gastrocnemius); EMGrfa = EMG recorded from the right forearm (m. flexor digitorum superficialis); stRL = stimulation of the right leg; stLL — stimulation of the left leg; stimulus re peated every 30 sec; ▲ = early components of the EMG responses. Other symbols, calibration and abbreviations, as in figure 2. a 1st and 8th stimuli (sensitization and irradiation are present), b 20th stimulus (habituation after sensitization).
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other two limbs, the SPR were present during alarm reaction (groups I and II), sensitization (group III), or if these limbs were stimulated. The patterns of the EMG responses did not differ from those ob served before the block (fig. 4a). A change of the sensory thresholds was observed. The new values de pended upon the basal values before the block (fig. 1). Group I; tingling and tactile thresholds rose, pain threshold decreased both in the blocked and in the contralateral limb. All thresholds of the other two limbs decreased. Group II: in the limbs with low basal thresholds, the thresholds rose; in the limbs with high basal thresholds they decreased. Group III: the thresholds of all limbs rose.
Procacci/Francini/Maresca/Zoppi 1st stimulus
^LL
132 o
■■..........................................
» S P BL S PL L
emgll sp rfa
SPl f a
---------------------------------------------------------------------- — ’
EMGrfa
s tRFA
..... own.
IM
b
SttL
A
A
Fig. 4. Skin potential and EMG traces recorded in the same subject as in figure 3 (group III). 48 h after the block, alarm reaction is present. A = Early and late components of the EMG; • = components of the SPR. Other symbols and calibra tion, as in figure 3. a 1 h after local anesthetic block of the right sympathetic gan glia L2-L4. b 48 h after the block. Responses to the 1st stimulus.
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Observations 48 h after the Block In the subjects of group I and IIA, the sensory thresholds (fig. 1), SPR and EMG became similar to those described in normal subjects. In the subjects of group IIB, the sensory thresholds and SPR became similar to those observed in the subjects of group IIA in basal conditions. In the subjects of group III, generalized SPR and EMG responses, not present in basal conditions, appeared (fig. 4b). The sensory thresholds (fig. 1), SPR and EMG were similar to those observed in the subjects of group IIA in basal conditions.
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Discussion
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The results obtained in subjects suffering from sympathetic reflex dys trophies differed from those observed in normal subjects [4], In the neurodystrophic subjects, the SPR, EMG and sensory thresholds showed dif ferent patterns in different limbs. In the normal subjects, the SPR of one limb was the same as that of the contralateral one, but in the neurodystrophic subjects it had different amplitude and shape. It was therefore possible to deduce that in these pa tients, the sympathetic activity differed in the various limbs. In the nor mal subjects, the shape of the SPR was regular, while in the neurodys trophic subjects it was often irregular. In the subjects of group II, the shape of the SPR became regular during sensitization. It can be deduced that the SPR was irregular not because of an anatomical or functional al teration in the peripheral tissues but because of a state of central inhibi tion. In the present research, it was also possible to correlate the severity of the disease with different patterns of responses and sensory thresholds. In particular, in the patients with slight dystrophies, lower sensory thresh olds were present in the affected or in the contralateral limb. In patients with severe dystrophies, lower thresholds were always present in the affected limb. 1 h after the sympathetic block, the sensory thresholds changed in all patients. This finding indicates that the sensory thresholds are under the control of sympathetic efferents. The disappearance of SPR both in the ipsilateral and in the contralateral limb confirms that the loop, ‘peripheryafferent discharge-efferent sympathetic discharge-periphery’ controls the same contralateral loop through mechanisms of central transfer. Similar results were obtained on measuring the cutaneous pain threshold with a thermal algometer in another group of patients suffering from sympathetic reflex dystrophies [10]. The present data also confirm the well-known clinical picture of reflex sympathetic dystrophy i.e. the contralateral ex tension of the dystrophic process (‘mirror image’). 48 h after the block (a) in the subjects with slight dystrophies, a nor mal pattern of the sensory thresholds and of the cutaneous and muscular responses were observed, and (b) in the subjects with severe dystrophies, a pattern similar to the basal pattern of the subjects with slight dystrophies was observed. These findings show that the variations of the sensory thresholds and
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of the cutaneous and muscular reflexes are correlated with the clinical re sults of the block. In the patients with severe dystrophies, only a clinical improvement was observed after the sympathetic block, while in the pa tients with slight dystrophies complete disappearance of pain, paresthesia and dystrophies was evident. Therefore, the sympathetic block provides a resetting of the sensory thresholds and of the reflexes to another steady state similar to that observed in normal subjects.
References
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Bonica, J. J.: The management of pain (Lea & Febiger, Philadelphia 1953). De Takats, G.: Causalgic states in peace and war. J. Am. med. Ass. 128: 699-704 (1945). De Takats, G.: Sympathetic reflex dystrophy. Med. Clins. N. Am. 49: 117-129 (1965). Francini, F.; Zoppi, M.; Maresca, M., and Procacci, P.: Skin potential and EMG changes induced by cutaneous electrical stimulation. I. Normal man in arousing and non-arousing environment. Appl. Neurophysiol. 42: 113-124 (1979). Galletti, R.; Procacci, P.; Marchetti, P. G.; Rocchi, P. e Buzzelli, G.: Esplorazione della funzione sensitiva dell’arto superiore e dei fenomeni cutanei correlati nelle fibromialgie. Effetti del blocco delle vie sensitive e del ganglio stellate. Archo Fisiol. 62: 313-331 (1963). Gross, D.: Pain and autonomic nervous system; in Bonica Int. Symp. on Pain. Advances in Neurology, vol. 4, pp. 93-103 (Raven Press, New York 1974). Leriche, R.: De la causalgie envisagée comme une névrite du sympathique et de son traitement par la dénudation et l’excision des plexus nerveux péri-artériels. Presse méd. 24: 178-180 (1916). Livingston, W. K.: Pain mechanisms (Macmillan, New York 1943). Procacci, P.; Zoppi, M.; Bolletti, A.; Francini, F.; Maresca, M. e Nuzzaci, G.; Il sistema nervoso vegetativo nel dolore delle arteriopatie obliteranti. 9th Int. Congr. of Angiology, vol. 4, pp. 170-178 (Minerva Medica, Torino 1979). Procacci, P.; Francini, F.; Zoppi, M., and Maresca, M.: Cutaneous pain threshold changes after sympathetic block in reflex dystrophies. Pain 1 :167-175 (1975). Paolo Procacci, Cattedra di Terapia Medica Sistemática, Viale Morgagni 85, Universitá di Firenze, 50134 Firenze (Italy)
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Skin Potential and EMG Changes Induced by Cutaneous Electrical Stimulation II. Subjects with ReHcx Sympathetic Dystrophies
Paolo Procacci, Fabio Francini, Marco Maresca and Massimo Zoppi Cattedra di Terapia Medica Sistematica and Cattedra di Fisiologia Generale, Universität di Firenze, Firenze
Key Words. Skin potential • Electromyography • Reflex sympathetic dystrophy • Skin potential response • Sympathetic nervous system Abstract. In a group of patients suffering from reflex sympathetic dystrophies, the skin potential and EMG responses induced by electrical stimuli applied to the skin were recorded in the four limbs in order to study somato-sympathetic and so mato-motor reflexes. In most patients, the amplitude, delay and shape of the cuta neous responses as well as the pattern of the EMG responses were different from those observed in normal subjects. In particular, it was possible to correlate the pat tern of the cutaneous and muscular responses with the severity of the disease. The cutaneous sensory thresholds to electrical stimuli (tactile, tingling and pain thresh old) showed different values in the dystrophic and in the contralateral limb. In all patients, a block of the sympathetic chain ipsilateral to the dystrophic limb was per formed with local anesthetics. 1 h after the block, the cutaneous responses disap peared not only in the blocked limb but also in the contralateral limb. 48 h after the block, muscular and cutaneous responses as well as sensory thresholds showed a pattern similar to that observed in normal subjects. These findings show that the sympathetic block provides a resetting of the sensory thresholds and reflexes.
Introduction
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Some diseases of the limbs, such as causalgia, Sudeck’s atrophy, posttraumatic osteoporosis and post-traumatic edema, are generally classified under the name of ‘reflex sympathetic dystrophies’ or ‘neurodystrophic syndromes’. Such syndromes have the following common characteristics: (a) the main symptoms are pain, paresthesia, vasomotor disturbances and trophic changes and (b) block of the sympathetic ganglia with local anesthetics induces long-lasting relief of the symptoms.
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126
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The prevalent role of the sympathetic nervous system in the patho genesis of these syndromes was generally accepted after the observation that good results could be obtained with procaine block of the sympa thetic chain. Sympathetic block for the treatment of causalgia was intro duced by Leriche [7] in 1916. Afterwards, many authors [1, 2, 8] extend ed this therapy to other reflex dystrophies. Livingston [S] first proposed a model for the interpretation of the re flex sympathetic dystrophies. A peripheral lesion, often traumatic, acts as a trigger exciting the sensory receptors and the afferent fibers. At the spinal level, this afferent discharge sets up disturbances of an ‘intemuncial pool’ of interneurons. The consequence is an increased activity of the somatic and mainly of the sympathetic efferent pathways which induces modifications of microvascular regulation and of tissue metabolism. The receptors of the trigger point are thus maintained in a state of hyperexcit ability and neighboring receptors are excited. The ‘vicious circle’, periph ery - CNS - periphery, is thus established and maintained. In more recent years, many investigators [3, 5, 6, 9] proposed that this abnormal reflex activity induced and maintained trophic disturbances, pain and other sensory alterations in many diseases classified variously as limb vascular diseases (erythromelalgia, Raynaud’s disease, occlusive ar terial diseases, post-phlebitic syndromes) or some rheumatic diseases (muscular rheumatism with myalgic spots). In a previous report [10] the afferent branch of the vicious circle was investigated in a group of patients with reflex sympathetic dystrophies of the limbs. The cutaneous pain thresholds of the affected and of the con tralateral limb were measured with a thermal algometer in basal condi tions and at different times after a local anesthetic block of the sympa thetic ganglia innervating the affected limb. The basal threshold was sig nificantly different in the two limbs; this difference was not present in normal subjects. After the sympathetic block, damped oscillations of the threshold were observed not only in the blocked limb but also in the con tralateral limb; 48 h after the block, the thresholds of the two limbs did not significantly differ. On the basis of these observations, it was possible to conclude that the cutaneous pain threshold is under the control of the sympathetic nervous system and that the afferent information from one limb controls through central transfer mechanisms the contralateral effer ent sympathetic activity and consequently the cutaneous pain threshold. This control mechanism is altered in neurodystrophic subjects. The sympa thetic block resets the system to a normal steady state.
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In the present research, the efferent sympathetic and motor branches of the vicious circle were investigated and correlated with a detailed anal ysis of the thresholds of various kinds of sensations induced by electrical stimuli in a group of neurodystrophic patients. The sensory thresholds and the reflex cutaneous and muscular responses were investigated before and after a local anesthetic block of the sympathetic ganglia innervating the affected limb. This research follows a similar investigation carried out in a group of normal subjects [4]. Material and Methods The investigation was performed on 20 subjects, 15 males and 5 females, rang ing in age from 33 to 59 years, suffering from the following diseases of the limbs: (a) causalgia, 6 subjects; (b) neurodystrophic syndromes consequent to vascular dis eases (occlusive arterial diseases, 8 subjects; post-phlebitic syndromes, 2 subjects), and (c) painful and paresthesic syndromes (Schultze and Putnam syndromes, shoulder-hand syndrome) with evident dystrophies, 4 subjects. In all subjects, the dystrophy was present or prevalent in one limb. The clinical picture of the disease varied from slight to severe dystrophies. The general procedure was the same as described in the previous paper [4],The sensory thresholds, the cutaneous potentials and the EMG responses were recorded from the same cutaneous and muscular sites. The method used was the same as in normal subjects. The arousing environment was never induced. The stimulating and the recording electrodes were applied to the dystrophic limb in areas not apparently affected by the dystrophy. In every subject, a pharmacological block of the sympathetic chain ipsilateral to the affected limb was induced with 5-10 ml of 0.50°/o bupivacaine (Marcaine®). The blocks were induced at the following levels: (a) stellate ganglion and T2 and T3 thoracic ganglia for the upper limb and (b) lumbar sympathetic ganglia from L2 to L4 for the lower limb. The experimental sessions were (a) 4-5 sessions before the block; (b) 1 session 1 h after the block; and (c) 1 session 48 h after the block, when the action of bupi vacaine had completely vanished.
Results
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In every limb of all subjects the shape of the skin potential responses (SPR) was correlated with the skin potential level (SPL) in the same manner as that reported for the normal subjects [4]. In many patients, the shape of the SPR differed in the various limbs, in that the SPL showed the most negative values in the limbs with the lowest thresholds.
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FO REARM S
Fig. 1. Sensory thresholds in 4 male patients of different groups (I, IIA, IIB, III) with reflex sympathetic dystrophy of the right upper limb, before and after local anesthetic block of the ipsilateral stellate ganglion. A similar pattern was observed in the other patients of the various groups. • = Tactile threshold; ■ = tingling threshold; ▲ = pain threshold; ----= right l i m b s ; ------ = left limbs. Ab scissa: B = Before the block; 1 and 48 h = hours after the block. Ordinate: threshold values in mA.
In the habituated subjects in every experimental session the three fol lowing sensory thresholds in the four limbs were identified: tactile thresh old, tingling threshold and pain threshold.
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Observations before the Block The subjects were divided into three groups according to the charac teristics of the sensory thresholds (fig. 1) and of the cutaneous and mus cular responses.
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s' il S P RL * S P LL EMG r l
sprfa S P LFA
stRL
StRFA
....HijiW ^ IHIlii^lllltWliIttWHWiA’iiRC^MI?!WWIl>?!i?U,r>’i;|)>tKjj
n comparison to the previous alarm reactions: the SPR of the right leg has a regular shape; all responses have greater amplitudes. stLL = Stimulation of the left leg; sîrl = stimulation of the right leg; stRFA = stimulation of the right fo rearm; SPrl = skin potential of the right leg; SPll = skin potential of the left leg; SPr?a = skin potential of the right forearm; SPlfa = skin potential of the left fo rearm; EMG rl = EMG recorded from the right leg (musculus gastrocnemius); * = dystrophic limb; arrow = stimulus; • = SPR; vertical bar = 0.5 mV for EMG responses, 2 mV for SPR. a Responses to the 1st stimulus (alarm reaction), b Re sponses to the 10th stimulus (habituation). Stimulus repeated every 30 sec.
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Group I (3 subjects). The subjects of this group suffered from very slight dystrophies. In this group, SPR, EMG and sensory thresholds did not differ from those observed in normal subjects. Group II (6 subjects). In the subjects of this group, the disease was recent or did not evolve. In the segment of the dystrophy, during the alarm reaction, the amplitude of the SPR was higher in the affected limb (3 sub jects; group IIA) or in the contralateral one (3 subjects; group IIB). The response with lower amplitude showed also an irregular shape. The late
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components of the SPR and of the EMG response were not present (fig. 2a). In these subjects, it was impossible to induce sensitization. In all patients of this group, the sensory threshold of the limbs of one side were lower than those of the contralateral side. The lower thresh olds were observed in the limbs in which during alarm reaction the SPR showed the higher amplitude (fig. 1). In the habituated subjects, when the stimuli were applied to the limb with lower thresholds, the SPR was bilateral. When the stimuli were ap plied to the limb with higher thresholds, the SPR was observed only in the stimulated limb. The EMG did not differ from that of the normal sub jects (fig. 2b). Group III (11 subjects). In these subjects, the stage of the disease was advanced. The preliminary tests did not induce SPR in the four limbs nor EMG responses. The electrical stimulation of the affected or the contralateral limb in duced a SPR of low amplitude, irregular and present only in the stimulat ed limb. In the EMG, all components of the response were absent. When one of the other two limbs was stimulated, the SPR was bilateral and reg ular. Sensitization and irradiation of the SPR to the four limbs was ob served on repeating many times the same pattern of stimulation intervals of 30 sec. During this stage, the SPR of the four limbs showed a regular shape, but the amplitude was lower in the dystrophic limb. In the EMG, the sec ond burst and generalized responses were observed, but the periodic vari ations described in normal subjects were never present. During the ex perimental session, an obvious decrease of the interferential activity was observed (fig. 3). The sensory thresholds were lower in the affected limb than in the contralateral limb. A difference was present also in the other two limbs but with higher thresholds in the limb ipsilateral to the dystrophic process (f'g- !)• After the thresholds were determined, if the trains of pulses were again applied every 50 sec in order to avoid sensitization, the SPR were present only in the stimulated limb.
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Observations 1 h after the Block The SPR disappeared not only in the blocked limb but also in the contralateral limb. In these two limbs, the basal SPL was -20, -30 mV. This value did not change for the whole experimental session. In the
Skin Potentials in Reflex Sympathetic Dystrophies stR L 1st stimulus
s ^ fh_
20th stim ulus
131
stR|_
8th stim ulus
stn_
20th stimulus
—I------------------- -
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Fig. 3. Skin potential and EMG traces recorded in a subject suffering from re flex sympathetic dystrophy of the right leg before the sympathetic block; in this sub ject the thresholds of the right leg were lower than of the left leg, the thresholds of the right forearm were higher than of the left forearm (group III). During sensitiza tion the SPL of all limbs increases; the increase is greater in the left leg than in the other limbs. EMG ll = EMG recorded from the left leg (m. gastrocnemius); EMGrfa = EMG recorded from the right forearm (m. flexor digitorum superficialis); stRL = stimulation of the right leg; stLL — stimulation of the left leg; stimulus re peated every 30 sec; ▲ = early components of the EMG responses. Other symbols, calibration and abbreviations, as in figure 2. a 1st and 8th stimuli (sensitization and irradiation are present), b 20th stimulus (habituation after sensitization).
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other two limbs, the SPR were present during alarm reaction (groups I and II), sensitization (group III), or if these limbs were stimulated. The patterns of the EMG responses did not differ from those ob served before the block (fig. 4a). A change of the sensory thresholds was observed. The new values de pended upon the basal values before the block (fig. 1). Group I; tingling and tactile thresholds rose, pain threshold decreased both in the blocked and in the contralateral limb. All thresholds of the other two limbs decreased. Group II: in the limbs with low basal thresholds, the thresholds rose; in the limbs with high basal thresholds they decreased. Group III: the thresholds of all limbs rose.
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^LL
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» S P BL S PL L
emgll sp rfa
SPl f a
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Fig. 4. Skin potential and EMG traces recorded in the same subject as in figure 3 (group III). 48 h after the block, alarm reaction is present. A = Early and late components of the EMG; • = components of the SPR. Other symbols and calibra tion, as in figure 3. a 1 h after local anesthetic block of the right sympathetic gan glia L2-L4. b 48 h after the block. Responses to the 1st stimulus.
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Observations 48 h after the Block In the subjects of group I and IIA, the sensory thresholds (fig. 1), SPR and EMG became similar to those described in normal subjects. In the subjects of group IIB, the sensory thresholds and SPR became similar to those observed in the subjects of group IIA in basal conditions. In the subjects of group III, generalized SPR and EMG responses, not present in basal conditions, appeared (fig. 4b). The sensory thresholds (fig. 1), SPR and EMG were similar to those observed in the subjects of group IIA in basal conditions.
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Discussion
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The results obtained in subjects suffering from sympathetic reflex dys trophies differed from those observed in normal subjects [4], In the neurodystrophic subjects, the SPR, EMG and sensory thresholds showed dif ferent patterns in different limbs. In the normal subjects, the SPR of one limb was the same as that of the contralateral one, but in the neurodystrophic subjects it had different amplitude and shape. It was therefore possible to deduce that in these pa tients, the sympathetic activity differed in the various limbs. In the nor mal subjects, the shape of the SPR was regular, while in the neurodys trophic subjects it was often irregular. In the subjects of group II, the shape of the SPR became regular during sensitization. It can be deduced that the SPR was irregular not because of an anatomical or functional al teration in the peripheral tissues but because of a state of central inhibi tion. In the present research, it was also possible to correlate the severity of the disease with different patterns of responses and sensory thresholds. In particular, in the patients with slight dystrophies, lower sensory thresh olds were present in the affected or in the contralateral limb. In patients with severe dystrophies, lower thresholds were always present in the affected limb. 1 h after the sympathetic block, the sensory thresholds changed in all patients. This finding indicates that the sensory thresholds are under the control of sympathetic efferents. The disappearance of SPR both in the ipsilateral and in the contralateral limb confirms that the loop, ‘peripheryafferent discharge-efferent sympathetic discharge-periphery’ controls the same contralateral loop through mechanisms of central transfer. Similar results were obtained on measuring the cutaneous pain threshold with a thermal algometer in another group of patients suffering from sympathetic reflex dystrophies [10]. The present data also confirm the well-known clinical picture of reflex sympathetic dystrophy i.e. the contralateral ex tension of the dystrophic process (‘mirror image’). 48 h after the block (a) in the subjects with slight dystrophies, a nor mal pattern of the sensory thresholds and of the cutaneous and muscular responses were observed, and (b) in the subjects with severe dystrophies, a pattern similar to the basal pattern of the subjects with slight dystrophies was observed. These findings show that the variations of the sensory thresholds and
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of the cutaneous and muscular reflexes are correlated with the clinical re sults of the block. In the patients with severe dystrophies, only a clinical improvement was observed after the sympathetic block, while in the pa tients with slight dystrophies complete disappearance of pain, paresthesia and dystrophies was evident. Therefore, the sympathetic block provides a resetting of the sensory thresholds and of the reflexes to another steady state similar to that observed in normal subjects.
References
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Bonica, J. J.: The management of pain (Lea & Febiger, Philadelphia 1953). De Takats, G.: Causalgic states in peace and war. J. Am. med. Ass. 128: 699-704 (1945). De Takats, G.: Sympathetic reflex dystrophy. Med. Clins. N. Am. 49: 117-129 (1965). Francini, F.; Zoppi, M.; Maresca, M., and Procacci, P.: Skin potential and EMG changes induced by cutaneous electrical stimulation. I. Normal man in arousing and non-arousing environment. Appl. Neurophysiol. 42: 113-124 (1979). Galletti, R.; Procacci, P.; Marchetti, P. G.; Rocchi, P. e Buzzelli, G.: Esplorazione della funzione sensitiva dell’arto superiore e dei fenomeni cutanei correlati nelle fibromialgie. Effetti del blocco delle vie sensitive e del ganglio stellate. Archo Fisiol. 62: 313-331 (1963). Gross, D.: Pain and autonomic nervous system; in Bonica Int. Symp. on Pain. Advances in Neurology, vol. 4, pp. 93-103 (Raven Press, New York 1974). Leriche, R.: De la causalgie envisagée comme une névrite du sympathique et de son traitement par la dénudation et l’excision des plexus nerveux péri-artériels. Presse méd. 24: 178-180 (1916). Livingston, W. K.: Pain mechanisms (Macmillan, New York 1943). Procacci, P.; Zoppi, M.; Bolletti, A.; Francini, F.; Maresca, M. e Nuzzaci, G.; Il sistema nervoso vegetativo nel dolore delle arteriopatie obliteranti. 9th Int. Congr. of Angiology, vol. 4, pp. 170-178 (Minerva Medica, Torino 1979). Procacci, P.; Francini, F.; Zoppi, M., and Maresca, M.: Cutaneous pain threshold changes after sympathetic block in reflex dystrophies. Pain 1 :167-175 (1975). Paolo Procacci, Cattedra di Terapia Medica Sistemática, Viale Morgagni 85, Universitá di Firenze, 50134 Firenze (Italy)
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