H. A. J. M. Kurvers

Reflex sympathetic dystrophy: evolution of microcirculatory disturbances in time.

&NA; Reflex sympathetic dystrophy (RSD) is a pain syndrome that is characterised by autonomic, motor and sensory disturbances. The syndrome has often been associated with sympathetic dysfunction. Therefore, we investigated whether there are disturbances in the sympathetic function of skin microcirculation in the various clinical stages of RSD. Laser Doppler flowmetry (LDF) was used to obtain information about total (mainly thermoregulatory) skin blood flow (TSBF), since blood flow in arteriovenous anastomoses and subpapillary plexus, which are richly innervated by sympathetic nerve endings, contributes predominantly to the flow signal as obtained by LDF. Capillary microscopy was used to appraise whether the trophic changes, as observed in RSD, result from an impaired nutritive skin blood flow (NSBF). Transcutaneous oximetry (TCPO2) was employed as a measure of the oxygenation of superficial skin layers. Skin temperature (ST) was also determined. Patients were divided into 3 clinical stages: stage I in case of a chronic warmth sensation, stage II in case of an intermittent warmth and cold sensation, and stage III in case of a chronic cold sensation. As compared to controls: (1) TSBF was increased (P < 0.05) at stage I and decreased at stages II (P < 0.05) and III (P < 0.001), (2) NSBF was decreased at stages II (P < 0.05) and III (P < 0.001), (3) TCPO2 was not impaired at any stage, (4) ST was increased (P < 0.01) at stage I and decreased (P < 0.05) at stage III. The present study is the first to report an increase of TSBF at stage I of RSD, which may be caused by a decrease in efferent sympathetic nerve impulses. At stages II and III both TSBF and NSBF were decreased which may reflect increased sensitivity of skin microvessels to (circulating) catecholamines.

NEUROGENIC INFLAMMATION IN AN ANIMAL MODEL OF NEUROPATHIC PAIN

Loose ligation of a rat sciatic nerve (chronic constriction injury (CCI) model) provokes signs and symptoms like those observed in reflex sympathetic dystrophy (RSD) patients. Primary afferent nociceptive C-fibers seem to be involved in an afferent orthodromic as well as in an efferent antidromic manner. In this study we hypothesize that consequent to development of antidromic impulses in C-nociceptive afferents, neuropeptides released from peripheral endings of these fibers, increase skin blood flow (SBF), vascular permeability, and tissue accumulation of polymorphonuclear leukocytes (PMNs). Collectively, these phenomena have been referred to as neurogenic inflammation. To investigate the presence of neurogenic inflammation in the CCI-model, we assessed skin blood flow (SBF) as well as the level of edema and accumulation of PMNs in muscle tissue obtained from the affected hindpaw. SBF was measured, by means of laser Doppler flowmetry, before ligation as well as at day 4 after ligation. At day 4, SBF measurements were performed before and after abolition of the capability of C-fibers to mediate a vasodilator response. To this end, capsaicin was applied perineurally. Increased vascular permeability was inferred from the level of edema of muscle tissue as determined by assessment of wet/dry weight ratios of muscle biopsies. PMN accumulation was investigated by enzymatic detection of myeloperoxidase (MPO) activity in muscle biopsies. Compared with preligation values, at day 4 SBF was increased more than twofold (p < 0.05). The latter response was annihilated by capsaicin application. Compared with sham operated controls, wet/dry ratios were higher in the ligated animals (1.104 vs. 1.068; p < 0.05). Likewise, when compared with sham operated controls, MPO activity was found to be increased in the ligated hindpaw (Optic Density 0.15 vs. 0.89; p < 0.001). In conclusion, the findings of this study indicate that loose ligation of a sciatic nerve induces an inflammatory response in the ipsilateral hindpaw, which most likely is mediated by release of neuropeptides from the peripheral endings of antidromically acting nociceptive C-fibres.

Skin blood flow abnormalities in a rat model of neuropathic pain: Result of decreased sympathetic vasoconstrictor outflow?

Loose ligation of a sciatic nerve in rats provokes signs and symptoms like those observed in human conditions of neuropathic pain. Some of these have been associated with sympathetic dysfunction. Since the skin microcirculation in the rat is strongly influenced by sympathetic tone, abnormalities in skin blood flow may be used as an indirect measure of sympathetic dysfunction. We measured, by means of laser Doppler flowmetry, skin blood flow at the plantar surface of the rat hind paw before and after ipsilateral loose sciatic nerve ligation. We assessed basal skin blood flow as well as the vasoconstrictor response which follows cooling of the rat abdomen. The effectiveness of this response may be used as a measure of sympathetic vasoconstrictor outflow. As compared to the values obtained before ligation (= 100%): (1) the vasoconstrictor response was impaired (65%, P < 0.01) from day 1 onwards, whereas (2) basal skin blood flow was increased (171%; P < 0.01) from day 3 until day 5, and decreased (51%, P < 0.0001) from day 7 until day 28. At day 28, blockade of impulse propagation in the loosely ligated sciatic nerve (by means of lidocaine) did not increase the lowered level of skin blood flow. These findings suggest that in the chronic construction injury model loose ligation of a sciatic nerve reduces sympathetic vasoconstrictor outflow, which, in turn may induce supersensitivity of skin microvessels to catecholamines.

Chlamydia pneumoniae Serology Is Associated With Thrombosis-Related but Not With Plaque-Related Microembolization During Carotid Endarterectomy

Background and Purpose— Chlamydia pneumoniae has repeatedly been associated with atherosclerotic disease. Our study was designed to clarify whether this association is based on C pneumoniae-induced transformation of a stable into an unstable atherosclerotic plaque or on stimulation of hypercoagulability leading to increased thrombotic arterial occlusions by C pneumoniae infection. Transcranial Doppler ultrasonographic monitoring of the middle cerebral artery during carotid endarterectomy offers the opportunity to study, before removal of the plaque, atherothrombotic emboli dislodging from an unstable carotid plaque (plaque-related emboli) and emboli related to (excessive) thrombus formation at the endarterectomy site after removal of the plaque and restoration of flow (thrombosis-related emboli). Methods— C pneumoniae IgA (≥1/16) and IgG (≥1/64) seropositivity was assessed in 53 patients with symptomatic carotid artery disease undergoing carotid endarterectomy. The removed carotid plaques were studied histologically to assess plaque instability. Results— Plaque- and thrombosis-related emboli were registered in 43 patients with an adequate transtemporal window. IgA seropositivity (58%) was associated significantly with thrombosis-related embolization (P =0.030) but not with plaque-related embolization or with histological plaque instability. Conclusions— C pneumoniae serology is associated with microembolization after endarterectomy and restoration of flow. Since these microemboli represent platelet aggregations and are related to cerebrovascular complications, our data suggest that C pneumoniae infection contributes to cerebrovascular events in patients with carotid artery disease through stimulation of thrombosis.

Reflex sympathetic dystrophy : does sympathetic dysfunction originate from peripheral neuropathy ?

BACKGROUND Sympathetic dysfunction in reflex sympathetic dystrophy (RSD) has been purported to consist of an afferently-induced increase in efferent sympathetic nerve impulses (somato-sympathetic reflex) and/or denervation-induced supersensitivity to catecholamines. In addition, both the central and peripheral nervous systems have been claimed to be involved. It was the aim of this study to obtain more insights into these underlying mechanisms. METHODS In the affected extremeties of 42 patients with RSD we investigated as indirect measures of sympathetic (dys)function: (1) skin blood flow and the vasoconstrictive response to dependency of skin microvessels by means of laser Doppler flowmetry (distal to the site of trauma), (2) relative distention of the brachial artery and changes in relative distention consequent to a cold pressor test by means of ultrasonic vessel wall tracking (proximal to the site of trauma), and (3) arterial blood pressures by means of the Finapres technique. Both provocation tests induce a sympathetically mediated response. Patients were divided into three categories according to their perception of skin temperature in their injured limb (stage I, stationary warmth sensation; stage II, intermittent warmth and cold sensation; or stage III, stationary cold sensation). RESULTS Distal to the site of trauma, when compared with controls, skin blood flow was increased at stage I and decreased at stages II and III, whereas the vasoconstrictive response to dependency was impaired at all three stages. Proximally, when compared with controls, relative distention of the brachial artery and its response to the cold pressor test were decreased at all three stages. No differences were observed in pulse pressure between patient groups and controls. CONCLUSIONS These results suggest that sympathetic dysfunction in extremities of patients with RSD distal to the site of trauma consists of hypersensitivity to catecholamines at stages II and III as a result of autonomic denervation at stage I, whereas proximal to the site of trauma sympathetic nerve impulses may be increased at all three stages.

Motor denervation induces altered muscle fibre type densities and atrophy in a rat model of neuropathic pain

Loose ligation of a sciatic nerve in rats (chronic constriction injury; CCI) provokes sensory, autonomic, and motor disturbances like those observed in humans with partial peripheral nerve injury. So far, it is unknown whether these motor disturbances result from (mechanical) allodynia or from damage to the motor neuron. These considerations prompted us to assess, in CCI rats, the density of motor axons in both the ligated sciatic nerve and the ipsilateral femoral nerve. To this end, we determined the number of cholinesterase positive fibres. It has been demonstrated previously that muscle fibre type density may be used as a measure of motor denervation and/or hypokinesia. Therefore, the myofibrillar ATPase reaction was employed to assess fibre type density in biopsies obtained from the lateral gastrocnemius muscle (innervated by sciatic nerve) and rectus femoris muscle (innervated by femoral nerve). We observed axonal degeneration of motor fibres within the loosely ligated sciatic nerve, both at an intermediate (day 21) and at a late stage (day 90) after nerve injury. The reduction in the number of motor nerve fibres was more pronounced distal to the site of the ligatures than proximal. A (less pronounced) reduction of motor fibres was observed in the ipsilateral (non-ligated) femoral nerve. In line with these findings, we observed altered fibre type densities in muscle tissue innervated by the ligated sciatic nerve as well as the non-ligated femoral nerve indicative of motor denervation rather than hypokinesia. The findings of this study suggest that the motor disorder induced by partial nerve injury involves degeneration of motor nerve fibres not only within the primarily affected nerve but also within adjacent large peripheral nerves. This spread outside the territory of the primarily affected nerve suggests degeneration of motor neurons at the level of the central nervous system.

Influence of partial nerve injury in the rat on efferent function of sympathetic and antidromically acting sensory nerve fibers.

OBJECTIVE To investigate how partial injury of a large peripheral nerve affects efferent (vasomotor) function of sympathetic and antidromically acting sensory nerve fibers. DESIGN Randomized animal study. MATERIALS AND METHODS We assessed, by laser Doppler flowmetry, skin blood flow (SBF) in the hindpaw of male Lewis rats before partial injury of the ipsilateral sciatic nerve (through loose ligation) as well as at an early stage (day 4) and at a later stage (day 21) after this procedure. This procedure has been reported to induce signs and symptoms like those observed in patients with causalgia. At the two time points after nerve injury, SBF was assessed before and after (chemical) blockade of sensory and nonsensory (sympathetic) sciatic nerve fibers. Furthermore, at day 21 we measured the density of sympathetic nerve fibers in footpad arteries. MEASUREMENTS AND MAIN RESULTS At day 4, compared with preligation values, we observed an increase in SBF that was reduced by blockade of sensory nerve fibers. Subsequent blockade of nonsensory nerve fibers further reduced SBF. At day 21, SBF was decreased compared with preligation values. Blockade of sensory nerve fibers further reduced SBF, and subsequent blockade of nonsensory nerve fibers did so as well. The density of sympathetic nerve fibers was lower on the ligated side than on the nonligated side. CONCLUSIONS Partial injury of the rat sciatic nerve causes an ipsilateral increase in SBF at an early stage, which is followed by a decrease at a later stage. At both stages, antidromically acting sensory and orthodromically acting nonsensory (sympathetic) nerve fibers are involved in the vasodilator response. At a later stage, however, neurogenic vasodilator mechanisms are overruled by a nonneurogenic vasoconstrictor mechanism. The latter may consist of supersensitivity of skin microvessels to catecholamines consequent to reduced neurogenic disposition of catecholamines.

The influence of local skin heating and reactive hyperaemia on skin blood flow abnormalities in patients with reflex sympathetic dystrophy (RSD).

Abstract. Skin blood flow in reflex sympathetic dystrophy (RSD) patients has been reported to develop from an increase at an early stage to a decrease at later stages. So far, it remains unclear whether these abnormalities are solely of microcirculatory origin, and result from functional vasospasm or structural vessel wall changes. Eighty‐seven RSD patients were categorized as follows: stage I in case of a stationary warmth sensation; stage II in case of an intermittent warmth and cold sensation; and stage III in case of a stationary cold sensation. Laser Doppler flowmetry (LDF) was used as a measure of total skin blood flow and transcutaneous oximetry (TCPO2) as a measure of vascular reactivity in the more superficial skin layers. Local skin heating and reactive hyperaemia were used to study the relative reserve capacity of skin microvessels. Finapres was used to assess digital arterial pressures. As compared to healthy volunteers (n=16), LDF under control conditions demonstrated an increase in skin blood flow at stage I (P<0.01). A decrease in skin blood flow under control conditions was seen at stages II (P<0.05) and III (P<0.05), but the relative flow reserve capacity, as measured with LDF, was not impaired at these stages. Regression analysis did not show a relation between LDF parameters and duration of the syndrome. TCPO2 revealed no differences between patient groups and controls. Regression analysis did not demonstrate a relation between TCPO2 parameters and duration of the syndrome. Digital systolic blood pressures were increased at stages II (P<0.05) and III (p<0.001). These findings indicate that abnormalities in skin blood flow, as observed in RSD patients, are of microcirculatory origin. The observed decrease in skin blood flow at stages II and III most likely results from functional vasospasm rather than from structural vessel wall changes.

Skin blood flow disturbances in the contralateral limb in a peripheral mononeuropathy in the rat

Electrical excitation of nociceptive afferents in an extremity has been demonstrated to increase skin blood flow in the contralateral extremity. Hence, one would expect that loose sciatic nerve ligation, which induces an experimental painful peripheral neuropathy, may also provoke a vasodilator response in the contralateral hindpaw. On the non-ligated side, such a response may involve inhibited skin vasoconstrictor activity as well as neurogenically mediated active vasodilation. We studied skin blood flow changes in the rat hindpaw consequent to contralateral loose sciatic nerve ligation. After ligation, we also investigated whether blockade of afferent input from the ligated sciatic nerve to the spinal cord, by means of lidocaine, overrules the vasodilator response in the non-ligated paw. On the non-ligated side, we assessed the vasoconstrictor response of skin microvessels to cooling of the rat abdomen as a measure of skin vasoconstrictor activity in this paw. In order to investigate the involvement of sensory and/or non-sensory nerve fibers in the non-ligated sciatic nerve on skin blood flow abnormalities in the non-ligated paw, we studied the influence of blockade of these fibers through successive capsaicin and lidocaine application. We show that loose ligation of the sciatic nerve induces a vasodilator response in the contralateral hindpaw, which is completely abolished by blockade of afferent input from the ligated sciatic nerve. From day 1 after ligation, skin vasoconstrictor activity in the non-ligated paw was reduced, as indicated by an impaired vasoconstrictor response to cooling of the rat abdomen. Besides, blockade of sensory but not of non-sensory nerve fibers on the non-ligated side attenuated the vasodilator response in this paw. The data presented here indicate that loose ligation of the rat sciatic nerve induces a vasodilator response in the contralateral hindpaw. On the non-ligated side, this vasodilator response may involve inhibition of skin vasoconstrictor activity, as well as antidromically acting sensory nerve fibers.

Effects of Surgical Sympathectomy on Skin Blood Flow in a Rat Model of Chronic Limb Ischemia

Abstract. The role of lumbar sympathectomy in the treatment of limb ischemia secondary to arteriosclerosis obliterans has been controversial. Increased temperature and rubor of the skin, which usually follow sympathectomy, have generally been interpreted as indicative of improved nutritive skin blood flow. However, the existence of a (nonnutritive) thermoregulatory level of skin microcirculation makes such an extrapolation questionable. We investigated the total (mainly thermoregulatory) skin blood flow (TSBF) in the hindlimb of 15 male Lewis rats by means of laser Doppler flowmetry and the nutritive skin blood flow (NSBF) by means of capillary microscopy (red blood cell velocity). Transcutaneous oximetry was used to assess skin oxygenation (SO). Measurements were performed before and 2 and 28 days after ligation of the common iliac and iliolumbar artery. Subsequently, either a surgical resection of the sympathetic chain (L 2 –L 6 ) was performed or a sham operation. Measurements were repeated 2 and 28 days later. For the group of 15 rats as a whole, TSBF (p < 0.05), NSBF (p < 0.05), and SO (p < 0.05) were found to be drastically reduced at day 2 after ligation compared to preligation values. This reduction partially recovered during the following weeks. TSBF (p < 0.05) and NSBF (p < 0.05), however were still reduced at day 28 after ligation compared to preligation values, whereas the SO at this time tended to be lower (p= 0.11). In the sympathectomy group the TSBF was found to be increased at day 2 (p < 0.05) and day 28 (p < 0.05) after sympathectomy, both compared to values obtained at day 28 after ligation. Sympathectomy did not have an effect on NSBF and SO. The sham procedure had no effect on the TSBF, NSBF, or SO. These results indicate that in case of lower limb ischemia, sympathectomy improves skin blood flow at the thermoregulatory but not the nutritive level of skin microcirculation. This may be related to the fact that the thermoregulatory vessels are mainly sympathetically controlled, whereas the nutritive capillaries are mainly controlled by local (nonneural) factors.