Changes in sympathetic thermoregulatory function with aging

We recorded skin sympathetic nerve activity (SSNA), SSR, and SVR in 30 subjects. SSNA and SVR showed a slight decrease and spontaneous changes in resting SSR were significantly less frequent in older subjects compared with younger subjects (p < 0.05). There was no significant relationship between age and the reflex latency or amplitude of SSNA, SSR, and SVR in response to electrical stimulation.     

Sympathetic skin responses: the influence of electrical stimulus intensity and habituation on the waveform

Abstract Repeated stimulation of the sympathetic skin response (SSR) causes habituation. The aim of this study was to determine the effects of electrical stimulus intensity on SSR in 40 healthy controls (mean age±SD, 28.0±6.7 years). Electrical stimuli at three intensities (5, 15 and 30 mA) were applied to the median nerve at the wrist in four consecutive sessions, after which a magnetic stimulus was applied to the neck. SSR were classified according to the proportion of positive (P) and negative (N) waveform components.Twentyfour subjects had both P and N waveforms. In the first session, 75% of these subjects had a P waveform, indicative of a greater SSR, in response to the 30 mA shock. In the progressive sessions, the SSR waveform was predominately negative (N waveform, session 2, 65%; session 3, 83%; session 4, 75% in response to 30 mA shock), indicating that the SSR was weaker as a result of habituation. There was no clear relationship between stimulus intensity and waveform type, indicating that SSR waveforms are more strongly influenced by habituation than stimulus intensity. However, there was a directly proportional relationship between stimulus intensity and amplitude of the SSR wave (F=70.9, P<0.0001, two-way repeated measure ANOVA), be it positive or negative. The relationship between stimulus intensity and amplitude persisted, even after habituation. Suddenly switching to a magnetic stimulus reverted the SSR wave back to positive (80%), indicating that habituation was rapidly reversible if stimulation of the SSR is altered.     

The significance of intact sympathetic skin responses in carpal tunnel syndrome

The current study aimed to investigate the impact of carpal tunnel syndrome (CTS) on sympathetic skin response (SSR) recorded from the median and ulnar territory. Thirty patients were studied and idiopathic CTS was documented in a total of 46 hands. These were classified, according to electrophysiological criteria, into two groups; a group of 31 hands with severe CTS and a group of 15 hands with mild/moderate CTS, and were compared with a group of 30 hands of age-matched controls. SSR was recorded simultaneously from the median and ulnar side of the palm following electrical stimulation at the wrist, in a mid-point between median and ulnar nerve. Latency, amplitude, habituation and the median-to-ulnar ratio were estimated. In all controls clear recordings of SSR were obtained. In the patient groups, absence of SSR was never observed either in mild/moderate or in the severe CTS hands. The mean SSR latency and amplitude values recorded from both the median and ulnar nerves did not significantly differ between mild/moderate or severe CTS hands and controls. Likewise, the median-to-ulnar ratio and habituation of SSR latencies and amplitudes did not significantly differ between groups. SSR does not seem to be a sensitive method for evidence of autonomic involvement in CTS, even in patients manifesting sudomotor or other autonomic symptoms. In the present setting, SSR appeared to be independent of somatic afferent function and the corresponding sensory action potentials.     

Excitability recovery curve of the sympathetic skin response in healthy volunteers and patients with palmar hyperhidrosis.

OBJECTIVES: Patients with primary palmar hyperhidrosis (PPH) might exhibit hyperexcitability of the reflex circuits involved in sweating. We hypothesized that this hyperexcitability could become evident in the study of the excitability recovery curve of the sympathetic sudomotor skin response (SSR). METHODS: In 10 patients with PPH and 10 healthy volunteers used as control subjects, we recorded the SSR in the palm of the right hand to pairs of median nerve electrical shocks separated by inter-stimuli intervals (ISIs) ranging from 0.5 to 3.5 s. The amplitude of the SSR generated by the second stimulus (SSR2) was expressed as a percentage of that generated by the first (SSR1), and compared between control subjects and patients for each ISI. RESULTS: None of the control subjects showed a recovery of the SSR for ISIs of 1.5 s or less. On the contrary, patients showed a statistically significant enhancement of the SSR excitability recovery curve, with onset of recovery at 1.5 s in 5 patients. Two patients showed a double peak response to single electrical stimulation and were not considered in the calculation of the SSR recovery curve. Mean excitability recovery percentages were larger in patients than in control subjects at ISIs of 2, 2.5 and 3 s. CONCLUSIONS: The enhancement of the SSR recovery curve in patients with PPH suggests hyperexcitability of the somatosympathetic polisynaptic pathway involved in sweating. This could partly underlie the pathophysiology of PPH.     

The sympathetic skin response habituation in sedentary subjects and sportsmen

The aim of the present study was to investigate the habituation rates of the sympathetic skin response (SSR) in sedentary subjects and trained sportsmen. A total of 52 voluntary male students (30 sedentary subjects and 22 trained sportsmen) participated in the experiment. SSR was recorded with the contralateral electrical stimulation of the ulnar nerve (of the upper extremities). In order to initiate the SSRs, 16 square-wave consecutive electrical shock stimuli were presented to each subject over the left ulnar nerve. In 52 subjects, 16 stimuli were applied at random time intervals (20-50 s). In sedentary subjects, the mean amplitude of the SSRs decreased from 4.83 +/- 0.36 mV at the first stimulus, to 0.80 +/- 0.12 mV at the 16th stimulus. In trained sportsmen, the mean amplitude of the SSRs decreased from 3.95 +/- 0.51 mV at the first stimulus, to 0.80 +/- 0.17 mV at the 16th stimulus. In the sedentary subjects, at the S1-S9 stimuli, the mean amplitudes of SSRs were higher than those of trained sportsmen. Depending upon these findings we can say that the trained sportsmen showed a more rapid habituation than sedentary subjects. In these processes, changes of amplitude and latency values reflect changes in amount of neuronal activation. Amplitude reflects the amount of neuronal activation, which is concerned with number of neuronal populations. Neuroplasticity, known as the habituation of the brain, is the adaptation of autonomic nervous system, which can be reflected by SSRs.     

Characteristics of habituation of the sympathetic skin response to repeated electrical stimuli in man.

OBJECTIVES: To study the effect of repeating electrical peripheral nerve stimulation on latency, duration and amplitude of the sympathetic skin response (SSR). METHODS: SSRs were elicited in all limbs by median and peroneal nerves stimuli. In 10 subjects, 20 stimuli were applied at random time intervals (15-20 s). Another test was performed in 7 subjects using the same protocol, but switching the stimulation site every 5 or 10 stimuli without warning. RESULTS: The mean amplitude of right palmar response to right peroneal nerve stimulation decreased from 5.05+/-0.76 (SEM) mV at the first stimulus to 1.23+/-0.42 mV at the 20th stimulus (P<0.001). The latency did not change significantly (1473+/-82 to 1550+/-90 ms, P>0.1), while the duration increased (1872+/-356 to 3170+/-681 ms, P<0.001). Stimulation and recording at other sites showed similar trends. Changing the stimulation site failed to alter the adaptation process in terms of amplitude, latency or duration. CONCLUSIONS: Changes in amplitude and duration of the SSRs to repeated electrical stimuli can occur in presence of constant latency and appear to be independent of the source of sensory input. Peripheral sweat gland mechanisms may be involved in the loss of amplitude and increase in duration of the SSR during habituation.     

Evaluation of sympathetic skin response in Parkinson's disease

There is no clear definition on the role of sympathetic skin response (SSR) in the evaluation of patients with Parkinson's disease (PD). We recorded the SSR of the palms of 64 controls and 46 patients with PD to electrical stimulation of the median nerve at the wrist. We analyzed onset latency and peak-to-peak amplitude. A study of parasympathetic function (R–R interval analysis) was also undertaken. We found that patients with PD had more absent SSRs than controls. The mean amplitude of the SSR was significantly reduced in both lower and upper limbs of PD patients in comparison with control subjects (p<0.001). The onset latency was longer in the lower limbs of these patients in respect to the control group (p<0.003). There was a significant inverse correlation between SSR amplitudes and age, severity and late onset of the disease. There was no association of these parameters with dysautonomic symptoms or R–R interval variation. In conclusion, there is a significant association between altered SSR and PD and an inverse correlation in this group of patients between SSR values and older age, greater severity and later onset of disease. Therefore, the study of SSR may provide valuable information on cholinergic sympathetic function in patients with PD.     

Sympathetic sudomotor and vasoconstrictive neural function in patients with Parkinson's disease

To evaluate sympathetic sudomotor and vasoconstrictive neural function in Parkinson's disease (PD), we simultaneously recorded sympathetic skin response (SSR) and skin blood flow (SVR; skin vasomotor reflex), as well as skin sympathetic nerve activity (SSNA) measured in peroneal nerves by microneurography, comparing 12 patients with idiopathic PD with 16 healthy controls. Resting SSNA frequency (8.8 ± 4.3 bursts/min) was significantly lower in PD patients than in controls (p < 0.01). Frequency increases in response to performing mental arithmetic were slightly smaller in PD patients than in controls. PD patients exhibited normal SSNA reflex latencies compared with controls. Although no significant relationship was found between resting SSNA frequency and disease duration or degree of disability, a significantly negative correlation between increases in SSNA with mental arithmetic and PD duration was observed. Occurrence of SSR and SVR following SSNA bursts induced by electrical stimuli was reduced in PD (p < 0.05). In patients with PD, sympathetic sudomotor and vasoconstrictive neural function was decreased at rest, but SSNA reflex latencies in the legs were nearly normal. Since responses of peripheral target organs may be impaired, both central and peripheral factors may contribute to autonomic symptoms in PD.     

Sleep stage-related changes in sympathetic sudomotor and vasomotor skin responses in man.

OBJECTIVES: The aim of the study was to evaluate the characteristics of the spontaneous and evoked sympathetic skin responses (SSR) during sleep and wakefulness in comparison with the skin vasomotor responses (SVR). METHODS: Five healthy subjects underwent a night of videopolysomnographic recording. Spontaneous SSR were recorded via surface electrodes placed on the dorsal and ventral aspect of the hand while SVR were evaluated by means of an infrared photoelectric transducer placed on the index finger. SSR and SVR were evoked via electrical stimuli applied to the left supraorbital nerve. RESULTS: Spontaneous SSR frequency was highest during stage 4 of NREM sleep and lowest during REM phases. On the contrary, spontaneous SVR frequency reached its lowest value during stage 4 and its highest value during stage 2 of NREM sleep, remaining at levels above waking values during REM. SSR could be elicited by stimuli inducing arousal during light sleep but it was absent during deep NREM and REM sleep. SVR could be evoked throughout NREM and REM sleep. CONCLUSIONS: Spontaneous SSR and SVR act differently during physiological modifications of vigilance. Evoked SSR is strictly dependent upon the state of vigilance, whereas evoked SVR shows no modifications during the different stages of the wake-sleep cycle.     

Muscle and skin sympathetic activities in Ross syndrome

ObjectivesRoss syndrome (RS) is a rare degenerative disorder characterized by tonic pupil, areflexia and anhydrosis. The underlying lesion affects postganglionic skin sympathetic nerve fibers whereas the postganglionic muscle sympathetic branch is thought to be spared. Microneurography explores both skin and muscle peripheral sympathetic branches and it does not usually detect peripheral sympathetic outflow in either branch in chronic autonomic failure syndromes. The aim of this study was to record sympathetic activity by microneurography for the first time in RS patients to confirm the selective involvement of skin sympathetic nerve activity (SSNA) with spared muscle sympathetic nerve activity (MSNA).MethodsWe studied seven patients (49 ± 14 years, four males) with a typical clinical picture and skin biopsy findings. Patients underwent cardiovascular reflexes and microneurography from the peroneal nerve (anhydrotic skin) to record MSNA, SSNA and the corresponding organ effector responses (skin sympathetic response-SSR and skin vasomotor response-SVR) in the same innervation field. The absence of sympathetic bursts was established after exploring at least three different corresponding nerve fascicles. Twenty age-matched healthy subjects served as controls.ResultsRS patients complained of diffuse anhydrosis and they showed tonic pupil and areflexia. Cardiovascular reflexes were normal. All patients displayed absent SSNA, SSR and SVR whereas MSNA was always recorded showing normal characteristics.ConclusionMicroneurographic study of sympathetic activity from affected skin confirmed the selective involvement of skin sympathetic activity with spared muscle sympathetic activity and it may represent the neurophysiological hallmark of the disease.SignificanceMicroneurography together with clinical and skin biopsy findings may contribute to RS diagnosis. Our data also suggest that autonomic damage in RS does not involve cardiovascular activity.     

Sympathetic skin response (SSR) is abnormal in multiple sclerosis

As the function of the autonomic nervous system is often compromised in multiple sclerosis (MS), different standardized tests are used to detect disseminated abnormalities in cardiovascular autonomic functions. Sympathetic skin response (SSR), a slow wave generated in deep layers of the skin, is induced by reflex activation of sudomotor sympathetic efferent fibers. SSR was studied in 70 patients classified into different categories according to the diagnostic criteria for MS. We also obtained pattern reversal visually evoked potentials and brainstem auditory evoked potentials as well as somatosensory evoked potentials (by median and posterior tibial nerve stimulation). SSR was abnormal in 66 patients (94.2%), including abnormal foot latency with normal hand latency in 30 (42.8%), delayed foot and hand latencies in 30 (42.8%), and no response in 6 (8.6%). The percentages of SSR abnormalities were similar in the different patient categories. Pathological SSR were more common than abnormal evoked potentials in suspected and probable MS. SSR appears to be a simple and effective means of assessing sympathetic sudomotor outflow disturbances in MS, providing a valuable addition to current electrophysiological procedures for the detection of MS lesions.© 1995 John Wiley &Sons, Inc.     

脑梗死患者交感神经皮肤反应分析

交感神经皮肤反应（sympathetic skin response,SSR）是由内源或外源性刺激所诱发的皮肤 瞬时电位变化,属于脑和脊髓参与的交感催汗运动。本文主要概述近年来SSR在脑梗死患者中应用 价值,阐述其对脑梗死患者自主神经功能紊乱的临床诊断作用,与脑梗死患者运动功能的相关性, 以及SSR在推断交感神经可能的中枢传导通路中的价值。     

Within-subject consistency of sympathetic-skin-response waveform across different modalities of stimulation

This study was conducted to investigate the intra-subject consistency of the waveform type and the size of the sympathetic skin response (SSR) evoked by different modalities of stimulation. Thirty-eight normal volunteers were enrolled as subjects. SSRs were obtained using three different modalities of stimulations: auditory (a-SSR), electrical (e-SSR), and magnetic (m-SSR). Four stimuli of each modality were applied. The waveforms were classified into two types, P (positive component larger the than negative component) and N (vice versa). P-type waveforms were less frequent in the a-SSR than in the e- and m-SSR. The occurrence of the respective waveforms and the values of maximum amplitudes were significantly correlated among the SSRs evoked by different types of stimulation. Judging from these results, the SSR waveforms and size seemed to be consistent in individuals. The results also suggested that endogenous factors in an individual related to the development of SSRs e.g., individual's emotional state, susceptibility to the surprise effect, and anatomical characteristic were important determinants of the SSR waveforms and maximum amplitude.     

Sympathetic skin response in carpal tunnel syndrome.

OBJECTIVES: Sudomotor efferent nerve fiber function was studied in carpal tunnel syndrome (CTS). METHODS: Bilateral median and ulnar sympathetic skin response (SSR) were recorded by sternal stimulation in 22 bilateral and 9 unilateral patients and compared with 21 healthy volunteers. RESULTS: There was no significant difference between median and ulnar nerve SSR latency, amplitude or area. The median nerve SSR was not different from that of the controls. The median-to-ulnar ratios of SSR parameters were not different in patients and controls. However, the median-to-ulnar ratios of SSR amplitude and area were lower than normal in 3 out of 7 patients with normal nerve conduction whereas this abnormality was found in only 4 out of 46 patients with abnormal nerve conduction. CONCLUSIONS: Normal SSR results, even in patients with complaints related to sudomotor sympathetic dysfunction, indicate that the SSR does not seem to be a sensitive diagnostic method in CTS.     

Peripheral autonomic involvement in the carpal tunnel syndrome

The sympathetic skin response (SSR), evoked from the middle finger of both hands by electrical stimuli to the median nerve (MN) at the wrist, was studied in 21 patients with bilateral carpal tunnel syndrome (CTS) and in 16 patients with monolateral CTS (14 at the right and 2 at the left side) without clinical signs of autonomic involvement. In monolateral and bilateral CTS there was a decrease in the SSR areas of both sides. In monolateral CTS the decrease was greater contralaterally to the lesion. A decrease in the SSR in CTS generally indicates a local blockade of sympathetic nerve excitability due to MN entrapment. Contralateral reduction of the sympathetic response suggests an involvement of the efferent pathway of the autonomic reflex far from the lesion at the wrist. However, dispersion of the excitement over a long distance and throughout numerous synaptic connections may affect contralateral more than homolateral SSR excitability. Finally, sympathetic damage in CTS is in accord with the anatomofunctional correlation (in the peripheral nerve and ganglia) between somatic sensory, which were most markedly involved in our patients, and sympathetic afferent nerve fibers.     

Sympathetic skin response following thermal, electrical, acoustic, and inspiratory gasp stimulation in familial dysautonomia patients and healthy persons

To determine whether sympathetic skin response (SSR) testing evaluates afferent small or efferent sympathetic nerve fiber dysfunction, we studied SSR in patients with familial dysautonomia (FD) in whom both afferent small and efferent sympathetic fibers are largely reduced. We analyzed whether the response pattern to a combination of stimuli specific for large or small fiber activation allows differentiation between afferent and efferent small fiber dysfunction. In 52 volunteers and 13 FD patients, SSR was studied at palms and soles after warm, cold and heat as well as electrical, acoustic, and inspiratory gasp stimulation. In addition, thermal thresholds were assessed at four body sites using a Thermotest device (Somedic; Stockholm, Sweden). In volunteers, any stimulus induced reproducible SSRs. Only cold failed to evoke SSR in two volunteers. In all FD patients, electrical SSR was present, but amplitudes were reduced. Five patients had no acoustic SSR, four had no inspiratory SSR. Thermal SSR was absent in 10 patients with abnormal thermal perception and present in one patient with preserved thermal sensation. In two patients, thermal SSR was present only when skin areas with preserved temperature perception were stimulated. In patients with FD, preserved electrical SSR demonstrated the overall integrity of the SSR reflex but amplitude reduction suggested impaired sudomotor activation. SSR responses were dependent on the perception of the stimulus. In the presence of preserved electrical SSR, absent thermal SSR reflects afferent small fiber dysfunction. A combination of SSR stimulus types allows differentiation between afferent small or efferent sympathetic nerve fiber dysfunction.     

抑郁症患者的交感神经皮肤反应探讨

目的探讨交感神经皮肤反应(SSR)对抑郁症患者的临床价值。方法对45例抑郁症患者治疗前后和43例正常健康者分别进行SSR测定和汉密尔顿抑郁量表(HAMD)评定,并加以比较。结果抑郁症组治疗前SSR测定的异常率为84.4%(38/45),而治疗后异常率为13.3%(6/45)。治疗前SSR测定波潜伏期及波幅值较治疗后及对照组分别延长和降低,差异有统计学意义(P<0.01);治疗后抑郁症组HAMD评定分值较治疗前降低,差异有统计学意义(P<0.01)。相关分析结果表明,抑郁症患者SSR波潜伏期与HAMD分值呈显著正相关(P<0.01),其波幅与HAMD分值呈显著负相关(P<0.01)。结论交感神经皮肤反应测定可作为判定抑郁症患者自主神经功能的参考指标应用于临床。     

偏头痛患者交感神经皮肤反应的研究

目的:探讨交感神经系统在偏头痛伤害性信息传递中的作用。方法:应用神经电生理测定了56例偏头痛患者和30例健康人交感神经皮肤反应。结果:偏头痛患者发作期、间歇期交感神经皮肤反应的潜伏期均明显长于正常对照组,而波幅显著低于对照组;偏头痛发作期的潜伏期显著长于间歇期,波幅显著低于间歇期。结论:偏头痛患者存在交感神经功能低下。     

Sympathetic skin response evoked by respiratory stimulation as a measure of sympathetic function.

OBJECTIVES: To compare respiratory and electrical methods of evoking a sympathetic skin response (SSR). METHODS: SSRs evoked by both electrical and respiratory stimulation were recorded from the palms of 47 healthy volunteers. Expiration and inspiration were used as separate stimuli. The correlation coefficients between the amplitude and latency of the SSR from the palm electrodes and the various components of heart rate variability were calculated. RESULTS: Waveform patterns of the SSRs obtained from electrical stimulation showed varied responses to and habituation to this type of stimulation. On the other hand, no subjects showed a phase change in SSR waveform patterns between the first and last expiratory stimuli. The potentials recorded after expiratory stimulation had significantly greater amplitudes than those recorded after electrical stimuli. The low frequency component of heart rate variability induced by expiratory stimulation was significantly greater than that induced by electrical stimulation. The SSR may also correlate strongly with the change of respiratory rate since a more rapid pressure change occurs during expiratory movement than during inspiratory movements. CONCLUSIONS: The SSR evoked by expiratory stimulation is more reliable than either electrical stimulation or inspiratory stimulation for determining sympathetic function.     

Sympathetic co-activation of skin blood vessels and sweat glands

Abstract. Skin blood vessels and sweat glands are both innervated by sympathetic C fibers. We investigated whether during diverse respiratory maneuvers the vasomotor responses (VRs) and the sympathetic skin responses (SSRs) were frequently or occasionally co-activated. We simultaneously recorded the amplitude of the vasomotor responses and the sympathetic skin responses, the ECG and the respiratory movements in 30 healthy subjects during natural breathing at rest, rhythmic respirations at 6 per minute, sudden deep inspiration and Valsalva maneuver. We found: 1) The SSR habituates with all respiratory maneuvers whereas the VRs do not habituate. 2) There was slight co-activation between the SSRs and VRs during natural default breathing (56 percent). 3) During rhythmic breathing at 6 per minute the VRs and the SSRs were frequently co-activated (97 percent). The SSR appeared at the end of the inspiration coinciding with the end of the decreased blood flow. However the SSR habituated after few rhythmic respirations. 4) During sudden deep inspiration one hundred percent of co-activations were between the initial phase of the VRs and the SSR. The SSR is large in amplitude and longer in duration than during rhythmic breathing. 5) During the Valsalva maneuver there was a strong co-activation (100 percent) particularly during the phases II and III that are characterized by vaso-constriction but also during phase IV. The SSR is the longest of duration in all of the maneuvers. The sympathetic innervation to the sweat glands of the palm of the hand and to the skin blood vessels of the fingertips is differentiated. Under normothermic conditions sudden deep inspiration and Valsalva maneuver induced a large sympathetic simultaneous outflow to the skin blood vessels and sweat glands. The simultaneous recording of skin blood flow and the SSRs provides a more complete assessment of the sympathetic outflow to the skin than either one alone.