Sympathetic Skin Response Amplitude Research Articles

Sympathetic skin response in idiopathic and diabetic carpal tunnel syndrome

In carpal tunnel syndrome (CTS), certain changes were expected in sympathetic skin response (SSR) because median nerve carries postganglionic unmyelinated fibres. To investigate the median and ulnar SSR in idiopathic and diabetic CTS without autonomic dysfunction in hands and to find possible relations with electrophysiological features of these diseases. SSRs were elicited by electrical stimulation on the supraorbital nerve and recorded from the median and ulnar territories in the hand from 20 diabetic patients with only CTS (29 hands), 24 idiopathic CTS patients (42 hands) and 13 normal subjects (26 hands). Hands with ulnar neuropathy at the wrist without symptoms and normal hands of unilateral CTS were excluded. In addition to classical parameters and comparative methods, SSR waveform changes and percentile method was used in finding abnormality. Median SSRs had significant delayed latency compared to ulnar latency in both CTS patients but this was not important clinically (1.38/1.37 s for idiopatic CTS; 1.43/1.36 s for diabetic CTS). Median and ulnar SSR amplitude, area, median/ulnar latency difference, amplitude and area ratio were compared and only median/ulnar latency difference and median/ulnar latency ratio were found different between the three groups. Four idiopathic CTS hands were outside of the limits or absent (9.5%). SSR waveforms were significantly different from normal subjects in CTS patients. P type SSR replaced M type in idiopathic CTS and N type in diabetic CTS. Findings regarding SSR parameters suggest that unmyelinated C fibers were affected in CTS. These values were not useful because they were too small. Data on SSR were not normally distributed and the percentile method seems to be more convenient for finding any abnormality in clinical practice. Also, SSR waveform analysis could give us valuable data and should add to the SSR examination parameters.

Relationship between sympathetic skin response and power spectral analysis of heart rate variation in patients with type 2 diabetes

We measured sympathetic skin response (SSR), a measure of sympathetic sudomotor function, and compared SSR with other quantitative neurological tests including power spectral analysis (PSA) of heart rate variations in 60 type 2 diabetic subjects. SSR was detected in all 20 age-matched healthy subjects but was absent in 17 patients with type 2 diabetes (28%) (P<.01). Even after exclusion of diabetic patients with absent SSR, the SSR amplitude in diabetic patients was significantly lower than in healthy subjects (P<.05). Both the low frequency power of R-R intervals, which reflects both cardiac sympathetic and parasympathetic function, and the postural fall in systolic blood pressure were significantly lower in the diabetic patients with absent SSR than in those with present SSR (P<.05 and.001, respectively). However, we found no significant difference in the high frequency power of R-R intervals, which reflects accurately cardiac parasympathetic function, between the diabetic patients with absent SSR and those with present SSR. In the diabetic patients with present SSR, SSR amplitude was also positively correlated with the postural fall in systolic blood pressure, low-frequency (LF) power, and high-frequency (HF) power. These results suggest that SSR is a useful and sensitive method for evaluating diabetic autonomic neuropathy, and that sympathetic sudomotor neuropathy may be preceded by cardiac parasympathetic neuropathy in patients with type 2 diabetes.

Sympathetic skin response in women receiving hormone replacement therapy

The peripheral skin sympathetic nerve function is continuously hyperstimulated in women with climacteric complaints, and one study concluded that, although the reason is not clear, sympathetic nerve dysfunction must be the main cause for this hyperstimulation w1x. Postmenopausal hormone replacement therapy (HRT) has significant effects on the amplitude of sympathetic skin response (SSR), but no significant effects on latency values. Another study concluded that estrogens have a significant inhibitory effect on the sympathetic neuron pool at the spinal cord level w2x. The present study investigated the effects of HRT on SSR. Forty-one postmenopausal women admitted to our menopause clinic were enrolled in the study. Women with heart failure, ischemic cardiopathy, chronic renal failure, severe hypertension, diabetes mellitus, or other disorders that might affect the autonomic nervous system were excluded. All women had hot flushes and sweating complaints. Before initiation of HRT, SRR tests were

R-R interval variation and the sympathetic skin response in the assessment of the autonomic nervous system in leprosy patients.

The aim of this study was to evaluate possible autonomic nervous system (ANS) dysfunction in leprosy patients with the sympathetic skin response (SSR) and the heart rate (R-R) interval variation (RRIV) measurements which are easy and reliable methods for evaluation of autonomic functions. We studied 37 lepromatous leprosy patients (mean age: 38 +/- 17 years, range 23-62 years, 20 females and 17 males) and 35 age-matched healthy subjects (mean age: 34.19 +/- 12.74 years, range 24-48 years, 20 females and 15 males). Non-invasive bedside tests (orthostatic test, Valsalva ratio), R-R interval variation (RRIV) during at rest and deep breathing, the SSR latency and amplitude from both palms, and nerve conduction parameters were studied in all the subjects. The mean values of RRIV in leprosy patients during at rest [mean RRIV in patients, 17.42 +/- 8.64% vs controls, 22.71 +/- 3.77% (P < 0.05)] and during deep breathing [mean RRIV in patients, 21.64 +/- 9.08% vs controls, 30.70 +/- 5.99% (P < 0.005)] was significantly lower compared with the controls. The mean latency of SSR in leprosy patients [mean SSR latency in patients, 1.72 +/- 1.13 ms vs controls, 1.30 +/- 0.41 ms (P < 0.05)] was significantly prolonged compared with the controls. The mean amplitude of SSR in leprosy patients [mean SSR amplitude in patients, 0.54 +/- 0.57 microV vs controls, 1.02 +/- 0.56 microV (P > 0.05)] was smaller compared with the controls, but this difference was not significant. The mean Valsalva ratio in leprosy patients [mean in patients, 1.11 +/- 0.13 vs controls, 1.16 +/- 0.07 (P > 0.05)] was smaller compared with the controls, but not statistically significant. The mean difference of systolic and diastolic blood pressure between supine rest and during standing in leprosy patients were higher compared with the controls [mean systolic pressure in patients, 7 +/- 6 mmHg vs controls, 6 +/- 8 mmHg (P > 0.05) and mean diastolic pressure in patients, 3 +/- 3 mmHg vs controls, 3 +/- 2 mmHg (P > 0.05)], but they did not reach statistical significance. Furthermore, lower RRIV and the prolonged SSR latencies in leprosy patients were closely correlated to some parameters of sensorimotor nerve conduction and each other [median nerve distal latency and RRIV, r = -0.67 (P < 0.05), ulnar nerve distal latency and RRIV, r = -0.59 (P < 0.05), RRIV and SSR latency, r = -0.33 (P < 0.02)]. These data indicate that leprosy patients have the functional abnormalities of ANS. We conclude that combined use of these two tests, both of which can be easily and rapidly performed in the electromyogram (EMG) laboratory using standard equipment, allows separate testing of parasympathetic and sympathetic function, and are very sensitive methods in assessing of ANS function in peripheral neuropathy in leprosy patients.

Autonomic nervous system function in Huntington's disease

Objective: To investigate whether Huntington's disease (HD) affects autonomic nervous system (ANS) functioning. Methods: Twenty patients with HD who had positive genetic test results underwent standardised ANS function tests including...

Comparison of SSR and QSART in early diabetic neuropathy—the value of length-dependent pattern in QSART

We evaluated postganglionic sympathetic function using the sympathetic skin response (SSR) and quantitative sudomotor axon reflex test (QSART) on the feet of 31 patients with early diabetic neuropathy and 20 age-matched normal controls. The amplitude of SSR and the sweat volume of QSART were significantly decreased in the diabetic patients. We evaluated the sensitivity of the tests in detecting autonomic failure. Out of 31 patients, 14 (45%) had abnormal SSR (14 absent; 17 present), while 16 of 31 patients (52%) had abnormal QSART (1 absent; 5 absolutely reduced and 10 showed a length-dependent pattern of reduction). More important than differences in sensitivity is the specificity of QSART, which specifically evaluates the postganglionic axon (instead of polysynaptic pathways in SSR) and provides quantitative data on the severity and pattern of autonomic deficit. In normal controls under 65 years of age, there was a significant correlation between the amplitude of SSR and the sweat volume of QSART. However, there was no significant relationship between these in diabetic patients. These results suggest that QSART can evaluate early diabetic neuropathy more precisely than SSR.

Sympathetic skin response and cardiovascular autonomic function tests in Parkinson's disease and multiple system atrophy with autonomic failure.

The relationship between sympathetic skin response (SSR) and cardiovascular autonomic function tests (CVTs) was investigated in 15 patients with idiopathic Parkinson's disease (PD), 15 patients with clinical evidence of multiple system atrophy (MSA) with autonomic failure, and in 15 healthy control subjects. SSR was elicited by electrical stimulation of the right and left median nerves and simultaneously recorded on the palms of both hands. CVTs included the following sympathetic and parasympathetic tests: orthostatism, head-up tilt, cold pressor test, deep breathing, Valsalva maneuver, and hyperventilation. The SSR was normal in all patients with PD and control subjects but was abnormal or absent in all patients with MSA. For patients with MSA, SSR latency was significantly longer and amplitude was significantly smaller than that of patients with PD and control subjects. For patients with PD, SSR did not differ from that of control subjects. In these patients, SSR latency was significantly longer and SSR amplitude was smaller when the side with more marked motor symptoms was stimulated, both ipsilaterally and contralaterally to the side of stimulation. A statistically significant difference in SSR latencies and amplitudes was found between patients with PD and control subjects only when motor asymmetries were considered. CVTs showed severe sympathetic and parasympathetic hypofunction in patients with MSA, but not in patients with PD or control subjects. No correlation was found between SSR and CVTs that assess sympathetic function in patients and control subjects. SSR is indicated as an additional test for the evaluation of sympathetic degeneration in patients with MSA.

Preserved sympathetic skin response at the distal phalanx in patients with carpal tunnel syndrome

To assess the viability of sympathetic sudomotor fibers in carpal tunnel syndrome (CTS). We recorded sympathetic skin response (SSR) with a multichannel recording system. Forty-four patients with CTS (51 hands), 7 patients (7 hands) with asymptomatic median mononeuropathy at the wrist (MMW), and 20 normal subjects (20 hands) were studied. We classified the patients into 4 grades of increasing severity. In the hands of normal subjects, SSR was evoked easily at all recorded sites. SSR at the wrist in patients with asymptomatic MMW decreased in amplitude. SSR was markedly distorted at the wrist in severe grades of CTS. The SSR amplitude ratio (wrist/distal phalanx) decreased significantly with more severe grade (rh=-0.4; P<0.05), but the sensitivity was lower than that of other electrodiagnostic criteria. A patient with persistent allodynia at the wrist after surgery showed the slight recovery of SSR amplitude ratio; the other two patients without allodynia showed substantial recovery of SSR amplitude ratio within 24 weeks after surgery. SSR amplitude ratio is a poor indicator of CTS diagnosis, but may be useful in assessing the viability of sympathetic sudomotor fibers and may assist in evaluating the response to surgery.

Sympathetic skin response in carpal tunnel syndrome

Sudomotor efferent nerve fiber function was studied in carpal tunnel syndrome (CTS). 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. 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. 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.

POSSIBLE USE OF SYMPATHETIC SKIN RESPONSE AND THERMOGRAPHY IN ASSESSING THE EFFECTS OF SYMPATHECTOMY: A CASE REPORT

The objective assessment of sympathectomy is clinically difficult. Its success is usually judged in terms of patient's improvement.Aim: This study tested the hypothesis of possible use of Thermography and Sympathetic Skin Response (SSR) in assessing the effects of sympathectomy.Case history: A man suffering from chronic, disabling palmar hyperhidrosis underwent a bilateral, localised, endoscopic resection of the thoracic sympathetic chain, immediately below the second thoracic ganglion. After the operation he had a significant reduction of palmar hyperhidrosis, but he did not feel satisfied with the operation due to distal paresthesias associated with thermal allodynia in the upper limbs and excessive, troublesome compensatory sweating of the trunk and lower limbs. We evaluated him fifteen months after the operation and symptoms were still present. Standard neurological examination was normal apart from a mild heat hyperesthesia in the distal portions of upper limbs.Methods: SSR was evoked by auditory, alerting stimuli and recorded simultaneously from palm and sole bilaterally. We preferred to use auditory stimulation because of the low variability of SSR waveform usually obtained with this method. The amplitude of SSR in the palm and sole were measured and a palm/sole ratio was calculated. Total body thermography was also performed.Results: A clear reduction in SSR palm/sole ratio was observed. Thermography showed a thoracic thermal level with the upper part of the body being warmer than the lower.Conclusion: Judging from the results obtained in this single case, both SSR and Thermography appear to be objective, simple, noninvasive tools for assessment of thoracic simpathectomy effectiveness. Studies on a large population of patients are needed.

Supression of cardiac parasympathetic functions in patients with right hemispheric stroke.

The aim of this study was to investigate the relationship between sympathetic and cardiac parasympathetic function and the side of the lesion in stroke patients. Thirty-two patients with stroke and 29 healthy age-matched control subjects were studied. Sympathetic skin responses (SSR) and RR interval variations (RRIV) during rest and deep breathing were recorded for the assessment of sympathetic and vagal parasympathetic function, respectively. The mean SSR amplitude values in patients compared with controls were 337 +/- 244 versus 1897 +/- 848 (P < 0.0001) for right hemispheric lesions and 466 +/- 398 versus 1873 +/- 843 (P < 0.0001) for left hemispheric lesions. The mean SSR latencies in patients compared with controls were 1526 +/- 163 versus 1395 +/- 109 (P < 0.05) for right hemispheric lesions and 1490 +/- 125 versus 1423 +/- 112 (P < 0.05) for left hemispheric lesions. RRIV (during deep breathing)/RRIV (at rest) ratios in patients compared with controls were 1.20 +/- 0.25 versus 1.84 +/- 0. 52 (P < 0.0001), and 1.55 +/- 0.88 versus 1.84 +/- 0.52 (P < 0.05) for right and left hemispheric lesions, respectively. Supression of vagal parasympathetic activity was more apparent in stroke patients with right hemispheric lesions in our series. Therefore, the right hemisphere seems to have a greater effect upon parasympathetic activity.

Sympathetic Skin Response in Hemodialysis Patients: Correlation with Nerve Conduction Studies and Adequacy of Dialysis

A sympathetic skin response (SSR) test was performed in diabetic and nondiabetic patients undergoing regular hemodialysis and the results correlated with nerve conduction studies (NCS): sensory conduction velocity (SCV) and motor conduction velocity (MCV). Comparisons were made between diabetic and nondiabetic patients and between cuprophane and polyacrylonitrile membrane dialyzed patients. Six nondiabetic uremic patients (30%) and all diabetic patients had no SSR. Eight nondiabetic uremic patients (40%) had a mildly impaired response. Nondiabetic patients with a normal response were younger (31.1 ± 16.4 years) than the patients with abnormal SSR, whether mildly impaired response (58.3 ± 20.3 years; p < 0.05, Anova) or absent response (65.3 ± 13.8 years; p < 0.01, Anova). SCV, MCV, and SSR values were reduced (p < 0.01) in uremic patients with respect to normal subjects. Severity and frequencies of sensory NCS abnormalities in nondiabetic patients were: normal 20%, mildly impaired 75%, and severely impaired 5%. Severity and frequencies of motor conduction abnormalities were: normal 80%, mildly impaired 20%, severely impaired 0%. The SSR abnormality incidence in patients with a normal NCS was similar to that in patients with either mildly or severely impaired NCS (chi-square test). There was a positive linear correlation between the SSR amplitude and SCV (r = 0.52, p < 0.01) and MCV (r = 0.49, p < 0.01). The SSR latency was also significantly related to SCV (r = 0.66, p < 0.01) and MCV (r = 0.61, p < 0.01). A significant negative correlation was found between age and SSR parameters, amplitude (r = –0.56, p < 0.01) and latency (r = –0.66, p < 0.01). No correlation was found between duration of hemodialysis or Kt/V and SSR. No differences were found in SSR, NCS, or Kt/V values between cuprophane membrane and polyacrylonitrile membrane dialyzed patients (Student’s t test). The relationship between NCS and SSR in uremic patients was confirmed. Old age and diabetes mellitus, but not the dialysisis membrane used, were confirmed as synergistic factors of neuropathic impairment. It appeared that SSR is more sensitive than NCS in detecting polyneuropathy in uremic patients on hemodialysis.

Normative data of sympathetic skin response and RR interval variation in Turkish children

Sympathetic skin response (SSR) and RR interval variation (RRIV) are used commonly for the assessment of sympathetic and parasympathetic nervous system function, respectively. We determined the normal values of SSR and RRIV in 23 (14 females, nine males) Turkish children aged 5 to 14 (mean 9.86, SD 2.48) years. SSR was recorded on the hands and feet during the electrical stimulation of both median and posterior tibial nerves, respectively. Similar response was elicited on both feet during the stimulation of the right median nerve. RRIV testing was performed during rest on the supine position and deep inspiration at a frequency of 6 times/min. The SSR was elicited in all children. The mean SSR latencies recorded on the feet during the stimulation of median or posterior tibial nerve were significantly more prolonged than those recorded at the hands (P < 0.001). There was no significant difference between the mean latencies of SSR recorded at the ipsilateral and contralateral palms or soles. The mean latencies recorded at the sole during stimulation of the median nerve were not significantly different compared to those that recorded at the sole during the posterior tibial nerve (P > 0.05). The SSR amplitudes were not assessed because of great variability and rapid habituation. The mean RRIV (46.54+/-11.29%) during deep breathing was significantly increased as compared to that (35.90+/-10.63%) during rest (P < 0.003). As a result, SSR and RRIV are preferred non-invasive tests for evaluation of autonomic nervous system in children. The SSR is useful and reliable if it is obtained in the optimum technical conditions. Further research is necessary to establish strict criteria for abnormality.

Sympathetic skin response asymmetry in early stage idiopathic Parkinson's disease

Simultaneous bilateral plantar sympathetic skin response (SSR) was studied in 25 patients with early stage idiopathic Parkinson's disease (IPD), characterized by monolateral motor involvement (Hoehn and Yahr, stage <2) and without clinical evidence of autonomic dysfunctions. Thirteen (mean age: 68.69 +/- 7.70, range 55-76) had extrapyramidal clinical signs only at the left body side, 12 (mean age 66.60 +/- 7.43, range 51-73) at the right body side. A group of 25 healthy, age-matched, subjects were also evaluated. To evoke the responses, trains of 10 electrical pulses were applied at different intensities and frequencies. Only intensities of stimulation > or = 5 times the sensory electrical threshold always assured bilateral plantar responses in all the examined subjects. Amplitude asymmetry between left and right responses was found only in the IPD patients (P < 0.05). The amplitude reduction corresponded to the motor affected side. No analogue latency variation was observed in any group. Independently from the peripheral or central origins of such phenomena, these findings suggest that simultaneous bilateral SSR amplitude evaluation could be useful, in early IPD patients, to demonstrate and to monitor the sympathetic cholinergic dysfunction, despite the lack of autonomic symptoms.

The effects of postmenopausal hormone replacement therapy on sympathetic skin response

To determine the effects of postmenopausal hormone replacement therapy on 'sympathetic skin response' test which is one of the tests to evaluate autonomic functions. Sixty postmenopausal women, 30 of whom taking hormone replacement therapy and the remaining 30 without hormone replacement therapy, were enrolled in this study. Sympathetic skin responses were recorded in each subject by Medelec Premiere electromyograph. Latency and amplitude of sympathetic skin response and area under the negative component of sympathetic skin response were measured and the groups were compared statistically regarding these results. Latency values of the groups were not significantly different, whilst the difference between the sympathetic skin response amplitudes of the groups, as well as the difference between the measurements of area under the negative component of sympathetic skin response of the groups were statistically significant. The results of the current study seem to indicate that estrogen has a significant inhibitory effect on the sympathetic neuron pool at the spinal cord level.

Electrophysiologic assessment of autonomic function in epilepsy

Sudden unexpected death associated with epilepsy (SUDEP) is an important clinical problem. Peri-ictal autonomic dysfunction is thought to play a role in SUDEP and few means exist for clinical identification of patients at risk. Sympathetic function was assessed by measuring sympathetic skin responses (SSR) elicited in the hand by auditory or tactile stimulation or by inspiration. Parasympathetic function was assessed by recording the R-R interval (RRI) and determining its variability in subsequent heartbeats. Fifty epilepsy patients had significantly greater SSR amplitudes and latencies than controls. The RRI was shorter in patients than in controls and the mean successive difference (MSD) was less, but significance was not reached. Twenty patients at possible risk for SUDEP (male, generalized seizures, intermittent medication noncompliance, drug and alcohol abuse, traumatic or structural aetiology) differed significantly from controls in SSR and RRI. Epilepsy patients may differ in autonomic function from the general population, and these differences may be relevant to SUDEP. The SSR and the RRI may be a simple means of assessing autonomic function in epilepsy outpatients.

Sympathetic skin response and patient satisfaction on long-term follow-up after throacoscopic sympathectomy for hyperhidrosis

To determine effect of sympathectomy for hyperhidrosis on sympathetic skin response (SSR) during long-term follow-up. Patient satisfaction was assessed and surgical complications noted. Prospective, Open, Non-randomised study. Patients who had undergone bilateral thoracoscopic sympathectomy for hyperhidrosis underwent postoperative assessment of SSRs. A 15 mA stimulus was applied over the median nerve contralateral to the sympathectomy and evoked electrodermal activity was recorded from the sympathectomised palm using a Dantec Counterpoint Mk 2. Patient satisfaction with surgery was assessed by questionnaire and visual analogue score (0-1.0). Of 26 patients, 21 were female. Mean (range) age was 23 (9-36) years. Mean (range) follow up was 39 (4-138) months. 12% of cases had residual or recurrent symptoms. Median (range) patient satisfaction was 0.83 (0.06-1.0). In 7/52 palms recurrent SSRs were not detected. Repeated measures analysis of variance found amplitude of SSR to be of low significance with respect to time since surgery (F = 0.48; p = 0.49) and incidence of compensatory sweating (F = 2.38; p = 0.14). Thoracoscopic sympathectomy for hyperhidrosis is an effective procedure. Following sympathectomy SSRs are not permanently abolished, but return of SSRs does not correspond with symptom recurrence. As such, SSRs are a poor tool for objective assessment of long-term outcome following sympathectomy.

Modulation of cerebral cortex in acupuncture stimulation: a study using sympathetic skin response and somatosensory evoked potentials.

Although acupuncture has been widely used for treating disorders, its therapeutic mechanism remains unclear. In order to study the physiological mechanism of acupuncture stimulation, both palm recordings of sympathetic skin response (SSR) were evoked by electrical stimulation of the right median nerve on 13 normal adult volunteers. Median nerve evoked short-latency somatosensory evoked potential (SEPs) recordings were taken at least one week after SSR recording. The latencies and amplitudes were calculated. N13 component was obtained from Cv7, and N20 and P25 were from somatosensory cortex. The control did not receive acupuncture stimulation. Acupuncture needles were inserted into both Zusanli (St-36) acupoints as follows: 1) manual acupuncture (MA): using fingers to twist the acupuncture needle until so-called Der-Qi was obtained, 2) 2 Hz electroacupuncture (EA): 2 Hz square-wave electrical pulses were applied between the Zusanli needle and the Shangjuxu (St-37) needle bilaterally. Our results indicated that the mean latencies of SSR were largest during 2 Hz EA followed by MA stimulation, whereas the period of control exhibited the shortest mean latencies. In contrast, the mean amplitudes of SSR were smallest during the period of 2Hz EA, followed by the period of MA, and the period of control exhibited the largest mean amplitudes of SSR. The latencies of N13, N20 and P25 remained unchanged, but the amplitudes of P25 were largest during the period of 2Hz EA, followed by the period of MA; the period of control exhibited the smallest mean amplitudes of SEPs. The results suggest that acupuncture stimulation of both Zusanli acupoints inhibited SSR, which implies that the cerebral cortex contributed at least in part to this inhibition. The stimulation effect of 2Hz EA is stronger than MA.

Local heat effect on sympathetic skin responses after pain of electrical stimulus

To investigate the analgesic effort of local superficial heating by studying sympathetic skin responses. Randomized trial. Electromyography laboratory in the department of physical therapy and rehabilitation of a university hospital. Twenty healthy volunteers participated with informed consent. Sympathetic skin response (SSR) amplitudes following electrical stimulation of the right peroneal nerve and skin temperatures in both hands were recorded simultaneously. All of the recordings were repeated at 5-minute intervals during local heat application over the right palm and within 15 minutes after heat application was stopped. SSR amplitudes in both hands decreased significantly during local heating (p < .05) and did not return to their initial levels within 15 minutes of the recovery period; the reductions remained statistically significant (p < .05). Amplitude reductions were statistically more significant on the heated hand compared with those on the contralateral hand (p < .05). Therapeutic local heat application reduces the sudomotor response to a painful stimulus. This analgesic effect may be due to suppression of cortical pain sensation resulting from increased levels of endorphins, and may also be a result of local inhibition of both afferent and efferent C fibres.

Auditory and inspiratory gasp-evoked sympathetic skin response: age effects

The sympathetic skin response (SSR) has been employed to assess peripheral neuropathy as an index of sympathetic sudomotor activity. A variety of stimuli can be used to elicit the SSR, but their relative ease of use and reliability have not been studied. In addition, the extent to which age affects the SSR remains unresolved. We compared two different stimuli, a sudden loud noise and an inspiratory gasp, whilst recording SSRs from the hand and foot. We also investigated the effects of age on SSR amplitude and latency in 58 healthy volunteers (ages 13-79). SSRs evoked by the auditory stimulus were recorded in all subjects, while gasp-induced SSRs were not elicited in two subjects. We found that SSRs evoked by the auditory stimulus had less inter- and intra-subject latency and waveform variability than the gasp-induced response. The increased latency variability associated with the inspiratory gasp technique was probably due to triggering errors. Our results confirmed that the amplitude of the SSR is extremely variable and appears to be affected by many factors. Auditory-evoked SSR latencies revealed a significant non-linear increase with age, while SSRs evoked by an inspiratory gasp did not demonstrate age dependence. We conclude that an auditory stimulus is superior to an inspiratory gasp in evoking SSRs, both in terms of consistent appearance and reduced latency variability. As the SSR latency increases significantly with age, this effect should be carefully considered when interpreting the response.