Influence of stimulus intensity on waveform of sympathetic skin response evoked by magnetic stimulation

A Temporospatial Study of Sympathetic Skin Response and Electroencephalogram in Oral Mucosa Thermal Perception

Objective

To investigate the temporospatial changes in sympathetic skin response (SSR) and electroencephalogram (EEG) under thermal stimuli and to draw a topographic map of SSR threshold temperature of the oral mucosa.

Materials and Methods

A total of 40 healthy volunteers (24 men, 16 women, mean age of 23 ± 3) were enrolled. Thermal stimuli were applied to the 35 partitions of oral mucosa starting from 36°C at the gradience of 1°C and the lowest temperature evoked SSR was defined as SSR threshold temperature. SSR and EEG signals at 45, 48, 51, and 54°C were then recorded synchronously.

Results

The SSR threshold temperature increased from the anterior areas to the posterior areas. No significant difference between bilateral corresponding areas or between genders was observed. The SSR amplitude value increased from 45 to 54°C in the same area, while the highest value was recorded on the tip of the tongue and decreased backwardly from the anterior area. There were significant differences in latency of SSR between the tip of the tongue and the molar areas of the oral cavity (p < 0.05). Reduction in the alpha frequency band was observed after thermal stimuli, and there were statistical differences between baseline and thermal stimuli in all four degrees of temperatures (p < 0.05).

Conclusion

The result of the experiment revealed that the autonomic and central nervous system (CNS) played important roles in thermal perception of oral mucosa and could be helpful for better understanding of pathological mechanism of burning mouth syndrome (BMS).

Comparison of Sympathetic Skin Response (SSR) between Electrical and Acoustic Stimuli in a Healthy Pediatric Population

Data in the literature report that latency and morphology in the cutaneous sympathetic skin response (SSR) do not change according to the type of stimulus delivered, unlike the amplitude which shows greater values in relation to the intensity of the physical impact caused in patient. Since the acoustic stimulus represents a method better tolerated by the pediatric patient, the aim of this study is to evaluate the presence or absence of significant differences in SSR between electrical and acoustic stimuli. The SSR was performed for each child of 18 recruited in this study, deriving from the palm of the hand and the sole of the foot and initially delivering an electrical stimulus at the level of the median nerve at the wrist. Two acoustic stimuli were subsequently delivered with the aid of audiometric headphones. Our results show no significant differences for the amplitude values obtained (p values > 0.05). For the latency there was a statistically significant difference (p-value = 0.001) for the left hand, subsequently not confirmed by the comparison performed between the two sides (p-values = 0.28 and 0.56). If these preliminary data are confirmed by a larger sample, the acoustic stimulus could be introduced in a standardized protocol for performing SSR in pediatric patients.

Sympathetic skin response in patients with primary premature ejaculation

To evaluate the possible role of the autonomic (sympathetic) nervous system function among the patients with primary premature ejaculation (PPE) and determine whether there is an etiological basis for this condition. We performed sympathetic skin response located in the penis (PSSR) in 52 patients with PPE and 46 normally potent men. The latencies and amplitudes of PSSR were measured. The PSSR waveforms were classified into P type and N type according to the waveform characteristics. The waveform distribution in the PPE patients was not statistically different from that in the control group (P=0.609). Mean latency of the PSSR was significantly shorter in the patients than that in the normally potent men (P<0.001). Mean amplitude of the PSSR was significantly greater in patients than that in the normal men (P<0.001). Patients with PPE have hyperactivity of the sympathetic nervous system, which may be another factor involved in the pathological mechanisms of PPE, and the PSSR is an objective test to evaluate patients with PPE.

Sympathetic skin responses from the scalp evoked by electrical stimulation in seborrheic dermatitis

Although the role of autonomic nervous system in seborrheic dermatitis (SD) is still unclear, seborrhea is sometimes accepted as a sign of autonomic dysfunction in several nervous system diseases. Therefore, we aimed to investigate the sympathetic nervous system (SNS) activity in SD by recording sympathetic skin responses (SSR) from the scalp (S-SSR). Thirty-one control subjects and 22 SD patients were studied by evoking right and left S-SSR with electrical stimulation of the right median nerve at the wrist. Mean latencies and maximum amplitudes were calculated for both sides in each group. In seven out of 31 control subjects and in 13 out of 22 patients, the S-SSR could not be elicited on either side. There were four subjects with unilateral response in the patient group. There were significantly more non-responders among the patients with SD (P < 0.000). This study suggests that in SD, the autonomic nervous system may be involved. The S-SSR is a new site for recording SSR. The responses are relatively symmetrical and can be evoked easily by electrical stimulation, and may be used to evaluate the SNS function in SD patients and also in healthy subjects.

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 responses evoked by muscle contraction

INTRODUCTION

Voluntary muscle contraction is accompanied by an increase in sympathetic nerve activity. The sympathetic skin response (SSR) is a simple and non-invasive method of autonomic assessment that reflects a synchronized activity of the sweat glands. The aim of our study was to examine the possible relationship between isometric muscle contraction (IC) and changes in the SSR.

METHODS

In 11 healthy right-handed volunteers, we recorded the SSR from the palm of the hand induced by contralateral triceps IC (mSSR) of variable intensities and durations. We measured the latency, duration, amplitude, waveform and habituation index (HI) of the mSSR, in comparison to the SSR induced by supramaximal electrical stimulation (eSSR) of the brachial plexus at the axillae.

RESULTS

A single mSSR was always present at a mean latency of 1.34+/-0.5s after the onset of IC. Response amplitude, but not latency or duration, correlated positively with the intensity of IC (r=0.67; p<0.001). The latency was shorter, the duration was longer and the HI was reduced in the mSSR in comparison to the eSSRs (ANOVA; p<0.05 for all comparisons).

CONCLUSIONS

The mSSR is likely generated endogenously together with the motor commands since inputs from muscle afferents cannot account for response onset. This, together with its low level of habituation, underscores the possibilities of physiological and clinical studies using the mSSR, especially in the assessment of autonomic function in patients with nerve afferent problems.

Sympathetic Skin Responses Evoked by Different Stimuli Modalities in Spinal Cord Injury Patients

Objective. By using a combination of physiological and electrical peripheral nerve stimuli, the authors aimed to characterize the expected dysfunction of the circuits responsible for sympathetic skin response (SSR) in persons with spinal cord injury (SCI). Methods. The authors examined SSR induced in the hand and foot in 50 SCI patients and 15 age-matched and gender-matched healthy volunteers. SSR was induced by deep inhalation, unexpected acoustic stimuli, brisk hand muscle contraction, and median and peroneal nerve electrical stimulation (PNS). Results. SSRs to any stimulus modality were absent in hand and foot in patients with complete SCI above the T4 level. They were present in the hand and absent in the foot in complete SCI patients at levels between T4 and T11 for all stimuli modalities except PNS. The elicitability of SSR was lower with peroneal nerve stimulation than the other stimuli in hand and foot. The mean latency difference between SSRs of the hand and foot was significantly longer in patients than in controls, regardless of stimulus modality. The amplitude of SSR was larger in volunteers than in patients. Conclusion . SSR to various stimuli confirms the importance of supraspinal centers and the integrity of sympathetic descending pathways. Simultaneous recording of the SSR in the hands and feet provides information about the degree of sympathetic impairment possibly in the efferent pathway. To monitor spontaneous recovery or the efficacy of a drug or biological therapeutic intervention, changes in the latency delay between the hand and foot may be valuable.

Paradoxical shortening of sympathetic skin response latency at distal recording sites

OBJECTIVE

The purpose of this study was to investigate and to discuss the neurophysiological mechanism of paradoxical shortening of the sympathetic skin response (SSR) latency at distal recording sites.

METHODS

The latency and peak-to-peak amplitude of SSRs evoked by magnetic stimuli were analyzed. Eight active electrodes were placed on the palmar (anterior) and dorsal (posterior) sides of the hand (forearm) proximal to the distal arrangement.

RESULTS

SSRs from two palm sites had significantly shorter latencies and larger amplitudes than the SSRs at the other six sites, including the proximal sites of the forearm.

CONCLUSIONS

This finding indicated that the SSR latency at different sites was not linearly prolonged as the distance of the recording sites from the proximal to distal areas increased. The paradoxical shortening of the latency and the large amplitude of the SSR from the palm can be explained by a recent model of the equivalent current dipole caused by the Na+ concentration gradient. The high density of sweat glands in the palm possibly produced the present findings.

SIGNIFICANCE

We should carefully interpret the sudomotor conduction velocity derived from latency difference between two sites, especially for thermal and emotional sweating.

Sympathetic skin responses of the face and neck evoked by electrical stimulation

The sympathetic skin responses (SSRs) were recorded from different facial regions and neck in 25 subjects evoked by electrical stimulation of the median nerve at the wrist. Recordings from all regions were cross-compared with each other and within right and left sides individually. In one subject postauricular SSR, and in another subject upper lip SSR could not be elicited on both sides. Other responses could be obtained in all the remaining subjects. In 11 subjects, the responses did not appear by the first stimulus, and began to appear by repeated stimuli. Mean latencies and the highest amplitudes of the responses were similar for both sides. Gradual amplitude increase was observed in the first three or four set of responses in 20 subjects, although the stimulus intensity was constant. In conclusion, face and neck SSRs are symmetric, can be evoked by electrical stimulation and can be used to investigate the sympathetic innervation of these areas.

The effect of stimulation technique on sympathetic skin responses in healthy subjects

The aim of this study was to collect normative data for sympathetic skin responses (SSR) elicited by electrical stimulus of the ipsilateral and contralateral peripheral nerves, and by magnetic stimulus of cervical cord. SSRs were measured at the mid-palm of both hands following electrical stimulation of the left median nerve at the wrist and magnetic stimulation at the neck in 40 healthy adult volunteers (mean age 52.2 ± 12.2 years, 19 males). The onset latency, peak latency, amplitude and area were estimated in “P” type responses (i.e., waveforms with a larger positive, compared to negative, component). SSR onset and peak latency were prolonged when the electrical stimulus was applied at the contralateral side (i.e., the SSR recorded in the right palm P < 0.001). The onset latency was similar on both sides during cervical magnetic stimulation. However, peak latency was faster on the left side (P < 0.03). Comparison of electrical and magnetic stimulation revealed that both the onset and peak latency were shorter with magnetic stimulation (P < 0.001). The latency of a SSR varies depending on what type of stimulation is used and where the stimulus is applied. Electrically generated SSRs have a longer delay and the delay is prolonged at the contralateral side. These factors should be taken into account when interpreting SSR data.

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

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. Twenty-four 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.

Changes in the sympathetic skin response after thoracoscopic sympathectomy in patients with primary palmar hyperhidrosis

OBJECTIVE

To investigate whether thoracic sympathectomy induced any change in the pattern of abnormalities or in the waveform of the sudomotor skin response (SSR) in patients with primary palmar hyperhidrosis (PPH).

METHODS

We recorded the SSR to median nerve electrical stimuli before and after bilateral thoracoscopic sympathectomy in 27 patients with PPH. We analyzed the changes in amplitude, type of waveform and pattern of abnormality.

RESULTS

All patients reported symptomatic improvement. The amplitude of the SSR decreased significantly in patients examined within 1 year after surgery, but was not different in patients examined after 1 year. The number of abnormally enhanced responses reduced after surgery, but there was no significant change in the number of patients with enhanced excitability recovery or with double-peak responses to single stimuli. There was a significant increase in the number of SSRs with a predominantly negative waveform after surgery.

CONCLUSIONS

The persistence of SSR abnormalities after surgery suggests that the central nervous system dysfunction is not modified by sympathectomy. The change of the waveform to predominantly negative type after surgery could be the consequence of the decrease in the production of sweating.

SIGNIFICANCE

Our results show the effects of sympathectomy on the SSR and on its abnormal patterns in patients with PPH.