Sudomotor Reflexes Research Articles

Feasibility and Effectiveness of Electrochemical Dermal Conductance Measurement for the Screening of Diabetic Neuropathy in Primary Care. Decoding Study (Dermal Electrochemical Conductance in Diabetic Neuropathy).

Diabetes mellitus (DM) is the leading cause of polyneuropathy in the Western world. Diabetic neuropathy (DNP) is the most common complication of diabetes and is of great clinical significance mainly due to the pain and the possibility of ulceration in the lower limbs. Early detection of neuropathy is essential in the medical management of this complication. Early unmyelinated C-fiber dysfunction is one of the typical findings of diabetic neuropathy and the first clinical manifestation of dysfunction indicating sudomotor eccrine gland impairment. In order to assess newly developed technology for the measurement of dermal electrochemical conductance (DEC), we analyzed the feasibility and effectiveness of DEC (quantitative expression of sudomotor reflex) as a screening test of DNP in primary health care centers. The study included 197 people (with type 2 diabetes, prediabetes and normal tolerance) who underwent all the protocol tests and electromyography (EMG). On comparing DEC with EMG as the gold standard, the area under the receiver operating characteristic (ROC) curve (AUC, area under the curve) was 0.58 in the whole sample, AUC = 0.65 in the diabetes population and AUC = 0.72 in prediabetes, being irrelevant in subjects without glucose disturbances (AUC = 0.47). Conclusions: In usual clinical practice, DEC is feasible, with moderate sensitivity but high specificity. It is also easy to use and interpret and requires little training, thereby making it a good screening test in populations with diabetes and prediabetes. It may also be useful in screening general populations at risk of neuropathy.

Feasibility and effectiveness of electrochemical dermal conductance measurement for the screening of diabetic neuropathy in primary care. DECODING Study (Dermal Electrochemical Conductance in Diabetic Neuropathy). Rationale and design.

Diabetes mellitus is the leading cause of polyneuropathy in the Western world. Diabetic neuropathy is a frequent complication of diabetes and may have great clinical transcendence due to pain and possible ulceration of the lower extremities. It is also a relevant cause of morbidity and mortality in patients with diabetes. Although the cause of polyneuropathy in patients with diabetes is only partially known, it has been associated with chronic hyperglycemia suggesting the possible etiopathogenic implication of advanced glycosylation end products. The strategy of choice in the medical management of diabetic neuropathy is early detection since glycaemic control and the use of certain drugs may prevent or slow the development of this disease. Diabetic neuropathy most often presents with a dysfunction of unmyelinated C-fibers, manifested as an alteration of the sweat reflex of the eccrine glands. This dysfunction can now be demonstrated using a newly developed technology which measures dermal electrochemical conductivity. This noninvasive test is easy and cost-effective. The aim of the present study is to evaluate the feasibility and effectiveness of dermal electrochemical conductance measurement (quantitative expression of the sudomotor reflex) as a screening test for the diagnosis of diabetic neuropathy in patients in primary care.

Seasonal influence of the surgical outcome after thoracic sympathectomy for hyperhidrosis

Analyze the seasonal variation of the surgical results after sympathectomy through the seasons of the year. The surgical results are better in the spring, and the sudomotor reflex is worst in summer. Comparison of surgical results of distinct techniques should be done under the same climatic conditions.

Factors affecting long-term satisfaction after thoracic sympathectomy for palmar and plantar hyperhidrosis. Is the sudomotor reflex the only villain?

The main objective of this study was to determine if there are variations in the level of improvement of the palmar and plantar hyperhidrotic symptoms, as well as the incidence and intensity of the sudomotor reflex, throughout the seasons of the year, after thoracic sympathectomy for hyperhidrosis. The study also looks for the real impact of these variables in the long-term satisfaction. A cohort of 75 patients was followed through distinct seasons. A multivariate analysis was performed to identify possible variables responsible for dissatisfaction. Both the palmar (P=0.002) and plantar (P<0.001) symptoms and the presence and the intensity of the sudomotor reflex varies significantly throughout the seasons of the year. The sudomotor reflex was the main factor associated with low satisfaction in our patients in the summer (P=0.025) and winter (P<0.001) but in spring the lack of improvement in the hyperhidrosis in the foot was the unique factor related to dissatisfaction (P<0.001). The sudomotor reflex is the main negative factor in the summer and in the winter, independent of its intensity. However, at least in spring, the lack of removal of the plantar symptoms had a negative impact on satisfaction.

Sympathetic sudomotor skin activity in human after complete spinal cord injury

Spinal cord injury (SCI) causes serious disturbances in autonomic innervation and malfunction of the sympathetic nervous system that controls the pelvic organs, blood pressure, skin temperature and sweating. We studied sympathetic sudomotor pathways in 6 healthy subjects and 14 patients with sensory and motor complete SCI on cervical, thoracic and lumbar level. Sympathetic skin responses (SSRs) were provoked by auditory bursts and electrical stimulation of median, pudendal and tibial nerve and recorded from the palmar and plantar skin. The SSRs in healthy subjects occurred generally with the same pattern and with similar latencies suggesting a common sudomotor pathway mediating the SSR. Appearance or absence of the SSRs in SCI following stimulation above the lesion depend on the spinal level of lesion and on the location of stimulation. Lesions below T3 show palmar and lesions below T12 palmar and plantar SSR. Pudendal nerve stimulation evoked plantar SSRs in patients with complete cervical and thoracic SCI. No SSRs were obtained in patients with lesions at L1 and more caudal. SSRs following pudendal nerve stimulation in complete SCI above the level L1 are mediated by sacral somatic afferents and a sympathetic pathway originating at the upper lumbar level. The underlying sacro-lumbar reflex circuit is organized on spinal level and requires intact lumbar segments. Tibial nerve stimulation was not found to elicit SSRs below a SCI lesion and we suppose that this type of electrical stimulation cannot activate the spinal sudomotor reflex circuit.

Measurement of Sympathetic Blockade: Effect of Epidural and Spinal Anesthesia

Consultant in Anesthesiology Akureyri Central HospitalAkureyri, IcelandDirectorklaus.kirno@medfak.gu.seProfessorDepartment of Cardiothoracic Anesthesiology and Intensive CareAssociate ProfessorDepartment of Clinical NeurophysiologySahlgrenska University HospitalUniversity of GöteborgGöteborg, SwedenIn Reply:—We appreciate the interest and comments expressed by Drs. Introna, Blair, Martin, and Yodlowski. We fully agree that indirect methods of measuring sympathetic nerve activity can provide useful, qualitative information. Quantification of sympathetic nerve activity, however, is difficult with these techniques.The main issue raised by Introna et al. is whether a high thoracic epidural anesthesia (TEA) completely inhibits cardiac sympathetic activity. Based on studies measuring heart rate variability, these authors are convinced that TEA with T1–T5 sensory blockade does not result in complete cardiac sympathetic blockade. However, a comparative study of heart rate variability, cardiac norepinephrine spillover, and muscle sympathetic nerve activity in humans by Kingwell et al. 1invites some caution because it showed heart rate variability to be dependent on multiple factors in addition to cardiac sympathetic nerve activity and not directly related to cardiac norepinephrine spillover.The degree of thoracic sympathetic blockade was not specifically addressed in our recent study, 2which was primarily aimed at evaluating sympathetic function caudal to the TEA-induced sensory blockade and showed no sign of sympathetic blockade. However, previous microneurographic studies of lumbar epidural and spinal anesthesia have shown a fairly close relation between the extent of sensory and sympathetic blockade. 3,4Because the nerves to internal organs are not accessible to microneurographic recording in humans, we previously used biochemical measurements of nerve transmitter release to quantify cardiac sympathetic nerve activity. 5We used an isotope dilution technique with radiolabeled norepinephrine to demonstrate that TEA prevented the sympathetically mediated surgical stress response during coronary artery bypass surgery. Although this finding could be explained by an afferent nociceptive blockade or an efferent blockade of cardiac sympathetic nerve fibers, supportive evidence for the existence of a cardiac sympathetic blockade after TEA has been provided by Taniguchi et al. , 6who directly measured efferent cardiac sympathetic nerve activity after TEA in an experimental study on cats. Our recent finding 2that vasomotor and sudomotor reflexes were abolished in the hands but remained in the feet after TEA also suggests a thoracic sympathetic blockade. Therefore, although we agree with Introna et al. that “sympathetic fibers above and below the segment of epidural anesthesia could travel cephalad or caudad within the sympathetic chain” and “continue to innervate the heart,” we remain convinced that TEA can abolish sympathetic reflexes within thoracic segments.

Autonomic dysfunction in the Lambert-Eaton myasthenic syndrome: serologic and clinical correlates.

Autonomic dysfunction is a recognized feature of the Lambert-Eaton myasthenic syndrome (LES). However, the characteristic pattern of dysautonomia has not been clearly documented and its pathophysiologic basis is not known. We therefore abstracted autonomic symptomatology and results of quantitative tests for salivation, and vasomotor, cardiovagal, and sudomotor reflexes from records of 30 LES patients. Dry mouth (77%) and impotence (45% of men) were the most common symptoms. Composite Autonomic Scoring Scale results were abnormal in 93% of patients, and autonomic failure was severe in 20%. The frequency of specific test abnormalities were the following: sudomotor function, 83%; cardiovagal reflexes, 75%; salivation, 44%; and adrenergic function, 37%. Although voltage-gated N-type calcium (Ca2+) channels are implicated in autonomic transmission, the low frequency of serum antibodies to N-type Ca2+ channels found in the patients of this study (31% positive) argues against a pathogenic role in mediating LES-related dysautonomia. In contrast, 93% of the patients were seropositive for P/Q-type Ca2+ channel antibodies. A subset of these antibodies is thought to impair neuromuscular transmission. Autoantibodies of thyrogastric or glutamic acid decarboxylase specificity (markers of predisposition to type 1 diabetes mellitus) were found in 45% of patients, and type 1 antineuronal nuclear antibody (or anti-Hu, a marker of autoimmune neuropathy associated with small-cell lung carcinoma) was found in 3%. No autoantibody correlated with autonomic dysfunction severity. Sensorimotor neuropathy was documented in five patients, and was not significantly associated with autonomic neuropathy. Autonomic failure was most severe in older subjects with cancer (p = 0.02, age by cancer interaction).

Quantitative assessment of sudomotor activity by capacitance hygrometry.

A commercial capacitive hygrometer device manufactured for use in technical or chemical laboratory environments has been used for quantitative and dynamic assessment of sweat gland activity in selected skin areas. For this purpose the hygrometer device was supplemented by a chamber attached to the skin for collecting evaporated water and a supply of dry nitrogen gas providing a gas flow through the chamber and through the hygrometer capsule. The accuracy of the technique was proven in pilot experiments in which fixed amounts of water were evaporated. A positive correlation was found between the weight of the water and the water evaporation computed from the hygrometer readings (r = 0.997). The time constant of the device was in the range of 10 s. This time constant appears to be fast enough for recording physiological changes in the sweating rate of human subjects. In experiments on healthy subjects sudomotor reflexes were assessed and compared to vasoconstrictor responses and to thermographically measured temperature changes of the skin during the Valsalva manoeuvre and a painful mechanical stimulus. Direct measurement of water evaporation such as by this technique may provide information on sympathetic reactions which could be utilized in both physiological and pathophysiological states.

Idiopathic autonomic denervation in eight patients presenting with functional gastrointestinal disease

Gut dysmotility may result from disease of the extrinsic neural pathways supplying the gut. We report the results of studies on sweating, cardiovascular, and sudomotor reflexes in eight prospectively evaluated patients with apparently functional gastrointestinal disorders. There was no personal or family history of neurologic disease, except for one patient with known atony of the bladder. Motility of the esophagus, stomach, and small intestine were, respectively, abnormal in two, six, and seven patients and showed either uncoordination of contractions between segments or postcibal hypomotility. All had generalized or patchy anhidrosis; quantitative sudomotor axon reflex tests were also abnormal in four patients and borderline in one. Plasma levels of catecholamines were abnormal in one patient. All patients had evidence of sympathetic denervation: preganglionic in two patients, postganglionic in five patients, and mixed in one patient. Three patients also had abnormal heart-rate responses to deep breathing, suggesting parasympathetic dysfunction. No underlying cause for the autonomic dysfunction was identified in any of these patients despite extensive investigations. Thus, these data support the hypothesis that apparently functional gastrointestinal disorders may be due to idiopathic autonomic denervation.

Evidence for two distinct sympathoinhibitory bulbo-spinal systems

Yohimbine hydrochloride (0.5 mg kg , i.v.) caused a long-lasting potentiation of electrodermal (sympathetic-cholinergic) reflexes in intact anaesthetized and decerebrate unanaesthetized cats. Transection of the cervical spinal cord also resulted in an increased amplitude of the sudomotor reflex in unanaesthetized decerebrate preparations. Depletion of monoamines in the CNS by pretreatment with reserpine (5 mg kg , i.p.) and α-methyl- p-tyrosine (2 × 300 mg kg , i.p.) reduced the concentrations of norepinephrine, dopamine and serotonin to less than 93% of control levels in the thoracic spinal cord. In monoamine-depleted preparations, yohimbine no longer facilitated the reflex amplitude whereas the effect of spinal transection was not altered. These results suggest that there are two distinct sympathoinhibitory systems in the lower brain stem that converge on spinal sympathetic neurons, one of which is monoaminergic and one of which is not. Evidence for the baroreceptor-independent nature of these descending inhibitory systems is discussed.

Organization of the sympathetic innervation supplying the hairless skin of the cat's paw

The sympathetic outflow supplying the hairless skin of the cat's hind paw has been analyzed in brain-intact and chronic low spinal animals. For this purpose the activity of postganglionic axons in fascicles of the medial plantar nerve which innervate the central pad and the respective responses of the target organs (transient skin potentials, skin temperature) have been recorded. (1) Blood vessels and sweat glands in the hairless skin of the cat's hind paw are under efferent control of vasoconstrictor neurons, sudomotor neurons, and possibly vasodilatator neurons. (2) Vasoconstrictor neurons are largely under inhibitory control of various afferent input systems from the body surface and from the internal milieu, and sudomotor neurons under excitatory control in brain-intact as well as in chronic spinal cats. (3) The basic neuronal network or "machinery" for the this reciprocal organization is probably located in the spinal cord. (4) Effects of anesthetics on the sudomotor reflexes indicate that this spinal neuronal organization is controlled in a complex manner by descending spinal systems from the brain stem. (5) The existence of vasodilatator neurons, a third efferent control system supplying the hairless skin, which can only be activated by spinal cord warming in brain-intact as well as in chronic spinal cats is not very well established. Neurons with this property are rare and it is unclear whether they course through the sympathetic trunk or dorsal roots or through both. The axons of these neurons are unmyelinated. (6) The organization of the neuronal control of vessels and sweat glands in the hairless skin may be a paradigmatic model for studying the respective neuronal organization in the spinal cord and its descending control.

Effects of anaesthetics on reflexes elicited in the sudomotor system by stimulation of Pacinian corpuscles and of cutaneous nociceptors

Sudomotor neurones supplying sweat glands in the hairless skin of the cat's paws can be activated by the cutaneous afferent inputs deriving from vibrational receptors (Pacinian corpuscles) in the paws and from cutaneous nociceptors. Both reflexes probably have separate spinal pathways. In the present investigation the effects of the anaesthetics ketamine, methohexital, chloralose, halothane and Althesin on both types of sudomotor reflexes were examined. For this purpose the skin potentials were recorded from the hairless skin of the paws with Ag-AgCl-electrodes. Before application of any anaesthetic the cats were in a state of light ketamine anaesthesia. The following results were obtained: (1) the resting activity in the sudomotor system and the synchronization of the activity between both hindpaws and between hind- and forepaws were depressed by all anaesthetics to a variable degree. After chloralose application large synchronous potentials of low frequency appeared; (2) ketamine (18–25 mg/kg injected intramuscularly) enhanced the reflexes on vibrational stimulation and depressed the reflexes on noxious stimulation of skin; (3) methohexital (3–10 mg/kg injected intramuscularly) mostly depressed the reflexes on vibrational stimulation and enhanced the reflexes on noxious cutaneous stimuli; (4) chloralose (4.5–20 mg/kg injected intraperitoneally) enhanced both types of reflexes; (5) halothane (1–1.5 vol. %) and Althesin (2.5–5 mg/kg injected intramuscularly) depressed both types of reflexes; (6) in chronic spinal cats ketamine, methohexital and chloralose had a slightly depressive effect on the resting activity of the sudomotor system, but practically no influence on the reflexes induced by cutaneous stimuli; and (7) these results argue that the effects of anaesthetics on the sudomotor system depend on the type of