Evaluación clínica de las disautonomías / Clinical evaluation of dysautonomia

INTRODUCCIÓN: Disfunción del sistema nervioso autonómico ocurre en enfermedades del sistema nervioso central y periférico. Es importante cuantificar el compromiso simpático y parasimpático, diagnosticar la disfunción, monitorizar la evolución y la respuesta a terapias. Las principales pruebas funcionales son las cardiovasculares y sudomotoras. Existen además exámenes para estudiar la disfunción autonómica en distintos órganos y que son específicos de las especialidades médicas respectivas. DESARROLLO: Se describen los síntomas, las pruebas funcionales y métodos de estudio a nivel cardiovascular: simpáticas vasomotoras (noradrenérgicas) y cardiovagales (colinérgicas) y las pruebas para la sudoración: sudomotoras simpáticas (colinérgicas). Se describen los síntomas y exámenes a nivel pupilar, urogenital y gastrointestinal. Se señala la utilidad de las pruebas funcionales autonómicas en el estudio de distintas patologías neurológicas. CONCLUSIONES: la evaluación conjunta de los hallazgos clínicos y de las pruebas funcionales autonómicas permiten determinar el nivel anatómico y el grado de severidad de la disfunción autonómica con un fundamento fisiopatológico.

INTRODUCTION: Autonomic dysfunction occurs in patients with central and peripheral nervous system diseases. It is important to quantify the sympathetic and parasympathetic involvement for the diagnosis of the autonomic failure, for follow up and evaluate the response to a specific treatment. The most important studies are cardiovascular and sudomotor functional tests. There are other tests for the study of autonomic dysfunction in different organs, that are specific to respectively medical specialty. DEVELOPMENT: we describe main symptoms, functional autonomic tests and other methods to study cardiovascular: sympathetic vasomotor (noradrenergic) and cardiovagal (cholinergic) and sudomotor: sympathetic (cholinergic) functions. We describe symptoms and tests for assessment pupillary, genitourinary and gastrointestinal autonomic dysfunction. The indications for autonomic function testing in the different clinical scenarios are reported. CONCLUSIONS: combined evaluation of clinical and tests of autonomic function results allow to obtain the level and severity of autonomic dysfunction based upon pathophysiological support.

Screening for peripheral artery disease among diabetics using sudomotor function testing / 中华健康管理学杂志

Objective To explore the relationship between sudomotor function and peripheral artery disease (PAD),and to evaluate the effectiveness of sudomotor function testing to screen diabetic patients at high risk of PAD comparing to ankle-brachial index (ABI) and toe-brachial index (TBI).Methods A total of 263 diabetes mellitus (DM) outpatients in the 306th Hospital of PLA from August 2014 to April 2015 were enrolled in the study.ABI and TBI were measured by the Doppler method.Sudomotor function was evaluated by measuring the electrochemical skin conductance (ESC) of the hands and feet using the Sudoscan instrument.Cardiovascular autonomic neuropathy (CAN) was assessed and recorded as cardiac autonomic neuropathy risk-score (CAN-RS) by Sudoscan.Results ESC values of the feet and hands were positively correlated with ABI and TBI.The diabetes patients with abnornal ABI and TBI had significantly lower hand ESC [(45.63±12.87) μS vs.(68.10±17.40) μS,(59.17±19.58) μS vs.(68.57±17.11) μS;P＜ 0.05] and feet ESC [(44.54±25.48) μS vs.(70.92±19.46) μS,(59.21±24.52) μS vs.(71.71±19.02) μS;P＜ 0.05],and higher CAN-RS[(49.17± 15.41)％ vs.(36.33±16.25)％,(44.90±16.09)％ vs.(35.39±16.05)％;P＜ 0.05],than diabetes patients with normal ABI and TBI.Using ABI as the gold standard,the areas under the receiver operating characteristics (ROC) curve of the diagnostic performance of hands ESC,feet ESC and CAN-RS to identify PAD were 0.87,0.84 and 0.74,respectively (P＜0.001).Conclusion Sudomotor function testing can be helpful and beneficial to identify PAD in patients with diabetes.

Comparison of Somatic and Sudomotor Nerve Fibers in Type 2 Diabetes Mellitus

BACKGROUND AND PURPOSE: The objective of this study was to find a sensitive method for the early detection of diabetic polyneuropathy (DPN) and determine the relationship between the functions of somatic and autonomic small nerve fibers in DPN. METHODS: Patients with type 2 diabetes mellitus and DPN based on clinical symptoms, signs, intraepidermal nerve fiber density (IENFD), and findings in the quantitative sudomotor axon reflex test (QSART) were enrolled retrospectively. Neurological examinations and nerve conduction studies were performed on all patients. Heart-rate variability during deep breathing (DB ratio) and the Valsalva maneuver (Valsalva ratio) were used to quantify the cardiovagal function. Patients were divided into two groups: 1) normal nerve conduction, defined as small-fiber neuropathy (SFN) and 2) abnormal nerve conduction, defined as mixed-fiber neuropathy. RESULTS: In total, 82 patients were enrolled (age: 60.7±10.7 years, mean±SD). A decreased IENFD was the most frequent abnormality across all of the patients, followed by abnormalities of the QSART and cardiovagal function. A decreased IENFD was more sensitive than the QSART, DB ratio, and Valsalva ratio for detecting diabetic SFN. The DB ratio was significantly correlated with the duration of diabetes mellitus and clinical symptoms and signs. There was no correlation between the IENFD and the findings of the QSART for the distal leg. CONCLUSIONS: Measuring the IENFD was a more sensitive method than the QSART for the early detection of DPN. The degree of involvement of the somatic small nerve fibers and sudomotor nerve fibers was independent in DPN.

Seasonal acclimation in sudomotor function evaluated by QSART in healthy humans

The quantitative sudomotor axon reflex testing (QSART) is a classic test of routine postganglionic sudomotor function. We investigated sudomotor function by QSART after summer (July 2012) and winter (January 2013) seasonal acclimation (SA) in the Republic of Korea. QSART with acetylcholine (ACh) iontophoresis were performed to determine directly activated (DIR) and axon reflex-mediated (AXR1, 2) sweating rate. Onset time of axon reflex, activated sweat gland density (ASGD), activated sweat gland output (ASGO), tympanic and skin temperatures (T(ty), T(sk)), basal metabolic rate (BMR), and evaporative loss volume changes were measured. Tympanic and mean body temperature (T(b); calculated from T(ty), T(sk)) were significantly lower after summer-SA than that of winter-SA. Sweat onset time was delayed during winter-SA compared to that after summer-SA. BMR, AXR(1), AXR(2), and DIR sweat rates, ASGD and ASGO, and evaporative loss volume were significantly diminished after winter-SA relative to after summer-SA. In conclusion, changes in sweating activity measured by QSART confirmed the involvement of the peripheral nervous system in variation of sudomotor activity in seasonal acclimation.

Idiopathic Pure Sudomotor Failure Presented With Generalized Anhidrosis

No abstract available.

Idiopathic Pure Sudomotor Failure Presented With Generalized Anhidrosis

No abstract available.

Autonomic Function Tests: Some Clinical Applications

Modern autonomic function tests can non-invasively evaluate the severity and distribution of autonomic failure. They have sufficient sensitivity to detect even subclinical dysautonomia. Standard laboratory testing evaluates cardiovagal, sudomotor and adrenergic autonomic functions. Cardiovagal function is typically evaluated by testing heart rate response to deep breathing at a defined rate and to the Valsalva maneuver. Sudomotor function can be evaluated with the quantitative sudomotor axon reflex test and the thermoregulatory sweat test. Adrenergic function is evaluated by the blood pressure and heart rate responses to the Valsalva maneuver and to head-up tilt. Tests are useful in defining the presence of autonomic failure, their natural history, and response to treatment. They can also define patterns of dysautonomia that are useful in helping the clinician diagnose certain autonomic conditions. For example, the tests are useful in the diagnosis of the autonomic neuropathies and distal small fiber neuropathy. The autonomic neuropathies (such as those due to diabetes or amyloidosis) are characterized by severe generalized autonomic failure. Distal small fiber neuropathy is characterized by an absence of autonomic failure except for distal sudomotor failure. Selective autonomic failure (which only one system is affected) can be diagnosed by autonomic testing. An example is chronic idiopathic anhidrosis, where only sudomotor function is affected. Among the synucleinopathies, autonomic function tests can distinguish Parkinson's disease (PD) from multiple system atrophy (MSA). There is a gradation of autonomic failure. PD is characterized by mild autonomic failure and a length-dependent pattern of sudomotor involvement. MSA and pure autonomic failure have severe generalized autonomic failure while DLB is intermediate.

Ezscan: A new non-invasive technology to evidence cardiac autonomic neuropathy in diabetes / 中华内分泌代谢杂志

Objective To assess the efficacy of Ezscan in evaluating the risk of cardiac autonomic neuropathy (CAN) in diabetes. Methods This study included 144 patients with diabetes. Their serum lipid profile and HbA1c were determined. The heart rate variability was assessed by Holter, and the cardiac autonomic neuropathy by classic experiments. Meanwhile, Ezscan was carried out. Results There was a positive correlation between low frequency (LF) measurements by Holter and Ezscan score( r=0. 39, P＜0. 01 ), so did LF/HF and Ezscan score( r=0. 28, P＜0. 01 ). Correlations between Ezscan score and other Holter parameters were weaker. There was no correlation between HbA1c and LF measurements. In patients with positive classic experiments, the sensitivity and specificity of Ezscan were 58. 3% and 57.8% respectively. Conclusions Ezscan test is a valuable screening procedure for detecting diabetic complications. It is more facilitative and takes shorter time than does the classical autonomic function assessment.

Effect of the Heat-exposure on Peripheral Sudomotor Activity Including the Density of Active Sweat Glands and Single Sweat Gland Output

Tropical inhabitants are able to tolerate heat through permanent residence in hot and often humid tropical climates. The goal of this study was to clarify the peripheral mechanisms involved in thermal sweating pre and post exposure (heat-acclimatization over 10 days) by studying the sweating responses to acetylcholine (ACh), a primary neurotransmitter of sudomotor activity, in healthy subjects (n=12). Ten percent ACh was administered on the inner forearm skin for iontophoresis. Quantitative sudomotor axon reflex testing, after iontophoresis (2 mA for 5 min) with ACH, was performed to determine directly activated (DIR) and axon reflex-mediated (AXR) sweating during ACh iontophoresis. The sweat rate, activated sweat gland density, sweat gland output per single gland activated, as well as oral and skin temperature changes were measured. The post exposure activity had a short onset time (p<0.01), higher active sweat rate [(AXR (p<0.001) and DIR (p<0.001)], higher sweat output per gland (p<0.001) and higher transepidermal water loss (p<0.001) compared to the pre-exposure measurements. The activated sweat rate in the sudomotor activity increased the output for post-exposure compared to the pre-exposure measurements. The results suggested that post-exposure activity showed a higher active sweat gland output due to the combination of a higher AXR (DIR) sweat rate and a shorter onset time. Therefore, higher sudomotor responses to ACh receptors indicate accelerated sympathetic nerve responsiveness to ACh sensitivity by exposure to environmental conditions.

Long-Term Tropical Residency Diminishes Central Sudomotor Sensitivities in Male Subjects

Tropical natives (TROP) are capable of tolerating tropical heat because of their long-term adaptation to tropical environments. When exposed to heat stress, these natives tend to respond with lower sweat output, which is generally thought to be the result of heat acclimatization. The main objective of this study was to clarify central mechanisms inherent to suppressed thermal sweating in tropical natives (Malaysians) by comparing their sweating responses to those of temperate native (TEMP) (Koreans). This experiment was conducted in a thermoneutral climatic chamber (24+/-0.5 degrees C, 40+/-3% relative humidity). Heat loads were applied to each subject by the immersion of their lower legs in a hot water bath (43 degrees C for 30 min). Sweat onset-time and sweat volume were compared between TROP and TEMP. The sweat onset-times on four selected points on the body ranged from 10.25 to 13.47 min in TEMP subjects, and from 16.24 to 17.83 min in TROP subjects (p<0.001). The local sweat volumes at the same sites ranged from 4.30 to 9.74 mg/cm2 in TEMP subjects, and from between 1.80 to 4.40 mg/cm2 in TROP subjects (p<0.001). These results demonstrated a significant difference between TROP and TEMP subjects with regard to the manner in which they regulate their body temperatures when exposed to heat loads, and verified that long-term thermal adaptation blunts sweating sensitivities.