Autonomic peripheral neuropathy

Heart rate variability biofeedback for critical illness polyneuropathy: a randomized sham-controlled study

BACKGROUND AND PURPOSE

Critical illness polyneuropathy (CIP) has been linked to neurocardiac dysfunction mediated by autonomic nervous system dysregulation, which increases mortality. We aimed to assess if heart rate variability (HRV) biofeedback could improve neurocardiac function in CIP.

METHODS

We randomly allocated (1:1) patients with electrophysiologically confirmed CIP undergoing early inpatient neurological rehabilitation to additional HRV or sham biofeedback over 14 days. We evaluated neurocardiac function via standard deviation of normal-to-normal intervals (SDNN) as the primary outcome, as well as HRV frequency domains, sympathetic cutaneous sudomotor and vasomotor functions and disability at baseline, post intervention and 4 weeks later. The study is registered on the German Clinical Trials Register (DRKS00028911).

RESULTS

We included 30 patients with CIP (40% females, median [interquartile range] age 64.6 [56, 72] years). We observed an increase in SDNN and the predominantly parasympathetic high frequency domain post intervention (ß = 16.4, 95% confidence interval [CI] 0.2, 32.6 [p = 0.047] and ß = 1179.2, 95% CI 119.9, 2158.5 [p = 0.018]), which was sustained at the 4-week follow-up (ß = 25.7, 95% CI 6.0, 45.4 [p = 0.011] and ß = 25.7, 95% CI 6.0, 45.4 [p = 0.011]). Patients who underwent HRV biofeedback displayed a higher adjusted Barthel index, indicating less severe disability 4 weeks after the intervention compared to those in the sham group (ß = 23.3, 95% CI 5.5, 41.1 [p = 0.014]). Low frequency and sympathetic skin functions did not differ between groups (p = nonsignificant).

CONCLUSIONS

Our study provides pilot data suggesting that, in patients with CIP, HRV biofeedback can improve neurocardiac function with a predominant effect on the parasympathetic nervous system and has a beneficial effect on functional recovery.

Disentangling the phenotypic patterns of hypertension and chronic hypotension

OBJECTIVE

2017 blood pressure (BP) categories focus on cardiac risk. We hypothesize that studying the balance between mechanisms that increase or decrease BP across the medical phenome will lead to new insights. We devised a classifier that uses BP measures to assign individuals to mutually exclusive categories centered in the upper (Htn), lower (Hotn) and middle (Naf) zones of the BP spectrum; and examined the epidemiologic and phenotypic patterns of these BP-categories.

METHODS

We classified a cohort of 832,560 deidentified electronic health records by BP-category; compared the frequency of BP-categories and four subtypes of Htn and Hotn by sex and age-decade; visualized the distributions of systolic, diastolic, mean arterial and pulse pressures stratified by BP-category; and ran Phenome-wide Association Studies (PheWAS) for Htn and Hotn. We paired knowledgebases for hypertension and hypotension and computed aggregate knowledgebase status (KB-status) indicating known associations. We assessed alignment of PheWAS results with KB-status for phecodes in the knowledgebase, and paired PheWAS correlations with KB-status to surface phenotypic patterns.

RESULTS

BP-categories represent distinct distributions within the multimodal distributions of systolic and diastolic pressure. They are centered in the upper, lower, and middle zones of mean arterial pressure and provide a different signal than pulse pressure. For phecodes in the knowledgebase, 85% of positive correlations align with KB-status. Phenotypic patterns for Htn and Hotn overlap for several phecodes and are separate for others. Our analysis suggests five candidates for hypothesis testing research, two where the prevalence of the association with Htn or Hotn may be under appreciated, three where mechanisms that increase and decrease blood pressure may be affecting one another's expression.

CONCLUSION

PairedPheWAS methods may open a phenome-wide path to disentangling hypertension and chronic hypotension. Our classifier provides a starting point for assigning individuals to BP-categories representing the upper, lower, and middle zones of the BP spectrum. 4.7 % of individuals matching 2017 BP categories for normal, elevated BP or isolated hypertension, have diastolic pressure < 60. Research is needed to fine-tune the classifier, provide external validation, evaluate the clinical significance of diastolic pressure < 60, and test the candidate hypotheses.

A Practical Approach to Diagnosing Peripheral Neuropathies

Polyneuropathies are common, with the incidence increasing with older age. The causes of polyneuropathies are diverse and numerous, and it can be challenging for clinicians to determine the etiology of a particular patient's neuropathy. In this article, we systematically detail a practical approach to polyneuropathies, beginning with the most important aspects of the workup, the history and physical. We then discuss the limited diagnostic approach required for patients who present with a distal symmetric polyneuropathy and the more comprehensive approach for patients who present with other neuropathy subtypes.

Tunable Hydrogel Electronics for Diagnosis of Peripheral Neuropathy

Peripheral neuropathy characterized by rapidly increasing numbers of patients is commonly diagnosed via analyzing electromyography signals obtained from stimulation-recording devices. However, existing commercial electrodes have difficulty in implementing conformal contact with skin and gentle detachment, dramatically impairing stimulation/recording performances. Here, this work develops on-skin patches with polyaspartic acid-modified dopamine/ethyl-based ionic liquid hydrogel (PDEH) as stimulation/recording devices to capture electromyography signals for the diagnosis of peripheral neuropathy. Triggered by a one-step electric field treatment, the hydrogel achieves rapid and wide-range regulation of adhesion and substantially strengthened mechanical performances. Moreover, hydrogel patches assembled with a silver-liquid metal (SLM) layer exhibit superior charge injection and low contact impedance, capable of capturing high-fidelity electromyography. This work further verifies the feasibility of hydrogel devices for accurate diagnoses of peripheral neuropathy in sensory, motor, and mixed nerves. For various body parts, such as fingers, the elderly's loose skin, hairy skin, and children's fragile skin, this work regulates the adhesion of PDEH-SLM devices to establish intimate device/skin interfaces or ensure benign removal. Noticeably, hydrogel patches achieve precise diagnoses of nerve injuries in these clinical cases while providing extra advantages of more effective stimulation/recording performances. These patches offer a promising alternative for the diagnosis and rehabilitation of neuropathy in future.

Gastrointestinal manifestations seen in pediatric patients diagnosed with small fiber neuropathy

OBJECTIVES

Small fiber neuropathy (SFN) affects the fibers involved in cutaneous and visceral pain and temperature sensation and are a crucial part of the autonomic nervous system. Autonomic dysfunction secondary to SFN and autoimmune receptor antibodies is being increasingly recognized, and gastrointestinal (GI) manifestations include constipation, early satiety, nausea, vomiting, and diarrhea. Enteric nervous system involvement may be a possible explanation of abnormal GI motility patterns seen in these patients.

METHODS

Children suspected to have SFN based on symptoms underwent skin biopsy at the Child Neurology clinic at Arnold Palmer Hospital for Children, which was processed at Therapath™ Neuropathology. SFN was diagnosed using epidermal nerve fiber density values that were below 5th percentile from the left distal leg (calf) as reported per Therapath™ laboratory.

RESULTS

Twenty-six patients were diagnosed with SFN. Retrospective chart review was performed, including demographic data, clinical characteristics, and evaluation. A majority of patients were white adolescent females. Autonomic dysfunction, including orthostasis and temperature dysregulation were seen in 61.5% of patients (p = 0.124). Somatosensory symptoms, including pain or numbness were seen in 85% of patients (p < 0.001). GI symptoms were present in 85% of patients (p < 0.001) with constipation being the most common symptom seen in 50% of patients. This correlated with the motility testing results.

CONCLUSIONS

Pediatric patients with SFN commonly have GI symptoms, which may be the main presenting symptom. It is important to recognize and look for symptoms of small fiber neuropathy in children with refractory GI symptoms that may explain multisystemic complaints often seen in these patients.

Autoimmune Autonomic Neuropathy: From Pathogenesis to Diagnosis

Autoimmune autonomic ganglionopathy (AAG) is a disease of autonomic failure caused by ganglionic acetylcholine receptor (gAChR) autoantibodies. Although the detection of autoantibodies is important for distinguishing the disease from other neuropathies that present with autonomic dysfunction, other factors are important for accurate diagnosis. Here, we provide a comprehensive review of the clinical features of AAG, highlighting differences in clinical course, clinical presentation, and laboratory findings from other neuropathies presenting with autonomic symptoms. The first step in diagnosing AAG is careful history taking, which should reveal whether the mode of onset is acute or chronic, followed by an examination of the time course of disease progression, including the presentation of autonomic and extra-autonomic symptoms. AAG is a neuropathy that should be differentiated from other neuropathies when the patient presents with autonomic dysfunction. Immune-mediated neuropathies, such as acute autonomic sensory neuropathy, are sometimes difficult to differentiate, and therefore, differences in clinical and laboratory findings should be well understood. Other non-neuropathic conditions, such as postural orthostatic tachycardia syndrome, chronic fatigue syndrome, and long COVID, also present with symptoms similar to those of AAG. Although often challenging, efforts should be made to differentiate among the disease candidates.

New Horizons in Diabetic Neuropathies: An Updated Review on their Pathology, Diagnosis, Mechanism, Screening Techniques, Pharmacological, and Future Approaches

BACKGROUND

One of the largest problems for global public health is diabetes mellitus (DM) and its micro and macrovascular consequences. Although prevention, diagnosis, and treatment have generally improved, its incidence is predicted to keep rising over the coming years. Due to the intricacy of the molecular mechanisms, which include inflammation, oxidative stress, and angiogenesis, among others, discovering treatments to stop or slow the course of diabetic complications is still a current unmet need.

METHODS

The pathogenesis and development of diabetic neuropathies may be explained by a wide variety of molecular pathways, hexosamine pathways, such as MAPK pathway, PARP pathway, oxidative stress pathway polyol (sorbitol) pathway, cyclooxygenase pathway, and lipoxygenase pathway. Although diabetic neuropathies can be treated symptomatically, there are limited options for treating the underlying cause.

RESULT

Various pathways and screening models involved in diabetic neuropathies are discussed, along with their possible outcomes. Moreover, both medicinal and non-medical approaches to therapy are also explored.

CONCLUSION

This study highlights the probable involvement of several processes and pathways in the establishment of diabetic neuropathies and presents in-depth knowledge of new therapeutic approaches intended to stop, delay, or reverse different types of diabetic complications.

Peripheral neuropathy associated with monomethyl auristatin E-based antibody-drug conjugates

Since the successful approval of gemtuzumab ozogamicin, antibody-drug conjugates (ADCs) have emerged as a pivotal category of targeted therapies for cancer. Among these ADCs, the use of monomethyl auristatin E (MMAE) as a payload is prevalent in the development of ADC drugs, which has significantly improved overall therapeutic efficacy against various malignancies. However, increasing clinical observations have raised concerns regarding the potential nervous system toxicity associated with MMAE-based ADCs. Specifically, a higher incidence of peripheral neuropathy has been reported in ADCs incorporating MMAE as payloads. Considering the increasing global use of MMAE-based ADCs, it is imperative to provide an inclusive overview of diagnostic and management strategies for this adverse event. In this review, we examine current information and what future research directions are required to better understand and manage this type of clinical challenge.

A de novo heterozygous variant in ACOX1 gene cause Mitchell syndrome: the first case in China and literature review

BACKGROUND

Mitchell syndrome (MITCH) is a rare autosomal dominant hereditary disorder, characterized by episodic demyelination, sensorimotor polyneuropathy and hearing loss. MITCH is caused by heterozygous mutation in the ACOX1 gene, which encodes straight-chain acyl-CoA oxidase, on chromosome 17q25.1.  Only 5 unrelated patients have been reported so far, and no reports from China. Here, we describe the first MITCH case in a Chinese individual.

CASE PRESENTATION

A 7-year-old girl initially presented with diffuse desquamatory rash at age 3. Her clinical symptoms in order of presentation were diffuse desquamatory rash, gait instability, ptosis with photophobia, hearing loss, abdominal pain, diarrhea, nausea, and dysuria. Genetic analysis demonstrated that the patient carried a heterozygous variant c.710A>G(p.Asp237Ser) in the ACOX1 gene, which can cause MITCH symptoms. This is the first MITCH case with gastrointestinal and urinary tract symptoms. After administrating N acetylcysteine amide (NACA), some symptoms were relieved and the patient's condition improved.

CONCLUSION

This is the first MITCH case in the Chinese population, and we expanded the genotype spectrum of it. The p.Asp237Ser may be a mutational hotspot in ACOX1 regardless of race. In terms of diagnosis, patients with recurrent rash, gait instability, and hearing loss with some autonomic symptoms should raise the suspicion of MITCH and proper and prompt treatment should be given.

Autonomic nervous system disorders in multiple sclerosis

Multiple sclerosis (MS) is a chronic progressive demyelinating disease of the central nervous system (CNS), which also affects the autonomic nervous system (ANS). Manifestations of MS in the ANS include urological, sexual, gastrointestinal, cardiovascular, and thermoregulatory disorders as well as increased fatigue. These problems are common yet are often underestimated due to the non-specificity of the symptoms and the limited evaluation of the ANS in the usual clinical practice. Most of these symptoms seem to be related to localized lesions in the CNS. However, the mechanisms by which these disorders are caused in MS have not been fully investigated, thus preventing any focused etiological treatment. The most common disorders of the ANS in MS represent a challenge for clinicians due to the variability of the clinical picture and our minimal data on their diagnosis and treatment. Early diagnosis and initiation of individualized treatment regimens, often in need of multiple approaches, seem to yield the best results in managing ANS dysfunction in MS patients.

Biomarkers in diabetic neuropathy

CONTEXT

The prevalence of diabetic neuropathy is drastically increasing in the world. To halt the progression of diabetic neuropathy, there is an unmet need to have potential biomarkers for the diagnosis and new drug discovery.

OBJECTIVE

To study various biomarkers involved in the pathogenesis of diabetic neuropathy.

METHODS

The literature was searched with the help of various scientific databases and resources like PubMed, ProQuest, Scopus, and Google scholar from the year 1976 to 2020.

RESULTS

Biomarkers of diabetic neuropathy are categorised as inflammatory biomarkers such as MCP-1, VEGF, TRPV1, NF-κB; oxidative biomarkers such as adiponectin, NFE2L2; enzyme biomarkers like NADPH, ceruloplasmin, HO-1, DPP-4, PARP α; miscellaneous biomarkers such as SIRT1, caveolin 1, MALAT1, and microRNA. All biomarkers have a significant role in the pathogenesis of diabetic neuropathy.

CONCLUSION

These biomarkers have a potential role in the progression of diabetic neuropathy and can be considered as potential targets for new drug discovery.

Functional and structural markers of peripheral microvascular autonomic neuropathy

INTRODUCTION/AIMS

Autonomic dysfunction is a common complication of small-fiber neuropathy (SFN). In this study we aimed to assess the applicability of autonomic microvascular indices as a potential marker for SFN assessment.

METHODS

Fifteen patients with confirmed SFN (idiopathic neuropathy [n = 10], chemotherapy-induced peripheral neuropathy [n = 2], impaired glucose tolerance [n = 1], hereditary transthyretin amyloidosis (hATTR) [n = 1], pulmonary sarcoidosis [n = 1]) and 15 matched control subjects underwent assessment of vascular skin responses assessed through laser Doppler flowmetry and evaluation of microvascular vessel and nerve density in skin biopsies. All participants underwent peripheral autonomic evaluation by quantitative sudomotor axon reflex testing (QSART).

RESULTS

We found no significant differences in vascular skin responses, or in any microvascular skin biopsy markers, when comparing SFN with control subjects. We found no correlation between vascular skin responses and skin biopsy indices. We saw no significant difference in any microvascular indices when comparing subjects with and without impaired sudomotor function.

DISCUSSION

Our findings suggest markers of peripheral microvascular innervation and function are not associated with the diagnosis of SFN. Furthermore, we saw no association between microvascular markers and sudomotor function, suggesting that these are independent and unrelated components of the autonomic nervous system.

Sympathetic and electrochemical skin responses in the assessment of sudomotor function: a comparative study

OBJECTIVES

The sympathetic skin response (SSR) is a well-established test, whereas the electrochemical skin conductance (ESC) is still under evaluation. Our aim was therefore to assess the diagnostic accuracy of ESC to detect abnormal sudomotor function, using SSR as a reference test.

METHODS

A cross sectional observational study was performed of 61 neurological patients assessed for possible sudomotor dysfunction and 50 age-matched healthy controls (HC). Patients with diagnoses of vasovagal syncope (VVS, n=25), Parkinson's disease (PD, n=15), multiple system atrophy (MSA, n=11) and peripheral neuropathies (PN, n=10) were included. Sudomotor function was assessed with SSR and ESC tests in all participants. The absence of SSR in the palms or soles indicates abnormal sudomotor function. Receiver operating characteristic (ROC) analysis was used to assess the diagnostic value of the ESC. Cardiovascular autonomic (CV-Aut) function was evaluated through the Ewing score, based on the following tests: Heart rate change with deep breathing, Valsalva ratio, 30:15 ratio, blood pressure changes on standing and during isometric exercise. A Ewing score ≥ 2 indicates the presence of CV-Aut dysfunction.

RESULTS

Mean SSR amplitudes and ESC values showed differences between HC and patients with MSA or PN (p < 0.05), but not in patients with VVS or PD. Absence of SSR was associated with abnormal ESC (p < 0.05). Patients with abnormal CV-Aut dysfunction had lower ESC (p< 0.05). Palm ESC (P-ESC) and sole ESC (S-ESC) assessment had a sensitivity of 0.91 and 0.95 to predict sudomotor dysfunction, with a specificity of 0.78 and 0.85, respectively. The area under ROC curve was 0.905 and 0.98, respectively.

CONCLUSIONS

ESC in palms and soles has a high diagnostic accuracy for sudomotor dysfunction as detected by absent SSR in patients with MSA and PN.

Differential impact of individual autonomic domains on clinical outcomes in Parkinson's disease

INTRODUCTION

While autonomic failure is a well-known prognostic factor for more aggressive disease progression in Parkinson's disease (PD), with a three- to sevenfold higher risk of dementia and death within 10 years after the diagnosis, the individual impact of cardiovascular, gastrointestinal, urogenital, thermoregulatory, and pupillomotor autonomic domains on PD clinical outcomes remains unclear.

OBJECTIVES

We sought to determine the 5-year risk of developing dementia, falls, postural instability, dysarthria, and dysphagia in PD patients with and without autonomic impairment at baseline and to assess the joint and individual association of each autonomic domain on these key functional outcomes. In addition, we aimed to determine the impact of each autonomic domain on activities of daily living (ADLs) and health-related quality of life (HRQoL).

METHODS

We enrolled 65 consecutive PD patients in a 5-year cohort study involving standardized evaluations of autonomic symptoms, orthostatic hypotension, and motor and non-motor features, including cognitive function. Associations were estimated as odds ratio and adjusted for PD duration, age, and baseline motor impairment.

RESULTS

Cardiovascular dysautonomia was associated with a sevenfold higher risk of developing dementia (95%CI: 1.154-50.436; p = 0.035) and a fivefold higher risk of falls (95%CI: 1.099-18.949; p = 0.039), as well as significantly higher impairment in ADLs (p = 0.042) and HRQoL (p = 0.031). No relevant associations were found between the other autonomic domains and these outcomes.

CONCLUSIONS

Cardiovascular dysautonomia, but not other domains, showed an association with worse 5-year clinical outcomes in PD. Our data suggest a specific role for cardiovascular autonomic dysregulation in the pathogenic mechanisms of PD progression.

Population Study of Hand and Wrist Manifestations of Congenital Insensitivity to Pain

Background: Congenital insensitivity to pain is a rare autosomal recessive condition characterized by insensitivity to painful stimuli due to absence of sensory and sympathetic post ganglionic neurons in the skin and skeletal system leading to lack of protective sensation and altered joint propioception. This study was performed to assess hand and wrist manifestations of patients with congenital insensitivity to pain in the Maltese Islands. Methods: Records of public and private hospitals were reviewed to identify patients suffering from this condition. A review of notes, patients, and imaging was performed. A Disabilities of the Arm, Shoulder, and Hand score was obtained to assess level of function. Results: Nine patients were identified. Mean age of diagnosis was 8.9 years. Interphalangeal joints were most commonly affected. Multiple spontaneous or posttraumatic fingertip ulceration occurred in 5 patients. Anhidrosis resulted in more protracted ulcers and infections, requiring amputation of distal and middle phalanges due to osteomyelitis. The wrist joint was less commonly involved and showed more complex joint involvement. Conclusion: The hand and wrist are involved in different ways, with fingertip ulceration leading to potential infection and osteomyelitis in the hand, whereas the wrist joint is involved in cases of increased axial loading and load transfer, such as following prolonged use of walking and mobility aids. The latter should be borne in mind during management of lower limb conditions. Hand care and hygiene is important in all patients, especially in cases of anhidrosis due to the increased rate of ulceration and osteomyelitis requiring surgical intervention. Despite the severity of the condition, patients report good overall function.

Diabetic Foot Risk Classification at the Time of Type 2 Diabetes Diagnosis and Subsequent Risk of Mortality: A Population-Based Cohort Study

AIM

We aimed to compare the mortality of individuals at low, moderate, and high risk of diabetic foot disease (DFD) in the context of newly diagnosed type 2 diabetes, before developing active diabetic foot problem.

METHODS

This was a population-based cohort study of adults with newly diagnosed type 2 diabetes utilizing IQVIA Medical Research Data. The outcome was all-cause mortality among individuals with low, moderate, and high risk of DFD, and also in those with no record of foot assessment and those who declined foot examination.

RESULTS

Of 225,787 individuals with newly diagnosed type 2 diabetes, 34,061 (15.1%) died during the study period from January 1, 2000 to December 31, 2019. Moderate risk and high risk of DFD were associated with increased mortality risk compared to low risk of DFD (adjusted hazard ratio [aHR] 1.50, 95% CI 1.42, 1.58; aHR 2.01, 95% CI 1.84, 2.20, respectively). Individuals who declined foot examination or who had no record also had increased mortality risk of 75% and 25% vs. those at low risk of DFD, respectively (aHR 1.75, 95% CI 1.51, 2.04; aHR 1.25, 95% CI 1.20, 1.30).

CONCLUSION

Individuals with new-onset type 2 diabetes who had moderate to high risk of DFD were more likely to die compared to those at low risk of DFD. The associations between declined foot examination and absence of foot examinations, and increased risk of mortality further highlight the importance of assessing foot risk as it identifies not only patients at risk of diabetic foot ulceration but also mortality.

Burden of caregiving for cardiovascular dysautonomia in Parkinson's disease

PURPOSE

We sought to estimate the impact of cardiovascular autonomic neuropathy (cAN) on informal caregivers of patients with Parkinson's disease (PD), defined as individuals providing regular care to a friend, partner, or family member with PD, and to evaluate the mutual relationship between caregiver burden and patient health-related quality of life (HRQoL).

METHODS

We enrolled 36 consecutive patients with PD and their informal caregivers. Patients underwent a detailed motor, autonomic, cognitive, and functional assessment. Caregivers were assessed using the Zarit Burden Interview (ZBI). Differences in caregiver burden, expressed by the ZBI score, and strength of association between caregiver burden, cAN, and HRQoL were assessed using analysis of covariance (ANCOVA), logistic regression, and linear regression analyses. Analyses were adjusted for patients' age, PD duration, and motor and cognitive disability, as well as caregivers' age.

RESULTS

Moderate-severe caregiver burden was reported in 41.7% of PDcAN⁺ versus 8.7% of PDcAN^- (p < 0.001). The ZBI score was increased in PDcAN⁺ versus PDcAN^- (31.5 ± 3.4 versus 15.2 ± 2.3; p < 0.001), with tenfold higher odds (p = 0.012) of moderate-severe caregiver burden in PDcAN⁺, even after adjusting for potential confounders. The ZBI score correlated with cAN severity (p = 0.005), global autonomic impairment (p = 0.012), and HRQoL impairment (p < 0.001).

CONCLUSION

These results highlight the significant impact of cAN on PD caregivers and the need for targeted interventions addressing this frequently overlooked and insufficiently treated source of nonmotor disability in PD.

Pathophysiological Mechanisms That Alter the Autonomic Brain-Liver Communication in Metabolic Diseases

The brain influences liver metabolism through many neuroendocrine and autonomic mechanisms that have evolved to protect the organism against starvation and hypoglycemia. Unfortunately, this effective way of preventing death has become dysregulated in modern obesogenic environments, although the pathophysiological mechanisms behind metabolic dyshomeostasis are still unclear. In this Mini-Review, we provide our thoughts regarding obesity and type 2 diabetes as diseases of the autonomic nervous system. We discuss the pathophysiological mechanisms that alter the autonomic brain-liver communication in these diseases, and how they could represent important targets to prevent or treat metabolic dysfunctions. We discuss how sympathetic hyperactivity to the liver may represent an early event in the progression of metabolic diseases and could progressively lead to hepatic neuropathy. We hope that this discussion will inspire and help to frame a model based on better understanding of the chronology of autonomic dysfunctions in the liver, enabling the application of the right strategy at the right time.

Validation and Reliability of a Novel Vagus Nerve Neurodynamic Test and Its Effects on Heart Rate in Healthy Subjects: Little Differences Between Sexes

Background

The vagus nerve (VN), also called the pneumogastric nerve, connects the brainstem to organs contained in the chest and abdomen. Physiologically, VN stimulation can rapidly affect cardiac activity and heart rate (HR). VN neuropathy can increase the risk of arrhythmias and sudden death. Therefore, a selective test of VN function may be very useful. Since peripheral neurodynamic tests (NDT) are reliable for the assessment of neuropathies in somatic nerves, we aimed to validate a novel NDT to assess VN activity, namely, the VN-NTD.

Methods

In this cross-sectional double-blind, sex-balanced study, 30 participants (15 females) completed a checklist of autonomic dysfunction symptoms. During the VN-NDT administration, HR and symptoms (i.e., mechanical allodynia) were monitored in parallel to a real-time ultrasonography imaging (USI) and motion capture analysis of the neck. The VN-NDT impact on HR and its accuracy for autonomic symptoms reported in the last 7 days were tested.

Results

The VN-NDT induced a significant HR reduction of about 12 and 8 bpm in males and females [t(1, 119) = 2.425; p < 0.017; η_p² = 0.047, 95% confidence interval (CI): 0.93–9.18], respectively. No adverse events were observed during VN-NDT. A substantial interexaminer agreement between the evaluators in symptoms induction by VN-NDT was detected [F(1, 119) = 0.540; p = 0.464; η_p² = 0.005, low effect]. Notably, mechanical allodynia accuracy for gastrointestinal dysfunctions was excellent (p < 0.05; 95% CI: 0.52–0.73; p < 0.001; 95% CI: 0.81–0.96).

Conclusions

The novel VN-NDT is a valid and accurate test capable of detecting VN activation with high sensitivity. Data provided are suitable for both sexes as a hallmark of HR variation due to VN normal response. The proposed VN-NDT may be reliable as daily routine neurological examination tests for the evaluation of neuropathic signs related to neuroinflammation of the VN.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT04192877.

Acute Autonomic Neuropathy as a Rare Cause of Severe Arterial Hypertension in a Child

A 7-year-old boy was admitted to the Pediatric Cardiology Department with blood pressure of 160/120 mmHg accompanied by burning pain in his hands and feet and tachycardia, followed by a seizure attack for the first time in his life, which presented shortly after admission. The child underwent a widespread diagnostic process - including laboratory tests and imaging - showing inconclusive results. Acute autonomic neuropathy was eventually diagnosed and successfully treated with intravenous immunoglobulin. The described case illustrates the need for a careful and open-minded approach to patients with hypertension.

A practical approach to peripheral autonomic neuropathies

PURPOSE OF THE REVIEW

The review focuses on the practical evaluation and management of patients with autonomic neuropathies.

RECENT FINDINGS

Autonomic neuropathies are complex disorders and result in diverse clinical manifestations that affect the cardiovascular, gastrointestinal, urogenital, and sudomotor systems. The autonomic medical history is key when seeing a patient with suspected autonomic neuropathy. The history guides the clinical evaluation, laboratory testing, and autonomic testing in patients with autonomic neuropathies. The treatment of autonomic neuropathies is based on the combination of disease-modifying therapies, symptomatic pharmacologic therapies, and nonpharmacological management. Response to treatment can be assessed with quantitative autonomic biomarkers.

SUMMARY

Treatment of autonomic neuropathies should be individualized, guided by disease state, medications' mechanism of action and adverse event profile as well as cost. Genetic discoveries and pathologic understanding lead to the development of disease-modifying therapies as seen in familial amyloid polyneuropathy.

Electrodiagnostic assessment of the autonomic nervous system: A consensus statement endorsed by the American Autonomic Society, American Academy of Neurology, and the International Federation of Clinical Neurophysiology

Evaluation of disorders of the autonomic nervous system is both an art and a science, calling upon the physician's most astute clinical skills as well as knowledge of autonomic neurology and physiology. Over the last three decades, the development of noninvasive clinical tests that assess the function of autonomic nerves, the validation and standardization of these tests, and the growth of a large body of literature characterizing test results in patients with autonomic disorders have equipped clinical practice further with a valuable set of objective tools to assist diagnosis and prognosis. This review, based on current evidence, outlines an international expert consensus set of recommendations to guide clinical electrodiagnostic autonomic testing. Grading and localization of autonomic deficits incorporates scores from sympathetic cardiovascular adrenergic, parasympathetic cardiovagal, and sudomotor testing, as no single test alone is sufficient to diagnose the degree or distribution of autonomic failure. The composite autonomic severity score (CASS) is a useful score of autonomic failure that is normalized for age and gender. Valid indications for autonomic testing include generalized autonomic failure, regional or selective system syndromes of autonomic impairment, peripheral autonomic neuropathy and ganglionopathy, small fiber neuropathy, orthostatic hypotension, orthostatic intolerance, syncope, neurodegenerative disorders, autonomic hyperactivity, and anhidrosis.

Autonomic Peripheral Neuropathy

PURPOSE OF REVIEW

This article provides a summary of the autonomic neuropathies, including neuropathies associated with diabetes mellitus, neuropathies due to amyloid deposition, immune-mediated autonomic neuropathies (including those associated with a paraneoplastic syndrome), inherited autonomic neuropathies, and toxic autonomic neuropathies. The presenting features, diagnostic investigations, and natural history of these neuropathies are discussed.

RECENT FINDINGS

Recent findings in autonomic peripheral neuropathy include data on the epidemiology and atypical presentations of diabetic autonomic neuropathy, treatment-induced neuropathy of diabetes mellitus, the presentation of immune-mediated neuropathies, and advances in hereditary neuropathy associated with amyloidosis and other hereditary neuropathies.

SUMMARY

Knowledge and recognition of the clinical features of the autonomic neuropathies, combined with appropriate laboratory and electrophysiologic testing, will facilitate accurate diagnosis and management.

Randomized controlled three-arm study of NADA acupuncture for alcohol addiction

INTRODUCTION

Alcohol addiction compromises cardiovascular health, possibly due to impaired control of the heart and vasculature by the autonomic nervous system. We aimed to assess the effects of National Acupuncture Detoxification Association (NADA) acupuncture on cardiovascular autonomic functions, psychiatric comorbidities and abstinence in patients addicted to alcohol.

MATERIAL AND METHODS

A randomized sham controlled three-arm study was undertaken in 72 patients (nine females, aged 43.7 ± 9.2 years, mean ± SD) undergoing in-patient rehabilitation for alcohol addiction. Patients were randomly allocated (1:1:1) to receive twenty 30-minute NADA or sham acupuncture sessions within six weeks or no intervention. They were evaluated for craving, depression, anxiety and autonomic control of the heart (heart rate variability, HRV), vasculature (laser Doppler flowmetry) and sweat glands (sympathetic skin response). Testing was performed at baseline, immediately post intervention (sham intervention or control period, respectively) and another four weeks later. Abstinence was assessed one year after study completion.

RESULTS

Patients in the NADA arm displayed increased HRV immediately post-intervention compared to baseline (SDNN: 72.8 ms ± 34.2 ms vs. 57.9 ms ± 31.2 ms, p = 0.001). This increase was sustained four weeks later (66.2 ms ± 32.4 ms, p = 0.015). HRV remained unaltered following sham or no acupuncture (p = n.s.). Autonomic function of vasculature and sweat glands, psychiatric comorbidities and one-year abstinence did not differ between study arms.

CONCLUSIONS

NADA acupuncture may improve autonomic cardiac function. However, this improvement appears not to translate into alleviation of psychiatric comorbidities or sustained abstinence.

Differential diagnosis of orthostatic hypotension

Orthostatic hypotension (OH) is a common clinical manifestation characterized by a significant fall in blood pressure with postural change and is frequently accompanied by debilitating symptoms of orthostatic intolerance. The reported prevalence of OH ranges between 5 and 10% in middle-aged adults with a burden that increases concomitantly with age; in those over 60 years of age, the prevalence is estimated to be over 20%. Unfortunately, the clinical course of OH is not necessarily benign. OH patients are at an increased risk of adverse clinical outcomes including death, falls, cardiovascular and cerebrovascular events, syncope, and impaired quality of life. The differential diagnosis of OH is broad and includes acute precipitants as well as chronic underlying medical conditions, especially of neurological origin. Appropriate diagnosis relies on a systematic history and physical examination with particular attention to orthostatic vital signs, keeping in mind that ambient conditions during diagnostic testing may affect OH detection due to factors such as diurnal variation.

Is sudoscan a reliable tool in detecting small fiber neuropathy in Parkinson's disease patients?

Aim: Previous studies have revealed uncertainties concerning the utility of sudoscan in identifying small fiber neuropathy in Parkinson's disease (PD). Patients & methods: We searched for a significant reduction of electrochemical skin conductance (ESC) in 67 PD patients versus 66 controls with similar characteristics. We conducted analysis of the subgroups of PD patients without diabetes using sudoscan technology. Results: There is no discrimination between patients and controls relative to feet ESC, the modified Hoehn and Yahr Scale and/or Unified Parkinson's Disease Rating Scale. ESC in patients did not differ significantly according to the Unified Parkinson's Disease Rating Scale score. The oldest PD patients with cardiovascular risk factors have more marked small fibers dysfunction. Conclusion: The sudoscan procedure did not show advantage in the diagnosis of small fiber neuropathy. Its diagnostic value increases in some subgroups of patients with cardiovascular co-morbidity.

Assessment of cutaneous axon-reflex responses to evaluate functional integrity of autonomic small nerve fibers

Cutaneous autonomic small nerve fibers encompass unmyelinated C-fibers and thinly myelinated Aδ-fibers, which innervate dermal vessels (vasomotor fibers), sweat glands (sudomotor fibers), and hair follicles (pilomotor fibers). Analysis of their integrity can capture early pathology in autonomic neuropathies such as diabetic autonomic neuropathy or peripheral nerve inflammation due to infectious and autoimmune diseases. Furthermore, intraneural deposition of alpha-synuclein in synucleinopathies such as Parkinson’s disease can lead to small fiber damage. Research indicated that detection and quantitative analysis of small fiber pathology might facilitate early diagnosis and initiation of treatment. While autonomic neuropathies show substantial etiopathogenetic heterogeneity, they have in common impaired functional integrity of small nerve fibers. This impairment can be evaluated by quantitative analysis of axonal responses to iontophoretic application of adrenergic or cholinergic agonists to the skin. The axon-reflex can be elicited in cholinergic sudomotor fibers to induce sweating and in cholinergic vasomotor fibers to induce vasodilation. Currently, only few techniques are available to quantify axon-reflex responses, the majority of which is limited by technical demands or lack of validated analysis protocols. Function of vasomotor small fibers can be analyzed using laser Doppler flowmetry, laser Doppler imaging, and laser speckle contrast imaging. Sudomotor function can be assessed using quantitative sudomotor axon-reflex test, silicone imprints, and quantitative direct and indirect testing of sudomotor function. More recent advancements include analysis of piloerection (goose bumps) following stimulation of adrenergic small fibers using pilomotor axon-reflex test. We provide a review of the current literature on axon-reflex tests in cutaneous autonomic small fibers.

Metabolic and Non-Metabolic Peripheral Neuropathy: Is there a Place for Therapeutic Apheresis?

As the rate of obesity and the incidence of diabetes mellitus have been increasing, diabetic neuropathy has become the most common cause of peripheral neuropathy in developed countries. In addition, a variety of pathogenetically heterogeneous disorders can lead to impairment of the peripheral nervous system including amyloidosis, vitamin deficiencies, uremia and lipid disorders, alcohol abuse, autoimmune and infectious diseases as well as exposure to environmental toxins. We have noted that a combination of these disorders may aggravate the manifestations of peripheral diabetic neuropathy, an effect, which is most pronounced when metabolic and non-metabolic pathologies lead to cumulative damage. Current treatment options are limited and generally have unsatisfactory results in most patients. Therapeutic apheresis (INUSpherese®) allows the removal of metabolic, inflammatory, immunologic and environmental contributors to the disease process and may be an effective treatment option. We reviewed the developments in therapeutic apheresis for metabolic and non-metabolic peripheral neuropathy, including the current literature as well as data from our university diabetes center.

Correlation between type 2 diabetes, dry eye and Meibomian glands dysfunction

PURPOSE

To assess the Meibomian glands, ocular surface and tear function in patients with type 2 diabetes, and study the correlation between these conditions.

METHODS

Prospective study of 76 males, 37 with type 2 diabetes with an average of duration between 7±5 years, and 36 males from control group. After completing an ocular surface disease index (OSDI) questionnaire, the non-invasive tear film break-up time (NIBUT) and the tear lipid layer pattern was performed using interferometry system and tear meniscus height/TMH. Ocular surface was studied with lissamine green staining and morphology of the glands with evaluation of Marx's line (lid margin abnormalities); meibomian secretion was expressed and was also assessed the quality. The results were analyzed using the statistical Kruskal-Wallis and Mann-Whitney, and correlations by Spearman Rho.

RESULTS

The mean age was 59±8 years; 71% of participants presented MGD (76% diabetics and 67% controls). OSDI were significantly higher (p=0.01) in the diabetic group. A positive correlation was found between glycemia and symptoms (p=0.0005) and strong correlation between Hb1Ac and OSDI in MGD. NIBUT was lower in the control group (2.47±1.2s) than for the diabetic group (2.9±1.2s), with a significant inverse correlation (52.22%) with MG inflammation.

CONCLUSIONS

MGD in type 2 diabetic patients is more severe compared with nondiabetic patients. Longer duration of diabetes is associated with major symptoms and changes in MG. Diabetic group showed major changes in lids and tear function, accounting for evaporative dry eye and presenting a high degree of correlation with MG inflammation and obstruction.

Architecture of the Cutaneous Autonomic Nervous System

The human skin is a highly specialized organ for receiving sensory information but also to preserve the body's homeostasis. These functions are mediated by cutaneous small nerve fibers which display a complex anatomical architecture and are commonly classified into cutaneous A-beta, A-delta and C-fibers based on their diameter, myelinization, and velocity of conduction of action potentials. Knowledge on structure and function of these nerve fibers is relevant as they are selectively targeted by various autonomic neuropathies such as diabetic neuropathy or Parkinson's disease. Functional integrity of autonomic skin nerve fibers can be assessed by quantitative analysis of cutaneous responses to local pharmacological induction of axon reflex responses which result in dilation of cutaneous vessels, sweating, or piloerection depending on the agent used to stimulate this neurogenic response. Sensory fibers can be assessed using quantitative sensory test. Complementing these functional assessments, immunohistochemical staining of superficial skin biopsies allow analysis of structural integrity of cutaneous nerve fibers, a technique which has gained attention due to its capacity of detecting pathogenic depositions of alpha-synuclein in patients with Parkinson's disease. Here, we reviewed the current literature on the anatomy and functional pathways of the cutaneous autonomic nervous system as well as diagnostic techniques to assess its functional and structural integrity.

Autonomic Disorders

Autonomic complaints are frequently encountered in clinical practice. They can be due to primary autonomic disorders or secondary to other medical conditions. Primary autonomic disorders can be categorized as orthostatic intolerance syndromes and small fiber neuropathies; the latter are associated with autonomic failure, pain, or their combinations. The review outlines orthostatic intolerance syndromes (neurally mediated syncope, orthostatic hypotension, postural tachycardia syndrome, inappropriate sinus tachycardia, orthostatic cerebral hypoperfusion syndrome, and hypocapnic cerebral hypoperfusion) and small fiber neuropathies (sensory/autonomic/mixed, acute/subacute/chronic, idiopathic/secondary, inflammatory and noninflammatory). Several specific autonomic syndromes (diabetic neuropathy, primary hyperhidrosis, paroxysmal sympathetic hyperactivity, autonomic dysreflexia), neurogenic bladder, and gastrointestinal motility disorders are discussed as well.

Temporal changes in the incidence and predictors of severe hypoglycaemia in type 2 diabetes: The Fremantle Diabetes Study

AIM

To determine the incidence of severe hypoglycaemia and its predictors in community-based patients with type 2 diabetes studied between 2008 and 2013 compared with those in a cohort of patients with type 2 diabetes from the same geographical area assessed a decade earlier.

METHODS

We studied 1551 participants (mean age 65.7 years, 51.9% men) with type 2 diabetes from the longitudinal observational Fremantle Diabetes Study Phase II (FDS2). Severe hypoglycaemia was ascertained as that requiring ambulance attendance, emergency department services and/or hospitalization. Cox proportional hazards modelling was used to determine predictors of a first episode of severe hypoglycaemia, and negative binomial regression was used to identify predictors of frequency.

RESULTS

Sixty-three participants (4.1%) experienced 83 episodes, representing an incidence of 1.34/100 participant-years (95% confidence interval [CI] 1.08 to 1.67; vs 1.67/100 participant-years [95% CI 1.31-2.13] in the Fremantle Diabetes Study Phase I [FDS1]; P = 0.18). Those experiencing severe hypoglycaemia experienced one to four episodes in both cohorts. The independent predictors of incident severe hypoglycaemia in the FDS2 were: older age; higher educational attainment; alcohol consumption; current smoking; sulphonylurea/insulin treatment; prior severe hypoglycaemia; renal impairment; and plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP). The same variables except smoking were associated with frequency of severe hypoglycaemia. Most of these risk factors paralleled those in the FDS1, but current smoking and plasma NT-proBNP were novel.

CONCLUSIONS

The incidence and frequency of severe hypoglycaemia did not change between the Fremantle Diabetes Study phases but novel risk factors, including plasma NT-proBNP, were observed in the FDS2.

Peripheral Neuropathy

Peripheral neuropathy is a commonly encountered disorder in clinical practice. In light of an aging population and the diabetes and obesity pandemic, the prevalence of peripheral neuropathy is increasing, posing a significant public health concern. This article provides a diagnostic framework for neuropathies and summarizes treatment options.

An update on the diagnosis and treatment of diabetic somatic and autonomic neuropathy

Diabetic peripheral neuropathy (DPN) is the most common chronic complication of diabetes. It poses a significant challenge for clinicians as it is often diagnosed late when patients present with advanced consequences such as foot ulceration. Autonomic neuropathy (AN) is also a frequent and under-diagnosed complication unless it is overtly symptomatic. Both somatic and autonomic neuropathy are associated with increased mortality. Multiple clinical trials have failed because of limited efficacy in advanced disease, inadequate trial duration, lack of effective surrogate end-points and a lack of deterioration in the placebo arm in clinical trials of DPN. Multifactorial risk factor reduction, targeting glycaemia, blood pressure and lipids can reduce the progression of DPN and AN. Treatment of painful DPN reduces painful symptoms by about 50% at best, but there is limited efficacy with any single agent. This reflects the complex aetiology of painful DPN and argues for improved clinical phenotyping with the use of targeted therapy, taking into account co-morbid conditions such as anxiety, depression and sleep disturbance.

The Investigation of the Cardiovascular and Sudomotor Autonomic Nervous System-A Review

The autonomic nervous system as operating system of the human organism permeats all organ systems with its pathways permeating that it is involved with virtually all diseases. Anatomically a central part, an afferent part and sympathetic and parasympathetic efferent system can be distinguished. Among the different functional subsystems of the autonomic nervous system, the cardiovascular autonomic nervous system is most frequently examined with easily recordable cardiovascular biosignals as heart rate and blood pressure. Although less widely established, sudomotor tests pose a useful supplement to cardiovascular autonomic assessment as impaired neurogenic sweating belongs to the earliest clinical signs of various autonomic neuropathies as well as neurodegenerative disorders and significantly reduces quality of life. Clinically at first, the autonomic nervous system is assessed with a detailed history of clinical autonomic function and a general clinical examination. As a lof of confounding factors can influence autonomic testing, subjects should be adequately prepared in a standardized way. Autonomic testing is usually performed in that way that the response of the autonomic nervous system to a well-defined challenge is recorded. As no single cardiovascular autonomic test is sufficiently reliable, it is recommended to use a combination of different approaches, an autonomic test battery including test to measure parasympathetic and sympathetic cardiovascular function (deep breathing test, Valsalva maneuver, tilt, or pressor test). More specialized tests include carotid sinus massage, assessment of baroreceptor reflex function, pharmacological tests or cardiac, and regional hemodynamic measurements. Techniques to measure functional integrity of sudomotor nerves include the quantitative sudomotor axon reflex sweat test, analysis of the sympathetic skin response as well as the thermoregulatory sweat test. In addition to these rather established techniques more recent developments have been introduced to reduce technical demands and interindividual variability such as the quantitative direct and indirect axon reflex testing or sudoscan. However, diagnostic accuracy of these tests remains to be determined. We reviewed the current literature on currently available autonomic cardiovascular and sudomotor tests with a focus on their physiological and technical mechanisms as well as their diagnostic value in the scientific and clinical setting.

The Orthopedic Manifestations of Congenital Insensitivity to Pain: A Population-based Study

BACKGROUND

Congenital insensitivity to pain (CIP) is an extremely rare condition in which there is a failure of the development of the afferent sensory nerves in the dorsal root ganglia resulting in indifference to painful stimuli. The associated orthopedic manifestations are various and often present a diagnostic quandary for the treating surgeon.

PURPOSE

This population study provides insight into the orthopedic manifestations and functional scores in patients with CIP, to guide prognosis and management.

PATIENTS AND METHODS

We retrospectively review and describe the orthopedic manifestations of all cases of CIP in Malta. All patients were then scored for upper and lower limb function using the abridged version of the Disability of Arm, Shoulder, and Hand score (QuickDASH) and the Lower Extremity Functional Score (LEFS).

RESULTS

Nine patients were recruited in total. Mean age at the time of recruitment into this study was of 33.7 years (range 15-58). All patients were Caucasian of Maltese heritage. None had consanguineous parents. All patients had been diagnosed with the condition in childhood (mean age 8.9 years). In total, these patients had 6 long bone fractures, 1 vertebral fracture, 39 upper limb surgical procedures, 88 lower limb surgical procedures, and 7 major lower limb amputations. These are discussed in detail. The main QuickDASH score was 23.97. The main LEFS was 42.22.

CONCLUSIONS

This paper is the first population-based study of this condition and one of the largest series with functional scores. A multidisciplinary approach is essential in managing these patients. The surgical treatment of these conditions is often difficult and protracted, and judicious and careful consideration to both the bony and soft tissues aspects of the management need to be taken into account, with functional limb amputation not necessarily being considered as a last resort.

Diagnosing and managing diabetic somatic and autonomic neuropathy

The diagnosis and management of diabetic neuropathy can be a major challenge. Late diagnosis contributes to significant morbidity in the form of painful diabetic neuropathy, foot ulceration, amputation, and increased mortality. Both hyperglycaemia and cardiovascular risk factors are implicated in the development of somatic and autonomic neuropathy and an improvement in these risk factors can reduce their rate of development and progression. There are currently no US Food and Drug Administration (FDA)-approved disease-modifying treatments for either somatic or autonomic neuropathy, as a consequence of multiple failed phase III clinical trials. While this may be partly attributed to premature translation, there are major shortcomings in trial design and outcome measures. There are a limited number of partially effective FDA-approved treatments for the symptomatic relief of painful diabetic neuropathy and autonomic neuropathy.

Incomplete intestinal obstruction as an initial and persistent presentation in chronic inflammatory demyelinating polyneuropathy: A case report

RATIONALE

Autonomic symptoms are not uncommon in chronic inflammatory demyelinating polyneuropathy (CIDP), but they are mostly mild and transient and are overshadowed by somatic manifestations. Here, we report a very unusual case of CIDP with severe autonomic symptom, intestinal obstruction, as initial and persistent symptom which responded well to high-dose glucocorticoid and intravenous immunoglobulin treatment.

PATIENT CONCERNS

We described a patient with CIDP with precedent and long-lasting incomplete intestinal obstruction. Clinical manifestations were precedent and chronic abdominal pain, distension and constipation, and later numbness and weakness of lower and upper limbs. Radiograph showed incomplete intestinal obstruction, cerebrospinal fluid (CSF) showed albuminocytological dissociation and electromyography indicated neurogenic lesion.

DIAGNOSES

CIDP with incomplete intestinal obstruction was diagnosed based on the history, related symptoms, typical abdominal radiograph, CSF albuminocytological dissociation, and electromyographic findings.

INTERVENTIONS

The patient was treated with intravenous methylprednisolone and immunoglobulin.

OUTCOMES

After treatment, the intestinal obstruction disappeared and the somato-symptoms improved greatly and gradually.

LESSONS

This case highlights the need for diagnostic vigilance in cases of incomplete intestinal obstruction of unknown cause. We recommend CSF and electromyography examination in view of rare but possibility of CIDP.

Assessment of sudomotor function

PURPOSE

To review the currently available literature on clinical autonomic tests of sudomotor function.

METHODS

We searched PubMED/MEDLINE for articles on technical principles and clinical applications of sudomotor tests with a focus on their drawbacks and perspectives in order to provide a narrative review.

RESULTS

The quantitative sudomotor axon reflex sweat test (QSART) is the most widely used test of sudomotor function. The technique captures pathology with low intra- and inter-subject variability but is limited by technical demands. The thermoregulatory sweat test comprises topographic sweat pattern analysis of the ventral skin surface and allows differentiating preganglionic from postganglionic sudomotor damage when combined with a small fiber test such as QSART. The sympathetic skin response also belongs to the more established techniques and is used in lie detection systems due to its high sensitivity for sudomotor responses to emotional stimuli. However, its clinical utility is limited by high variability of measurements, both within and between subjects. Newer and, therefore, less widely established techniques include silicone impressions, quantitative direct and indirect axon reflex testing, sensitive sweat test, and measurement of electrochemical skin conductance. The spoon test does not allow a quantitative assessment of the sweat response but can be used as bedside-screening tool of sudomotor dysfunction.

CONCLUSION

While new autonomic sudomotor function testings have been developed and studied over the past decades, the most were well-studied and established techniques QSART and TST remain the gold standard of sudomotor assessment. Combining these techniques allows for sophisticated analysis of neurally mediated sudomotor impairment. However, newer techniques display potential to complement gold standard techniques to further improve their precision and diagnostic value.

Orthostatic hypotension: A review

Orthostatic hypotension, defined by a drop in blood pressure of at least 20mmHg for systolic blood pressure and at least 10mmHg for diastolic blood pressure within 3minutes of standing up, is a frequent finding, particularly in elderly patients. It is associated with a significant increase in morbidity and mortality. Although it is often multifactorial, the first favoring factor is medications. Other etiologies are divided in neurogenic orthostatic hypotension, characterized by autonomic failure due to central or peripheral nervous system disorders, and non-neurogenic orthostatic hypotension, mainly favoured by hypovolemia. Treatment always requires education of the patient regarding triggering situations and physiological countermanoeuvers. Pharmacological treatment may sometimes be necessary and mainly relies on volume expansion by fludrocortisone and/or a vasopressor agents such as midodrine. There is no predefined blood pressure target, the goal of therapy being the relief of symptoms and fall prevention.

Long-Time Course of Idiopathic Small Fiber Neuropathy

Background: Small fiber neuropathy (SFN) is a challenging subtype of peripheral neuropathies. Once the diagnosis has been established, there is an uncertainty how SFN may progress, whether larger fibers will become involved over time, whether quality of life may be compromised, or whether repeated diagnostic workup in patients with unknown underlying cause may increase the yield of treatable causes of SFN. Methods: We evaluated 16 patients with documented long-time course of idiopathic SFN. Results: Clinical and electrophysiological course remained stable in 75% of the patients, while 25% SFN-patients developed large fiber neuropathies. Conclusions: Our data suggest that SFN represents a benign disease course in the majority of patients without severely limiting the quality of life.

Thymoma Associated with Myasthenia and Autonomic anti-Hu Paraneoplastic Neuropathy

Along with myasthenia, other paraneoplastic neurological syndromes (PNS) may occur in thymoma. Anti-Hu antibodies and a clinical “anti-Hu syndrome” characterized by encephalitis and/or painful neuropathies have been reported in only three patients at the time of the diagnosis of thymoma. We describe a severe anti-Hu-related autonomic neuropathy with gastrointestinal paresis and intestinal pseudo-obstruction with malabsorption that occurred concomitantly with the worsening of myasthenic symptoms long after the initial diagnosis of thymoma in a young patient. The clinical anti-Hu syndrome preceded the radiological diagnosis of thymoma recurrence. Treatment with plasma exchange led to a transient improvement of neurological symptoms.

Should Skin Biopsies Be Performed in Patients Suspected of Having Parkinson's Disease?

In patients with Parkinson's disease (PD), the molecularly misfolded form of α-synuclein was recently identified in cutaneous autonomic nerve fibers which displayed increased accumulation even in early disease stages. However, the underlying mechanisms of synucleinopathic nerve damage and its implication for brain pathology in later life remain to be elucidated. To date, specific diagnostic tools to evaluate small fiber pathology and to discriminate neurodegenerative proteinopathies are rare. Recently, research has indicated that deposition of α-synuclein in cutaneous nerve fibers quantified via immunohistochemistry in superficial skin biopsies might be a valid marker of PD which could facilitate early diagnosis and monitoring of disease progression. However, lack of standardization of techniques to quantify neural α-synuclein deposition limits their utility in clinical practice. Additional challenges include the identification of potential distinct morphological patterns of intraneural α-synuclein deposition among synucleinopathies to facilitate diagnostic discrimination and determining the degree to which structural damage relates to dysfunction of nerve fibers targeted by α-synuclein. Answering these questions might improve our understanding of the pathophysiological role of small fiber neuropathy in Parkinson's disease, help identify new treatment targets, and facilitate assessment of response to neuroprotective treatment.