Skin Biopsy Detection of Phosphorylated α-Synuclein in Patients With Synucleinopathies.

Importance: Finding a reliable diagnostic biomarker for the disorders collectively known as synucleinopathies (Parkinson disease [PD], dementia with Lewy bodies [DLB], multiple system atrophy [MSA], and pure autonomic failure [PAF]) is an urgent unmet need. Immunohistochemical detection of cutaneous phosphorylated α-synuclein may be a sensitive and specific clinical test for the diagnosis of synucleinopathies. Objective: To evaluate the positivity rate of cutaneous α-synuclein deposition in patients with PD, DLB, MSA, and PAF. Design, Setting, and Participants: This blinded, 30-site, cross-sectional study of academic and community-based neurology practices conducted from February 2021 through March 2023 included patients aged 40 to 99 years with a clinical diagnosis of PD, DLB, MSA, or PAF based on clinical consensus criteria and confirmed by an expert review panel and control participants aged 40 to 99 years with no history of examination findings or symptoms suggestive of a synucleinopathy or neurodegenerative disease. All participants completed detailed neurologic examinations and disease-specific questionnaires and underwent skin biopsy for detection of phosphorylated α-synuclein. An expert review panel blinded to pathologic data determined the final participant diagnosis. Exposure: Skin biopsy for detection of phosphorylated α-synuclein. Main Outcomes: Rates of detection of cutaneous α-synuclein in patients with PD, MSA, DLB, and PAF and controls without synucleinopathy. Results: Of 428 enrolled participants, 343 were included in the primary analysis (mean [SD] age, 69.5 [9.1] years; 175 [51.0%] male); 223 met the consensus criteria for a synucleinopathy and 120 met criteria as controls after expert panel review. The proportions of individuals with cutaneous phosphorylated α-synuclein detected by skin biopsy were 92.7% (89 of 96) with PD, 98.2% (54 of 55) with MSA, 96.0% (48 of 50) with DLB, and 100% (22 of 22) with PAF; 3.3% (4 of 120) of controls had cutaneous phosphorylated α-synuclein detected. Conclusions and Relevance: In this cross-sectional study, a high proportion of individuals meeting clinical consensus criteria for PD, DLB, MSA, and PAF had phosphorylated α-synuclein detected by skin biopsy. Further research is needed in unselected clinical populations to externally validate the findings and fully characterize the potential role of skin biopsy detection of phosphorylated α-synuclein in clinical care.

A double-blind placebo-controlled pilot study of immunoglobulin for small fiber neuropathy associated with TS-HDS and FGFR-3 autoantibodies.

INTRODUCTION/AIMS: Small fiber neuropathies (SFN) have been associated with two autoantibodies, trisulfated heparin disaccharide (TS-HDS) and fibroblast growth factor receptor 3 (FGFR-3), and intravenous immune globulin (IVIG) has been suggested as a potential therapy. The study objective is to determine the efficacy of IVIG on nerve density, pain and neurologic examinations in patients with SFN associated with TS-HDS and FGFR-3 autoantibodies. METHODS: This was a double-blind placebo-controlled pilot study. Subjects with SFN confirmed by history, examination, and skin biopsy with elevated autoantibodies to TS-HDS and/or FGFR-3 received IVIG (or blinded placebo) 2 grams/kg followed by 1 gram/kg every 3 wk for a total of 6 treatments. All subjects had Utah Early Neuropathy Scores (UENS), questionnaires and skin biopsies with quantitation of intra-epidermal nerve fiber density (IENFD) taken from adjacent sites at the distal leg at baseline and 6 mo later. The primary outcome was the change in IENFD over 6 mo. RESULTS: Twenty subjects were enrolled; 17 completed treatment (8 IVIG, 9 placebo). Three did not have final data due to coronavirus disease 2019 (COVID-19). Skin biopsy IENFD improved by 0.5 ± 0.8 fibers/mm in the placebo group and improved by 0.6 ± 0.6 fibers/mm in the IVIG-treated group (p = NS).Over 24 wk the change in pain scores (11 point pain scale) was -1.9 ± 2.6 in the placebo group, and - 1.7 ± 0.9 in the IVIG group (p = NS), the UENS improved by 3.0 ± 5.8 in the placebo group and improved by 1.8 ± 3.9 in the IVIG group (p = NS). DISCUSSION: This pilot study did not detect a benefit of treatment with IVIG in patients with SFN and autoantibodies to TS-HDS and FGFR-3.

Two-Year observational study of autonomic skin function in patients with Parkinson's disease compared to healthy individuals.

BACKGROUND AND PURPOSE: We characterized autonomic pilomotor and sudomotor skin function in early Parkinson's disease (PD) longitudinally. METHODS: We enrolled PD patients (Hoehn and Yahr 1-2) and healthy controls from movement disorder centers in Germany, Hungary, and the United States. We evaluated axon-reflex responses in adrenergic sympathetic pilomotor nerves and in cholinergic sudomotor nerves and assessed sympathetic skin response (SSR), predominantly parasympathetic neurocardiac function via heart rate variability, and disease-related symptoms at baseline, after 2 weeks, and after 1 and 2 years. CLINICALTRIALS: gov: NCT03043768. RESULTS: We included 38 participants: 26 PD (60% females, aged 62.4 ± 7.4 years, mean ± SD) and 12 controls (75% females, aged 59.5 ± 5.8 years). Pilomotor function was reduced in PD compared to controls at baseline when quantified via spatial axon-reflex spread (78 [43-143], median [interquartile range] mm2 vs. 175 [68-200] mm2 , p = 0.01) or erect hair follicle count in the axon-reflex region (8 [6-10] vs. 11 [6-16], p = 0.008) and showed reliability absent any changes from baseline to Week 2 (p = not significant [ns]). Between-group differences increased over the course of 2 years (p < 0.05), although no decline was observed within groups (p = ns). Pilomotor impairment in PD correlated with motor symptoms (rho = -0.59, p = 0.017) and was not lateralized (p = ns). Sudomotor axon-reflex and neurocardiac function did not differ between groups (p = ns), but SSR was reduced in PD (p = 0.0001). CONCLUSIONS: Impairment of adrenergic sympathetic pilomotor function and SSR in evolving PD is not paralleled by changes to cholinergic sudomotor function and parasympathetic neurocardiac function, suggesting a sympathetic pathophysiology. A pilomotor axon-reflex test might be useful to monitor PD-related pathology.

X-Linked Dystonia-Parkinsonism ("Lubag") May Present with Peripheral Synucleinopathy.

BACKGROUND: X-linked dystonia parkinsonism (XDP) or "Lubag" is a genetic dystonia syndrome observed among Filipinos that can present with levodopa-responsive parkinsonism and abnormal dopamine transporter (DAT) imaging. OBJECTIVE: The aim of this study is to describe the results of skin biopsies for phosphorylated α-synuclein (P-SYN) in XDP. METHOD: This study used the retrospective chart review. RESULTS: We report 6 patients who carried the XDP gene mutation with DAT imaging and skin biopsies to detect P-SYN. Five had segmental or multifocal dystonia and parkinsonism: 4 were levodopa-responsive and 1 non-levodopa-responsive. One patient was asymptomatic but had mild bradykinesia. Cutaneous P-SYN and abnormal DAT scans were noted in the 4 levodopa-responsive patients and 1 asymptomatic patient. CONCLUSION: We report for the first time the presence of cutaneous P-SYN in XDP. Our findings suggest that XDP may be a hitherto-undescribed synucleinopathy or that some XDP patients may have concurrent Parkinson's disease.

Clinical Trial-Ready Patient Cohorts for Multiple System Atrophy: Coupling Biospecimen and iPSC Banking to Longitudinal Deep-Phenotyping.

Multiple system atrophy (MSA) is a fatal neurodegenerative disease of unknown etiology characterized by widespread aggregation of the protein alpha-synuclein in neurons and glia. Its orphan status, biological relationship to Parkinson's disease (PD), and rapid progression have sparked interest in drug development. One significant obstacle to therapeutics is disease heterogeneity. Here, we share our process of developing a clinical trial-ready cohort of MSA patients (69 patients in 2 years) within an outpatient clinical setting, and recruiting 20 of these patients into a longitudinal "n-of-few" clinical trial paradigm. First, we deeply phenotype our patients with clinical scales (UMSARS, BARS, MoCA, NMSS, and UPSIT) and tests designed to establish early differential diagnosis (including volumetric MRI, FDG-PET, MIBG scan, polysomnography, genetic testing, autonomic function tests, skin biopsy) or disease activity (PBR06-TSPO). Second, we longitudinally collect biospecimens (blood, CSF, stool) and clinical, biometric, and imaging data to generate antecedent disease-progression scores. Third, in our Mass General Brigham SCiN study (stem cells in neurodegeneration), we generate induced pluripotent stem cell (iPSC) models from our patients, matched to biospecimens, including postmortem brain. We present 38 iPSC lines derived from MSA patients and relevant disease controls (spinocerebellar ataxia and PD, including alpha-synuclein triplication cases), 22 matched to whole-genome sequenced postmortem brain. iPSC models may facilitate matching patients to appropriate therapies, particularly in heterogeneous diseases for which patient-specific biology may elude animal models. We anticipate that deeply phenotyped and genotyped patient cohorts matched to cellular models will increase the likelihood of success in clinical trials for MSA.

Phase 2a randomized controlled study investigating the safety and efficacy of PDA-002 in diabetic peripheral neuropathy.

Neuropathy is a major cause of morbidity and mortality in individuals with diabetes, with no effective therapy to alter the inevitable progression of nerve damage. We hypothesized that mesenchymal stroma cell-like populations, that are characterized as immune modulators also have the potential of inducing angiogenesis and neurite outgrowth, might be useful in treating diabetic peripheral neuropathy (DPN). The aims of this study were to investigate the efficacy and safety of mesenchymal stem cell-like product (PDA-002) in treating DPN. A phase-2 randomized placebo-controlled trial was conducted in 26 patients with DPN. Treatment consisted of three rounds of intramuscular injections in one lower limb using one of the three randomized treatment arms PDA-002 (low-dose 3 × 106 cells), PDA-002 (high-dose 30 × 106 cells), or placebo. Three treatments per patient occurred on days 1, 29, and 57. Study endpoints included efficacy and safety of PDA-002 in treating DPN in both lower extremities following unilateral local injection. Outcome measures included intra-epidermal nerve fiber density (IENFD) up to 1 year from the day of treatment with 6-month as the primary outcome measurement. In this phase 2 study of DPN, PDA-002 was well tolerated in both doses. No significant changes were noted in IENFD in both the treated and untreated leg in the NIS-LL, NTSS-6, or UENS. Mesenchymal stem cells represent a novel mechanism for treating diabetic neuropathy and are well tolerated. Preliminary results highlight the need of further investigation of PDA-001 as a disease modifying agent for treatment of DPN.

Fludrocortisone for orthostatic hypotension.

BACKGROUND: Orthostatic hypotension is an excessive fall in blood pressure (BP) while standing and is the result of a decrease in cardiac output or defective or inadequate vasoconstrictor mechanisms. Fludrocortisone is a mineralocorticoid that increases blood volume and blood pressure. Fludrocortisone is considered the first- or second-line pharmacological therapy for orthostatic hypotension alongside mechanical and positional measures such as increasing fluid and salt intake and venous compression methods. However, there has been no Cochrane Review of the benefits and harms of this drug for this condition. OBJECTIVES: To identify and evaluate the benefits and harms of fludrocortisone for orthostatic hypotension. SEARCH METHODS: We searched the following databases on 11 November 2019: Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase and CINAHL. We also searched trials registries. SELECTION CRITERIA: We included all studies evaluating the benefits and harms of fludrocortisone compared to placebo, another drug for orthostatic hypotension, or studies without comparators, including randomized controlled trials (RCTs), quasi-RCTs and observational studies. We included studies in people with orthostatic hypotension due to a chronic peripheral neuropathy, a central autonomic neuropathy, or autonomic failure from other causes, but not medication-induced orthostatic hypotension or orthostatic hypotension from acute volume depletion or blood loss. DATA COLLECTION AND ANALYSIS: We used Cochrane methodological procedures for most of the review. We developed and used a tool to prioritize observational studies that offered the best available evidence where there are gaps in the evidence from RCTs. We assessed the certainty of evidence for fludrocortisone versus placebo using GRADE. MAIN RESULTS: We included 13 studies of 513 participants, including three cross-over RCTs and 10 observational studies (three cohort studies, six case series and one case-control study). The included RCTs were small (total of 28 participants in RCTs), short term (two to three weeks), only examined fludrocortisone for orthostatic hypotension in people with two conditions (diabetes and Parkinson disease), and had variable risk of bias (two had unclear risk of bias and one had low risk of bias). Heterogeneity in participant populations, comparators and outcome assessment methods prevented meta-analyses of the RCTs. We found very low-certainty evidence about the effects of fludrocortisone versus placebo on drop in BP in people with diabetes (-26 mmHg versus -39 mmHg systolic; -7 mmHg versus -11 mmHg diastolic; 1 cross-over study, 6 participants). For people with Parkinson disease, we found very-low certainty evidence about the effects of fludrocortisone on drop in BP compared to pyridostigmine (-14 mmHg versus -22.1 mmHg diastolic; P = 0.036; 1 cross-over study, 9 participants) and domperidone (no change after treatment in either group; 1 cross-over study, 13 participants). For orthostatic symptoms, we found very low-certainty evidence for fludrocortisone versus placebo in people with diabetes (4 out of 5 analyzed participants had improvements in orthostatic symptoms, 1 cross-over study, 6 participants), for fludrocortisone versus pyridostigmine in people with Parkinson disease (orthostatic symptoms unchanged; 1 cross-over study, 9 participants) or fludrocortisone versus domperidone (improvement to 6 for both interventions on the Composite Autonomic Symptom Scale-Orthostatic Domain (COMPASS-OD); 1 cross-over study, 13 participants). Evidence on adverse events was also very low-certainty in both populations, but indicated side effects were minimal. Observational studies filled some gaps in evidence by examining the effects in larger groups of participants, with more diverse conditions, over longer periods of time. One cohort study (341 people studied retrospectively) found fludrocortisone may not be harmful in the long term for familial dysautonomia. However, it is unclear if this translates to long-term improvements in BP drop or a meaningful improvement in orthostatic symptoms. AUTHORS' CONCLUSIONS: The evidence is very uncertain about the effects of fludrocortisone on blood pressure, orthostatic symptoms or adverse events in people with orthostatic hypotension and diabetes or Parkinson disease. There is a lack of information on long-term treatment and treatment of orthostatic hypotension in other disease states. There is a need for standardized reporting of outcomes and for standardization of measurements of blood pressure in orthostatic hypotension.

A novel method to quantify cutaneous vascular innervation.

INTRODUCTION: To develop a new method to quantify the density of nerves, vessels, and the neurovascular contacts, we studied skin biopsies in diabetes and control subjects. METHODS: Skin biopsies with dual immunofluorescent staining were used to visualize nerves and blood vessels. The density of nerves, vessels, and their neurovascular contacts were quantified with unbiased stereology. Results were compared with examination findings, validated questionnaires, and autonomic function. RESULTS: In tissue from 19 controls and 20 patients with diabetes, inter-rater and intra-rater intraclass correlation coefficients were high (>0.85; P < .001) for all quantitative methods. In diabetes, the nerve densities (P < .05), vessel densities (P < .01), and the neurovascular densities (P < .01) were lower compared with 20 controls. Results correlated with autonomic function, examination and symptom scores. DISCUSSION: We report an unbiased, stereological method to quantify the cutaneous nerve, vessel and neurovascular density and offer new avenues of investigation into cutaneous neurovascular innervation in health and disease.

Human papillomavirus (HPV) vaccine and autonomic disorders: a position statement from the American Autonomic Society.

INTRODUCTION: Human papillomavirus (HPV) vaccination has been anecdotally connected to the development of dysautonomia, chronic fatigue, complex regional pain syndrome and postural tachycardia syndrome. OBJECTIVES: To critically evaluate a potential connection between HPV vaccination and the above-noted conditions. METHODS: We reviewed the literature containing the biology of the virus, pathophysiology of infection, epidemiology of associated cancers, indications of HPV vaccination, safety surveillance data and published reports linking HPV vaccination to autonomic disorders. RESULTS: At this time, the American Autonomic Society finds that there are no data to support a causal relationship between HPV vaccination and CRPS, chronic fatigue, and postural tachycardia syndrome to other forms of dysautonomia. CONCLUSION: Certain conditions are prevalent in the same populations that are vaccinated with the HPV vaccine (peri-pubertal males and females). This association, however, is an insufficient proof of causality.

Orthostatic heart rate changes in patients with autonomic failure caused by neurodegenerative synucleinopathies.

OBJECTIVE: Blunted tachycardia during hypotension is a characteristic feature of patients with autonomic failure, but the range has not been defined. This study reports the range of orthostatic heart rate (HR) changes in patients with autonomic failure caused by neurodegenerative synucleinopathies. METHODS: Patients evaluated at sites of the U.S. Autonomic Consortium (NCT01799915) underwent standardized autonomic function tests and full neurological evaluation. RESULTS: We identified 402 patients with orthostatic hypotension (OH) who had normal sinus rhythm. Of these, 378 had impaired sympathetic activation (ie, neurogenic OH) and based on their neurological examination were diagnosed with Parkinson disease, dementia with Lewy bodies, pure autonomic failure, or multiple system atrophy. The remaining 24 patients had preserved sympathetic activation and their OH was classified as nonneurogenic, due to volume depletion, anemia, or polypharmacy. Patients with neurogenic OH had twice the fall in systolic blood pressure (SBP; -44 ± 25 vs -21 ± 14 mmHg [mean ± standard deviation], p < 0.0001) but only one-third of the increase in HR of those with nonneurogenic OH (8 ± 8 vs 25 ± 11 beats per minute [bpm], p < 0.0001). A ΔHR/ΔSBP ratio of 0.492 bpm/mmHg had excellent sensitivity (91.3%) and specificity (88.4%) to distinguish between patients with neurogenic from nonneurogenic OH (area under the curve = 0.96, p < 0.0001). Within patients with neurogenic OH, HR increased more in those with multiple system atrophy (p = 0.0003), but there was considerable overlap with patients with Lewy body disorders. INTERPRETATION: A blunted HR increase during hypotension suggests a neurogenic cause. A ΔHR/ΔSBP ratio < 0.5 bpm/mmHg is diagnostic of neurogenic OH. Ann Neurol 2018;83:522-531.

Sudomotor function testing by electrochemical skin conductance: does it really measure sudomotor function?

OBJECTIVE: Electrochemical skin conductance (ESC) is a non-invasive test of sweat function developed as a potential marker of small fiber neuropathy. Here we systematically review the evolution of this device and the data obtained from studies of ESC across different diseases. METHODS: Electronic databases, including MEDLINE, and Google Scholar were searched through to February 2018. The search strategy included the following terms: "electrochemical skin conductance," "EZSCAN," and "Sudoscan." The data values provided by each paper were extracted, where available, and input into tabular and figure data for direct comparison. RESULTS: Thirty-seven studies were included this systematic review. ESC did not change by age or gender, and there was significant variability in ESC values between diseases, some of which exceeded control values. Longitudinal studies of disease demonstrated changes in ESC that were not biologically plausible. Of the 37 studies assessed, 25 received support from the device manufacturer. The extracted data did not agree with other published normative values. Prior studies do not support claims that ESC is a measure of small fiber sensory function or autonomic function. CONCLUSIONS: Although many papers report significant differences in ESC values between disease and control subjects, the compiled data assessed in this review raises questions about the technique. Many of the published results violate biologic plausibility. A single funding source with a vested interest in the study outcomes has supported most of the studies. Normative values are inconsistent across publications, and large combined data sets do not support a high sensitivity and specificity. Finally, there is insufficient evidence supporting the claim that Sudoscan tests sudomotor or sensory nerve fiber function.

Association of innervation-adjusted alpha-synuclein in arrector pili muscles with cardiac noradrenergic deficiency in autonomic synucleinopathies.

BACKGROUND: Autonomic synucleinopathies feature deposition of the protein alpha-synuclein (AS) in neurons [e.g., Lewy body neurogenic orthostatic hypotension (nOH)] or glial cells (multiple system atrophy, MSA). AS in skin biopsies might provide biomarkers of these diseases; however, this approach would be complicated or invalidated if there were substantial loss of AS-containing nerves. We report AS content in arrector pili muscles in skin biopsies after adjustment for local innervation in patients with Lewy body nOH or MSA. Cardiac sympathetic neuroimaging by myocardial 18F-dopamine positron emission tomography (PET) was done to examine pathophysiological correlates of innervation-adjusted AS. METHODS: Thirty-one patients (19 Lewy body nOH, 12 MSA) underwent thoracic 18F-dopamine PET and skin biopsies. AS signal intensity analyzed by immunofluorescence microscopy was adjusted for innervation by the ratio of AS to protein gene product (PGP) 9.5, a pan-axonal marker (Harvard lab site), or the ratio of AS to tyrosine hydroxylase (TH), an indicator of catecholaminergic neurons (NIH lab site). RESULTS: The Lewy body nOH group had higher ratios of AS/PGP 9.5 or log AS/TH than did the MSA group (0.89 ± 0.05 vs. 0.66 ± 0.04, -0.13 ± 0.05 vs. -1.60 ± 0.33; p < 0.00001 each). All 19 Lewy body patients had AS/PGP 9.5 > 0.8 or log AS/TH > 1.2 and had myocardial 18F-dopamine-derived radioactivity < 6000 nCi-kg/cc-mCi, the lower limit of normal. Two MSA patients (17%) had increased AS/PGP or log AS/TH, and two (17%) had low 18F-dopamine-derived radioactivity. CONCLUSIONS: Lewy body forms of nOH are associated with increased innervation-adjusted AS in arrector pili muscles and neuroimaging evidence of myocardial noradrenergic deficiency.

Natural history of pure autonomic failure: A United States prospective cohort.

OBJECTIVE: To define the clinical features and biomarkers that predict which patients with pure autonomic failure will develop Parkinson disease, dementia with Lewy bodies, or multiple system atrophy. METHODS: One hundred patients who presented with pure autonomic failure were recruited at 5 medical centers in the United States. Seventy-four patients agreed to be followed prospectively. Patients underwent clinical evaluations including neurological rating scales, sleep questionnaires, smell test, and sympathetic and parasympathetic cardiovascular autonomic function tests. RESULTS: At enrollment, patients were 68 ± 12 years old (median ± interquartile range) and had had autonomic failure for 5 ± 7 years. Within 4 years of follow-up, 25 of 74 subjects (34%) developed dementia with Lewy bodies (n = 13), Parkinson disease (n = 6), or multiple system atrophy (n = 6). The presence of probable rapid eye movement (REM) sleep behavior disorder was strongly associated with the development of a manifest central nervous system (CNS) synucleinopathy (odds ratio = 7.1). Patients who phenoconverted to multiple system atrophy had younger age at onset of autonomic failure, severe bladder/bowel dysfunction, preserved olfaction, and a cardiac chronotropic response upon tilt > 10 beats per minute. Those who phenoconverted to Parkinson disease or dementia with Lewy bodies had decreased olfaction, a lesser chronotropic response to tilt, and a longer duration of illness. The small group of patients retaining the pure autonomic failure phenotype had very low plasma norepinephrine levels, slow resting heart rate, no REM sleep behavior disorder, and preserved smell. INTERPRETATION: Patients presenting with pure autonomic failure are at high risk of phenoconverting to a manifest CNS synucleinopathy. Specific clinical features predict future diagnosis. Ann Neurol 2017;81:287-297.

Treatment-Induced Neuropathy of Diabetes.

PURPOSE OF REVIEW: Treatment-induced neuropathy of diabetes (TIND) is an under-recognized iatrogenic painful sensory and autonomic neuropathy. This review highlights the clinical symptoms and signs, raises awareness of the cause, and provides education about prevention of TIND. RECENT FINDINGS: TIND may be triggered by a rapid decline in the blood glucose levels following the use of insulin, oral hypoglycemic medications, or even diet only to control diabetes. This may be seen in up to 10% of patients with diabetic neuropathy and has the potential for significant long-term complications that could be avoided through careful disease management. Based on the available evidence, a decrease in the glycosylated hemoglobin A1C of more than 3 points in 3 months in individuals with chronic hyperglycemia increases the risk of developing TIND. TIND is more common than previously suspected, and is tied to rates of glycemic control. Slower changes to glucose control are suggested, although there is no prospective data on disease prevention. Future research is necessary to guide treatment recommendations.

Microvascular Complications Associated With Rapid Improvements in Glycemic Control in Diabetes.

PURPOSE OF REVIEW: Aggressive glycemic control has become the standard clinical approach to diabetes care. Unintended consequences have included the development of microvascular complications that are related to the rapidity of glycemic improvement. RECENT FINDINGS: Diabetic neuropathy may develop in up to 10% of individuals secondary to aggressive glycemic control. The neuropathy is predominantly small fiber sensory and autonomic, and the severity of the neuropathy is tied to the change in the glycosylated hemoglobin A1C. Other microvascular complications such as retinopathy and nephropathy are common and may occur in parallel with the neuropathy. Eating disorders are a common comorbid risk factor. Individuals with uncontrolled diabetes for prolonged periods, particularly those with a history of eating disorders involving insulin restriction for calorie purging, are at high risk for developing treatment-induced microvascular complications. Gradual glycemic improvements should be encouraged but future research is needed to optimize treatment and prevention strategies.

Treatment-induced neuropathy of diabetes: an acute, iatrogenic complication of diabetes.

Treatment-induced neuropathy in diabetes (also referred to as insulin neuritis) is considered a rare iatrogenic small fibre neuropathy caused by an abrupt improvement in glycaemic control in the setting of chronic hyperglycaemia. The prevalence and risk factors of this disorder are not known. In a retrospective review of all individuals referred to a tertiary care diabetic neuropathy clinic over 5 years, we define the proportion of individuals that present with and the risk factors for development of treatment-induced neuropathy in diabetes. Nine hundred and fifty-four individuals were evaluated for a possible diabetic neuropathy. Treatment-induced neuropathy in diabetes was defined as the acute onset of neuropathic pain and/or autonomic dysfunction within 8 weeks of a large improvement in glycaemic control-specified as a decrease in glycosylated haemoglobin A1C (HbA1c) of ≥2% points over 3 months. Detailed structured neurologic examinations, glucose control logs, pain scores, autonomic symptoms and other microvascular complications were measured every 3-6 months for the duration of follow-up. Of 954 patients evaluated for diabetic neuropathy, 104/954 subjects (10.9%) met criteria for treatment-induced neuropathy in diabetes with an acute increase in neuropathic or autonomic symptoms or signs coinciding with a substantial decrease in HbA1c. Individuals with a decrease in HbA1c had a much greater risk of developing a painful or autonomic neuropathy than those individuals with no change in HbA1c (P < 0.001), but also had a higher risk of developing retinopathy (P < 0.001) and microalbuminuria (P < 0.001). There was a strong correlation between the magnitude of decrease in HbA1c, the severity of neuropathic pain (R = 0.84, P < 0.001), the degree of parasympathetic dysfunction (R = -0.52, P < 0.01) and impairment of sympathetic adrenergic function as measured by fall in blood pressure on tilt-table testing (R = -0.63, P < 0.001). With a decrease in HbA1c of 2-3% points over 3 months there was a 20% absolute risk of developing treatment-induced neuropathy in diabetes, with a decrease in HbA1c of >4% points over 3 months the absolute risk of developing treatment-induced neuropathy in diabetes exceeded 80%. Treatment-induced neuropathy of diabetes is an underestimated iatrogenic disorder associated with diffuse microvascular complications. Rapid glycaemic change in patients with uncontrolled diabetes increases the risk of this complication.

Blood pressure oscillations in baroreflex failure.

A 67-year-old man presented with labile hypertension and orthostatic hypotension after radical neck dissection and radiotherapy for squamus cell carcinoma. Baroreflex failure is clearly evident on autonomic testing.