Alcohol-related peripheral neuropathy: Clinico-neurophysiological characteristics and diagnostic utility of the neuropathy symptoms score and the neuropathy impairment score

Alcohol overconsumption is well known to cause damage to the peripheral nervous system, affecting both small and large nerve fibers. The aim of this descriptive study was to investigate peripheral nerve damage, and to correlate clinical, epidemiological and neurophysiological findings, in patients diagnosed with Alcohol Use Disorder (AUD). Ninety alcohol-dependent subjects on inpatient basis were enrolled in this prospective study over a 3-year period. Every subject was assessed by the Neuropathy Symptoms Score (NSS) questionnaire and the Neuropathy Impairment Score (NIS) clinical examination grading scale, followed by Nerve Conduction Studies, Quantitative Sensory Testing and Sympathetic Skin Response (SSR) testing. Peripheral neuropathy was diagnosed in 54 subjects (60%), by abnormal neurophysiological tests and presence of clinical signs or symptoms. Among them, pure large fiber neuropathy (LFN) was found in 18 subjects, pure small fiber neuropathy (SFN) in 12 subjects, and both large and small fiber neuropathy was diagnosed in 24 subjects. Using linear regression, we found that higher NSS and NIS scores correlated with lower amplitudes of the sural sensory nerve action potential and of the SSR. We also found a significant longer duration of alcohol abuse in subjects with neuropathy, using Student's t-test (p = 0.024). Additionally, applying NIS abnormal cut-off score ≥4, using ROC analysis, we predicted the majority of subjects with LFN, confirming 95.23% sensitivity and 93.75% specificity. Our study confirmed that peripheral neuropathy involving large and small nerve fibers, with a symmetrical length-dependent pattern, is common between patients with AUD and related to the duration of the disorder. We suggest that NSS and NIS scales could be used for the assessment of neuropathy in clinical practice, when the essential neurophysiological testing is not available.

Assessment of Neuropathy by Temperature Threshold Testing in Type 2 Diabetes Mellitus

Introduction

Diagnosing diabetic neuropathy is a challenge at times as it is asymptomatic. Diagnosing diabetic neuropathy involves the use of quantitative sensory testing, nerve conduction study, and autonomic testing. Tempearture threshold testing (TTT) can aid in diagnosing small fiber neuropathy at early stages. This study aimed to assess the small fiber neuropathy using TTT in diabetes mellitus (DM) and correlate with age, duration of diabetes, and lipid profile.

Materials and Methods

The study was commenced after obtaining ethics approval from the institute ethics committee. The study participants included 100 patients with type 2 DM of both genders between the ages of 40 and 65 years. The glycemic status and lipid profile were noted along with physical examination. Neuropathy assessment was done using Michigan Neuropathy Screening Instrument (MNSI) and TTT.

Results

The prevalence of small fiber neuropathy based on TTT was 63%. The lipid profile was similar in both the groups. The MNSI B scale had significantly higher scores in the neuropathy group. In the neuropathy group, the thresholds for hot were significantly greater in all four limbs and cold were significantly lower. Age and years of DM were positively correlated with the neuropathy. Hot threshold in the lower limb had shown a strong positive correlation.

Conclusion

The age and duration of diabetes are independent risk factors for diabetic peripheral neuropathy. Small fiber neuropathy is a prequel to the motor neuropathy. Hot threshold testing in the lower limb is more sensitive than cold threshold testing for diagnosing small fiber neuropathy.

Sensory Involvement in Amyotrophic Lateral Sclerosis

Although amyotrophic lateral sclerosis (ALS) is pre-eminently a motor disease, the existence of non-motor manifestations, including sensory involvement, has been described in the last few years. Although from a clinical perspective, sensory symptoms are overshadowed by their motor manifestations, this does not mean that their pathological significance is not relevant. In this review, we have made an extensive description of the involvement of sensory and autonomic systems described to date in ALS, from clinical, neurophysiological, neuroimaging, neuropathological, functional, and molecular perspectives.

Small Fibre Peripheral Alterations Following COVID-19 Detected by Corneal Confocal Microscopy

A large spectrum of neurological manifestations has been associated with coronavirus disease 2019 (COVID-19), and recently, the involvement of small fibers has been suggested. This study aims to investigate the involvement of small peripheral nervous fibers in recovered COVID-19 patients using in-vivo corneal confocal microscopy (CCM). Patients recovered from COVID-19 and a control group of healthy subjects underwent in-vivo CCM. Corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length (CNFL), corneal nerve fiber total branch density (CTBD), corneal nerve fiber area (CNFA), corneal nerve fiber width (CNFW), fiber tortuosity (FT), number of beadings (NBe), and dendritic cells (DC) density were quantified. We enrolled 302 eyes of 151 patients. CNBD and FT were significantly higher (p = 0.0131, p < 0.0001), whereas CNFW and NBe were significantly lower (p = 0.0056, p = 0.0045) in the COVID-19 group compared to controls. Only CNBD and FT resulted significantly correlated to antiviral drugs (increased) and corticosteroids (decreased). No significant relationship with disease severity parameters was found. COVID-19 may induce peripheral neuropathy in small fibers even months after recovery, regardless of systemic conditions and therapy, and CCM may be a useful tool to identify and monitor these morphological changes.

Corneal Confocal Microscopy Identifies Parkinson's Disease with More Rapid Motor Progression

BACKGROUND

Corneal confocal microscopy (CCM) is a noninvasive, reproducible ophthalmic technique to quantify corneal small nerve fiber degeneration. CCM demonstrates small nerve fiber damage in Parkinson's disease (PD), but its role as a longitudinal biomarker of PD progression has not been explored.

OBJECTIVE

The aim of this study was to assess corneal nerve morphology using CCM in relation to disease progression in PD.

METHODS

Sixty-four participants with PD were assessed at baseline and at 12-month follow-up. Participants underwent CCM with automated corneal nerve quantification and assessment of Movement Disorder Society Unified Parkinson's Disease Rating Scale, Hoehn and Yahr stage, and Montreal Cognitive Assessment.

RESULTS

Corneal nerve fiber density (CNFD), corneal nerve branch density, corneal nerve fiber length, corneal total branch density, and corneal nerve fiber area were significantly lower in participants with PD compared with healthy control subjects. Worsening of Movement Disorder Society Unified Parkinson's Disease Rating Scale part III score over 12 months was significantly greater in participants with a CNFD in the lowest compared with the highest quartile at baseline (mean difference: 6.0; 95% CI: 1.0-10.9; P = 0.019). There were no significant changes in CNFD, corneal nerve branch density, corneal nerve fiber length, corneal total branch density, corneal nerve fiber area, or corneal nerve fiber width between baseline and 12-month follow-up.

CONCLUSIONS

CCM identifies neurodegeneration in patients with PD, especially those who show the greatest progression in neurological disability. CCM may be a useful tool to help enrich clinical trials with those likely to exhibit more rapid progression and reduce required sample size and cost of studies. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Assessment of small sensory fiber function in myotonic dystrophy type 1

BACKGROUND

Myotonic dystrophy type 1 (DM1) is a multisystem disorder affecting the peripheral nervous system. However, studies evaluating somatic small fiber sensory nerve function, which may contribute to pain in DM1, are lacking.

METHODS

Using quantitative sensory testing of the hand and foot, we evaluated Aδ and C-fiber function. Of 20 adult DM1 patients recruited, 16 were analyzed. Their results were compared with those of 32 age- and sex-matched controls.

RESULTS

No DM1 patient had diabetes mellitus or clinical evidence of small fiber neuropathy. In DM1, hand (P < .01) and foot (P = 0.02) warm detection thresholds were higher than those of controls. Cool detection thresholds were lower in the foot (P < .001).

CONCLUSIONS

Subclinical small sensory fiber dysfunction occurs in DM1 patients without large fiber neuropathy. Further research with other modalities is required to characterize these disturbances as disease modifying therapies are developed.

Hereditary transthyretin-related amyloidosis

Hereditary transthyretin(TTR)-related amyloidosis (ATTRm amyloidosis) is an endemic/non-endemic, autosomal-dominant, early- and late-onset, rare, progressive disorder, predominantly manifesting as length-dependent, small fiber dominant, axonal polyneuropathy and frequently associated with cardiac disorders and other multisystem diseases. ATTRm amyloidosis is due to variants in the TTR gene, with the substitution Val30Met as the most frequent mutation. TTR mutations lead to destabilization and dissociation of TTR tetramers into variant TTR monomers, and formation of amyloid fibrils, which are consecutively deposited extracellularly in various tissues, such as nerves, heart, brain, eyes, intestines, kidneys, or the skin. Neuropathy may not only include large nerve fibers but also small fibers, and not only sensory and motor fibers but also autonomic fibers. Types of TTR variants, age at onset, penetrance, and clinical presentation vary between geographical areas. Suggestive of a ATTRm amyloidosis are a sensorimotor polyneuropathy, positive family history, autonomic dysfunction, cardiomyopathy, carpal tunnel syndrome, unexplained weight loss, and resistance to immunotherapy. If only sensory A-delta or C fibers are affected, small fiber neuropathy ensues. Diagnostic tests for small fiber neuropathy include determination of intraepidermal nerve fiber density, laser-evoked potentials, heat- and cold-detection thresholds, and measurement of the electrochemical skin conductance. Therapy currently relies on liver transplantation and TTR-stabilizers (tafamidis, diflunisal).

Small Fiber Neuropathy: Disease Classification Beyond Pain and Burning

Small fiber neuropathy (SFN) has a poorly understood pathology, but patients would benefit from determination of clinical phenotypes that allows for better diagnosis and treatment planning. I propose that patients should be classified dependent on whether there is sodium channel dysfunction, classic neurologic symptoms only, widespread neuropathic pain, or autonomic symptoms. Patients with SFN can then be considered in light of their clinical phenotype, allowing for focus on subsets of patients who might have diagnosable conditions or be more prone to responding to a particular type of therapy that may not be efficacious in the broader patient population with SFN. There are several therapies currently available that can address the symptoms of SFN; however, to develop novel therapeutic strategies, it will be imperative to classify patients to understand and target the underlying pathology.

Corneal confocal microscopy detects small fiber damage in chronic inflammatory demyelinating polyneuropathy (CIDP)

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an autoimmune-mediated peripheral neuropathy with multifocal involvement. Reliable biomarkers for diagnosis, disease progression, and treatment response remain to be developed. We assessed the utility of corneal confocal microscopy (CCM) as a diagnostic marker for CIDP in 16 patients. CCM parameters including corneal nerve fiber density (NFD), nerve fiber length, number of main nerve trunks, number of nerve branches, nerve tortuosity, and dendritic cell density (DCD) were compared to those from 15 healthy controls and correlated with clinical and electrophysiological findings. CIDP patients had a significantly lower corneal NFD compared to healthy controls. The total nerve fiber length and the number of nerve branches were significantly decreased, whereas nerve tortuosity was increased in patients with CIDP. There was no positive correlation between corneal NFD and clinical or electrophysiological assessments. The average DCD was not significantly different in CIDP patients and controls. CCM measures suggest damage to small sensory afferents in the cornea in CIDP patients. Further studies are needed to compare different neuropathic conditions and to explore longitudinal changes of CCM parameters.