[Neuropathies and chronic respiratory insufficiency: electrophysiologic study]

Peripheral neuropathy: A neglected cause of disability in COPD - A narrative review

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory syndrome with systemic involvement leading to various cardiovascular, metabolic, and neurological comorbidities. It is well known that conditions associated with oxygen deprivation and metabolic disturbance are associated with polyneuropathy, but current data regarding the relationship between COPD and peripheral nervous system pathology is limited. This review summarizes the available data on the association between COPD and polyneuropathy, including possible pathophysiological mechanisms such as the role of hypoxia, proinflammatory state, and smoking in nerve damage; the role of cardiovascular and metabolic comorbidities, as well as the diagnostic methods and screening tools for identifying polyneuropathy. Furthermore, it outlines the available options for managing and preventing polyneuropathy in COPD patients. Overall, current data suggest that optimal screening strategies to diagnose polyneuropathy early should be implemented in COPD patients due to their relatively common association and the additional burden of polyneuropathy on quality of life.

Association Between Severe Chronic Obstructive Pulmonary Disease and Polyneuropathy

Background

Chronic obstructive pulmonary disease (COPD) is a life-threatening and devastating disease associated with low-grade systemic inflammation. In adults, the most common disease of the peripheral nervous system is peripheral neuropathy. While most polyneuropathy has a mixed presentation, some cases are motor dominant and others are sensory dominant. We investigated polyneuropathy in patients with COPD and hypothesized that low-grade systemic inflammation and other pathologies in patients with COPD cause peripheral axonal polyneuropathy.

Material/Methods

We included 62 patients with COPD without any neurological signs or symptoms, and 30 healthy volunteers with no known neurological or pulmonary diseases as controls. There were 38 men in the COPD group and 17 men in the control group; the mean ages of the 2 groups were 64.88 and 62.7 years, respectively. According to the Global Initiative for Chronic Obstructive Lung Disease COPD report, all COPD patients were group D. After collecting demographic and clinical characteristics of the participants, we performed an electrophysiological examination to investigate polyneuropathy and pulmonary function test results. C-reactive protein, hemoglobin, creatinine, partial carbon dioxide pressure (pCO₂) levels were recorded. Electrophysiological examination was performed with a Medelec Synergy device using standard neurographic procedures, and the results were assessed.

Results

Significant differences were found for forced expiratory volume in 1 sec (FEV1), %FEV1, forced vital capacity (FVC), %FVC, pCO₂, and hemoglobin and creatinine levels, but all participants had a creatinine level within the normal range. There was no difference in sensory neuropathy between the groups, but a significant difference was found in terms of motor neuropathy.

Conclusions

As noted in previous studies, systemic inflammation, increased oxidative stress, decreased oxygen pressure, and multiple comorbidities in patients with COPD may all contribute to the development of neuropathy.

The impact of COPD on polyneuropathy: results from the German COPD cohort COSYCONET

Background

Peripheral neuropathy is a common comorbidity in COPD. We aimed to investigate associations between alterations commonly found in COPD and peripheral neuropathy, with particular emphasize on the distinction between direct and indirect effects.

Methods

We used visit 4 data of the COPD cohort COSYCONET, which included indicators of polyneuropathy (repeated tuning fork and monofilament testing), excluding patients with diabetes a/o increased HbA1c. These indicators were analysed for the association with COPD characteristics, including lung function, blood gases, 6-min walk distance (6-MWD), timed-up-and-go-test (TUG), exacerbation risk according to GOLD, C-reactive protein (CRP), and ankle-brachial index (ABI). Based on the results of conventional regression analyses adjusted for age, BMI, packyears and gender, we utilized structural equation modelling (SEM) to quantify the network of direct and indirect relationships between parameters.

Results

606 patients were eligible for analysis. The indices of polyneuropathy were highly correlated with each other and related to base excess (BE), ABI and TUG. ABI was linked to neuropathy and 6-MWD, exacerbations depended on FEV₁, 6-MWD and CRP. The associations could be summarized into a SEM comprising polyneuropathy as a latent variable (PNP) with three measured indicator variables. Importantly, PNP was directly dependent on ABI and particularly on BE. When also including patients with diabetes and/or elevated values of HbA1c (n = 742) the SEM remained virtually the same.

Conclusion

We identified BE and ABI as major determinants of peripheral neuropathy in patients with COPD. All other associations, particularly those with lung function and physical capacity, were indirect. These findings underline the importance of alterations of the micromilieu in COPD, in particular the degree of metabolic compensation and vascular status.

Evaluation of central and peripheral neuropathy in patients with chronic obstructive pulmonary disease

Background

The aim of the study was to investigate the frequency and characteristics of peripheral nervous system (PNS) and central nervous system (CNS) involvement in COPD.

Methods

The study included 41 COPD patients and 41 healthy volunteers. Electrophysiological studies were carried out: electromyography (EMG) and visual evoked potentials (VEPs). The median nerve, ulnar nerve, common peroneal nerve, and tibial nerve were evaluated for latency, amplitude, and conduction velocity.

Results

The mean age of patients with COPD was 61.8 years and disease duration 10.3 years. There was no difference between patient and control groups in terms of age, BMI, smoking status, or biochemical parameters. Upon VEP examination, latencies were significantly prolonged and amplitudes shortened in the patient group compared to the control group. In EMG measurements, conduction velocity and amplitudes in all nerves were low in the patient group. Similarly, latencies in all nerves were higher in patients with COPD.

Conclusion

Central and peripheral nervous system involvement could develop in patients with moderate-severe COPD, and these patients should be monitored for neuropathic changes in combination with neurological examination.

Chronic obstructive pulmonary disease is not a risk factor for polyneuropathy: A prospective controlled study

Polyneuropathy has been observed in patients with chronic obstructive pulmonary disease (COPD). If polyneuropathy occurs as a complication or extrapulmonary manifestation of COPD, one would expect an increased prevalence among patients with a cryptogenic axonal polyneuropathy. This case-control study aimed to investigate the association between COPD and polyneuropathy. We prospectively included 345 patients with cryptogenic axonal polyneuropathy and 465 controls. A standardized questionnaire assessed the presence of COPD and we verified this diagnosis by contacting the family physician. The severity of COPD was based on the Global Initiative for Chronic Obstructive Lung Disease classification. The prevalence of COPD did not differ between patients with polyneuropathy and controls (15/345 vs. 12/465 respectively; odds ratio (OR) 1.7; 95% confidence interval (CI) [0.8-3.7]). Adjusting for age, gender and possible confounders did not affect these results (adjusted OR 1.7, 95% CI 0.7-4.1). The severity of COPD was similar between patients with polyneuropathy and controls. This study does not support the hypothesis that COPD is a risk factor for polyneuropathy.

Diabetic Neuropathy: Models, Mechanisms and Mayhem

Rational treatment of diabetic polyneuropathy depends upon establishing its cause, which is at present unknown. A number of animal models of diabetes have been examined and although abnormalities are detectable in the peripheral nervous system they do not duplicate the degenerative neuropathy encountered in the human. The relevance of these abnormalities is therefore uncertain, although they may reflect the earlier changes in man. For human neuropathy, it is likely that vascular lesions or an abnormal susceptibility to mechanical injury are responsible for focal neuropathies. The evidence that ischaemia and hypoxia are responsible for the diffuse sensory neuropathy and autonomic polyneuropathy is still equivocal and it is often difficult to establish whether the vascular changes are primary or secondary. Metabolic explanations, such as sorbitol accumulation in nerve, have not so far been adequately validated by responses to treatment. The manifestations of diabetic neuropathy are complex and a single explanation should not be sought.

Peripheral neuropathies in patients with chronic obstructive pulmonary disease: a multicenter prevalence study

To investigate the prevalence and type of peripheral neuropathies (PNP) in patients with chronic obstructive pulmonary disease (COPD), we studied lung function and blood gases, clinical signs of PNP, and neurophysiological function in 151 patients with COPD without known risk factors for PNP. Mean (SD) age was 65 (10) years, mean arterial PO2 was 59 (9) mmHg, mean ratio of forced expiratory volume in the first second to vital capacity (FEV1.0/VC) was 42 (12%). Thirty patients (20%) had clinically detectable and 6 (4%) had subclinical PNP of mild degree. Fourteen (9%) of the patients with clinically detectable PNP had symptoms due to PNP. Prevalence of PNP increased with severity of hypoxemia (p less than 0.05) and was more pronounced in the lower than in the upper limbs. Age and the degree of hypoxemia were predictors to differentiate between COPD patients with and without PNP. Although the cause of PNP in COPD patients remains unknown, our observations suggest that chronic hypoxemia may contribute to PNP.

Peripheral neuropathies during treatment with almitrine: report of 46 cases

Almitrine bismesylate is thought to cause sensory peripheral neuropathy. Forty-six patients are reported who received almitrine bismesylate alone for chronic respiratory failure or in combination with raubasine for various cerebrovascular diseases. Polyneuropathy appeared between 9 and 25 months after the onset of treatment. Sensory signs and symptoms were confined to the distal parts of the lower limbs and involved large and small fibres. Histological and electrophysiological findings indicated axonal degeneration. Respiratory failure could have caused the polyneuropathy in some cases but many had no chest disease. Patients began to improve between 3 and 6 months after withdrawal of the drug. Recovery was usually complete after 12 months.