Subclinical neuropathy associated with chronic obstructive pulmonary disease: possible pathophysiologic role of smoking

Chronic Hypoxemia Triggers a Neuropathic Process in Chronic Obstructive Pulmonary Disease: Insight From In Vivo Neurophysiological Assessments

BACKGROUND AND PURPOSE

Peripheral neuropathies (PNs) are a common but poorly understood complication of chronic obstructive pulmonary disease (COPD). To clarify the initial trigger of a PN in COPD, we investigated the excitability of peripheral nerves in patients with COPD.

METHODS

The automated nerve excitability test (NET) using the threshold-tracking paradigm was applied to 20 COPD patients. The recording protocol calculated the strength-duration time constant, threshold electrotonus (TE), current-threshold relationship, and recovery cycle (RC). Each NET parameter was compared with two control groups: normal controls group (NC group) and smokers without COPD group (smoker group).

RESULTS

In the motor NETs, the change in the threshold in the mid-depolarizing phase of TE (40-60 ms) was smaller in the COPD group (50.7%±1.2%, mean±SEM; n=20) than in the NC group (54.5%±0.7%, n=25; p<0.01), as was the prominence of superexcitability in the RC (-22.6%±1.5% and -26.4%±1.1%, respectively; p=0.04). There were no significant differences in the sensory NETs. Comparisons between the COPD and smoker groups (n=25) also showed no differences in either the motor or sensory NETs.

CONCLUSIONS

The pattern of excitability in COPD revealed a membrane depolarization attributable to Na⁺-K⁺-ATPase failure in the axolemma of distal motor nerves. This finding suggests that chronic hypoxemia and adaptative process can alter axonal excitability and trigger a resultant neuropathic process that is antecedent to PN in COPD.

Postural control among individuals with and without chronic obstructive pulmonary disease: A cross-sectional study of motor and sensory systems

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is considered a heterogenic syndrome with systemic effects, including muscle dysfunction. There is evidence of postural control impairments among individuals with COPD, partly related to muscle weakness. However, research is scarce regarding the other underlying systems of postural control, such as the visual, somatosensory and vestibular system. The aim was to compare postural control, as well as the motor and sensory systems, between individuals with and without COPD.

METHODS

Twenty-two participants with COPD (mean age 74.0 ±6.2 years) and 34 non-obstructive references (mean age 74.9 ±4.9 years) participated in this cross-sectional study. Postural control was assessed with center of pressure trajectory of postural sway in quiet as well as a limits of stability test, calculating mediolateral and anteroposterior amplitudes for each test. Assessment of function in the motor system included maximum hand grip strength, as well as maximum strength in muscles around the hip, knee and ankle joints. Visual acuity, pressure sensibility, proprioception, vestibular screening, and reaction time were also included. Data was compared between groups, and significant differences in postural control were further analyzed with an orthogonal projection of latent structures regression model.

RESULTS

There was a significantly increased sway amplitude in the mediolateral direction in quiet stance on soft surface with eyes open (p = 0.014) as well as a smaller anteroposterior amplitude in the limits of stability test (p = 0.019) in the COPD group. Regression models revealed that the mediolateral amplitude was related to visual acuity and the burden of tobacco smoking assessed as pack-years. Further, muscle strength associated with anteroposterior amplitude in limits of stability test in the COPD group, and with age and ankle dorsal flexion strength among the referents. Besides for lower ankle plantar flexion strength in the COPD group, there were however no significant differences in muscle strength.

CONCLUSIONS

Individuals with COPD had a decreased postural control and several factors were associated with the impairments. The findings imply that the burden of tobacco smoking and reduced visual acuity relate to increased postural sway in quiet stance, and that muscle weakness is related to decreased limits of stability, among individuals with COPD.

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.

Chemotherapy-induced peripheral neuropathy after modern treatment of Hodgkin's lymphoma; symptom burden and quality of life

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting side effect of Hodgkin's lymphoma (HL) treatment. We aimed to describe the prevalence of CIPN associated symptoms in long-term HL survivors compared to controls, and determine associated factors, including impact on health-related quality of life (HRQoL).

MATERIAL AND METHODS

A questionnaire, including EORTC QLQ-CIPN-20 for CIPN related symptoms and SF-36 for HRQoL, was completed by 303 HL survivors at a median of 16 years after diagnosis. CIPN results were compared to a normative population (n = 606). CIPN associated factors were identified by linear regression analysis.

RESULTS

Total CIPN score and subscores were significantly higher in HL survivors compared to controls. In multivariate analysis of HL survivors, a number of comorbidities (p < 0.001) and female gender (p = 0.05) were significantly associated with more CIPN. No association with disease or treatment factors was found. In a multivariate analysis including survivors and controls, the number of comorbidities (p < 0.001) and caseness (p < 0.001) were significantly associated with more CIPN. In HL survivors higher CIPN score was associated with reduced HRQoL (p < 0.001).

CONCLUSION

HL survivors more than a decade after treatment report higher neuropathy-related symptom burden than controls, with a negative impact on HRQoL. Symptoms may be related to factors other than neurotoxic chemotherapy.

Impact of Body Mass Index and Comorbidities on Outcomes in Upper Extremity Nerve Transfers

BACKGROUND

 There is a paucity of research investigating the impact of patient comorbidities, such as obesity and smoking, on nerve transfer outcomes. The objective of this retrospective cohort study was to evaluate the impact of body mass index (BMI) and comorbidities on the clinical outcomes of upper extremity nerve transfers.

METHODS

 A retrospective cohort study was executed. Patients were eligible for inclusion if they had an upper extremity nerve transfer with a minimum of 12-months follow-up. Data was collected regarding demographics, comorbidities, injury etiology, nerve transfer, as well as preoperative and postoperative clinical assessments. The primary outcome measure was strength of the recipient nerve innervated musculature. Statistical analysis used the Mann-Whitney U test, Wilcoxon signed-rank test, and Spearman's rho.

RESULTS

 Thirty-eight patients undergoing 43 nerve transfers were eligible for inclusion. Patients had a mean age of 48.8 years and a mean BMI of 27.4 kg/m² (range:19.7-39.0). Injuries involved the brachial plexus (32%) or its terminal branches (68%) with the most common etiologies including trauma (50%) and compression (26%). Anterior interosseous nerve to ulnar motor nerve (35%) was the most common transfer performed. With a mean follow-up of 20.1 months, increased BMI (p = 0.036) and smoking (p = 0.021) were associated with worse postoperative strength.

CONCLUSION

 This retrospective cohort study demonstrated that increased BMI and smoking may be associated with worse outcomes in upper extremity nerve transfers-review of the literature yields ambiguity in both regards. To facilitate appropriate patient selection and guide expectations regarding prognosis, further experimental and clinical work is warranted.

Exercise Performance as a Predictor for Balance Impairment in COPD Patients

Background and objective: Six-minute walk test (6-MWT) is a widely used test for assessing exercise performance in chronic obstructive pulmonary (COPD). However, the association between reduced walking distance and balance impairment in COPD has not been directly investigated. Therefore, the aim of this study was to identify exercise performance as a predictor for balance impairment in COPD. Materials and Methods: The cross-sectional study was conducted at a single visit involving stable COPD patients in Maharaj Nakorn Chiang Mai Hospital, Chiang Mai, Thailand from November 2015 to October 2017. The 6-MWT was measured for in all subjects. The prognostic confounding factors were also collected for all subjects. Balance test was measured using the Berg Balance Scale (BBS) and the Timed Up and Go (TUG) test. A cut-off score of BBS < 46 and/or the TUG ≥ 13.5 s was classified as balance impairment. Multivariable logistic regressions were performed to identify the six-minute walk distance (6-MWD) as a predictor for balance impairment in COPD. Results: Of the 176 COPD subjects assessed for eligibility, 118 COPD patients were enrolled including 86 males (72.9%) with a mean age of 73.5 ± 8.1 years. Thirty-three (28.0%) cases were classified with a balance impairment. The 6-MWD < 300 m was the predictor of balance impairment in COPD with an adjusted risk ratio of 10.10 (95%CI; 2.87, 35.61, p-value < 0.001). Conclusions: The 6-MWT is not only useful for evaluation of exercise performance, but also for prediction of balance impairment in patients with COPD. Our study suggests that the 6-MWD < 300 m is an important risk factor for balance impairment in COPD.

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.

Gait abnormalities of COPD are not directly related to respiratory function

STUDY OBJECTIVE

To assess whether gait abnormalities in COPD depend on mere impairment of respiratory function.

METHODS

In 40 patients with COPD at different GOLD stages and 28 controls, we evaluated: forced expiratory volume in 1s (FEV1); partial pressure of oxygen; Mini-Mental State Examination (MMSE); dynamic balance through the Mini-BESTest (MBT); Timed Up and Go (TUG) test without and with dual task counting aloud back by three; 6-min walk test (6MWT); body sway during quiet stance (stabilometry); spatial-temporal variables of gait by a 4-m long sensorized walkway (baropodometry). Lower-limb muscle strength, tendon reflexes, and sensation were also clinically evaluated.

RESULTS

Muscle strength of proximal but not distal muscles was slightly reduced in patients, whereas reflexes and sensation were unaffected. FEV1, partial pressure of oxygen, MMSE, MBT, stabilometry, as well as baropodometry, were abnormal and unrelated to muscle weakness. The time taken to perform the TUG test was increased, and to a larger extent with than without dual task. At baropodometry, variability of step length was increased; abnormalities of gait variables were associated with larger body sway but not with FEV1 or hypoxemia. Gait speed at 6MWT was correlated with MBT score and with FEV1 as well as hypoxemia.

CONCLUSIONS

6MWT findings give a measure of gait disability linked to endurance-related respiratory failure. Gait at baropodometry is associated with impairment of balance, cognitive status and abnormal dual task performance. We suggest that central nervous lesions, presumably of vascular origin, are detrimental to balance and gait in COPD.

Influence of age, gender, and race on nitric oxide release over acupuncture points-meridians

This study examined the influence of age, gender and race on nitric oxide (NO) release over acupuncture points, meridian without acupoint, and non-meridian regions of the Pericardium (PC) and Bladder (BL) meridian as well as aging on LU meridian in 61 healthy subjects. Biocapture tubes were attached to the skin surface, and total nitrite and nitrate was biocaptured and quantified using chemiluminescence. In elder ages compared to adults, NO levels over the ventral forearm were significantly decreased over LU on radial regions but not altered over PC on medial regions. Conversely, NO content was elevated over BL regions only in overweight/obesity of elder ages. NO levels over PC regions were marginally elevated in overweight/obese males compared to females but did not alter between races. These results suggest a selective reduction of NO release over LU meridian with aging, which is consistent with a progressive decline in lung function and increase in chronic respiratory disease in elder ages. Increased NO levels along the BL meridian in older obese subjects may reflect a modified NO level along somatic-bladder pathway for counteracting bladder dysfunctions with aging. Both of them support somatic-organ connections in the meridian system associated with potential pathophysiological changes with aging.

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.

Correlation between optic nerve involvement and chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a major public health problem worldwide. The aim of this study was to evaluate the rate of optic neuropathy in COPD patients.

METHODS

Forty patients diagnosed with COPD and 60 healthy subjects as control group enrolled. After examination by a pulmonary subspecialist, patients were ranked by Global initiative for chronic Obstructive Lung Disease (GOLD) criteria, and patients with zero grades on GOLD criteria were excluded. Visual evoked potential by checkerboard (raster background) method with a frequency of 2 Hz were done for all participants. P-values less than 0.05 were considered as significant.

RESULTS

Fifty-five percent of COPD patients had visual evoked potential abnormalities. Mean P100 latency in both eyes was significantly longer in COPD patients. Average P100/N140 amplitude in both eyes were insignificantly higher in COPD.

CONCLUSION

Higher P100 latency in COPD patients shows demyelinating type of optic nerve involvement; however, further investigation in this area is needed.

Effects of peripheral neuropathy on exercise capacity and quality of life in patients with chronic obstructive pulmonary diseases

INTRODUCTION

Chronic obstructive pulmonary diseases (COPD) have some systemic effects including systemic inflammation, nutritional abnormalities, skeletal muscle dysfunction, and cardiovascular, skeletal and neurological disorders. Some studies have reported the presence of peripheral neuropathy (PNP) at an incidence of 28-94% in patients with COPD. Our study aimed to identify whether PNP affects exercise performance and quality of life in COPD patients.

MATERIAL AND METHODS

Thirty mild-very severe patients with COPD (male/female = 29/1, mean age = 64 ±10 years) and 14 normal subjects (male/female = 11/5, mean age = 61 ±8 years) were included in the present study. All subjects underwent pulmonary function testing (PFT), cardiopulmonary exercise testing, electroneuromyography and short form 36 (SF-36).

RESULTS

Peak oxygen uptake (PeakVO(2)) was lower in COPD patients (1.15 ±0.53 l/min) than healthy subjects (2.02 ±0.46 l/min) (p = 0.0001). There was no PNP in healthy subjects while 16 (53%) of the COPD patients had PNP. Forced expiratory volume in 1 s (FEV(1)) and PeakVO(2) were significantly different between patients with PNP and those without (p = 0.009, p = 0.03 respectively). Quality of life of patients with PNP was lower than that of patients without PNP (p < 0.05).

CONCLUSIONS

The present study demonstrates the exercise limitation in COPD patients with PNP. Thus, presence of PNP has a poor effect on exercise capacity and quality of life in patients with COPD. Furthermore, treatment modalities for PNP can be recommended to these patients in order to improve exercise capacity and quality of life.

Postural Control Is Impaired in People with COPD: An Observational Study

PURPOSE

We investigated deficits in postural control and fall risk in people with chronic obstructive pulmonary disease (COPD).

METHOD

Twenty people with moderate to severe COPD (mean age 72.3 years, standard deviation [SD] 6.7 years) with a mean forced expiratory volume in 1 second (FEV(1)) of 46.7% (SD 13%) and 20 people (mean age 68.2 years, SD 8.1) who served as a comparison group were tested for postural control using the Sensory Organization Test (SOT). A score of zero in any trial of the SOT was registered as a fall. On the basis of the SOT results, participants were categorized as frequent fallers (two or more falls) or as fallers (one fall). To explore the potential influence of muscle weakness on postural control, knee extensors concentric muscle torque was assessed with an isokinetic dynamometer. Physical activity level was assessed with the Physical Activity Scale for the Elderly.

RESULTS

People with COPD showed a 10.8% lower score on the SOT (p=0.016) and experienced more falls (40) than the comparison group (12). The proportion of frequent fallers and fallers during the SOT was greater (p=0.021) in the COPD group (four of 10) than in the comparison group (two of seven). People with COPD showed deficits in knee extensors muscle strength (p=0.01) and a modest trend toward reduced physical activity level. However, neither of these factors explained the deficits in postural control observed in the COPD group.

CONCLUSIONS

People with COPD show deficits in postural control and increased risk of falls as measured by the SOT. The deficits in postural control appear to be independent of muscle weakness and level of physical activity. Postural control interventions and fall risk strategies in the pulmonary rehabilitation of COPD are recommended.

MRI-based 3D shape analysis of thigh muscles patients with chronic obstructive pulmonary disease versus healthy adults

RATIONALE AND OBJECTIVE

Because lower limb muscles differ in architecture and function, the systemic effects of chronic obstructive pulmonary disease (COPD) and related disuse may result in regional abnormalities. The purpose of this study was to investigate the differences between patients with COPD and healthy controls in three-dimensional shape and size measurements of individual thigh muscles.

MATERIALS AND METHODS

Twenty patients with COPD and 20 healthy adults (aged 55-79 years) underwent magnetic resonance imaging of the thighs. After manual segmentation of individual knee extensor and flexor muscles, the three-dimensional shape of each muscle was obtained using specialized software. Eight shape descriptors were computed both globally (for the whole muscle) and regionally (for portions of the muscle). A two-tailed t test with a modified Bonferroni correction was used to compare group differences.

RESULTS

Compared to the thigh muscles of healthy subjects, vastus intermedius and semimembranosus showed the most shape abnormalities in the COPD group (P < .01). Greater regional shape anomalies in the COPD group were found in the middle to proximal regions of all knee extensor muscles and the middle region of the semimembranosus muscle, compared to those of the control group (P < .01). In the COPD group, more shape abnormalities were found in the knee extensors than in the knee flexors (P < .01).

CONCLUSIONS

A non-uniform distribution of atrophy and size changes was found across knee extensors and flexors in patients with COPD. Further research is required to investigate the underlying mechanisms of regional morphologic abnormalities of the thigh muscles and the increased susceptibility of the knee extensors to atrophy-related anatomic anomalies in COPD.

Predictors of pain intensity and persistence in a prospective Italian cohort of patients with herpes zoster: relevance of smoking, trauma and antiviral therapy

BACKGROUND

Herpes zoster (HZ) is a common disease, characterized by rash-associated localized pain. Its main complication, post-herpetic neuralgia (PHN), is difficult to treat and may last for months to years in the wake of rash resolution. Uncertainties remain as to the knowledge of predictors of HZ-related pain, including the role of antiviral therapy in preventing PHN in ordinary clinical practice. This prospective cohort study was aimed at investigating pain intensity at HZ presentation and its correlates, as well as the incidence of PHN and its predictors.

METHODS

Patients diagnosed with HZ were consecutively enrolled by a network of Italian General Practitioners and Hospital Units in the health district of Pescara, Italy, over two years. Uncertain cases were referred for microbiological investigation. Data were collected through electronic case report form (e-CRFs) at enrollment and at 1, 3, 6 and 12 months after enrollment. Pain intensity was coded on a five-degree semi-quantitative scale at each time point. PHN was defined as pain of any intensity during follow-up and quantified using an area-under-the-curve (AUC) method.

RESULTS

Four hundred and forty-one patients composed the final sample. Mean age was 58.1 years (SD = 20.4 years); 43.5% of patients were males; 7.9% did not receive prescription of antivirals. Intense/very intense pain at presentation was reported by 25.2% of patients and was significantly associated with female gender, older age, cigarette smoking, trauma and/or surgery at HZ site (logistic regression). PHN was diagnosed in 51.2% of patients at one month and in 30.0% of patients at three months. PHN was significantly associated with pain intensity at presentation, age, smoking, trauma and missed antiviral prescription (generalized estimating equations model). The same factors were also independent predictors of the overall pain burden as described by the AUC method (linear regression).

CONCLUSIONS

Smoking, traumas and surgery at the HZ site emerged as new predictors of both HZ-related pain intensity and persistence, opening new perspectives in the prevention of HZ-related pain. An independent line of evidence was provided for the efficacy of antiviral therapy in preventing PHN and reducing total pain burden.

Observational study of prevalence of long-term Raynaud-like phenomena and neurological side effects in testicular cancer survivors

Background

Sensory neuropathy (paresthesias), tinnitus, hearing impairment, and Raynaud phenomena are side effects of cisplatin-based chemotherapy used to treat testicular cancer patients. We assessed the long-term occurrence of these side effects among testicular cancer survivors according to the treatment they received.

Methods

A total of 1814 men who were treated for unilateral testicular cancer in Norway during 1980–1994 were invited to participate in a national multicenter follow-up survey conducted during 1998–2002. The men were allocated to six groups according to the treatment they had received. Self-reported symptoms were assessed by a mailed questionnaire that included the Scale for Chemotherapy-Induced Neurotoxicity. A total of 1409 participants who responded to the questionnaire and/or underwent audiometry were assessable in this study. Respondents to the questionnaire (n = 1402) scored the relevant symptoms according to how troubled they were by each (not at all, a little, quite a bit, or very much). Hearing impairment was objectively assessed by audiometry at 4000 Hz in 755 men (seven of whom did not respond to the questionnaire). Group comparisons of symptom assessments were performed with χ² or Kruskal–Wallis tests. Associations between relevant factors and self-reported symptoms or hearing impairment measured by audiometry were assessed using proportional odds ordinal logistic regression models and linear regression models, respectively. All statistical tests were two-sided.

Results

The median follow-up for the 1409 assessable men was 10.7 years (range = 4–21 years). All chemotherapy groups had statistically significantly higher odds for increasing severity of all assessed symptoms and inferior audiometric results compared with men who did not receive chemotherapy. Among chemotherapy-treated men, 39% (95% confidence interval [CI] = 35% to 43%) reported Raynaud-like phenomena (defined as white or cold hands or fingers [or feet or toes] on cold exposure), 29% (95% CI = 25% to 33%) reported paresthesias in the hands or feet, 21% (95% CI = 18% to 25%) reported hearing impairment, and 22% (95% CI = 19% to 26%) reported tinnitus as major symptoms troubling them quite a bit or very much. Hearing impairment (odds ratio [OR] = 5.3, 95% CI = 3.0 to 9.2) and tinnitus (OR = 7.1, 95% CI = 4.1 to 12.4) were particularly common in the dose-intensive chemotherapy group compared with the no chemotherapy group. Men who were treated with radiotherapy had higher odds of self-reported paresthesias in feet compared with those not treated with radiotherapy (OR = 1.5, 95% CI = 1.01 to 2.1, P = .04).

Conclusion

Long-term survivors of testicular cancer who were treated with cisplatin-based chemotherapy were more often troubled by dose-dependent neurological side effects and Raynaud-like phenomena compared with those who were not treated with chemotherapy.

Falls in patients with chronic obstructive pulmonary disease: a call for further research

Chronic obstructive pulmonary disease (COPD) is a respiratory disease that results in airflow limitation and respiratory distress. The effects of COPD, however, are not exclusively limited to respiratory function and people with COPD face many non-respiratory manifestations that affect both function and mobility. Deficits in function and mobility have been associated with an increased risk for falling in older adults. The purpose of this study was to provide a theoretical framework to identify risks factors for falls in people with COPD. We have analyzed the literature to identify possible relationships between pathophysiological changes observed in COPD and common risk factors for falls. Well-established fall risk factors in people with COPD include lower limb muscle weakness and impaired activities of daily living. Other intrinsic risk factors such as gait and balance deficits, nutritional depletion, malnutrition, depression, cognitive impairments and medications are possible risk factors that need to be confirmed with more studies. There is no evidence that visual deficits are common in COPD. The role that precipitating factors such as syncope and postural hypotension may have on fall risk is unclear. Exacerbations and dyspnea do not have a precipitating effect on fall risk but they contribute to the progressive physical deterioration that may theoretically increase the risk for falls. While these results suggest that people with COPD might have an increased susceptibility to fall compared to their healthy peers, further research is needed to determine the prevalence of falls and specific risk factors for falls in people living with COPD.

Restless legs syndrome in patients with chronic obstructive pulmonary disease

OBJECTIVE

To evaluate the prevalence of restless legs syndrome (RLS) in patients with chronic obstructive pulmonary disease (COPD) and the relationship between RLS and clinical/laboratory findings of COPD.

METHODS

One hundred and thirty-four COPD patients without secondary causes of RLS were included. Thirty-nine (29.1%) patients were diagnosed with RLS and classified as Group 1. The control group consisted of 65 age-matched COPD patients without RLS. Group 1 was divided into subgroups according to the Johns Hopkins Severity (JHS) scale. Patients with a score of 0, 1, or 2 were classified as JHS 0-2 and those with a score of 3 as JHS 3. Group 1 and the control group and subgroups were compared for clinical and laboratory characteristics.

RESULTS

We found that the duration of COPD was longer and that airway obstruction, hypercapnia, and hypoxia were more evident in patients with RLS than those without. Similar differences were also detected between JHS subgroups 3 (more severe) and 0-2. Polyneuropathy frequency was significantly higher in Group 1 compared to controls. However, Group 1 subgroups showed a similar frequency of polyneuropathy. In a multivariate analysis, hypercapnia made a significant independent contribution to both JHS 0-2 and JHS 3 patients when RLS severity was set as the dependent variable. Polyneuropathy and the duration of COPD were significant independent variables for patients in the JHS 3 subgroup. Polyneuropathy was the strongest predictor for the JHS 3 patients.

CONCLUSIONS

We conclude that RLS is frequent in COPD, particularly in patients with severe hypoxemia/hypercapnia and in late stages of the disease.

Cranial optic nerve involvements in patients with severe COPD

OBJECTIVE

The relationship between neuropathy and increased morbidity in patients with COPD is clear, but few studies have assessed cranial neuropathies, especially optic nerve involvement, in COPD patients. We evaluated peripheral involvement of the optic nerve and determined factors influencing this condition in patients with severe COPD.

METHODOLOGY

Twenty-eight patients, mean age 59.4 +/- 9.4 years, diagnosed with severe stable COPD according to the GOLD criteria, and 20 age- and gender-matched healthy individuals, mean age 55.6 +/- 8.5 years, were included in the study. All subjects underwent visual evoked potential (VEP) assessment together with detailed clinical and laboratory examination to exclude concurrent risk factors for neuropathy.

RESULTS

VEP assessment showed significant abnormalities in COPD patients (82.1%) (commonly amplitude abnormalities) when compared with healthy controls.

CONCLUSIONS

The optic nerve is often involved in patients with severe COPD, possibly as part of a polyneuropathy, and this is related to acidosis, hypercarbia and airway obstruction, independent of disease duration, smoking and age. These results should be taken into consideration when determining management strategies for these patients.

Corticospinal control of respiratory muscles in chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) face an increased respiratory load and in consequence have an elevated respiratory drive. We used transcranial magnetic stimulation (TMS) to investigate associated changes in corticospinal excitability both at rest and during voluntary facilitation at different levels of inspiratory effort. Diaphragm and abdominal motor thresholds were significantly lower in COPD than healthy controls, but the quadriceps response was the same. In patients there was a significant increase in diaphragm response from rest during 20% inspiratory efforts but no further increase with greater efforts. In controls there was a further stepwise increase at 40% and 60% of inspiratory effort. The cortical silent period was significantly shorter in COPD. Using paired stimulation to study intracortical inhibitory and excitatory circuits we found significantly less excitability of intracortical facilitatory circuits in patients at long (>7 ms) interstimulus intervals. These results suggest that there is a ceiling effect in motor control output to the respiratory muscles of patients with COPD.

Cigarette smoking and ulnar mononeuropathy at the elbow

OBJECTIVE

To identify lifestyle risk factors for electrodiagnostically confirmed ulnar mononeuropathy at the elbow (UME).

DESIGN

A case-control study involving 101 subjects (12 with definite UME, 42 with probable UME, and 47 controls) who responded to a questionnaire requesting information on subject vocation, repetitive upper limb activity, and alcohol and cigarette use.

RESULTS

Subjects with definite UME reported greater tobacco usage as defined by cigarettes per day (mean +/- standard error; 20.1 +/- 5.2, 9.3 +/- 1.9, 8.6 +/- 1.5 cigarettes/day for definite, probable UME, and controls, respectively; P = 0.014) and pack-years (27.3 +/- 9.7, 12.5 +/- 3.0, 9.9 +/- 2.3, for definite, probable UME, and controls, respectively; P = 0.029). The association between cigarettes and definite UME persisted after adjustment for age, sex, and body mass index and was not confounded by alcohol use. Significant negative correlations between tobacco use and ulnar conduction velocities across the elbow and amplitudes above the elbow were identified.

CONCLUSIONS

Cigarette smoking and UME seem to be associated. The presence of a plausible mechanism for injury and a dose-response effect suggests that this association may be causative.

Quantification of myelinated endings and mechanoreceptors in human digital skin

We used immunohistochemistry and confocal microscopy applied to fingertip punch biopsy to study glabrous skin innervation in 14 healthy subjects. In addition to epidermal nerve fibers, we quantified mechanoreceptors and their myelinated afferents. Using digital images and dedicated software, we calculated caliber, internodal and nodal length, and G-ratio of the last four internodes of the myelinated endings. In our skin samples, we found a mean density of 59.0 +/- 29.3 myelinated endings per square millimeter with a mean diameter of 3.3 +/- 0.5 microm and an internodal length of 79.1 +/- 13.8 microm. These findings indicate that Abeta fibers undergo drastic changes in their course from the nerve trunk to the target organ, with repeated branching and consequent tapering and shortening of internodal length. Our work demonstrates that skin biopsy can give information on the status of large myelinated endings as well as unmyelinated sensory and autonomic nerves. Since distal endings are primarily involved in distal axonopathy, skin biopsy can be more suitable than sural nerve biopsy to detect early abnormalities. In addition to diagnostic applications, this technique allows clarification of the mode of termination of Abeta fibers and their relationship with mechanoreceptors, leading to relevant electrophysiological speculations.

Effects of tobacco smoke on recovery after nerve crush injury in rats

The effects of tobacco smoke on nerve healing after crush injury was studied in a rat model. Thirty-six animals were randomized equally into smoke-exposed or nonsmoke-exposed groups. Two nerve crush injuries were performed on the right posterior tibial nerve of each animal at 4-week intervals to mimic a sustained or chronic nerve injury. Recovery of the two groups was assessed with walking track analysis and nerve histomorphometry. There was no difference in the rate of nerve recovery based on walking track analysis in the smoke-exposed animals compared with nonexposed animals. The study also failed to demonstrate any significant difference between the two groups as assessed by histomorphometric criteria.

The brainstem auditory evoked potential abnormalities in severe chronic obstructive pulmonary disease

OBJECTIVE

The aim of the study was to investigate the abnormalities of brainstem auditory evoked potentials (BAEP) in patients with severe chronic obstructive pulmonary disease (COPD).

METHODOLOGY

Twenty-one patients with severe COPD (16 men, five women; mean age: 64 +/- 6.5 years), in whom other causes of BAEP abnormalities had been excluded, were studied. Age-matched, non-smoking, healthy subjects acted as a control group. We performed pulmonary function tests, arterial blood gas analysis and bilateral BAEP measurements in COPD patients and control groups.

RESULTS

Brainstem auditory evoked potentials were abnormal in 16 (76.1%) of the 21 COPD patients. Most prominent BAEP abnormalities were prolonged wave I peak latencies (42.8%), V wave peak latencies (38.1%), and III-V interpeak latencies (IPL) (38.1%). In five patients, a prolonged central transmission time (I-V IPL) was observed. No significant correlation was evident between the BAEP parameters and pH, PaO2, PaCO2, FEV1%, FEV1/FVC, haematocrit, duration of disease or cigarette consumption.

CONCLUSION

The functions of the eighth cranial nerve and brainstem were highly impaired in severe COPD. These pathological BAEP alterations in severe COPD might be due to the chronic hypoxic-hypercapnic status occurring in the brainstem.

Neurological manifestations in chronic mountain sickness: the burning feet-burning hands syndrome

OBJECTIVE

To characterise the clinical features and nerve biopsy findings in patients with chronic mountain sickness (CMS) living in the Peruvian Andes, with particular attention to the occurrence of the "burning feet-burning hands" syndrome.

METHODS

Symptoms and signs were documented clinically in 10 patients with CMS and compared with those in five healthy subjects all living at 4338 metres altitude. Sural nerve biopsies were obtained from three patients with CMS. The nerve fibre population and endoneurial microvessels were analyzed morphometrically.

RESULTS

All patients with CMS experienced burning and tingling paraesthesiae in the distal parts of their limbs. Similar but milder symptoms confined to the feet occurred in four of five controls. Three patients with CMS had a mild sensory neuropathy on examination, controls were clinically normal. Nerve biopsies showed a mild demyelinating neuropathy in all three with a reduction in the unmyelinated axon population in one. The endoneurial blood vessels showed a reduced thickness in the basal laminal zone compared with control values but were otherwise normal.

CONCLUSIONS

Apart from well recognised symptoms and signs of CMS, the study has shown that such patients may also exhibit a mild sensory neuropathy. Its relation to the burning feet-burning hands syndrome, which was not confined to the patients but was also found in controls at altitude, is uncertain. The time course and pattern of the centrifugal resolution of the burning paraesthesiae complex on low altitude sojourn of high altitude natives raises the possibility that a mechanism involving altered axonal transport may be involved. The reduced thickness of the basal laminal zone of microvessels implies that adaptive structural changes to hypobaric hypoxia may also occur in peripheral nerve and are similar to those reported in other tissues of high altitude natives.

The aetiology of diabetic neuropathy: the combined roles of metabolic and vascular defects

A combination of metabolic and vascular defects have been implicated in the pathogenesis of diabetic neuropathy. Animal studies have demonstrated that a reduction in nerve blood flow may be an important early defect and that vasodilators can prevent or ameliorate nerve dysfunction. The potential factors contributing to nerve ischaemia include structural defects in the endoneurial microvasculature together with rheological abnormalities, abnormalities in vasoactive agents which regulate nerve blood flow including nitric oxide and the eicosanoids, and alterations in tone of the autonomic innervation of the nerve vasculature. The principle metabolic defects which have been implicated include disruption of the polyol pathway, altered lipid metabolism, advanced glycosylated end-product formation, increased oxidative stress, and diabetes-induced defects in growth factors. The demonstration that activation of the polyol pathway in experimental diabetes may affect nerve blood flow, and conversely that vasoactive agents appear to be important in regulating some aspects of nerve metabolism, has highlighted the interdependence of the metabolic and vascular defects in the pathogenesis of this condition. Thus, selective intervention aimed at a key defect early in this cascade may subsequently correct a number of later abnormalities offering therapeutic hope in this chronic debilitating complication.

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.

AAEM minimonograph #34: polyneuropathy: classification by nerve conduction studies and electromyography

Electrodiagnostic evaluation of patients with suspected polyneuropathy is useful for detecting and documenting peripheral abnormalities, identifying the predominant pathophysiology, and determining the prognosis for certain disorders. The electrodiagnostic classification of polyneuropathy is associated with morphologic correlates and is based upon determining involvement of sensory and motor fibers and distinguishing between predominantly axon loss and demyelinating lesions. Accurate electrodiagnostic classification leads to a more focused and expedient identification of the etiology of polyneuropathy in clinical situations.

Polyneuropathy associated with chronic hypoxaemia: prevalence in patients with chronic obstructive pulmonary disease

The prevalence of clinical and electrophysiological signs of peripheral nerve disease was evaluated in 151 patients with chronic obstructive pulmonary disease. Patients with concomitant disorders affecting the peripheral nervous system were excluded. Thirty patients had clinical signs of a mild sensorimotor and distal neuropathy and 13 additional patients had only electrophysiological abnormalities. The rate and the severity of the neuropathy correlated with the severity of chronic hypoxaemia. Three out of 20 patients with mild hypoxaemia (PaO2 less than 15 mm Hg below normal) had polyneuropathy as compared with 15 out of 36 with severe hypoxaemia (PaO2 more than 30 mm Hg below normal (rates different at the 10% level)). PaO2 and age were the only variables discriminating between patients with and without peripheral neuropathy.

Hypoxic neuropathy: relevance to human diabetic neuropathy

Clinical and neurophysiological studies were conducted in 47 patients with chronic obstructive airways disease and compared with 46 age-matched control subjects. Symptomatic neuropathy was reported in 13% and ankle jerks were absent in 45% of hypoxic patients. Peroneal and median nerve conduction velocities and median and sural sensory nerve amplitudes were significantly reduced in hypoxic patients (p less than 0.01). Six hypoxic patients underwent biopsy of the sural nerve, soleus muscle and overlying skin. Nerve glucose, sorbitol, fructose and myo-inositol concentrations were normal. Detailed light and electronmicroscopy revealed both nerve fibre and microvascular pathology. Segmental demyelination (32%) and unmyelinated fibre degeneration were found to be prominent lesions. The sural nerve perineurium was thickened due to an increase in the number of perineurial lamellae and an increase in intraperineurial space. Basement membrane thickening was observed in capillaries of nerve, muscle and skin. Endothelial cell hyperplasia and hypertrophy were observed in nerve and muscle capillaries but not in skin capillaries. In conclusion, this study has provided neurological, neurophysiological and neuropathological evidence of a neuropathy in hypoxic patients with chronic obstructive airways disease. These findings may be of relevance to some aspects of the aetiology of human diabetic neuropathy.

Peripheral nerve function in patients with chronic bronchitis receiving almitrine or placebo

A double blind prospective study of the effect of almitrine bismesylate and placebo on peripheral-nerve function was carried out in 12 patients with chronic bronchitis and arterial hypoxaemia (mean (SD) FEV1% predicted 38 (16), arterial oxygen tension (PaO2) 7.56 (0.76) kPa). Of the seven patients who took placebo, none developed symptoms or signs of peripheral neuropathy. One patient who had abnormal lower limb sensory nerve conduction initially showed improvement of sensory conduction but deterioration in motor conduction during the 12 month study period. Two further patients developed some slowing of motor conduction velocities in their right lateral popliteal nerve. Five patients received almitrine and all showed an improvement in PaO2 (mean from 7.0 to 7.9 kPa). None had symptoms or signs of peripheral neuropathy on entry to the study; one patient had evidence of impaired nerve conduction on electrophysiological testing. Three patients developed symptoms and signs of peripheral neuropathy during the 12 months of the study and a fourth developed peripheral neuropathy at 18 months, having continued to receive almitrine. Studies of nerve physiology showed abnormalities in the lower limbs of all four patients. Recovery was poor, possibly because of the long half life of almitrine. The studies suggest that almitrine may precipitate peripheral neuropathy in patients with chronic obstructive pulmonary disease. Patients should be warned of this potential complication so that the drug can be stopped as soon as symptoms develop.

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.

Microangiopathy of endoneurial vessels in hypoxemic chronic obstructive pulmonary disease (COPD). A quantitative ultrastructural study

A peripheral neuropathy has been reported in patients with chronic respiratory insufficiency due to chronic obstructive pulmonary disease (COPD). It is mainly characterized by axonal degeneration, secondary demyelination and abnormal endoneurial vessels. The pathogenesis of these lesions remains obscure. To investigate whether relationships exist between neuritic and vascular lesions, a qualitative and quantitative ultrastructural study was performed on nerve biopsies in 13 patients with chronic respiratory insufficiency due to COPD, and in 9 normal controls without pulmonary lesions. A computer-assisted multiple regression analysis taking into account clinical, electrophysiological, biological and morphometric parameters was performed. Statistically significant differences in the endoneurial structure of microvessels were: (1) thickening of the basement membrane; (2) narrowing of the lumen; (3) mural pericytic debris deposits, occurring in the COPD group. In the latter, hypercapnia correlated positively with nerve fibers lesions (P = 0.03) and endothelial area (P = 0.03). No correlations were found between age and other parameters. These findings highlight the fact that the microangiopathy in peripheral nerves in patients with COPD may be diffuse and essentially due to hypoxia and reduction in blood flow, as in diabetic neuropathy.

Pattern of myelinated fibre loss in the sural nerve in neuropathy related to type 1 (insulin-dependent) diabetes

Sural nerve biopsies were obtained from 17 diabetic patients with neuropathy. All patients except three had both a symmetric distal sensory and autonomic polyneuropathy related to Type 1 (insulin-dependent) diabetes mellitus; 3 patients had a purely sensory polyneuropathy. Mean age was 34.5 years (range 18-53 years). The biopsies were compared with specimens from an age-matched control series. Myelinated fibre loss in the diabetic nerves was found to be nonuniform. Although patchy fibre loss has been considered to favour a vascular basis, an identical pattern of nonuniform loss was observed in a series of sural nerve biopsies from patients with Type I hereditary motor and sensory neuropathy, a subgroup within the spectrum of peroneal muscular atrophy, mainly of autosomal dominant inheritance, and a condition in which a vascular causation can be discounted. Possible reasons for nonuniform fibre loss other than vascular disease are discussed.

Almitrine neuropathy. A nerve biopsy study of 8 cases

We report the quantitative and qualitative, light and electron microscopic studies, including teased fiber preparations of nerve biopsies obtained from eight patients, treated with almitrine, presenting with the characteristic association of a sensory peripheral neuropathy with a recent body weight loss. The data were consistent with an axonal damage affecting myelinated fibers, predominantly large ones and to a lesser degree unmyelinated fibers, some degree of segmental demyelination. Marked axonal regeneration was observed when the nerve biopsy was delayed after withdrawal of the drug, Micro-angiopathy secondary to the formation of concentric lamellae from the basement membrane was observed in five patients suffering from chronic hypoxemia. Almitrine is an agonist of the chemoreceptors. The pathogenesis of the toxic neuropathy induced by this compound remains obscure. Clinical features do not fit with a purely hypoxic mechanism at the origin of the neuropathy.

Evidence of motor neuron involvement in chronic respiratory insufficiency

Nineteen patients with chronic respiratory insufficiency, mean age 61.4 +/- 12.2, have been investigated with pulmonary function tests, clinical neurological examination and neurophysiological methods including motor and sensory conduction studies and needle electromyography. None of them had conditions known to affect the peripheral nervous system such as diabetes, alcoholism, or uraemia. The motor and sensory conduction studies showed only a reduced mean amplitude of the ulnar nerve SAP and of the compound muscle action potential of the APB and EDB muscles. The EMG was abnormal in 94.7% of the cases and showed an increased percentage of polyphasic potentials and a reduced recruitment pattern of motor units firing at high frequency. The data seem to support the hypothesis of an involvement of motor neurons in this condition although the evidence for a neuropathy is lacking.

Chronic cryptogenic polyneuropathy. The search for a cause

91 patients with chronic symptoms of polyneuropathy without any previously known underlying disorder underwent extensive clinical and laboratory investigations in an attempt to reveal the cause of the polyneuropathy. A definite or probable origin of polyneuropathy was detected in only 8 patients (9%) and a possible but questionable cause was found in 16 (17%), while the cause in 74% remained undetermined. In only 1 patient could effective treatment be instituted. No evidence was found for an association between polyneuropathy and reduced glucose tolerance without manifest diabetes mellitus. The findings suggest that only a limited investigation is justified in most cases of chronic polyneuropathy without obvious cause.

Prognosis of symptoms in patients with diagnosed chronic organic solvent intoxication

The profile and prognosis of symptoms of 87 patients (mean age 38.6 years) in whom a chronic organic solvent intoxication due to tri- or perchloroethylene or mixtures of solvents had been diagnosed 3-9 years earlier were examined by means of an interview. Both at the time of diagnosis and upon reexamination, the most common symptoms were abnormal fatigue, memory disturbances and headache. Also dizziness, sleep disturbances, sensory symptoms in the extremities, mental depression, concentration difficulties, psychic irritability, emotional lability, tremor and nausea were present in over 60% of patients at the time of diagnosis. Upon reexamination, 52% of the intoxication patients with no other contributing neurological disease felt that their overall subjective condition was better than at the time of diagnosis, 21% felt that it was worse, and 27% reported no change. Most of the individual symptoms had more often changed for the better than for the worse; the differences were statistically significant with regard to abnormal fatigue, headache, dizziness, sleep disturbances, nausea, and emotional lability, whereas memory disturbances had changed in the opposite direction. Younger persons, who had had a longer follow-up period and without regular check-ups at the Institute of Occupational Health seemed to have better prognosis at the group level. Due to the great variation between the individuals, the prognosis was, however, impossible to predict in individual cases.