Prevalence of subclinical neuropathy in diabetic patients: assessment by study of conduction velocity distribution within motor and sensory nerve fibres

Skin keratinocyte-derived SIRT1 and BDNF modulate mechanical allodynia in mouse models of diabetic neuropathy

Diabetic neuropathy is a debilitating disorder characterized by spontaneous and mechanical pain. The role of skin mechanoreceptors in the development of mechanical pain (allodynia) is unclear. We discovered that mice with diabetic neuropathy had decreased sirtuin 1 (SIRT1) deacetylase activity in foot skin, leading to reduced expression of brain-derived neurotrophic factor (BDNF) and subsequent loss of innervation in Meissner corpuscles, a mechanoreceptor expressing the BDNF receptor TrkB. When SIRT1 was depleted from skin, the mechanical allodynia worsened in diabetic neuropathy mice, likely due to retrograde degeneration of the Meissner-corpuscle innervating Aβ axons and aberrant formation of Meissner corpuscles which may have increased the mechanosensitivity. The same phenomenon was also noted in skin BDNF knockout mice. Furthermore, overexpression of SIRT1 in skin induced Meissner corpuscle reinnervation and regeneration, resulting in significant improvement of diabetic mechanical allodynia. Overall, the findings suggested that skin-derived SIRT1 and BDNF function in the same pathway in skin sensory apparatus regeneration and highlighted the potential of developing topical SIRT1-activating compounds as a novel treatment for diabetic mechanical allodynia.

Risk Factors for Subclinical Diabetic Peripheral Neuropathy in Type 2 Diabetes Mellitus

Purpose

To investigate the risk factors associated with subclinical diabetic peripheral neuropathy (sDPN) in patients with type 2 diabetes mellitus (T2DM).

Patients and Methods

This cross-sectional, retrospective study involved 311 patients with T2DM who were successively admitted from January 2018 to December 2021 without any neurological symptoms. All participants underwent a nerve conduction study (NCS), and those asymptomatic patients with abnormal nerve conduction were diagnosed with sDPN. Differences between groups were evaluated by the chi-squared, Wilcoxon, or Fisher's exact test. Binary logistic regression analysis was performed to determine the independent risk factors for sDPN. Receiver operating characteristic (ROC) curves were constructed, and the areas under curves (AUCs) were detected.

Results

Among 311 asymptomatic patients with T2DM, 142 (45.7%) with abnormal nerve conduction were diagnosed with sDPN. Patients with sDPN significantly differed from those without diabetic peripheral neuropathy (DPN) in age, history of hypertension, duration of diabetes, anemia, neutrophil-to-lymphocyte ratio, fasting C-peptide level, serum creatinine level, and albuminuria (all p<0.05). Furthermore, the duration of diabetes (odds ratio [OR]: 1.062, 95% confidence interval [CI]: 1.016-1.110), fasting C-peptide level (OR: 2.427, 95% CI: 1.126-5.231), and presence of albuminuria (OR: 2.481, 95% CI: 1.406-4.380) were independently associated with the development of sDPN (all p<0.05). The AUCs for fasting C-peptide level, duration of diabetes, and the two factors combined were 0.6229 (95% CI: 0.5603-0.6855, p=0.0002), 0.6738 (95% CI: 0.6142-0.7333, p<0.0001), and 0.6808 (95% CI: 0.6212-0.7404, p<0.0001), respectively.

Conclusion

For patients with T2DM and longer duration of diabetes, lower fasting C-peptide levels, and presence with albuminuria, the risk for developing DPN is higher even if they have no clinical signs or symptoms. Identifying potential risk factors for the development of sDPN and effectively controlling them early are critical for the successful management of DPN.

Diabetic neuropathy is a generalized phenomenon with impact on hand functional performance and quality of life

BACKGROUND

Diabetic sensorimotor peripheral neuropathy (DSPN) is usually considered to affect predominantly the lower limbs (LL-N), while the impact of upper limb neuropathy (UL-N) on hand functional performance and quality of life (QoL) has not been evaluated systematically. This study aims to investigate the prevalence and characteristics of UL-N and its functional and psychosocial consequences in type 2 diabetes.

METHODS

Individuals with type 2 diabetes (n=141) and an age- and sex-matched control group (n=73) underwent comprehensive assessment of neuropathy, hand functional performance and psychosocial status.

RESULTS

The prevalence of UL-N was 30.5% in patients with diabetes and that of LL-N 49.6%, with 25.5% exhibiting both. Patients with diabetes showed similar sensory phenotype regarding both large and small fiber functions in hands and feet. Patients with UL-N showed reduced manual dexterity, but normal hand grip force. Additionally, there was a correlation between reduced dexterity and sensory deficits. Patients with UL-N had reduced estimates of psychosocial health including health-related QoL compared to control subjects and patients without UL-N. UL-N correlated with the severity of LL-N, but not with duration of diabetes, glycaemia, age, or sex.

CONCLUSIONS

This study points to a substantial prevalence of UL-N in type 2 diabetes. The sensory phenotype of patients with UL-N was similar to LL-N and was characterized by loss of sensory function. Our study demonstrated an association of UL-N with impaired manual dexterity and reduced health-related QoL. Thus, upper limb sensorimotor functions should be assessed early in patients with diabetes.

Neuroretinal dysfunction revealed by a flicker electroretinogram correlated with peripheral nerve dysfunction and parameters of atherosclerosis in patients with diabetes

AIMS/INTRODUCTION

Diabetic polyneuropathy (DPN) develops in the early stage of diabetes. However, no common diagnostic protocol has yet been established. Here, to verify that the flicker electroretinogram using a hand-held device can detect the early dysfunction of the peripheral nervous system in patients with diabetes, we investigated the correlation between the progression of DPN and neuroretinal dysfunction.

MATERIALS AND METHODS

In total, 184 participants with type 1 or 2 diabetes underwent a flicker electroretinogram (ERG) using a hand-held device RETeval™ and nerve conduction study. Participants were also evaluated for intima-media thickness, ankle-brachial index, toe brachial index and brachial-ankle pulse wave velocity. Parameters of the nerve conduction study were used to diagnose the severity according to Baba's classification. A multiple regression analysis was used to examine the associations of ERG parameters with the severity of DPN categorized by Baba's classification. Diagnostic properties of the device in DPN were evaluated using a receiver operating characteristic curve.

RESULTS

A multiple regression model to predict the severity of DPN was generated using ERG. In the model, moderate-to-severe DPN was effectively diagnosed (area under the receiver operating characteristic curve 0.692, sensitivity 56.5%, specificity 78.3%, positive predictive value 70.6%, negative predictive value 66.1%, positive likelihood ratio 2.60, negative likelihood ratio 0.56). In the patients without diabetic retinopathy, the implicit time and amplitude in ERG significantly correlated with the parameters of the nerve conduction study, brachial-ankle pulse wave velocity and intima-media thickness.

CONCLUSIONS

Electroretinogram parameters obtained by the hand-held device successfully predict the severity of DPN. The device might be useful to evaluate DPN.

The Physiological Significance of A-Waves in Early Diabetic Neuropathy: Assessment of Motor Nerve Fibers by Neurophysiological Techniques

Objective: This study aimed to investigate how early A-waves could occur in type II diabetes, and what it implied functionally. Methods: We performed conduction velocity distribution (CVD) test in peroneal nerves of 37 type II diabetic patients with normal nerve conduction study (NCS) and 22 age-matched controls. The electrophysiological data and clinical information were analyzed. Results: A-waves were observed in 45.9% of diabetic patients and only in 1 person in healthy controls, all detected in the tibial nerves. The diabetic patients with A-waves showed faster conduction velocity in all quartiles in the motor peroneal nerves compared to the patients without A-waves, and their CVD histograms were shifted to the right side, consisting of a significantly larger percentage of fast conducting fibers. There was no significant difference in the CVD values of the upper extremity nerves among the patients with and without A-waves and the healthy controls. Conclusion: A-waves could occur in type II diabetes as early as when NCS showed normal, and represented as a sign of neuropathy as well as a sign of rescued motor nerve function.

Point-of-care nerve conduction device predicts the severity of diabetic polyneuropathy: A quantitative, but easy-to-use, prediction model

Aims/Introduction

A gold standard in the diagnosis of diabetic polyneuropathy (DPN) is a nerve conduction study. However, as a nerve conduction study requires expensive equipment and well‐trained technicians, it is largely avoided when diagnosing DPN in clinical settings. Here, we validated a novel diagnostic method for DPN using a point‐of‐care nerve conduction device as an alternative way of diagnosis using a standard electromyography system.

Materials and Methods

We used a multiple regression analysis to examine associations of nerve conduction parameters obtained from the device, DPNCheck™, with the severity of DPN categorized by the Baba classification among 375 participants with type 2 diabetes. A nerve conduction study using a conventional electromyography system was implemented to differentiate the severity in the Baba classification. The diagnostic properties of the device were evaluated using a receiver operating characteristic curve.

Results

A multiple regression model to predict the severity of DPN was generated using sural nerve conduction data obtained from the device as follows: the severity of DPN = 2.046 + 0.509 × ln(age [years]) − 0.033 × (nerve conduction velocity [m/s]) − 0.622 × ln(amplitude of sensory nerve action potential [µV]), r = 0.649. Using a cut‐off value of 1.3065 in the model, moderate‐to‐severe DPN was effectively diagnosed (area under the receiver operating characteristic curve 0.871, sensitivity 70.1%, specificity 87.7%, positive predictive value 83.0%, negative predictive value 77.3%, positive likelihood ratio 5.67, negative likelihood ratio 0.34).

Conclusions

Nerve conduction parameters in the sural nerve acquired by the handheld device successfully predict the severity of DPN.

Validity and reliability of a point-of-care nerve conduction device in diabetes patients

AIMS/INTRODUCTION

Although nerve conduction study (NCS) using a standard electromyography system (EMGS) is considered to be the gold standard in evaluating diabetic polyneuropathy, this examination requires expensive equipment and well-trained technicians. We aimed to validate a point-of-care device, NC-stat/DPNCheck™, that has been developed for widespread use of NCS in diabetic polyneuropathy.

MATERIALS AND METHODS

Diabetes patients underwent two kinds of NCS: DPNCheck™ and electromyography system. Inter-/intrarater reliability of DPNCheck™ were also determined by the intraclass correlation coefficient.

RESULTS

A total of 57 patients were evaluated. The parameters of NCS between the two methods correlated well (r = 0.7734 for the sural nerve conduction velocity, r = 0.6155 for the amplitude of sural nerve action potential). The intraclass correlation coefficients were excellent (intrarater: the velocity 0.767, the amplitude 0.811; interrater: the velocity 0.974, the amplitude 0.834).

CONCLUSIONS

The point-of-care device has excellent reproducibility and good agreement with standard electromyography system. The device might be useful to evaluate diabetic polyneuropathy.

Dynamical Coordination of Hand Intrinsic Muscles for Precision Grip in Diabetes Mellitus

This study investigated the effects of diabetes mellitus (DM) on dynamical coordination of hand intrinsic muscles during precision grip. Precision grip was tested using a custom designed apparatus with stable and unstable loads, during which the surface electromyographic (sEMG) signals of the abductor pollicis brevis (APB) and first dorsal interosseous (FDI) were recorded simultaneously. Recurrence quantification analysis (RQA) was applied to quantify the dynamical structure of sEMG signals of the APB and FDI; and cross recurrence quantification analysis (CRQA) was used to assess the intermuscular coupling between the two intrinsic muscles. This study revealed that the DM altered the dynamical structure of muscle activation for the FDI and the dynamical intermuscular coordination between the APB and FDI during precision grip. A reinforced feedforward mechanism that compensates the loss of sensory feedbacks in DM may be responsible for the stronger intermuscular coupling between the APB and FDI muscles. Sensory deficits in DM remarkably decreased the capacity of online motor adjustment based on sensory feedback, rendering a lower adaptability to the uncertainty of environment. This study shed light on inherent dynamical properties underlying the intrinsic muscle activation and intermuscular coordination for precision grip and the effects of DM on hand sensorimotor function.

In-vivo reflectance confocal microscopy of Meissner's corpuscles in diabetic distal symmetric polyneuropathy

OBJECTIVE

To evaluate in-vivo reflectance confocal microscopy (RCM) of Meissner's corpuscles (MC) in diabetic distal symmetric polyneuropathy (DSP).

METHODS

Forty-three adults with diabetes and 21 control subjects underwent RCM of MC density at the fingertip of digit V, thenar eminence (TE), and arch of the foot, ankle skin biopsy for epidermal nerve fiber density (ENFD), electrophysiological studies, monofilament threshold testing, and timed vibration at the toe. Subjects with diabetes were subdivided into groups with and without clinical DSP using the American Academy of Neurology (AAN) case definition and neuropathy outcomes were compared across groups.

RESULTS

Both diabetic groups (with and without AAN clinical DSP criteria) had objective evidence of peripheral sensory involvement using conventional sensory measures, although those with clinical DSP criteria had greater abnormalities. MC densities were lower in the entire diabetic group at the TE and digit V relative to controls. MC densities at all imaging sites were associated with corresponding conventional sensory measures. MC densities were reduced in subjects without AAN clinical DSP criteria at the TE and digit V compared to controls whereas conventional upper limb sensory measures did not differ between these groups.

CONCLUSIONS

In-vivo RCM of MC density at digit V is a non-invasive, painless, objective marker in diabetes that offers a window into early large fiber sensory nerve terminal loss. Further studies are needed to determine whether RCM of MCs can identify quantitative changes in DSP associated with disease progression or treatment.

Do we underestimate influences of diabetic mononeuropathy or polyneuropathy on hand functional performance and life quality?

Aims/Introduction

The purpose of the present study was to identify whether there are differences in hand dexterity, hand functional performance and quality of life between diabetes patients with mononeuropathy and polyneuropathy of their hands to further present the importance regarding the impacts of diabetic neuropathic deficits on patients’ functional capacity.

Materials and Methods

The neurological deficits of 127 patients with type 2 diabetes were examined by electrophysiological tests for the median and ulnar nerves, and were stratified into the diabetic mononeuropathy, diabetic polyneuropathy and non‐diabetic neuropathy groups by sensory amplitude of these nerves. The Purdue pegboard test, Michigan Hand Outcomes Questionnaire, and Diabetes‐39 were carried out to understand patients’ hand dexterity, functional hand performance and quality of life, respectively.

Results

The results showed significant differences in all subtests of the Purdue pegboard test among the three groups. Furthermore, aesthetics, patient's satisfaction of the Michigan Hand Outcomes Questionnaire and diabetes control, sexual functioning, energy, and mobility of the Diabetes‐39 also showed significant differences among the three groups.

Conclusions

The present study shows the patients with polyneuropathy suffer from more negative impacts on hand functional performance and quality of life than those with mononeuropathy and without neuropathy. These findings might assist both patients and clinicians in better realizing the impacts of neuropathic hands, and planning suitable strategies of intervention or health education to prevent declines in hand functions.

Relationship of Vascular Factors on Electrophysiologic Severity of Diabetic Neuropathy

OBJECTIVE

To investigate the impact of vascular factors on the electrophysiologic severity of diabetic neuropathy (DPN).

METHODS

Total 530 patients with type 2 diabetes were enrolled retrospectively. We rated severity of DPN from 1 (normal) to 4 (severe) based on electrophysiologic findings. We collected the data concerning vascular factors (including brachial-ankle pulse wave velocity [PWV], ankle brachial index, ultrasound of carotid artery, lipid profile from the blood test, and microalbuminuria [MU] within 24 hours urine), and metabolic factors of diabetes (such as glycated hemoglobin [HbA1c]). We analyzed the differences among the four subgroups using χ(2) test and ANOVA, and ordinal logistic regression analysis was performed to investigate the relationship between significant variables and severity of DPN.

RESULTS

The severity of DPN was significantly associated with duration of diabetes, HbA1c, existence of diabetic retinopathy and nephropathy, PWV, presence of plaque, low density lipoprotein-cholesterol and MU (p<0.05). Among these variables, HbA1c and presence of plaque were more significantly related with severity of DPN in logistic regression analysis (p<0.001), and presence of plaque showed the highest odds ratio (OR=2.52).

CONCLUSION

Our results suggest that markers for vascular wall properties, such as PWV and presence of plaque, are significantly associated with the severity of DPN. The presence of plaque was more strongly associated with the severity of DPN than other variables.

Impacts of elevated glycaemic haemoglobin and disease duration on the sensorimotor control of hands in diabetes patients

BACKGROUND

To understand the impacts of disease chronicity and hyperglycaemia on sensorimotor control of hands of diabetic patients, this study investigated the differences in hand sensation, strength and motor control by applying the pinch-holding-up activity test for patients with diabetes mellitus (DM) with different levels of glycaemic control and disease chronicity.

METHODS

One hundred and fifty-nine patients with clinically defined DM were included. Semmes-Weinstein monofilament, static two-point discrimination and moving two-point discrimination, maximal pinch strength precision pinch performance tests and nerve conduction studies (NCS) of the subjects were carried out. Forty-seven (29.6%) patients were in the HbA(1c) < 7% category, and 112 (70.4%) patients were in the >7% group. There were 87 (54.7%) patients with the disease duration <10 years, and 72 (45.3%) patients with disease duration ≧10 years.

RESULTS

The severity of hyperglycaemia significantly impacts the results for Semmes-Weinstein monofilament, precision pinch force control, sensory and motor NCS tests (p < 0.05). In addition, the chronicity of disease influences the motor control of precision pinch performance and the amplitude of motor NCS (p < 0.05) for the diabetes patients.

CONCLUSIONS

The evidence suggests that disease chronicity and hyperglycaemia have impacts on sensorimotor control in the hands of DM patients. In addition, the efficiency of prehensile forces of hand-to-object interactions in the pinch-holding-up activity test could be significant for identifying hand function, as well as pathologic changes in median nerve function, for patients with DM.

How the impact of median neuropathy on sensorimotor control capability of hands for diabetes: an achievable assessment from functional perspectives

To comprehend the sensorimotor control ability in diabetic hands, this study investigated the sensation, motor function and precision pinch performances derived from a pinch-holding-up activity (PHUA) test of the hands of diabetic patients and healthy subjects. The precision, sensitivity and specificity of the PHUA test in the measurements of diabetic patients were also analyzed. We hypothesized that the diabetic hands would have impacts on the sensorimotor functions of the hand performances under functionally quantitative measurements. One hundred and fifty-nine patients with clinically defined diabetes mellitus (DM) and 95 age- and gender-matched healthy controls were included. Semmes-Weinstein monofilament (SWM), static and moving two-point discrimination (S2PD and M2PD), maximal pinch strength and precision pinch performance tests were conducted to evaluate the sensation, motor and sensorimotor status of the recruited hands. The results showed that there were significant differences (all p<0.05) in SWM, S2PD, M2PD and maximum pinch strength between the DM and control groups. A higher force ratio in the DM patients than in the controls (p<0.001) revealed a poor ability of pinch force adjustment in the DM patients. The percentage of maximal pinch strength was also significantly different (p<0.001) between the DM and control groups. The sensitivity, specificity and area under the receiver operating characteristic curve were 0.85, 0.51, and 0.724, respectively, for the PHUA test. Statistically significant degradations in sensory and motor functions and sensorimotor control ability were observed in the hands of the diabetic patients. The PHUA test could be feasibly used as a clinical tool to determine the sensorimotor function of the hands of diabetic patients from a functional perspective.

Multichannel surface electrodes increase the sensitivity of diagnosis of neuropathy in diabetic patients

This prospective study investigated the diagnostic sensitivity of a novel multichannel surface electrode for detecting electrophysiologic changes in symptomatic diabetic neuropathy. We recruited healthy subjects without neuropathic complaints and diabetic patients with distal symmetric sensory symptoms who had normal nerve conduction studies (NCS). Eight compound muscle action potentials (CMAPs) were recorded using a multichannel electrode from each subject's abductor pollicis brevis muscle by stimulating the median nerve at the wrist. Latency- and amplitude-related variables were obtained and analyzed to compare the two groups. We used the Classification and Regression Tree (CART) algorithm to determine the cut-off values for selected predictors of diabetic neuropathy. All of the variables related to CMAP latency showed statistically significant differences between the median values for the diabetic group and the healthy control group. For example, the median value of the maximum latency and standard deviation of the eight CMAP onset latencies in diabetic patients (3.82ms and 0.15ms, respectively) were significantly larger than those in controls (3.26ms and p<0.001; 0.09ms and p<0.001, respectively). The CART analysis revealed that these variables were the most sensitive and specific variables for discriminating between patients with diabetic neuropathy and normal subjects. The multichannel surface electrode demonstrated both high sensitivity and specificity in detecting neurophysiologic abnormality of diabetic neuropathy, even when conventional NCS did not detect the abnormality.

Dosing pattern comparison between duloxetine and pregabalin among patients with diabetic peripheral neuropathic pain

OBJECTIVE

To compare medication dosing patterns of duloxetine and pregabalin among patients with diabetic peripheral neuropathic pain (DPNP).

METHODS

Applying a retrospective cohort study design on a large U.S. healthcare claims database, we examined the dosing patterns of duloxetine and pregabalin among commercially insured patients with DPNP aged 18 to 64 who initiated (a 90-day medication gap) duloxetine or pregabalin therapy in 2006. Selected patients had continuous enrollment during the 12-month pre- and post-index periods. The index mediation was used to classified individuals into the duloxetine or pregabalin cohorts. Initial daily dose, average daily dose over the first post-index year, and average daily dose of the first several prescriptions were estimated and compared across the cohorts.

RESULTS

The study sample included 828 duloxetine and 1934 pregabalin-treated patients with a mean age of 50 years. Cardiovascular diseases, neuropathic pain other than DPNP, osteoarthritis, and diabetic retinopathy were the most common comorbid conditions. The average initial daily doses were 54.3 and 171.8 mg for duloxetine and pregabalin, respectively. The average daily dose over the first post-index year was 55.2 mg for duloxetine and 173.8 mg for pregabalin. The average daily dose for the first 10 duloxetine prescriptions ranged between 54.3 and 61.9 mg, but increased from 171.8 to 264.3 mg for pregabalin.

CONCLUSIONS

The commercially insured patients with DPNP who initiated duloxetine or pregabalin therapy had different dosing patterns. The average daily dose for duloxetine was relatively stable over time, while pregabalin-treated patients had significant dose increase over the 12-month post-index period.

Subclinical neuropathy in diabetic patients: a risk factor for bilateral lower limb neurological deficit following spinal anesthesia?

Total knee arthroplasty performed under spinal or general anesthesia is a common successful orthopedic procedure. Nonetheless, in patients with diabetes mellitus this procedure can present unique challenges to orthopedic surgeon and anesthesiologist alike. We describe a case of an elderly male diabetic patient who developed bilaterally symmetrical lower limb neurological deficit following an uneventful total knee arthroplasty performed under spinal anesthesia. Postoperative nerve conduction study with electromyography confirmed symmetrical extensive denervation of lower limb muscles, including low-voltage fibrillation potentials and positive sharp waves. These findings were consistent with a preexisting neuropathy, thereby suggesting a subclinical neuropathy as a potential risk factor for this neurological complication. Our case highlights the fact that patients with longstanding comorbidities, namely peripheral vascular disease and diabetes mellitus, may be at an increased risk of neurological injury following regional anesthesia. Hence, we believe that preoperative evaluation of diabetic patients should include neurophysiological studies to identify subclinical neuropathy and minimize the risk of neurological injury.

Medication adherence and healthcare costs among patients with diabetic peripheral neuropathic pain initiating duloxetine versus pregabalin

OBJECTIVE

To examine the impact of medication choice between duloxetine or pregabalin on medication adherence and direct healthcare costs among patients with diabetic peripheral neuropathic pain (DPNP).

METHODS

A retrospective cohort study design was used with a large US national administrative claims database. Commercially-insured DPNP patients aged 18-64 years who initiated duloxetine or pregabalin in 2006 were selected, with the first initiation date as the index date. All selected patients had 12 months continuous enrollment in the pre- and post-index periods, and were grouped into the duloxetine or pregabalin cohort based on the index agent. The duloxetine and pregabalin cohorts were constructed via propensity score stratification with similar demographics, co-morbid medical conditions, pre-index healthcare utilization and costs, and prior treatment patterns. Medication possession ratio (MPR), proportion of patients with MPR ≥ 0.8 and healthcare costs over the 12-month post-index period were compared between cohorts.

RESULTS

Both the duloxetine (n = 794) and pregabalin (n = 1779) cohorts had a mean age of 56 years, and 58% of female. Common co-morbid conditions among duloxetine and pregabalin patients were cardiovascular disease (82.5 vs. 82.2%), neuropathic pain other than DPNP (71.1 vs. 72.7%), osteoarthritis (39.0 vs. 41.3%), and low back pain (29.4 vs. 30.5%). More than 73% of the patients had opioid use prior to the initiation of duloxetine or pregabalin. Among patients with similar demographic, clinical and economic characteristics, and prior treatment patterns, duloxetine-treated patients had significantly higher MPR (0.34 vs. 0.13), higher proportion of patients with MPR ≥ 0.8 (15.5 vs. 0.7%), and significantly lower total healthcare costs ($34,146 vs. 34,897) over the 12-month post-index period than pregabalin-treated patients (all p < 0.05).

CONCLUSIONS

Commercially-insured DPNP patients initiating duloxetine had significantly higher medication adherence and lower healthcare costs than those initiating pregabalin.

Intact cutaneous C fibre afferent properties in mechanical and cold neuropathic allodynia

Patients with neuropathy, report changes in sensory perception, particularly mechanical and thermal allodynia, and spontaneous pain. Similar sensory changes are seen in experimental neuropathies, in which alteration in primary afferent properties can also be determined. The neural correlate of spontaneous pain is ongoing activity in sensory afferents. Mechanical and heat allodynia are thought to result from lowered activation thresholds in primary afferent and/or central neurones, but the mechanisms underlying cold allodynia are very poorly understood.

We investigated nociceptive behaviours and the properties of C and A fibre intact afferents running adjacent to damaged afferents following a partial ligation injury of the saphenous nerve (PSNI). Animals developed mechanical and cold allodynia by 3 days after PSNI. Intact mechanosensitive C fibre afferents developed ongoing activity, and had slower conduction velocities 3 and 7 days following nerve injury, with no change in mechanical threshold. There was a large increase (∼46-fold) in calculated afferent input 3 days after nerve injury, as a result of the ongoing activity in these fibres. Mechano-cooling-sensitive C fibre afferents showed both enhanced cooling-evoked firing, and increased ongoing activity. The afferent barrage associated with mechano-cooling-sensitive afferents was increased 26-fold 7 days after nerve injury. We observed no differences in the properties of intact A fibre mechanosensitive afferents.

These studies demonstrate for the first time that the altered nociception seen after PSNI is associated with ongoing activity and enhanced cooling-evoked activity in intact C fibre afferents in the saphenous nerve, with no concurrent alteration in A fibre afferents.

Surrogate markers of small fiber damage in human diabetic neuropathy

Surrogate markers of diabetic neuropathy are being actively sought to facilitate the diagnosis, measure the progression, and assess the benefits of therapeutic intervention in patients with diabetic neuropathy. We have quantified small nerve fiber pathological changes using the technique of intraepidermal nerve fiber (IENF) assessment and the novel in vivo technique of corneal confocal microscopy (CCM). Fifty-four diabetic patients stratified for neuropathy, using neurological evaluation, neurophysiology, and quantitative sensory testing, and 15 control subjects were studied. They underwent a punch skin biopsy to quantify IENFs and CCM to quantify corneal nerve fibers. IENF density (IENFD), branch density, and branch length showed a progressive reduction with increasing severity of neuropathy, which was significant in patients with mild, moderate, and severe neuropathy. CCM also showed a progressive reduction in corneal nerve fiber density (CNFD) and branch density, but the latter was significantly reduced even in diabetic patients without neuropathy. Both IENFD and CNFD correlated significantly with cold detection and heat as pain thresholds. Intraepidermal and corneal nerve fiber lengths were reduced in patients with painful compared with painless diabetic neuropathy. Both IENF and CCM assessment accurately quantify small nerve fiber damage in diabetic patients. However, CCM quantifies small fiber damage rapidly and noninvasively and detects earlier stages of nerve damage compared with IENF pathology. This may make it an ideal technique to accurately diagnose and assess progression of human diabetic neuropathy.

Electrophysiological findings of acute peripheral facial palsy in diabetic and non-diabetic patients

The aim of this study is to investigate the role of diabetes mellitus on the clinical and electrophysiological findings of peripheral facial palsy (PFP), the effect of the diabetes duration and polyneuropathy on the electrophysiological parameters. A total of 32 diabetic and 40 non-diabetic patients with peripheral facial palsy were included. All patients were divided into two subgroups based on the time of electrophysiological examinations: within the first 15 days versus within 16-30 days. Neuropathy symptoms and the results of neurological examinations and electrophysiological findings were recorded. The findings of electroneurography (EnoG), blink reflex (BR) evaluation, and needle electromyography (EMG) indicated statistically significant blink reflex abnormalities in diabetic patients compared to non-diabetics. Delay in the latency was more remarkable in the R2 component than in the R1 (p<0.001). The delay in the R1 latency was also observed in the non-affected side for diabetic patients. The longer duration of the diabetes caused significant delay on the blink reflex latency on both the affected and non-affected sides for R1 component (p=0.019, p=0.041, respectively). In contrary, neither the diabetes duration nor the age of the patients correlated with the clinical severity of facial palsy, fiber loss, fibular nerve compound muscle action potential amplitudes, and the nerve conduction velocities.

Conduction velocity distribution in neurologically well-recovered but fatigued Guillain–Barré syndrome patients

Many patients with Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP) suffer from excessive fatigue. To assess whether this fatigue might be related to changes in slow-conducting nerve fibers, we determined the conduction velocity distribution (CVD) in the median nerve. Thirteen fatigued but neurologically well-recovered GBS patients, 2 fatigued and stable CIDP patients, and 19 healthy controls participated in this study. Conventional maximal nerve conduction velocities (NCVs) did not show differences between GBS patients and healthy controls. However, in both GBS and CIDP patients the CVD was altered, showing significant narrowing of the velocity distribution with loss of the fastest- and slowest-conducting fibers. These changes were most pronounced in the subgroup of patients with the lowest fatigue scores. We therefore conclude that the observed CVD changes in patients are not likely to contribute to persisting complaints of fatigue after GBS.

Recent developments in the assessment of efficacy in clinical trials of diabetic neuropathy

A large number of measures may be employed in clinical practice and for epidemiologic studies to quantify and risk stratify diabetic patients with neuropathy. However, not all measures are suitable for assessing the benefits of therapeutic intervention. Therefore, for the purpose of this review we focus on measures that may be employed to define the efficacy of interventions in clinical trials of human diabetic neuropathy. Two major types of end points are used: 1) those that assess symptoms for defining efficacy in painful diabetic neuropathy, and 2) those that assess neurologic deficits that assess the effects of treatments that may prevent further degeneration or promote repair.

Electrophysiologic measures of diabetic neuropathy: mechanism and meaning

Whole nerve electrophysiologic procedures afford a battery of measures that can provide a noninvasive and objective index of the onset and progression of diabetic polyneuropathy (DPN). Advances in physiologic procedures, digital hardware, and mathematical models have allowed assessment of activity in slower conducting fibers, as well as measures that reflect changes in refractory periods and threshold excitability. These expanded options can augment standard measures of maximal conduction velocity and compound amplitude and greatly enhance the sensitivity of whole nerve measure to both structural (e.g. demyelination) and "nonstructural" (e.g. redistribution of ion channels) deficits associated with DPN. The mechanisms underlying the physiologic events in DPN are multifactorial and their sequence in complex, with different mechanisms contributing to change at overlapping, but distinct points in the progression. Factors influencing early change in velocity may differ from those contributing to chronic deficits and these mechanisms may also differ in their response to various putative therapies. This review attempts to summarize the pattern of whole nerve electrophysiologic change associated with DPN, outlines the strengths and limitations of the various measures that are feasible, and discusses the specific impact of know pathophysiologic mechanisms on these end points.

Measurement of somatic neuropathy for clinical practice and clinical trials

Distal sensory polyneuropathy is a common and unpleasant complication of diabetes mellitus. It is the main initiating factor for foot ulceration. The increasing prevalence of diabetes has important associated health implications, both in terms of morbidity and mortality, and results in the consumption of scarce medical resources. Identification of somatic neuropathy in clinical practice is therefore important for targeted educational and other interventions. In this article, we describe methods for detecting somatic neuropathy in clinical practice and highlight those tests that are proven to be predictors of foot ulceration. The approach for detecting and characterizing somatic neuropathy for clinical trials, however, differs significantly. These methods must ideally have high levels of reproducibility, sensitivity, and specificity. Currently, several neurophysiologic tests are employed in clinical trials in order to accurately characterize diabetic neuropathy. The recent introduction of the computer-assisted programs for the measurement of sensory modalities for clinical trials has been a major advance. Due to their invasive nature and associated morbidity, nerve biopsy studies are no longer used in clinical trials. Recently, using magnetic resonance imaging (MRI), significant spinal cord atrophy has been demonstrated in established neuropathy. If this observation proves to be an early feature, then a relatively rapid, noninvasive MRI technique may be used in the future to characterize diabetic neuropathy.

Assessment of temporal dispersion in motor nerves with normal conduction velocity

Demyelinated nerves attenuate high-frequency components of propagating action potentials. In order to study if there is diagnostic use of this in motor nerves, the spectral energy above 49 Hz, amplitude, area, and duration of the compound muscle action potentials were measured; values after distal and proximal stimulation of posterior tibial nerves were compared. Normative data were collected in 48 control subjects. The same measurements were made in 20 patients with polyneuropathy and reduced motor nerve conduction velocity, in 21 patients with mild polyneuropathy but normal motor nerve conduction velocity, and in 8 patients with myasthenia gravis. Overall, high-frequency attenuation was closely correlated with amplitude decay (r = 0.63, P<10(-19)) and with increase of action potential duration (r = 0.34, P = 10(-5)). In the group of patients with normal NCV, high-frequency attenuation was abnormal in 9 (43%), amplitude decay was abnormal in two (10%), and area decay was abnormal in one (5%) patient. The action potential duration was normal in all of these patients. High-frequency attenuation was not influenced by stimulus intensity, thus it is not changed by conduction block, and it was not influenced by impaired neuromuscular transmission. Hence, high-frequency attenuation, both sensitively and specifically does indicate abnormal temporal dispersion. In conclusion, the simple measurement of high-frequency attenuation markedly improves detection and characterization of demyelination of human motor fibers.