Identifying Peripheral Neuropathy in Colour Fundus Photographs Based on Deep Learning

The aim of this study was to develop and validate a deep learning-based system to detect peripheral neuropathy (DN) from retinal colour images in people with diabetes. Retinal images from 1561 people with diabetes were used to predictDN diagnosed on vibration perception threshold. A total of 189 had diabetic retinopathy (DR), 276 had DN, and 43 had both DR and DN. 90% of the images were used for training and validation and 10% for testing. Deep neural networks, including Squeezenet, Inception, and Densenet were utilized, and the architectures were tested with and without pre-trained weights. Random transform of images was used during training. The algorithm was trained and tested using three sets of data: all retinal images, images without DR and images with DR. Area under the ROC curve (AUC) was used to evaluate performance. The AUC to predict DN on the whole cohort was 0.8013 (±0.0257) on the validation set and 0.7097 (±0.0031) on the test set. The AUC increased to 0.8673 (±0.0088) in the presence of DR. The retinal images can be used to identify individuals with DN and provides an opportunity to educate patients about their DN status when they attend DR screening.

Obesity and decreased vibration perception associated with premature cardiovascular mortality in a single center prospective study of people with diabetes

Background and aims The aim of this prospective, single center study was to define factors associated with early cardiovascular mortality in diabetes. Materials and methods 1345 patients under age 75 were included who were undergoing assessment of their diabetes between January 2008 and May 2010 as part of standard practice in a specialist clinic at a regional teaching hospital in Serbia. Peripheral artery disease (PAD) was assessed by audible Doppler waveform and ABPI with cut-offs >1.4 and <0.9. Peripheral neuropathy was assessed by vibration perception threshold (VPT, using a semi-quantitative tuning fork: abnormal if ≤5), ankle reflexes (AR) and sudomotor function of the foot. Diabetic retinopathy (DR) was assessed by fundoscopy. Evidence of vascular disease: thromboendarterectomy and/or cerebrovascular insult (TEA/CVI), myocardial infarction (MI), heart failure (HF), diabetic foot ulcer (DFU), minor amputations (sAMP) and major amputations (mAMP) was also collected. Outcome was determined in 2021 and baseline characteristics were compared between those who had and had not suffered cardiovascular death under age 75 years within 10 years of review in two casually selected cohorts. Results Those who died (n2=70) were more frequently male (60 vs. 45.3%, p=0.08), younger (66.4±7.4 vs. 79.9±3.4, p<0.000), had a shorter period of follow-up (3.6±2.3 vs. 11.2±1.7 years, p<0.000) when compared to those still alive (n1=75). Those who died were also significantly (p<0.01) more likely to have had TEA/CVI (34.3 vs. 10.7%), HF (21.4 vs. 1.3%), MI (44.3 vs. 20%), PAD (48.6 vs. 9.3%), DFU (25.7 vs. 9.3%), mAMP (17.1 vs. 1.3%) at baseline. There were no differences in proliferative DR (17.1 vs. 8%, p=0.10) and laser photocoagulation (25.7 vs. 13.3%, p=0.06) Following multivariable logistic regression analysis significant differences between groups remained for only creatinine (123±45 vs. 88.9±16.9 mmol/L, p<0.003) and VPT <5 (7.8 [95% CI: 3.7–16.4)], p=0.008), estimated maximum lifetime BMI (3.4 [95% CI: 1.7–6.8)], p<0.000), alcohol usage (4.7 [95% CI: 1.5–14.7)], p=0.005), smoking habit (2.2 [95% CI: 1.1–4.3)], p<0.03) and earlier age of diabetes onset (43.4±12.5 vs. 49.2±9.9, p=0.0029). When the 72 patients with impaired vibration sense were compared with 73 with VPT>6, there were significant differences in TEA/CVI (4.2 [95% CI: 1.6–10.9)], p=0.003), PAD (3.9 [95% CI: 1.8–8.8)], p<0.001) and estimated maximum lifetime BMI (9.4 [95% CI: 3.4–25.7), p<0.000). Finally, when those who had had a previous MI at baseline (n=46) were compared with those who hadn't (n=99), MI was associated with increased death rate (3.2 [95% CI: 1.5–6.6)], p=0.002), as was PAD (2.9 [(1.3–6.1)], p=0.007). Conclusion Decreased VPT, the presence of PAD on clinical testing and higher maximum estimated lifetime BMI are strongly associated with premature cardiovascular death. These measures may be independent markers of greater risk of reduced life expectancy. FUNDunding Acknowledgement Type of funding sources: None.

Distal Corneal Small Nerve Fibre Damage in Subjects With Obesity

Background: We have previously shown that subjects with obesity have elevated vibration and thermal perception thresholds and central corneal nerve loss and patients with diabetic neuropathy have greater corneal nerve loss at the inferior whorl compared to the central cornea. In the current study, we assessed whether there is evidence for a dying-back neuropathy in subjects with obesity with and without diabetes. Methods: 57 obese subjects, with and without diabetes (DM+, n=30; DM-, n=27 respectively) and age- and sex‑matched controls (n=21) underwent venous blood sampling and assessment of the neuropathy symptom profile (NSP), neuropathy disability score (NDS), vibration, cold and warm threshold testing, cardiac autonomic function, and corneal confocal microscopy (CCM).Results: NSP and NDS were significantly elevated in obese DM+ (p<0.0001; p=0.001) and DM- (p<0.0001; p=0.001) subjects compared to controls. Vibration perception threshold was significantly higher in DM+ (p=0.001), but not in DM- (p=0.06), compared to controls, whilst cold (p = 0.87) and warm (p = 0.52) perception thresholds did not differ between groups. Deep breathing heart rate variability was significantly lower in DM+ (p=0.01), but not DM- (p=0.9) subjects compared to controls. Corneal nerve fibre density [26.8 ±6.22 vs 26.8 ±6.01 vs 35.3 ±7.41, p<0.0001], branch density [55.4 ±28.2 vs 58.4 ±28.5 vs 88.2 ±31.1, p<0.001], fibre length (CNFL) [17.6 ±4.43 vs 19.9 ±5.43 vs 26.7 ±5.31, p <0.0001], inferior whorl length (IWL) [17.9 ±6.10 vs 18.6 ±7.42 vs 35.3 ±9.70, p<0.0001] and total nerve fibre length (TNFL) [35.5 ±9.58 vs 38.5 ±11.0 vs 62.0 ±12.3, p<0.0001] were significantly lower in obese subjects without and with diabetes compared to controls. In comparison to controls, there was a greater relative reduction in IWL compared to CNFL in DM+ (47.3% vs 25.5%) and DM- (49.3% vs 34.1%).Conclusion: We demonstrate evidence of peripheral neuropathy characterised by neuropathic symptoms, neurological deficits, elevated vibration perception and autonomic dysfunction with a dying-back neuropathy affecting the corneal nerves in obese subjects with and without type 2 diabetes.

Frequency dependence of vertical whole-body vibration perception - is your car rattling or humming?

Humans perceive whole-body vibration in many daily life situations. Often they are exposed to whole-body vibration in combination with acoustic events. Sound and vibration usually stems from the same source, for example concerts or travelling in vehicles, such as automobile, aircrafts, or ships. While we can describe acoustic stimuli using psychoacoustic descriptors such as loudness or timbre, the description human perception of whole body vibration frequently has been reduced to comfort or quality in the past. Unlike loudness or timbre, comfort and quality are dependent on the overall context. Especially in vehicles expectations might differ lot between different vehicle classes. Previous studies have evaluated a large range of suitable descriptors for whole-body vibrations that are independent of context. They suggest that certain descriptors are driven to a large extend by the frequency content of the vibration. This study systematically investigates the influence of frequency content on the perception of whole-body vibration varying frequency content and intensity of the vibrations. The results verify the frequency dependence of specific descriptors and identify the respective frequency ranges.

Vibration Perception Thresholds of Skin Mechanoreceptors Are Influenced by Different Contact Forces

Determining vibration perception thresholds (VPT) is a central concern of clinical research and science to assess the somatosensory capacity of humans. The response of different mechanoreceptors to an increasing contact force has rarely been studied. We hypothesize that increasing contact force leads to a decrease in VPTs of fast-adapting mechanoreceptors in the sole of the human foot. VPTs of 10 healthy subjects were measured at 30 Hz and 200 Hz at the heel of the right foot using a vibration exciter. Contact forces were adjusted precisely between 0.3 N–9.6 N through an integrated force sensor. Significant main effects were found for frequency and contact force. Furthermore, there was a significant interaction for frequency and contact force, meaning that the influence of an increasing contact force was more obvious for the 30 Hz condition. We presume that the principles of contrast enhancement and spatial summation are valid in Meissner and Pacinian corpuscles, respectively. In addition to spatial summation, we presume an effect on Pacinian corpuscles due to their presence in the periosteum or interosseous membrane.

Low and High Frequency Vibration Perception Thresholds Can Improve the Diagnosis of Diabetic Neuropathy

Recent studies demonstrate neuropathic changes with respect to vibration sensitivity for different measurement frequencies. This study investigates the relationship between vibration perception thresholds (VPTs) at low and high frequencies at two plantar locations and diabetic peripheral neuropathy (DPN) severity in diabetes mellitus (DM) subjects with DPN. We examine differences of VPTs between participants with DM, with DPN, as well as healthy controls. The influence of anthropometric, demographic parameters, and DM duration on VPTs is studied. Thirty-three healthy control group subjects (CG: 56.3 ± 9.9 years) and 33 with DM are studied. DM participants are subdivided into DM group (DM without DPN, n = 20, 53.3 ± 15.1 years), and DPN group (DM with DPN, n = 13, 61.0 ± 14.5 years). VPTs are measured at the first metatarsal head (MTH1) and heel (30 Hz, 200 Hz), using a customized vibration exciter. Spearman and Pearson correlations are used to identify relationships between VPTs and clinical parameters. ANOVAs are calculated to compare VPTs among groups. Significant correlations are observed between DPN severity (by fuzzy scores) and VPTs at both locations and frequencies (MTH1_30 Hz vs. fuzzy: r = 0.68, p = 0.011; Heel_30 Hz vs. fuzzy: r = 0.66, p = 0.014; MTH1_200 Hz vs. fuzzy: r = 0.73, p = 0.005; Heel_200 Hz vs. fuzzy: r = 0.60, p = 0.032). VPTs in CG and DM groups are significantly smaller than the DPN group, showing higher contrasts for the 30 Hz compared to the 200 Hz measurement. The correlations between fuzzy scores and VPTs confirm the relevance of using low and high frequencies to assess a comprehensive foot sensitivity status in people with DM.

Vibration Perception Threshold and Related Factors for Balance Assessment in Patients with Type 2 Diabetes Mellitus

Diabetic peripheral neuropathy (DPN) is a common complication of type 2 diabetes mellitus (DM). DPN causes a decrease in proprioception, which could reduce balance ability. We investigated the association of impaired vibration sense, based on vibration perception threshold (VPT), with assessments of balance and other factors affecting balance impairment and fear of falling in patients with type 2 DM. Sixty-three patients with DM aged >50 years were categorized as having normal vibration sense (NVS; n = 34) or impaired vibration sense (IVS; n = 29) according to a VPT value of 8.9 μm. The following parameters were evaluated for all patients: postural steadiness through the fall index using posturography, functional balance through the Berg Balance Scale (BBS), the Timed Up and Go test (TUG), and fear of falling through the Falls Efficacy Scale-International (FES-I). The IVS group showed a significantly greater balance impairment in fall index, BBS, and TUG, as well as greater fear of falling on the FES-I than the NVS group. The linear regression analysis showed that the fall index was associated only with the VPT, whereas BBS, TUG, and FES-I were associated with the VPT, age, and/or lower extremity muscle strength. VPT, age, and/or muscle strength were identified as predictors of balance and fear of falling in patients with type 2 DM. Therefore, along with age and lower extremity strength, the VPT can be useful for balance assessment in patients with type 2 DM.