Cognitive function in individuals with and without painful and painless diabetic polyneuropathy—A cross‐sectional study in type 1 diabetes

Abstract Introduction Previous studies suggest that cognitive impairment is more prevalent in individuals with painful and painless diabetic peripheral neuropathy (DPN). However, the current evidence is not well described. This study investigated cognitive function in adults with type 1 diabetes mellitus (T1DM) and the association to painful/painless DPN and clinical parameters. Methods This cross‐sectional, observational, case–control study included 58 participants with T1DM, sub‐grouped into 20 participants with T1DM and painful DPN, 19 participants with T1DM and painless DPN, 19 participants with T1DM without DPN, and 20 healthy controls were included. The groups were matched for sex and age. The participants performed Addenbrooke's examination III (ACE‐III), which assesses attention, memory, verbal fluency, language and visuospatial skills. Working memory was evaluated using an N‐back task. Cognitive scores were compared between the groups and correlated to age, diabetes duration, HbA1c and nerve conduction measurements. Results Compared to healthy controls, T1DM participants showed lower total ACE‐III (p = .028), memory (p = .013) and language scores (p = .028), together with longer reaction times in the N‐back task (p = .041). Subgroup analyses demonstrated lower memory scores in those with painless DPN compared with healthy controls (p = .013). No differences were observed between the three T1DM subgroups. Cognitive scores and clinical parameters were not associated. Conclusions This study supports the notion of cognitive alterations in T1DM and indicates that cognitive function is altered in T1DM regardless of underlying neuropathic complications. The memory domain appears altered in T1DM, particularly in those with painless DPN. Further studies are needed to verify the findings

Alterations in functional connectivity of thalamus and primary somatosensory cortex in painful and painless diabetic peripheral neuropathy.

   Objective: This study aimed to investigate the functional connectivity of brain regions involved in sensory processing in diabetes with and without painful and painless diabetic peripheral neuropathy (DPN) and the association to peripheral nerve function and pain intensity. Research Design and Methods: This cross-sectional study utilized resting-state functional magnetic resonance imaging (MRI) to investigate functional brain connectivity of 19 individuals with type 1 diabetes and painful DPN, 19 with type 1 diabetes and painless DPN, 18 with type 1 diabetes without DPN, and 20 healthy controls. Seed-based connectivity analyses were performed for thalamus, postcentral gyrus, and insula and the connectivity z-scores were correlated to peripheral nerve function measurements and pain scores.  Results: Overall, compared to those with painful DPN and healthy controls, type 1 diabetes without DPN showed hyperconnectivity between thalamus and motor areas and between postcentral gyrus and motor areas (all p≤0.029). Poorer peripheral nerve functions and higher pain scores were associated with lower connectivity of the thalamus and postcentral gyrus (all p≤0.043). No connectivity differences were found in insula (all p≥0.071). Conclusions: Higher functional connectivity of thalamus and postcentral gyrus appeared only in diabetes without neuropathic complications. Thalamic/postcentral gyral connectivity measures demonstrated an association with peripheral nerve functions. Based on thalamic connectivity, it was possible to distinguish between type 1 diabetes with painful/painless DPN and type 1 diabetes without DPN. The current study supports that functional MRI can be used for phenotyping and, if validated, it may contribute to early detection and prevention of neuropathic complications.</p