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.