Thalamic Connectivity With Pain-Specific Brain Regions Reduced Among Patients With Small-Fiber Neuropathy

Alterations in structural brain connectivity may be a biomarker for neuropathic pain, according to results of a study published in the journal Pain.

Patients (n=41) diagnosed with small-fiber neuropathy (SFN) between 2011 and 2016 at the National Taiwan University Hospital and healthy control group participants (n=30) were recruited for this study. Participants underwent brain magnetic resonance imaging scans.

Patients and control group participants had a mean age of 53.0±13.4 and 47.0±16.3 years and 68.3% and 66.7% were women, respectively. Among the patient group, most had idiopathic neuropathy (68.3%), 63.4% reported tingling and 63.4% reported numbness, and their average pain score, out of 10, was 6.15±2.23 points.

White matter connectivity was reduced between the thalamus and left precentral gyrus (P =.0004), right postcentral gyrus (P =.004), and left insular cortex (P =.030) among the patients with SFN.

Stratified by pain-specific phenotypes and compared with control group participants, patients with burning pain had reduced white matter connectivity between the thalamus and left precentral gyrus (P =.004) and left anterior cingulate cortex (P =.016) and those with feelings of electrical shock, tingling pain, mechanical allodynia, and numbness had reduced connectivity with left precentral gyrus (all P £.010).

Patients with burning pain, as compared with patients without burning pain, exhibited greater thalamic connectivity with left supramarginal gyrus (P =.004) and left postcentral gyrus (P =.030).

Compared with age-matched control group participants, patients with SFN had reduced intraepidermal nerve fiber density (IENFd). IENFd was correlated with the thalamic connectivity with the left precentral gyrus (P =.006) and right posterior cingulate cortex (P =.047) among patients with SFN.

Among patients with burning pain, IENFd correlated with white matter thalamic connectivity with left middle frontal gyrus (P =.018) and left precentral gyrus (P =.015), with right anterior cingulate cortex (P =.023) among patients with electric shock-like pain, with left precentral gyrus (P =.016) and right posterior cingulate cortex (P =.022) among patients with tingling pain, with left precentral gyrus (P =.017) and right posterior cingulate cortex (P =.037) for patients with mechanical allodynia, and with left precentral gyrus (P =.019) among patients with numbness.

The thalamic connectivity with the left putamen (P =.041) was associated with pain intensity scores.

This study may have been limited by the choice to use specific pain phenotypes as binary measurements instead of incorporating an intensity component.

These data indicated white matter connectivity between the thalamus and pain-specific brain regions were reduced among patients with SFN. Connectivity with specific brain regions correlated with pain phenotypes.

Reference

Chao CC, Tseng MT, Lin YH, et al. Brain imaging signature of neuropathic pain phenotypes in small-fiber neuropathy: altered thalamic connectome and its associations with skin nerve degeneration. Pain. 2021;162(5):1387-1399. doi:10.1097/j.pain.0000000000002155