Functional and anatomical brain connectivity in psoriasis patients and healthy controls: a pilot brain imaging study after exposure to mentally induced itch

Abstract

Background Despite the prevalence of psoriasis, the processing of itch in psoriasis and its impact on the central nervous system (CNS) remain unclear. Objective We studied the influence of psoriasis on the CNS using magnetic resonance imaging techniques (fMRI and DTI, respectively) to investigate whether mentally induced itch can modify the functional connectivity or the white matter microstructure of the brain. Methods Fourteen patients with chronic psoriasis and 15 healthy controls were recruited. Itch was mentally induced in subjects by videos showing others scratching themselves. Results The observation of functional connectivity during viewing the video revealed an interconnected network of brain regions that are more strongly coupled in psoriasis patients than in healthy controls. This network links the cerebellum, the thalami, the anteroposterior cingulum, the inferior parietal lobules, the middle temporal poles and the parahippocampal, hippocampal, lingual and supramarginal gyri. We also found connections with the right precuneus and both left insula and superior temporal gyrus. The DTI analysis showed that chronic itch affects the microstructure of white matter, including the anterior thalamic radiations, the superior and inferior longitudinal fasciculi, the corticospinal tracts, the cingulum, the external capsules, the inferior frontal-occipital fasciculi and both minor and major forceps. Conclusion Our results indicate that there could exist a network which is more interconnected in psoriasis patients. Among two building blocks of this network, the subnetwork encoding the perception and control of itch sensation is more affected than the subnetwork representing mentalizing and empathy. With an approach consisting of measuring microstructural changes at a local level in the brain, we also contradict the findings obtained with global measures which stated that chronic psoriasis cannot alter the anatomy of the brain. This confirms that itchy pathophysiological conditions have similar effects on functional and structural connectivity as those observed in chronic pain.

Itch processing in the brain

“…96 By using other regions as seed regions, they have shown that resting-state functional connectivity between the right putamen and left precentral gyrus and between the right ventral striatum and right occipital cortex has increased. 97 In a recent study of our group, 94 we have observed that the psoriasis patients have different perception of audiovisual itch compared with the healthy control. In that study, we have shown that there is an interconnected network of regions in brain which is more connected in psoriasis patients compared with healthy control group, and this network consists of regions in cingulate cortex (PCC, ACC), parietal lobe (supramarginal gyrus and inferior parietal lobe), insular cortex, thalamus, temporal pole and cerebellum.…”

“…Newer studies suggest that the perception of itch can be different between patients with itch diseases and healthy subjects, which could be a direct result of the disease or could be traced back to differences in past experiences regarding itch and scratching. Recently, an increasing number of studies have been interested in understanding the central mechanisms of itch in different diseases, like AD, 42,68,83,83,[89][90][91] lichen simplex chronicus, 92 prurigo nodularis, 92 end-stage renal disease, 69 primary biliary cholangitis, 93 psoriasis, 94 diabetes 95 and chronic spontaneous urticaria. 96,97 Ishiuji et al 89 studied AD and showed that changes in the brain activation of the dlPFC and ACC were correlated with Eczema Area and Severity Index (EASI) scores, while the ACC and insular cortex were correlated with induced itch.…”

New Frontiers in Psoriatic Disease Research, Part II: Comorbidities and Targeted Therapies

“…Psoriatic itch may actually induce microstructural changes in the brain. A recent study showed that patients with psoriasis who were exposed to videos of other individuals scratching exhibited changes in the white matter and functional connectivity of their brains (Najafi et al, 2020). Furthermore, regions of the brain that were shown to have higher connectivity in these patients included the bilateral cingulate gyri as well as the insula, regions known to be involved in the stress response (Golpanian et al, 2020).…”

Dermato‐venereology in the year of coronavirus – Hot topics in research and patient care

“…Brain–skin interactions are a major focus of research in the field of pruritus. In a study on mentally induced itch (by watching a video of scratching persons), patients with psoriasis showed a significantly higher intra‐brain connectivity compared to healthy controls 24 …”