Reduced cortical folding in multi-modal vestibular regions in persistent postural perceptual dizziness

Persistent postural perceptual dizziness (PPPD) is a common functional vestibular disorder that is triggered and sustained by a complex interaction between physiological and psychological factors affecting spatial orientation and postural control. Past functional neuroimaging research and one recent structural (i.e., voxel-based morphometry-VBM) study have identified alterations in vestibular, visuo-spatial, and limbic brain regions in patients with PPPD and anxiety-prone normal individuals. However, no-one thus far has employed surface based morphometry (SBM) to explore whether cortical morphology in patients with PPPD differs from that of healthy people. We calculated SBM measures from structural MR images in 15 patients with PPPD and compared them to those from 15 healthy controls matched for demographics, personality traits known to confer risk for PPPD as well as anxiety and depressive symptoms that are commonly comorbid with PPPD. We tested for associations between SBM measures and dizziness severity in patients with PPPD. Relative to controls, PPPD patients showed significantly decreased local gyrification index (LGI) in multi-modal vestibular regions bilaterally, specifically the posterior insular cortices, supra-marginal gyri, and posterior superior temporal gyri ( p < 0.001). Within the PPPD group, dizziness severity positively correlated with LGI in visual areas and negatively with LGI in the right superior parietal cortex. These findings demonstrate abnormal cortical folding in vestibular cortices and correlations between dizziness severity and cortical folding in visual and somatosensory spatial association areas in PPPD patients, which provides new insights into the pathophysiological mechanisms underlying this disorder.