BACKGROUND: Mal de debarquement syndrome (MdDS) is a disorder of chronic 
self-motion perception that occurs though entrainment to rhythmic background 
motion, such as from sea voyage, and involves the perception of low-frequency 
rocking that can last for months or years. The neural basis of this persistent 
sensory perception abnormality is not well understood.
METHODS: We investigated grey matter volume differences underlying persistent 
MdDS by performing voxel-based morphometry on whole brain and pre-specified ROIs 
in 28 individuals with MdDS and comparing them to 18 age, sex, and handedness 
matched controls.
RESULTS: MdDS participants exhibited greater grey matter volume in the left 
inferior parietal lobule, right inferior occipital gyrus (area V3v), right 
temporal pole, bilateral cerebellar hemispheric lobules VIII/IX and left lobule 
VIIa/VIIb. Grey matter volumes were lower in bilateral inferior frontal, 
orbitofrontal, pregenual anterior cingulate cortex (pgACC) and left superior 
medial gyri (t = 3.0, p<0.005uncorr). In ROI analyses, there were no volume 
differences in the middle occipital gyrus (region of V5/MT) or parietal 
operculum 2 (region of the parietoinsular vestibular cortex). Illness duration 
was positively related to grey matter volume in bilateral inferior frontal 
gyrus/anterior insula (IFG/AI), right posterior insula, superior parietal 
lobule, left middle occipital gyrus (V5/MT), bilateral postcentral gyrus, 
anterior cerebellum, and left cerebellar hemisphere and vermian lobule IX. In 
contrast, illness duration was negatively related to volume in pgACC, posterior 
middle cingulate gyrus (MCC), left middle frontal gyrus (dorsolateral prefrontal 
cortex-DLPFC), and right cerebellar hemispheric lobule VIIIb (t = 3.0, 
p<0.005uncorr). The most significant differences were decreased volume in the 
pgACC and increased volume in the left IFG/AI with longer illness duration 
(qFDRcorr <0.05). Concurrent medication use did not correlate with these 
findings or have a relationship with duration of illness. MdDS participants 
showed positive correlations between grey matter volume in pgACC and bilateral 
cerebellar lobules VIII/IX, which was not seen in controls.
CONCLUSIONS: Individuals with MdDS show brain volume differences from healthy 
controls as well as duration of illness dependent volume changes in (a) 
visual-vestibular processing areas (IPL, SPL, V3, V5/MT), (b) default mode 
network structures (cerebellar IX, IPL, ACC), (c) salience network structures 
(ACC and IFG/AI) (d) somatosensory network structures (postcentral gyrus, MCC, 
anterior cerebellum, cerebellar lobule VIII), and (e) a structure within the 
central executive network (DLPFC). The identification of these associations may 
enhance future investigations into how exposure to oscillating environments can 
modulate brain function and affect motion perception as well cognitive and 
affective control.