Altered spontaneous functional activity of the right precuneus and cuneus in patients with persistent postural-perceptual dizziness

Persistent postural-perceptual dizziness (PPPD) is a functional vestibular disorder, and is the most common cause of chronic vestibular syndrome. However, the pathogenesis of PPPD is currently unclear. This study aimed to analyze the changes of brain spontaneous functional activities in PPPD patients during the resting state, and to explore the underlying pathogenesis of PPPD, particularly the abnormal integration of visual and vestibular information. Ten PPPD patients and 10 healthy controls were enrolled from January to June 2018, and baseline data were collected from all subjects. Videonystagmography (VNG), the vestibular caloric test, the video head impulse test (vHIT) and vestibular evoked myogenic potentials (VEMPs) were measured to exclude peripheral vestibular lesions. Functional MRI (fMRI) was conducted in PPPD patients and healthy controls. The amplitude of low frequency fluctuation (ALFF) and regional homogeneity (ReHo), and functional connectivity were calculated to explore changes in brain spontaneous functional activity during the resting state. Compared with healthy controls, ALFF and ReHo values in the right precuneus and cuneus were significantly lower in PPPD patients (both P < 0.05). Further seed-based functional connectivity analysis showed decreased functional connectivity between precuneus, cuneus and left precentral gyrus ( P < 0.05). Our findings suggest that the spontaneous functional activity of cuneus and precuneus in PPPD patients were altered, potentially leading to abnormal integration of visual and vestibular information. Weakened functional connectivity between the precuneus and the precentral gyrus may be associated with aggravated symptoms during upright posture, active or passive movements.