Chronic dizziness in older adults: Disrupted sensorimotor EEG beta oscillations during postural instability

Objective: Chronic dizziness is common in older adults, yet frequently occurs without a clear cause ('idiopathic dizziness'). Patients experience subjective unsteadiness with minimal objective imbalance, potentially related to small vessel disease. Here we examine the hypothesis that this syndrome is associated with disrupted cortical processing of postural instability. Methods: EEG and postural sway were recorded in 33 older adults with chronic, idiopathic dizziness (Age, Mean = 77.3 years, SD = 6.4, 61 % female) and 25 matched controls (Age, Mean = 76.9 years, SD = 6.0, 56 % female). EEG was time-locked to spontaneous instances of postural instability and analysed via time-frequency decomposition. Results: Significant between-group differences in EEG were observed during the early phase of postural instability (p < 0.05, cluster-corrected). Whilst controls exhibited broadband increase in EEG power across sensorimotor areas, dizzy patients displayed suppressed beta activity (19-24 Hz). Contrary to predictions, these differences did not relate to small vessel disease markers (rs < 0.05, ps > 0.720) but to fear of falling (r = -0.44, p = 0.001). Conclusions: Previous work implies that suppressing cortical beta enhances the relay of sensory information. We therefore propose that the modulation in beta EEG observed in patients reflects an anxious, top-down strategy to increase sensitivity to instability, which paradoxically causes persistent feelings of subjective imbalance. Significance: These results identify associations between idiopathic dizziness and disrupted sensorimotor beta activation during postural instability. Cortical beta during imbalance may be a possible biomarker of chronic, idiopathic dizziness in older adults and/or fear of falling.