Cortical activation and postural instability according to dizziness severity: A functional near-infrared spectroscopy...

Dizziness is a common clinical symptom that negatively affects balance, spatial orientation, and quality of life. While peripheral vestibular dysfunction has been widely studied, the central cortical mechanisms underlying dizziness remain poorly understood. Increasing evidence suggests that dizziness severity may alter multisensory integration and cortical compensation strategies. Therefore, the study aimed to investigate how the severity of dizziness influences cortical activation and postural stability using functional near-infrared spectroscopy (fNIRS) and center of pressure analysis during a tandem stance task.

Sixteen adults were divided into mild (n = 8) and moderate-to-severe (n = 8) dizziness groups based on dizziness handicap inventory and vertigo symptom scale-short form scores. Participants performed a tandem stance task under alternating eyes-open and eyes-closed conditions while cortical hemodynamics were recorded using fNIRS and postural sway was assessed using a force platform.

Compared to the mild group, the moderate-to-severe dizziness group showed significantly increased oxyhemoglobin concentrations in the bilateral superior parietal lobule and the left superior temporal gyrus, suggesting increased cortical activation during postural control. Moreover, under eyes-closed conditions, the moderate-to-severe group demonstrated significantly greater postural sway in terms of sway length, ellipse surface, anteroposterior displacement, and average speed.

These findings suggest that greater dizziness severity is associated with increased neural compensation and reduced balance stability, particularly in the absence of visual input. fNIRS may serve as a valuable tool to assess cortical mechanisms in individuals with vestibular dysfunction.