233. DYNAMIC POSTURAL CONTROL IN REMITTED BIPOLAR I DISORDER: A CDP STUDY

Abstract Background Postural sway is documented in Bipolar I disorder (BD). Emerging evidence suggests overlap between brain areas implicated in the pathophysiology of BD and vestibular activity in the brainstem. Computerized Dynamic Posturography (CDP) is a tool that quantifies the functional contributions of somatosensory, visual, and vestibular inputs, as well as the central mechanisms responsible for integrating these inputs, to maintain balance. As the only validated method to evaluate the roles of these sensory inputs and their integration with neuromuscular systems in postural and balance control, we employed CDP to understand the interplay between sensory processing and postural control in BD-I. Aims & Objectives To investigate the contributions of somatosensory, visual, and vestibular systems for postural control in BD-I compared to Healthy subjects (HS) Method Thirty participants aged 18-50 years with BD-I in remission (Female =12), according to ICD-11 criteria and not on known vestibular suppressants and matched HS (n=30; Female=14) with no history of vestibular dysfunction or psychiatric disorders were recruited. CDP includes the Sensory Organization Test, Adaptation Test, Motor Control Test (MCT), Fall Risk Test, and Optokinetic Test, which assess equilibrium scores, sensory analysis, degree of sway, stability post-tilt, latency, amplitude, weight symmetry, fall risk, and sway velocity index. The differences between the groups were assessed using independent samples t test. Results The BD and HS groups were comparable on age and gender. We found significant differences between the two groups (all p<0.05) on Sensory Organization Test (mean equilibrium BD= 70.21vs HS=77.88; t=4.32, p<0.001), Fall Risk test (Eyes open- normal and narrow stance, Eyes closed- normal and narrow stance; all p<0.001) and Optokinetic test (p<0.005). We did not find significant differences on the Adaptation test and MCT. Discussion & Conclusions BD-I exhibited greater postural sway compared to HS, highlighting imbalance in sensory integration mechanisms, when visual information was compromised or not. The prefrontal cortex, anterior cingulate cortex and anterior cingulate gyrus integrate sensory and cognitive inputs for stability & correcting balance errors through cognitive-motor integration, and adapting to dynamic and complex environments. Neuro imaging studies shows these structures are involved in BD1. Fall Risk test indicates the involvement of basal ganglia & brainstem circuit in motor function which is involved in the multisensory integration with proprioceptive information, could be impaired in BD even in remission. Optokinetic test results suggest that while the vestibular system may function normally in individuals with abnormal sensory processing, the Central Nervous System may fail to properly integrate visual and vestibular information, leading to postural instability, as seen in our subjects with BD compared to HS. Taken together, these three tests appear to be potential biomarker for BD and assessing postural control could enhance diagnostic and therapeutic approaches for BD. The absence of similar findings in the MCT and Adaptation tests that relies on reflexive and automatic pathways with minimal cognitive demands indicate that the primary motor cortex (M1), premotor cortex, SMA, basal ganglia, and cerebellum responsible for motor planning and execution may be relatively spared. Limitations include potentially confounding effect of medications.