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Vertigo is typically categorized into peripheral and central types. In clinical practice, MRI is pivotal for diagnosing suspected VERTIGOCENT to exclude other potential pathologies[7]. Although the imaging diagnosis of PERIPHVERTIGO, such as BPV remains controversial[8, 9], it is generally accepted that PERIPHVERTIGO arises from dysfunction within the vestibular terminal organ or the vestibular portion of the eighth cranial nerve in the labyrinth[10].However, advancements in MRI technology and more comprehensive imaging studies have revealed that vertigo is not solely linked to vestibular system dysfunction. It also involves the primary vestibular cortex, such as the parieto-insular vestibular cortex (PIC) and the occipital pole 2 (OP2), as well as the somatosensory cortex, higher visual areas (such as visual area 5/central temporal area), the cingulate sulcus visual area, and the thalamus vertigo network [11, 12]. In our study, we employed a bidirectional MR analysis to systematically explore the causal relationships between 3,935 structural and functional imaging-derived phenotypes (IDPs), such as gray matter volume (GMV), cortical properties, and functional connectivity, and various vertigo diseases.
The complexity of human spatial orientation and posture control is achieved through the effective central integration of the vestibular system with proprioception, visual, and auditory cues[13]. Specifically, vestibular signals are transmitted to the vestibular cortex via vestibular nerves, vestibular nuclei, the brainstem, and the thalamus[14]. Brandt et al.demonstrated that in cases of impaired central vestibular function, such as BPPV, the vestibular cortex and related subcortical regions enhance functional activities through central compensation to manage persistent vestibular stimulation[15]. This compensatory function of the central nervous system may persist even after the reduction of otolith particles[16].
The occipital lobe, pivotal in processing visual information, contains the primary visual cortices V1 and V2, along with the central temporal gyrus dedicated to visual motion. This specialization is crucial for integrating visual and vestibular data.[17]。Research has shown a marked decrease in neural activity in areas including the inferior frontal gyrus, left hippocampus, anterior cingulate cortex, and both the posterior and anterior insula among patients suffering from chronic subjective vertigo (CSD).Concurrently, there is a significant decrease in functional connectivity between these areas, the intraparietal sulcus-vestibular cortex (PIVC), and the occipital lobe's visual cortex, which likely hinders the processing of visual and vestibular signals and forces a greater reliance on visual cues for spatial orientation[18]. Additionally, connectivity disruptions between the anterior insula and the occipital cortex in CSD patients point to impaired visual-vestibular interactions, further deteriorating spatial orientation capabilities[18].Our analysis indicates that an increase in the volume of the occipital pole-occipital region, as measured by aparc-a2009s rh, is linked to an increased risk of peripheral vertigo. This may stem from a disrupted process of fusing visual and vestibular information. Given its role as the core of visual processing, an enlargement of the occipital lobe volume suggests a significant disruption in this essential integration process, thus heightening the risk of peripheral vertigo.
The hippocampus plays a crucial role in processing vestibular inputs for spatial localization [14]. Decreased hippocampal function in patients with chronic subjective dizziness may diminish their ability to contextualize spatial motion stimuli within an appropriate environmental setting. Additionally, diminished activity in the anterior insula and anterior cingulate cortex compromises their capacity to evaluate the relevance of such information[18]. Moreover, vertigo, characterized as an unpleasant and subjective experience, involves the hippocampus significantly in the contextual adjustment of memory [19]. In anxiety disorders, the left parahippocampal gyrus operates in concert with the hippocampus and the anterior cingulate cortex/medial prefrontal cortex; these areas are activated during the processing of pathogenic anxiety[20]. Our analysis indicates that an increase in IDP dMRI TBSS MD Cingulum hippocampus L is associated with an elevated risk of BPV, likely due to alterations or degradation of white matter microstructure, which affects the transmission of information between the hippocampus and other critical brain regions, such as the anterior cingulate cortex and anterior insula.
For example, the prefrontal area, closely related to spatial cognition and self-perception[21], was found in our analysis to be associated with a reduced risk of BPV when increased in volume, such as the BA-exvivo lh volume BA2 and the aparc-Desikan rh area rostral middle frontal. This increase in volume may reflect adaptive or compensatory changes in the nervous system in response to abnormal vestibular signal processing, potentially stabilizing vestibular input and thereby reducing the incidence of vertigo.In contrast, an increase in the aparc-a2009s rh volume Pole-occipital in the occipital region was associated with an increased risk of PERIPHVERTIGO. The occipital lobe, a center for visual processing, may exhibit increased volume due to disorders in the fusion process of visual and vestibular information, thereby elevating the risk of PERIPHVERTIGO.
The direct connection between the cerebellum and the vestibular nucleus is crucial for maintaining body balance and spatial positioning[4]. Research suggests a network involving the cortex, basal ganglia, cerebellum, and thalamus is essential for understanding the neural basis of vertigo[11]. The synergy between the cerebellum and basal ganglia plays a pivotal role in regulating target-related behavioral and emotional responses. This functional collaboration allows the brain to select appropriate cortical responses, inhibit inappropriate reactions, and adjust behavioral strategies based on environmental demands[22]. Qian Zhu observed significantly enhanced functional activities in specific regions of the pons and cerebellum in BPPV patients[23]. This finding aligns with our two-way MR analysis, which indicated that a reduction in specific functional connectivity, such as rfMRI connectivity (ICA100 edges 1323, 184, 1387), is associated with reduced BPV risk. These changes suggest that modifications in the cerebellum and its connections are crucial for normal vestibular function regulation, potentially involving inhibition or enhancement of network activities related to vestibular information processing. Moreover, studies have also indicated that compared to healthy controls, BPV patients exhibit significantly reduced functional connectivity between the left OP2 and the left angular gyrus, thalamus, precuneus parietal lobe, central prefrontal gyrus, and right cerebellum posterior lobe[24].. These declines in connectivity, consistent with our rfMRI data (ICA100 edges 357, 82, 236), underscore the cerebellum’s critical role in vestibular stability and input processing, pointing to these abnormal network connections as potential early biomarkers for vertigo-related brain dysfunction.Ultimately, the reverse MR analysis in our study did not reveal a significant causal effect of brain structure on vertigo, suggesting that while structural brain changes correlate with vertigo, they may not directly cause it.
In this MR study, we employed a variety of evaluation methods to assess the results of the two-way MR analysis, effectively mitigating heterogeneity and pleiotropy. We first screened potential instrumental variables to reduce the interference of potential confounding factors, thus enhancing the robustness of our causal assessments compared to traditional observational studies[25]. We highlighted the complex interactions between vertigo and specific neuroimaging indicators, providing new insights for future diagnostic and therapeutic strategies. Further, we enhanced the robustness of our findings through the MR-PRESSO distortion test and sensitivity analysis, ensuring the reliability of our conclusions.However, there are some limitations in our research. First, MRI features are derived from various regions of the brain and are processed using different brain maps and programs, our analysis faces inherent challenges. Moreover, our data on vertigo data originate from European populations, potentially leading to sample overlaps and limitations due to specific genetic backgrounds. Lastly, given the inherent constraints of the MR method, our study requires a larger cohort of observational samples to further validate these findings.