The "vestibular neuromatrix": A proposed, expanded vestibular network from graph theory in post-concussive vestibular dysfunction.

Convergent clinical and neuroimaging evidence suggests that higher vestibular function is subserved by a distributed network including visuospatial, cognitive-affective, proprioceptive, and integrative brain regions. Clinical vestibular syndromes may perturb this network, resulting in deficits across a variety of functional domains. Here, we leverage structural and functional neuroimaging to characterize this extended network in healthy control participants and patients with post-concussive vestibular dysfunction (PCVD). Then, 27 healthy control subjects (15 females) and 18 patients with subacute PCVD (12 female) were selected for participation. Eighty-two regions of interest (network nodes) were identified based on previous publications, group-wise differences in BOLD signal amplitude and connectivity, and multivariate pattern analysis on affective tests. Group-specific "core" networks, as well as a "consensus" network comprised of connections common to all participants, were then generated based on probabilistic tractography and functional connectivity between the 82 nodes and subjected to analyses of node centrality and community structure. Whereas the consensus network was comprised of affective, integrative, and vestibular nodes, PCVD participants exhibited diminished integration and centrality among vestibular and affective nodes and increased centrality of visual, supplementary motor, and frontal and cingulate eye field nodes. Clinical outcomes, derived from dynamic posturography, were associated with approximately 62% of all connections but best predicted by amygdalar, prefrontal, and cingulate connectivity. No group-wise differences in diffusion metrics or tractography were noted. These findings indicate that cognitive, affective, and proprioceptive substrates contribute to vestibular processing and performance and highlight the need to consider these domains during clinical diagnosis and treatment planning.

Technology-enhanced visual desensitization home exercise program for post-concussive visually induced dizziness: a case series.

PURPOSE: Post-concussive visually induced dizziness (VID), in which symptoms are provoked by exposure to complex visual motion, is associated with protracted recovery. Although vestibular rehabilitation therapy (VRT) is recommended to treat post-concussive dizziness, there is sparse literature reporting on specific VRT interventions treating VID. METHODS: A consecutive series of 26 individuals referred for VRT post-concussion were retrospectively assessed for inclusion in this case series. Each participant underwent a combination of conventional VRT and a technology-enhanced visual desensitization home exercise program (HEP). Self-report and objective measures were recorded from initial and discharge therapy evaluations. Twenty-three individuals (mean age 23.1 ± 12.4) with post-concussive dizziness (mean 109 ± 56 days post-injury) and no evidence for peripheral vestibular dysfunction were included. Treatment duration averaged 6.9 ± 2.5 weeks. RESULTS: There were significant improvements in post-intervention on subjective and objective measures of dizziness and gait (p < .05). The response to intervention was independent of pre-injury migraine history but pre-injury depression/anxiety increased self-report of post-treatment anxiety. Concurrent treatment with medications did not influence response to treatment. CONCLUSIONS: The combination therapy intervention improved outcome measures consistent with VRT treatment outcomes in both concussion and non-traumatic vestibular conditions. Individuals referred for VRT post-concussion warrant assessment for VID and may benefit from the addition of technology-enhanced visual desensitization.

Alterations in Resting-State Functional Brain Connectivity and Correlations with Vestibular/Ocular-Motor Screening Measures in Postconcussion Vestibular Dysfunction.

BACKGROUND AND PURPOSE: Vestibular symptoms after concussion are common and associated with protracted recovery. The purpose of this study is to define resting-state functional MRI (rs-fMRI) brain connectivity alterations in patients with postconcussion vestibular dysfunction (PCVD) and correlations between rs-fMRI connectivity and symptoms provoked during Vestibular/Ocular-Motor Screening (VOMS) assessment. METHODS: Prospective IRB approved study. STUDY GROUP: 12 subjects with subacute PCVD (2-10 weeks); control group: 10 age-matched subjects without history of concussion or vestibular impairment. Both groups underwent clinical vestibular assessment. rs-fMRI was acquired on 3.0T Siemens Trio with a 12-channel head coil. rs-fMRI data analysis included independent component analysis-based functional connectivity group differences, graph theory analysis, and ROI-to-ROI connectivity correlation analysis with VOMS clinical derivatives. Group difference maps between resting-state networks were calculated using dual regression method and corrected for multiple comparisons. Correlation analysis between ROI-to-ROI rs-fMRI brain activation and VOMS assessment ratings was performed using Pearson correlation coefficient, with a significance threshold of P ≤ .05. RESULTS: Compared to controls, PCVD group demonstrated significantly increased rs-fMRI connectivity between the default-mode network and right middle frontal gyrus and right postcentral gyrus; and between a vestibular-sensorimotor network and right prefrontal cortex. Significant positive correlations were found between clinical derivative VOMS scores and components of the vestibular, visual networks, and multisensory processing cortical representations. CONCLUSION: Altered rs-fMRI brain connectivity with increased connectivity of visual input, multisensory processing, and spatial memory in PCVD is correlative with clinical derivative VOMS scores, suggesting maladaptive brain plasticity underlying vestibular symptomatology.