Microstructural Differences in diffusion MRI in tinnitus population
Poster No:
1593
Submission Type:
Abstract Submission
Authors:
Cristina Tobias Figuerola1, Carine Signoret1, Josefine Andin1, Emil Holmer1, Marta Topor1, Rina Blomberg1, Åsa Elwér1, Lina Homman1, Mikael Skagenholt1, Kenny Skagerlund1, Mattias Ekberg1, Örjan Dahlström1
Institutions:
1Linköpings Universitet, Linköping, Östergötland
First Author:
Co-Author(s):
Introduction:
Tinnitus is defined as a phantom sound experienced by the individual as a ringing, hissing, or buzzing sound, even though there is no such sound in the external world [3,4]. This condition has been explained by deterioration at the peripheral level, which induces changes at the central neural level. At a neural level, it has been reported that increased connectivity between auditory areas could explain the prevalence of tinnitus symptoms. This study aims to examine microstructural differences in diffusion MRI for normal-hearing (NH) individuals with or without tinnitus, and between individuals with low and high tinnitus severity.
Methods:
Forty participants were included in the study (15 NH -7F and 8M, 25 TIN, 11F and 14M, mean age = 39.08) but only thirty-three participants (16 males and 17 females) with a mean age of 39.30 years (SD = 14.22 years) were eligible for diffusion tensor imaging (DTI). Twenty participants presented with a diagnosis of tinnitus (9 males and 11 females) and a mean tinnitus duration of 12.65 years (SD = 7.95 years). Participants with diagnosed tinnitus symptoms were recruited from the clinical population at the Department of Technical Audiology, Linköping University Hospital, Sweden. A correlational tractography analysis was performed to compare the tinnitus group with the control; the tinnitus group was then divided into two groups according to their severity and compared.
The study involved 33 MRI scans integrated into a connectometry database using a diffusion tensor imaging (DTI) scheme with 32 sampling directions, an 800 s/mm² b-value, 1.75 mm in-plane resolution, and 2 mm slice thickness. B-table accuracy was verified against a population-averaged template[10]. Restricted diffusion was quantified using restricted diffusion imaging[9], and data were reconstructed with generalized q-sampling imaging[6]. Tensor metrics were derived using DWI with a b-value below 1750 s/mm², and dti_fa values were employed in the connectometry analysis. Correlational tractography was performed using diffusion MRI connectometry[8], correlating diffusion metrics with the group.
A nonparametric Spearman correlation, a T-score threshold of 2.5, and a deterministic fiber tracking algorithm[7] were applied, excluding the cerebellum. Tracks were filtered using topology-informed pruning with 16 iterations. The selection criteria included an FDR threshold of 0.05 and a track coverage threshold of 5%, validated through 4000 randomized permutations for false discovery rate estimation.
The study involved 33 MRI scans integrated into a connectometry database using a diffusion tensor imaging (DTI) scheme with 32 sampling directions, an 800 s/mm² b-value, 1.75 mm in-plane resolution, and 2 mm slice thickness. B-table accuracy was verified against a population-averaged template[10]. Restricted diffusion was quantified using restricted diffusion imaging[9], and data were reconstructed with generalized q-sampling imaging[6]. Tensor metrics were derived using DWI with a b-value below 1750 s/mm², and dti_fa values were employed in the connectometry analysis. Correlational tractography was performed using diffusion MRI connectometry[8], correlating diffusion metrics with the group.
A nonparametric Spearman correlation, a T-score threshold of 2.5, and a deterministic fiber tracking algorithm[7] were applied, excluding the cerebellum. Tracks were filtered using topology-informed pruning with 16 iterations. The selection criteria included an FDR threshold of 0.05 and a track coverage threshold of 5%, validated through 4000 randomized permutations for false discovery rate estimation.
Results:
We obtained significantly correlated regions in fractional anisotropy (FA), mean diffusivity (MD) and axial diffusivity (AD) for the tinnitus vs control tractography (Fig 1). The severity comparison tractography yielded significant results (fig 2) for FA, MD, AD and radial diffusivity (RD).
For tinnitus vs control: the decrease in FA seems to indicate a demyelination[1,5] in regions correlated with emotional regulation and integration of sensory information (e.g., the anterior and posterior regions of the corpus callosum (CC) respectively)[2], with the CC tapetum also showing signs of axonal loss (increase in MD). The increase in MD and AD in the left hemisphere seems to suggest a reorganization of the brain white matter for tinnitus individuals which has been the subject of study in recent years[2].
For low vs high severity: CC tapetum, forceps major, and the fornix from both sides showed increased AD, MD, RD and decreased FA which could be indicators of axonal injuries and inflammation.
For tinnitus vs control: the decrease in FA seems to indicate a demyelination[1,5] in regions correlated with emotional regulation and integration of sensory information (e.g., the anterior and posterior regions of the corpus callosum (CC) respectively)[2], with the CC tapetum also showing signs of axonal loss (increase in MD). The increase in MD and AD in the left hemisphere seems to suggest a reorganization of the brain white matter for tinnitus individuals which has been the subject of study in recent years[2].
For low vs high severity: CC tapetum, forceps major, and the fornix from both sides showed increased AD, MD, RD and decreased FA which could be indicators of axonal injuries and inflammation.
Conclusions:
Our study found significant results in two different comparisons (tinnitus vs control; low severity and high severity) for correlational tractography analysis. The results suggest a potential demyelination in emotional regulation and sensory integration regions and a white matter reorganization in the left hemisphere. An increase in the perceived severity of the tinnitus condition might be correlated with injuries in the posterior parts of the CC and the fornix.
Modeling and Analysis Methods:
Connectivity (eg. functional, effective, structural) 2
Diffusion MRI Modeling and Analysis 1
Keywords:
Hearing
WHITE MATTER IMAGING - DTI, HARDI, DSI, ETC
1|2Indicates the priority used for review
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