Tinnitus Functional Connectivity Imaging in Single-Sided Deafness

Background: Treatment of bothersome tinnitus in single-sided deafness (SSD) presents an additional challenge as acoustical therapy cannot be delivered to the deaf ear. Behavioral therapy remains the dominant treatment modality. An alternative approach is neuromodulation of cortical or subcortical tinnitus treatment targets identified by functional neuroimaging.

Objectives: To evaluate differences in resting-state functional connectivity between SSD cohorts with and without bothersome tinnitus to identify neuromodulation treatment targets.

Methods: In this prospective, cross-sectional study, all enrolled subjects had normal hearing in one ear and severe or profound hearing loss in the other. The cutoff between bothersome tinnitus and non-bothersome or no tinnitus was a Tinnitus Functional Index (TFI) score of 13. There were 15 subjects with and 15 subjects without bothersome tinnitus. Functional magnetic resonance imaging resting-state connectivity data were collected using a gradient echo planar pulse sequence (GE Discovery 3.0T scanner). Data were preprocessed using SPM12 and analyzed using the CONN toolbox (https://www.nitrc.org/projects/conn/). Seeds, defined by the Automated Anatomical Labeling atlas, were left and right Heschl’s Gyrus (HG) and left and right caudate nucleus.

Results: The SSD cohort showed increased functional connectivity between left and right HG and the left dorsal caudate (p<0.005, k=100) and between the left and right caudate and HG bilaterally (p

Conclusion: Functional connectivity differences between SSD cohorts with and without bothersome tinnitus add to increasing evidence for a striatal gating model of tinnitus, where a dysfunctionally permissive caudate nucleus enables auditory phantoms to reach perceptual awareness. SSD functional connectivity results may inform target selection in neuromodulatory approaches to treat bothersome tinnitus.