Cortico-limbic morphology separates tinnitus from tinnitus distress

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Neuroimaging

Background:

• Tinnitus, a prevalent auditory disorder, involves chronic ringing or buzzing sensations.
• Neuroanatomical differences outside the auditory system are increasingly reported in tinnitus patients.
• It's debated whether these differences reflect tinnitus itself or emotional reactions to it.

Purpose of the Study:

• To identify neural markers of chronic tinnitus using anatomical MRI.
• To investigate the relationship between these markers and tinnitus characteristics, including distress, hearing loss, depression, and anxiety.

Main Methods:

• Anatomical magnetic resonance imaging (MRI) was used to assess brain structure.
• Gray matter volume, cortical surface area, cortical thickness, and gyrification were analyzed.
• Participants included individuals with chronic tinnitus and age- and hearing-loss-matched controls.

Main Results:

• Reduced gray matter in the ventromedial prefrontal cortex (vmPFC) was observed in tinnitus patients, driven by decreased cortical surface area.
• This vmPFC change was independent of tinnitus distress, depression, anxiety, or noise sensitivity.
• Tinnitus distress correlated with anterior insula thickness, while anxiety/depression correlated with subcallosal anterior cingulate cortex (scACC) thickness.
• Increased dorsomedial prefrontal cortex (dmPFC) gyrification was found in tinnitus patients, particularly those with constant tinnitus.

Conclusions:

• Structural brain differences in chronic tinnitus patients, such as reduced vmPFC gray matter, are distinct from neural correlates of emotional distress.
• Neural systems underlying the tinnitus perception itself differ from those involved in aversive reactions to tinnitus.
• Findings suggest that tinnitus may involve specific neuroanatomical dysregulations beyond emotional comorbidities.