Cerebellar Gray Matter Volume in Tinnitus

Abstract

Tinnitus is the perception of sound without an external source. The flocculus (FL) and paraflocculus (PFL), which are small lobules of the cerebellum, have recently been implicated in its pathophysiology. In a previous study, the volume of the (P)FL-complex correlated with tinnitus severity in patients that had undergone cerebellopontine angle (CPA) tumor removal. In this study, the relation between tinnitus and gray matter volume (GMV) of the (P)FL-complex, GMV of the other cerebellar lobules and GMV of the cerebellar nuclei is investigated in otherwise healthy participants. Data was processed using the SUIT toolbox, which is dedicated to analysis of imaging data of the human cerebellum. GMV of all cerebellar lobules and nuclei were similar between tinnitus and non-tinnitus participants. Moreover, no relation was present between tinnitus severity, as measured by the Tinnitus Handicap Inventory, and (P)FL-complex GMV, tonsil GMV, or total cerebellar cortical GMV. These results suggest that in otherwise healthy participants, in contrast to participants after CPA tumor removal, no relation between the GMV of neither the (P)FL-complex nor other cerebellar lobules and tinnitus presence and severity exists. These findings indicate that a relation only exists when the (P)FL-complex is damaged, for instance by a CPA tumor. Alternatively, it is possible that differences in (P)FL-complex GMVs are too small to detect with a voxel-based morphometry study. Therefore, the role of the (P)FL-complex in tinnitus remains to be further studied.

A Combined Image- and Coordinate-Based Meta-Analysis of Whole-Brain Voxel-Based Morphometry Studies Investigating Subjective Tinnitus

“…To date, structural neuroimaging studies using voxel-based morphometry (VBM) to investigate tinnitus have reported structural abnormalities in a variety of spatially distinct gray matter regions, including the auditory network (inferior colliculus, medial geniculate body, and primary or secondary auditory cortices), the default mode network (parietal cortices and prefrontal cortices), the salience network (anterior cingulate cortex and anterior insula), the limbic network (accumbens nucleus, amygdala, hippocampus, and parahippocampus), the visual network (primary or secondary visual cortices), the sensorimotor network (supplementary motor area), and the cerebellum [ 8 , 9 , 10 , 11 ]. In addition, VBM studies investigating tinnitus have also explored the relationships between these gray matter regions and clinical conditions that occur in conjunction with tinnitus, e.g., anxiety, depression, hearing loss, hyperacusis, and tinnitus burden [ 12 , 13 , 14 ]. However, the results have been highly inconsistent and sometimes contradictory.…”

Tinnitus Triggered by a Cerebellopontine Arachnoid Cyst in an Adolescent

“…The loudness of the tinnitus varies by ocular movements. Atrophy of the flocculus on the surgical side has been suggested to modulate tinnitus [ 15 , 16 ]. Functional MRI revealed that tinnitus is associated with activities of the Heschl’s gyrus, angular gyrus, cerebellar, and limbic system [ 17 ].…”

What is the role of the hippocampus and parahippocampal gyrus in the persistence of tinnitus?

“…Additionally, here we have intentionally focused particularly on the hippocampal system, to consider the nature of tinnitus as a persistent memory, a cognitive process in which the hippocampus/PHG are most‐commonly implicated, rather than discussing in detail other mechanisms behind tinnitus that are undoubtedly relevant. These mechanisms have implicated several other brain regions beyond the hippocampus and auditory system, including nucleus accumbens, ventromedial prefrontal cortex, thalamic reticular nucleus, middle frontal gyrus, fornix, and precuneus (Leaver et al, 2011 ; Rauschecker et al, 2010 ; Rauschecker et al, 2015 ; Rosemann & Rauschecker, 2022 ; Rosemann & Rauschecker, 2023a ; Rosemann & Rauschecker, 2023b ), cerebellum (Bauer et al, 2013 ; Mennink et al, 2022 ), insula (Chen et al, 2023 ; Lenhardt et al, 2008 ), and cingulate cortex (Chen, Liu, et al, 2018 ; Golm et al, 2013 ). These structures likely play roles in tinnitus that are not necessarily mutually exclusive, including—but not limited to—those involved in persistence of a memory trace, gating of pathological auditory activity and emotional responses to a chronic phantom percept.…”