Article

Subcallosal brain structure: Correlation with hearing threshold at supra-clinical frequencies (> 8 kHz), but not with tinnitus

Dept. of Otology and Laryngology, Harvard Medical School, Boston MA, USA
Hearing research (Impact Factor: 2.85). 04/2012; 295. DOI: 10.1016/j.heares.2012.03.013
Source: PubMed

ABSTRACT This study tested for differences in brain structure between tinnitus and control subjects, focusing on a subcallosal brain region where striking differences have been inconsistently found previously. Voxel-based morphometry (VBM) was used to compare structural MRIs of tinnitus subjects and non-tinnitus controls. Audiograms of all subjects were normal or near-normal at standard clinical frequencies (≤8 kHz). Mean threshold through 14 kHz, age, sex and handedness were matched between groups. There were no definitive differences between tinnitus and control groups in modulated or unmodulated maps of gray matter (GM) probability (i.e., GM volume and concentration, respectively). However, when the image data were tested for correlations with parameters that were either not measured or not matched between the tinnitus and control groups of previous studies, a notable correlation was found: Threshold at supra-clinical frequencies (above 8 kHz) was negatively correlated with modulated GM probability in ventral posterior cingulate cortex, dorsomedial prefrontal cortex, and a subcallosal region that included ventromedial prefrontal cortex and coincided with previously-reported differences between tinnitus and control subjects. The results suggest an explanation for the discrepant findings in subcallosal brain: threshold at supra-clinical frequencies may have differed systematically between tinnitus and control groups in some studies but not others. The observed correlation between (1) brain structure in regions engaged in cognitive and attentional processes and (2) hearing sensitivity at frequencies generally considered unnecessary for normal human auditory behavior is surprising and worthy of follow up.

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    • "However, there is mixed anatomical evidence to suggest a difference in the brain of those with and without tinnitus. While some studies report differences in gray matter in the emotional centers (subcallosal area) between those with tinnitus and those without it (e.g., Mü hlau et al, 2006), Melcher et al (2013) demonstrated that this effect could be due to differences in hearing thresholds between subjects, irrespective of the presence or absence of tinnitus. Emotional disturbance generally refers to the " stress response, " which is a constellation of physiological events that occurs in response to some stress-inducing stimulus (Iversen et al, 2000). "
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    ABSTRACT: Background: The authors reviewed practicable options of sound therapy for tinnitus, the evidence base for each option, and the implications of each option for the patient and for clinical practice. Purpose: To provide a general guide to selecting sound therapy options in clinical practice. Intervention: Practicable sound therapy options. Data Collection and Analysis: Where available, peer-reviewed empirical studies, conference proceedings, and review studies were examined. Material relevant to the purpose was summarized in a narrative. Results: The number of peer-reviewed publications pertaining to each sound therapy option reviewed varied significantly (from none to over 10). Overall there is currently insufficient evidence to support or refute the routine use of individual sound therapy options. It is likely, however, that sound therapy combined with education and counseling is generally helpful to patients. Conclusions: Clinicians need to be guided by the patient's point of care, patient motivation and expectations of sound therapy, and the acceptability of the intervention both in terms of the sound stimuli they are to use and whether they are willing to use sound extensively or intermittently. Clinicians should also clarify to patients the role sound therapy is expected to play in the management plan.
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    • "hearing loss increases annoyance [4]), 2. psychological strains and their underlying neurophysiological network [5] and 3. changes in the neural activity in the brain. Since there is no integrative knowledge about the underlying mechanisms generating tinnitus [6], different tinnitus models based on different aspects of these factors are under discussion. The " gain control " model [7] assumes that peripheral sensory deprivation due to cochlear damages increases neuronal activity in the central auditory system in order to adapt neural sensitivity to the reduced sensory inputs. "
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    ABSTRACT: A surprising fact in voxel-based morphometry (VBM) studies performed in tinnitus is that not one single region is replicated in studies of different centers. The question then rises whether this is related to the low sample size of these studies, the selection of non-representative patient subgroups, or the absence of stratification according to clinical characteristics. Another possibility is that VBM is not a good tool to study functional pathologies such as tinnitus, in contrast to pathologies like Alzheimer's disease where it is known the pathology is related to cell loss. In a large sample of 154 tinnitus patients VBM and QEEG (Quantitative Electroencephalography) was performed and evaluated by a regression analysis. Correlation analyses are performed between VBM and QEEG data. Uncorrected data demonstrated structural differences in grey matter in hippocampal and cerebellar areas related to tinnitus related distress and tinnitus duration. After control for multiple comparisons, only cerebellar VBM changes remain significantly altered. Electrophysiological differences are related to distress, tinnitus intensity, and tinnitus duration in the subgenual anterior cingulate cortex, dorsal anterior cingulate cortex, hippocampus, and parahippocampus, which confirms previous results. The absence of QEEG-VBM correlations suggest functional changes are not reflected by co-occurring structural changes in tinnitus, and the absence of VBM changes (except for the cerebellum) that survive correct statistical analysis in a large study population suggests that VBM might not be very sensitive for studying tinnitus.
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