Differences in resting state regional cerebral blood flow assessed with 99mTc-HMPAO SPECT and brain atlas matching between depressed patients with and without tinnitus

Invariant structural and functional brain regions associated with tinnitus: A meta-analysis

Tinnitus is a common, functionally disabling condition of often unknown etiology. Neuroimaging research to better understand tinnitus is emerging but remains limited in scope. Voxel-based physiology (VBP) studies detect tinnitus-associated pathophysiology by group-wise contrast (tinnitus vs controls) of resting-state indices of hemodynamics, metabolism, and neurovascular coupling. Voxel-based morphometry (VBM) detects tinnitus-associated neurodegeneration by group-wise contrast of structural MRI. Both VBP and VBM studies routinely report results as atlas-referenced coordinates, suitable for coordinate-based meta-analysis (CBMA). Here, 17 resting-state VBP and 8 VBM reports of tinnitus-associated regional alterations were meta-analyzed using activation likelihood estimation (ALE). Acknowledging the need for data-driven insights, ALEs were performed at two levels of statistical rigor: corrected for multiple comparisons and uncorrected. The corrected ALE applied cluster-level inference thresholding by intensity (z-score > 1.96; p < 0.05) followed by family-wise error correction for multiple comparisons (p < .05, 1000 permutations) and fail-safe correction for missing data. The corrected analysis identified one significant cluster comprising five foci in the posterior cingulate gyrus and precuneus, that is, not within the primary or secondary auditory cortices. The uncorrected ALE identified additional regions within auditory and cognitive processing networks. Taken together, tinnitus is likely a dysfunction of regions spanning multiple canonical networks that may serve to increase individuals’ interoceptive awareness of the tinnitus sound, decrease capacity to switch cognitive sets, and prevent behavioral and cognitive attention to other stimuli. It is noteworthy that the most robust tinnitus-related abnormalities are not in the auditory system, contradicting collective findings of task-activation literature in tinnitus.

Replicability of Neural and Behavioral Measures of Tinnitus Handicap in Civilian and Military Populations: Preliminary Results

Purpose In the past decade, resting-state functional connectivity, acquired using functional magnetic resonance imaging (fMRI), has emerged as a popular measure of tinnitus, especially as related to self-reported handicap or psychological reaction. The goal of this study was to assess replicability of neural correlates of tinnitus, namely, resting-state functional connectivity, in the same individuals acquired over 2 sessions. Method Data were collected at 2 different sites (University of Illinois at Urbana-Champaign and Joint Base San Antonio Wilford Hall Ambulatory Surgical Center) using similar 3T magnets and similar data acquisition paradigms. Thirty-six patients (all civilians) were scanned using resting-state fMRI at the University of Illinois at Urbana-Champaign. Ten patients, active-duty Service members and Veterans, were scanned at the Wilford Hall Ambulatory Surgical Center and the Department of Defense Hearing Center of Excellence. Each participant was scanned twice, a week apart, using identical protocols of 10 min resting-state fMRI. Results Tinnitus handicap scores using the Tinnitus Functional Index and the Tinnitus Primary Function Questionnaire ranged between no or mild handicap to moderately severe handicap but did not significantly differ between visits. We examined the default mode, dorsal attention, and auditory resting-state networks and found that the strength of the within-network functional connections across visit was similar for the attention and default mode networks but not for the auditory network. In addition, the functional connection between the attention network and precuneus, a region of the default mode network, was also replicable across visits. Conclusions Our results show that resting-state fMRI measures are replicable and reliable in patients with a subjective condition, although some networks and functional connections may be more stable than others. This paves the way for using resting-state fMRI to measure the efficacy of tinnitus interventions and as a tool to help propose better management options.

Theoretical Tinnitus Framework: A Neurofunctional Model

Subjective tinnitus is the conscious (attended) awareness perception of sound in the absence of an external source and can be classified as an auditory phantom perception. Earlier literature establishes three distinct states of conscious perception as unattended, attended, and attended awareness conscious perception. The current tinnitus development models depend on the role of external events congruently paired with the causal physical events that precipitate the phantom perception. We propose a novel Neurofunctional Tinnitus Model to indicate that the conscious (attended) awareness perception of phantom sound is essential in activating the cognitive-emotional value. The cognitive-emotional value plays a crucial role in governing attention allocation as well as developing annoyance within tinnitus clinical distress. Structurally, the Neurofunctional Tinnitus Model includes the peripheral auditory system, the thalamus, the limbic system, brainstem, basal ganglia, striatum, and the auditory along with prefrontal cortices. Functionally, we assume the model includes presence of continuous or intermittent abnormal signals at the peripheral auditory system or midbrain auditory paths. Depending on the availability of attentional resources, the signals may or may not be perceived. The cognitive valuation process strengthens the lateral-inhibition and noise canceling mechanisms in the mid-brain, which leads to the cessation of sound perception and renders the signal evaluation irrelevant. However, the “sourceless” sound is eventually perceived and can be cognitively interpreted as suspicious or an indication of a disease in which the cortical top-down processes weaken the noise canceling effects. This results in an increase in cognitive and emotional negative reactions such as depression and anxiety. The negative or positive cognitive-emotional feedbacks within the top-down approach may have no relation to the previous experience of the patients. They can also be associated with aversive stimuli similar to abnormal neural activity in generating the phantom sound. Cognitive and emotional reactions depend on general personality biases toward evaluative conditioning combined with a cognitive-emotional negative appraisal of stimuli such as the case of people with present hypochondria. We acknowledge that the projected Neurofunctional Tinnitus Model does not cover all tinnitus variations and patients. To support our model, we present evidence from several studies using neuroimaging, electrophysiology, brain lesion, and behavioral techniques.

Tinnitus Annoyance in Normal-Hearing Individuals: Correlation With Depression and Anxiety

OBJECTIVE

To assess and correlate tinnitus annoyance in normal-hearing patients with auditory brainstem response and with anxiety/depression.

METHODS

A sample of 84 individuals with tinnitus and normal hearing levels (pure-tone thresholds ≤25 dB HL) was compared to a matched control group of 47 normal-hearing individuals without tinnitus. All participants underwent auditory brainstem response testing. Tinnitus annoyance was assessed using the Tinnitus Handicap Inventory and depression and anxiety using the Beck Depression Inventory and Beck Anxiety Inventory, respectively. We compared auditory brainstem response and anxiety/depression symptoms between groups. In the study group, we correlated the degree of tinnitus annoyance with normal/abnormal auditory brainstem response and presence/level of anxiety/depression symptoms.

RESULTS

All controls had normal auditory brainstem response; 30 patients with tinnitus had abnormal results. Thirty-five patients with tinnitus had depression and 41 anxiety, while only 2 controls had depression and none had anxiety, with a significant between-group difference (P < .001). Normal/abnormal auditory brainstem response showed no association with tinnitus annoyance, anxiety, or depression. A higher degree of tinnitus annoyance was associated with severity of depression and anxiety.

CONCLUSIONS

Increased tinnitus annoyance was positively correlated with greater severity of anxiety and depression in normal-hearing patients but was unrelated to normal/abnormal auditory brainstem response.

Alterations of Regional Cerebral Blood Flow in Tinnitus Patients as Assessed Using Single-Photon Emission Computed Tomography

Tinnitus is the perception of phantom sound without an external auditory stimulus. Using neuroimaging techniques, such as positron emission tomography, electroencephalography, magnetoencephalography, and functional magnetic resonance imaging (fMRI), many studies have demonstrated that abnormal functions of the central nervous system are closely associated with tinnitus. In our previous research, we reported using resting-state fMRI that several brain regions, including the rectus gyrus, cingulate gyrus, thalamus, hippocampus, caudate, inferior temporal gyrus, cerebellar hemisphere, and medial superior frontal gyrus, were associated with tinnitus distress and loudness. To reconfirm these results and probe target regions for repetitive transcranial magnetic stimulation (rTMS), we investigated the regional cerebral blood flow (rCBF) between younger tinnitus patients (<60 years old) and the age-matched controls using single-photon emission computed tomography and easy Z-score imaging system. Compared with that of controls, the rCBF of tinnitus patients was significantly lower in the bilateral medial superior frontal gyri, left middle occipital gyrus and significantly higher in the bilateral cerebellar hemispheres and vermis, bilateral middle temporal gyri, right fusiform gyrus. No clear differences were observed between tinnitus patients with normal and impaired hearing. Regardless of the assessment modality, similar brain regions were identified as characteristic in tinnitus patients. These regions are potentially involved in the pathophysiology of chronic subjective tinnitus.

Memory networks in tinnitus: a functional brain image study

Tinnitus is characterized by the perception of sound in the absence of an external auditory stimulus. The network connectivity of auditory and non-auditory brain structures associated with emotion, memory and attention are functionally altered in debilitating tinnitus. Current studies suggest that tinnitus results from neuroplastic changes in the frontal and limbic temporal regions. The objective of this study was to use Single-Photon Emission Computed Tomography (SPECT) to evaluate changes in the cerebral blood flow in tinnitus patients with normal hearing compared with healthy controls.

METHODS

Twenty tinnitus patients with normal hearing and 17 healthy controls, matched for sex, age and years of education, were subjected to Single Photon Emission Computed Tomography using the radiotracer ethylenedicysteine diethyl ester, labeled with Technetium 99 m (99 mTc-ECD SPECT). The severity of tinnitus was assessed using the "Tinnitus Handicap Inventory" (THI). The images were processed and analyzed using "Statistical Parametric Mapping" (SPM8).

RESULTS

A significant increase in cerebral perfusion in the left parahippocampal gyrus (pFWE <0.05) was observed in patients with tinnitus compared with healthy controls. The average total THI score was 50.8+18.24, classified as moderate tinnitus.

CONCLUSION

It was possible to identify significant changes in the limbic system of the brain perfusion in tinnitus patients with normal hearing, suggesting that central mechanisms, not specific to the auditory pathway, are involved in the pathophysiology of symptoms, even in the absence of clinically diagnosed peripheral changes.

Brain regions responsible for tinnitus distress and loudness: a resting-state FMRI study

Subjective tinnitus is characterized by the perception of phantom sound without an external auditory stimulus. We hypothesized that abnormal functionally connected regions in the central nervous system might underlie the pathophysiology of chronic subjective tinnitus. Statistical significance of functional connectivity (FC) strength is affected by the regional autocorrelation coefficient (AC). In this study, we used resting-state functional MRI (fMRI) and measured regional mean FC strength (mean cross-correlation coefficient between a region and all other regions without taking into account the effect of AC (rGC) and with taking into account the effect of AC (rGCa) to elucidate brain regions related to tinnitus symptoms such as distress, depression and loudness. Consistent with previous studies, tinnitus loudness was not related to tinnitus-related distress and depressive state. Although both rGC and rGCa revealed similar brain regions where the values showed a statistically significant relationship with tinnitus-related symptoms, the regions for rGCa were more localized and more clearly delineated the regions related specifically to each symptom. The rGCa values in the bilateral rectus gyri were positively correlated and those in the bilateral anterior and middle cingulate gyri were negatively correlated with distress and depressive state. The rGCa values in the bilateral thalamus, the bilateral hippocampus, and the left caudate were positively correlated and those in the left medial superior frontal gyrus and the left posterior cingulate gyrus were negatively correlated with tinnitus loudness. These results suggest that distinct brain regions are responsible for tinnitus symptoms. The regions for distress and depressive state are known to be related to depression, while the regions for tinnitus loudness are known to be related to the default mode network and integration of multi-sensory information.

Low-frequency repetitive transcranial magnetic stimulation to the temporoparietal junction for tinnitus: four-week stimulation trial

IMPORTANCE

This research examines the impact of 4 weeks of repetitive transcranial magnetic stimulation (rTMS) stimulation to the temporoparietal junction and compares the results of this longer duration of treatment with a similar stimulus protocol of only 2 weeks' duration.

OBJECTIVE

To examine the effectiveness and safety of 4 weeks of low-frequency rTMS to the left temporoparietal junction in a cohort of patients with bothersome tinnitus.

DESIGN

Crossover, double-blind, randomized controlled trial.

SETTING

Outpatient academic medical center.

PARTICIPANTS

The study population comprised 14 adults aged between 22 and 59 years with subjective, unilateral or bilateral, nonpulsatile tinnitus of 6 months' duration or greater and a score of 34 or greater on the Tinnitus Handicap Inventory (THI).

INTERVENTIONS

Low-frequency (1 Hz) 110% motor threshold rTMS or sham to the left temporoparietal junction for 4 weeks.

MAIN OUTCOME AND MEASURE

The difference of the change in the THI score between active rTMS and sham rTMS.

RESULTS

Active treatment was associated with a median reduction in THI score of 10 (range, -20 to +4) points, and sham treatment was associated with a median reduction of 6 (range, -24 to +12) points. The median difference in THI score between the change associated with active and sham rTMS was 4 (95% CI, -9 to 10; and range, -32 to +14) points.

CONCLUSIONS AND RELEVANCE

Daily low-frequency active rTMS to the left temporoparietal junction area for 4 weeks was no more effective than sham for patients with chronic bothersome tinnitus. Possible explanations for this negative study include the failure of rTMS to stimulate deeper parts of auditory cortex within the sylvian fissure and more widespread cortical network changes not amenable to localized rTMS effects.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00567892.

Can Temporal Repetitive Transcranial Magnetic Stimulation be Enhanced by Targeting Affective Components of Tinnitus with Frontal rTMS? A Randomized Controlled Pilot Trial

Objectives: Low-frequency repetitive transcranial magnetic stimulation (rTMS) of the temporal cortex has been investigated as a new treatment tool for chronic tinnitus during the last years and has shown moderate efficacy. However, there is growing evidence that tinnitus is not a pathology of a specific brain region, but rather the result of network dysfunction involving both auditory and non-auditory brain regions. In functional imaging studies the right dorsolateral prefrontal cortex has been identified as an important hub in tinnitus related networks and has been shown to particularly reflect the affective components of tinnitus. Based on these findings we aimed to investigate whether the effects of left low-frequency rTMS can be enhanced by antecedent right prefrontal low-frequency rTMS. Study Design: Fifty-six patients were randomized to receive either low-frequency left temporal rTMS or a combination of low-frequency right prefrontal followed by low-frequency left temporal rTMS. The change of the tinnitus questionnaire (TQ) score was the primary outcome, secondary outcome parameters included the Tinnitus Handicap Inventory, numeric rating scales, and the Beck Depression Inventory. The study is registered in clinicaltrials.gov (NCT01261949). Results: Directly after therapy there was a significant improvement of the TQ-score in both groups. Comparison of both groups revealed a trend toward more pronounced effects for the combined group (effect size: Cohen’s d = 0.176), but this effect did not reach significance. A persistent trend toward better efficacy was also observed in all other outcome criteria. Conclusion: Additional stimulation of the right prefrontal cortex seems to be a promising strategy for enhancing TMS effects over the temporal cortex. These results further support the involvement of the right DLPFC in the pathophysiology of tinnitus. The small effect size might be due to the study design comparing the protocol to an active control condition.

Neural correlates of tinnitus duration and distress: a positron emission tomography study

Cerebral (18)F-deoxyglucose positron emission tomography (FDG-PET) has shown altered auditory pathway activity in tinnitus. However, the corresponding studies involved only small samples and analyses were restricted to the auditory cortex in most studies. Evidence is growing that also limbic, frontal, and parietal areas are involved in the pathophysiology of chronic tinnitus. These regions are considered to mediate perceptual, attentional, and emotional processes. Thus, the aim of the present study was the systematic evaluation of metabolic brain activity in a large sample of tinnitus patients. Ninety one patients with chronic tinnitus underwent FDG-PET. The effects of tinnitus severity (assessed by a tinnitus questionnaire score), duration and laterality were evaluated with statistical parametric mapping (SPM) in whole brain analyses. In addition, region of interest analyses were performed for primary auditory areas. Tinnitus duration correlated positively with brain metabolism in right inferior frontal, right ventro-medial prefrontal, and right posterior cingulate cortex. Tinnitus distress correlated positively with activation of left and right posterior inferior temporal gyrus as well as left and right posterior parahippocampal-hippocampal interface. Region of interest analysis demonstrated an overactivation of left in contrast to right Heschl's gyrus independently from tinnitus laterality and anatomical hemispheric differences. Tinnitus duration and distress were associated with areas involved in attentional and emotional processing. This is in line with recent findings indicating the relevance of higher order areas in the pathophysiology of tinnitus. Earlier results of asymmetric activation of the auditory cortices in tinnitus were confirmed, i.e., left-sided overactivation was found independently from tinnitus laterality.

Low-frequency repetitive transcranial magnetic stimulation to the temporoparietal junction for tinnitus

OBJECTIVE

To examine the effectiveness and safety of low-frequency repetitive transcranial magnetic stimulation (rTMS) to the temporoparietal junction in a cohort of patients with bothersome tinnitus.

DESIGN

Crossover, double-blind, randomized clinical trial.

SETTING

Outpatient academic medical center.

PARTICIPANTS

Fourteen adults aged 42 to 59 years with subjective, unilateral or bilateral, nonpulsatile tinnitus of 6 months' duration or longer and a score of 38 or greater on the Tinnitus Handicap Inventory (THI).

INTERVENTIONS

Low-frequency (1-Hz) 110% motor threshold rTMS or sham treatment to the left temporoparietal junction for 2 weeks.

MAIN OUTCOME MEASURE

The difference in the change of the THI score between active and sham rTMS.

RESULTS

Active treatment was associated with a median (95% confidence interval) reduction in THI score of 5 (0-14) points, and sham treatment was associated with a median reduction in THI score of 6 (-2 to 12) points. The difference in THI scores between the change associated with active and sham rTMS ranged from a 34-point reduction in THI score after active treatment to a 22-point increase after sham treatment, with a median difference change of only 1 point (-6 to 4 points).

CONCLUSIONS

Daily low-frequency rTMS to the left temporoparietal junction area for 2 weeks is no more effective than placebo for patients with chronic bothersome tinnitus. Possible explanations for the negative findings are short duration of treatment, failure of rTMS stimulation over the temporoparietal area to affect the auditory cortex buried within the Sylvian fissure, or more widespread cortical network changes associated with severe bothersome tinnitus not amenable to localized rTMS effects. Trial Registration clinicaltrials.gov Identifier: NCT00567892.

‘‘Ringing in the Ears’’: Narrative Review of Tinnitus and Its Impact

About 10% of the population experiences tinnitus, a common and distressing symptom characterized by the perception of sound in the absence of external stimuli. There is, however, marked heterogeneity in etiology, perception, and extent of distress among those who experience tinnitus. Reactions to tinnitus vary from simple awareness to severe irritation; some people have difficulty in hearing because of the loudness of the noise. Severe tinnitus causes many, often psychological, symptoms (e.g., tension, frustration, impaired concentration, disrupted sleep). For some, tinnitus is temporary, for others it is longstanding. Although many people adjust successfully, others are disabled by tinnitus; approximately 5% experience persistent and severe symptoms affecting their lifestyle and significantly reducing their quality of life. Because tinnitus is poorly understood and no single therapeutic approach is effective for all patients, many patients are told that ‘‘nothing can be done’’ and they must ‘‘learn to live with it.’’ In spite of these challenges, there is remarkably little relevant nursing literature on tinnitus. This literature review was conducted to explore current knowledge of tinnitus, including prevalence, causes and diagnosis, and assessment. Its psychosocial effects and impact on individuals are considered. Implications for practice are discussed—demonstrating that understanding the full impact of the condition and identifying patients’ needs are essential to effective care.

The mechanisms of tinnitus: perspectives from human functional neuroimaging

In this review, we highlight the contribution of advances in human neuroimaging to the current understanding of central mechanisms underpinning tinnitus and explain how interpretations of neuroimaging data have been guided by animal models. The primary motivation for studying the neural substrates of tinnitus in humans has been to demonstrate objectively its representation in the central auditory system and to develop a better understanding of its diverse pathophysiology and of the functional interplay between sensory, cognitive and affective systems. The ultimate goal of neuroimaging is to identify subtypes of tinnitus in order to better inform treatment strategies. The three neural mechanisms considered in this review may provide a basis for TI classification. While human neuroimaging evidence strongly implicates the central auditory system and emotional centres in TI, evidence for the precise contribution from the three mechanisms is unclear because the data are somewhat inconsistent. We consider a number of methodological issues limiting the field of human neuroimaging and recommend approaches to overcome potential inconsistency in results arising from poorly matched participants, lack of appropriate controls and low statistical power.

Mitochondrial function is related to alterations at brain SPECT in depressed patients

INTRODUCTION

99mTc-d,l-hexamethylpropylene amine oxime (99mTc-HMPAO) retention in brain is proportional to cerebral blood flow and related to both the local hemodynamic state and to the cellular content of reduced glutathione. Alterations of the regional distribution of 99mTc-HMPAO retention, with discrepant results, have been reported at functional brain imaging of unipolar depression. Since mitochondrial involvement has been reported in depressed patients, the aim of the study was to explore whether the 99mTc-HMPAO retention at single-photon emission computed tomography in depressed patients may relate to different levels of mitochondrial function.

METHODS

All patients had audiological and muscular symptoms, somatic symptoms that are common in depression. Citrate synthase (CS) activity assessed in muscle mitochondria correlated strongly with the activities of three mitochondrial respiratory chain enzymes and was used as a marker of mitochondrial function. K-means clustering performed on CS grouped eight patients with low and 11 patients with normal CS. Voxel-based analysis was performed on the two groups by statistical parametric mapping.

RESULTS

Voxel-based analysis showed significantly higher 99mTc-HMPAO retention in the patients with low CS compared with the patients with normal CS in the posterior and inferior frontal cortex, the superior and posterior temporal cortex, the somato-sensory cortex, and the associative parietal cortex.

CONCLUSION

Low muscle CS in depressed patients is related to higher regional 99mTc-HMPAO retention that may reflect cerebrovascular adaptation to impaired intracellular metabolism and/or intracellular enzymatic changes, as previously reported in mitochondrial disorder. Mitochondrial dysfunction in varying proportions of the subjects may explain some of the discrepant results for 99mTc-HMPAO retention in depression.

Lateralization of functional magnetic resonance imaging (fMRI) activation in the auditory pathway of patients with lateralized tinnitus

INTRODUCTION

Tinnitus is hypothesized to be an auditory phantom phenomenon resulting from spontaneous neuronal activity somewhere along the auditory pathway. We performed fMRI of the entire auditory pathway, including the inferior colliculus (IC), the medial geniculate body (MGB) and the auditory cortex (AC), in 42 patients with tinnitus and 10 healthy volunteers to assess lateralization of fMRI activation.

METHODS

Subjects were scanned on a 3T MRI scanner. A T2*-weighted EPI silent gap sequence was used during the stimulation paradigm, which consisted of a blocked design of 12 epochs in which music presented binaurally through headphones, which was switched on and off for periods of 50 s. Using SPM2 software, single subject and group statistical parametric maps were calculated. Lateralization of activation was assessed qualitatively and quantitatively.

RESULTS

Tinnitus was lateralized in 35 patients (83%, 13 right-sided and 22 left-sided). Significant signal change (P(corrected) < 0.05) was found bilaterally in the primary and secondary AC, the IC and the MGB. Signal change was symmetrical in patients with bilateral tinnitus. In patients with lateralized tinnitus, fMRI activation was lateralized towards the side of perceived tinnitus in the primary AC and IC in patients with right-sided tinnitus, and in the MGB in patients with left-sided tinnitus. In healthy volunteers, activation in the primary AC was left-lateralized.

CONCLUSION

Our paradigm adequately visualized the auditory pathways in tinnitus patients. In lateralized tinnitus fMRI activation was also lateralized, supporting the hypothesis that tinnitus is an auditory phantom phenomenon.

Moderate therapeutic efficacy of positron emission tomography-navigated repetitive transcranial magnetic stimulation for chronic tinnitus: a randomised, controlled pilot study

BACKGROUND

Tinnitus has been shown to respond to modulations of cortical activity by high-frequency and low-frequency repetitive transcranial magnetic stimulation (rTMS).

OBJECTIVE

To determine the tinnitus-attenuating effects of a 2-week daily regimen of rTMS, navigated to the maximum of tinnitus-related increase in regional cerebral blood flow.

METHODS

Six patients with chronic tinnitus were enrolled in this sham-controlled crossover study and treated with 2x2 weeks of suprathreshold 1 Hz rTMS (30 min) applied to the region with maximal tinnitus-related increase in regional cerebral blood flow delineated by functional imaging with [15O]H2O positron emission tomography and a control area. Tinnitus-related distress was assessed before and after each treatment and 2 weeks after the end of the 4-week course of stimulation using a validated tinnitus questionnaire. Additional self-assessment scores of tinnitus change, loudness and annoyance were obtained.

RESULTS

In five of six patients, rTMS induced greater reduction of the tinnitus questionnaire score than sham stimulation. In two patients, all parameters measured (tinnitus change score, tinnitus loudness, tinnitus annoyance) showed unequivocal improvement. At the group level, the degree of response in the tinnitus questionnaire score was correlated with tinnitus-associated activation of the anterior cingulate cortex. Two weeks after the final stimulation, tinnitus had returned to baseline in all patients but one.

CONCLUSION

Tinnitus can be attenuated by low-frequency rTMS navigated to each person's maximum tinnitus-related cortical hyperactivity. The effects are only moderate; interindividual responsiveness varies and the attenuation seems to wear off within 2 weeks after the last stimulation session. Notably, tinnitus-related anterior cingulate cortex activation seems to predict the response to rTMS treatment.

Tinnitus and Brain Activation: Insights from Transcranial Magnetic Stimulation

The mechanisms underlying tinnitus are still not completely elucidated, but advances in neuroimaging and brain stimulation have provided us with new insights. Evidence suggests that tinnitus might actually be generated by central rather than peripheral structures. To illustrate the importance of brain activity changes in the pathology of tinnitus, we report the cases of 2 patients who experienced a recurrence/worsening of their tinnitus after they had undergone treatment for major depression with repetitive transcranial magnetic stimulation. We suggest that the tinnitus in these 2 patients was induced by changes in brain activity resulting from transcranial magnetic stimulation of the prefrontal cortex. We also review the pathophysiology and other aspects of tinnitus, focusing on associated brain reorganization.

The effects of sertraline on severe tinnitus suffering--a randomized, double-blind, placebo-controlled study

OBJECTIVE

The relationship between tinnitus and anxiety and depressive disorders has been frequently alluded to, but there are few studies on antidepressants in the treatment of tinnitus, and the efficacy of sertraline on severe refractory tinnitus has not been reported.

METHOD

Consecutive tinnitus patients (n = 76) considered to be at high risk for severe and disabling tinnitus according to a recently developed screening procedure were randomly assigned to 16 weeks of double-blind treatment with placebo (n = 38) or sertraline (n = 38) at a fixed dose (25 mg/d on the first week and 50 mg/d on the following 15 weeks). Between-group comparisons of Tinnitus Severity Questionnaire scores over 16 weeks were made as the primary outcome measure. Secondary outcomes of tinnitus loudness and tinnitus annoyance were also measured using a visual analogue scale. Severity of depressive and anxiety symptoms was evaluated using the Hamilton rating scales (Hamilton Depression Rating Scale and Hamilton Anxiety Rating Scale, interview-based ratings) and the Comprehensive Psychopathological Rating Scale (self-ratings).

RESULTS

The intention-to-treat analysis showed sertraline to be more effective than placebo (P = 0.024) in decreasing reported tinnitus severity according to the Tinnitus Severity Questionnaire at 16 weeks' follow-up. There was also more improvement (P = 0.014) in perceived tinnitus loudness. There were significant correlations between reduction of tinnitus according to the Tinnitus Severity Questionnaire over 16 weeks and improvements in depressive (r = 0.42-0.46) and anxiety symptoms (r = 0.34-0.42). Sertraline was well tolerated after a somewhat high (17%) dropout rate within the first 2 weeks.

CONCLUSIONS

Sertraline is more effective than placebo in the treatment of severe refractory tinnitus.

The demystification of autoscopic phenomena: experimental propositions

Autoscopic phenomena (AP) are rare, illusory visual experiences during which the subject has the impression of seeing a second own body in extrapersonal space. AP consist of out-of-body experience, autoscopic hallucination, and heautoscopy. Recent neurologic reports support the role of multisensory integration deficits of body-related information and vestibular dysfunctions in AP at the temporo-parietal junction. A caveat to test the underlying neurologic and cognitive mechanisms of AP has been their rare and spontaneous occurrence. Recent evidence linked AP to mental own-body imagery engaging brain mechanisms at the temporo-parietal junction. These recent observations open a new avenue for testing AP-related cognitive mechanisms in selected clinical and normal populations. We review evidence on several clinical syndromes (psychosis, depression, anxiety, depersonalization, body dysmorphic disorder), suggesting that some of these syndromes may relate to AP-proneness, thereby leading to testable propositions for future research on body and self processing in addition to AP.

99mTc-HMPAO distribution at SPECT is associated with succinate-cytochrome c reductase (SCR) activity in subjects with psychiatric disorders

The origin of altered (99m)Tc-HMPAO distribution at SPECT in psychiatric disorders is unknown. Correlations between brain (99m)Tc-HMPAO distribution and muscle succinate-cytochrome c reductase (SCR, complex II + III) were assessed in 20 unmedicated psychiatric patients. Significant negative correlations were found between (99m)Tc-HMPAO distribution in associative sensory regions and SCR activity. Sensory cortices are normally enriched in complex II activity. The production of electrons and reactive oxygen species affecting the redox state is considered to be highest from complex III, but complex II may also contribute. The negative relationship between (99m)Tc-HMPAO uptake and SCR activity may be due to redox state alterations influencing fixation of the radiopharmaceutical.

Alterations of rCBF and mitochondrial dysfunction in major depressive disorder: a case report

OBJECTIVE

A mitochondrial disease might be considered when depressive disorder is associated with diabetes mellitus or other symptoms commonly found in mitochondrial disease. Scattered regional cerebral blood flow (rCBF) decreases and increases have been reported in depressive and mitochondrial disorders. A 61-year-old male patient with early adult onset of depressive disorder and a slowly developing multiorgan syndrome including diabetes mellitus was investigated.

METHOD

99mTc-HMPAO rCBF SPECT and muscle biopsy to assess mitochondrial functions were performed in the patient.

RESULTS

Alterations of rCBF were found in the patient, with the most pronounced decreases in the left dorsolateral frontal and inferior parietal lobes, and the most pronounced increases in the bilateral superior parietal lobes. Muscle biopsy revealed myopathy and decrease of mitochondrial adenosine triphosphate production rates (MAPRs).

CONCLUSION

The MAPRs decreases support the suspicion of mitochondrial dysfunction in the patient. A subgroup of depressed patients may have mitochondrial dysfunctions.

Transient suppression of tinnitus by transcranial magnetic stimulation

It has been proposed that tinnitus is associated with an irregular activation of the temporoparietal cortex. If this activity is a functionally relevant component of the tinnitus-related network, a virtual temporary lesion of this area should result in transient reduction of tinnitus. To test this hypothesis, we applied 10Hz repetitive transcranial magnetic stimulation to eight scalp and four control positions in 14 patients with chronic tinnitus. Stimulation of left temporoparietal cortex significantly reduced tinnitus (Friedman analysis of variance, p < 0.05; compared with control), indicating that secondary auditory areas can be critical for tinnitus perception, perhaps as a consequence of maladaptive cortical reorganization.