Silvia Kovacs

Universitair Ziekenhuis Leuven, Leuven, VLG, Belgium

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Publications (16)27.43 Total impact

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    ABSTRACT: Tinnitus is a distressing symptom that affects up to 15% of the population; no satisfactory treatment exists. We present a novel surgical approach for the treatment of intractable tinnitus based on electrical extradural stimulation of the dorsolateral prefrontal cortex via an electrode implant. Tinnitus can be considered an auditory phantom phenomenon similar to deafferentation pain in the somatosensory system. It is characterized by gamma-band activity in the frontal cortex that can be visualized with the use of electroencephalography, magnetoencephalography, and functional magnetic resonance imaging (fMRI). Transcranial magnetic stimulation (TMS) is a noninvasive technique capable of modulating the ongoing activity of the human brain. When linked with a neuronavigation system, fMRI-guided frontal cortex TMS can be performed in a placebo-controlled way. If it is successful in suppressing tinnitus, this focal and temporary effect can be maintained in perpetuity by implanting a cortical electrode. A neuronavigation-based auditory fMRI-guided frontal cortex TMS session was performed in a patient experiencing intractable tinnitus, yielding 50% tinnitus suppression. Two extradural electrodes were subsequently implanted, also based on auditory fMRI-guided navigation. Postoperatively the tinnitus has improved by 66.67% and progressively continues to improve for more than one year. Focal extradural electrical stimulation of the dorsolateral prefrontal cortex at the area of cortical plasticity is capable of suppressing contralateral tinnitus partially. TMS might be a possible method for noninvasive studies of surgical candidates for implantation of stimulating electrodes for tinnitus suppression.
    World Neurosurgery 11/2011; 77(5-6):778-84. · 1.77 Impact Factor
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    ABSTRACT: It has recently become clear that alcohol addiction might be related to a brain dysfunction, in which a genetic background and environmental factors shape brain mechanisms involved with alcohol consumption. Craving, a major component determining relapses in alcohol abuse has been linked to abnormal activity in the orbitofrontal cortex, dorsal anterior cingulated cortex (dACC) and amygdala. We report the results of a patient who underwent rTMS targeting the dACC using a double cone coil in an attempt to suppress very severe intractable alcohol craving. Functional imaging studies consisting of fMRI and resting state EEG were performed before rTMS, after successful rTMS and after unsuccessful rTMS with relapse. Craving was associated with EEG beta activity and connectivity between the dACC and PCC in the patient in comparison to a healthy population, which disappeared after successful rTMS. Cue induced worsening of craving pre-rTMS activated the ACC-vmPFC and PCC on fMRI, as well as the nucleus accumbens area, and lateral frontoparietal areas. The nucleus accumbens, ACC-vmPFC and PCC activation disappeared on fMRI following successful rTMS. Relapse was associated with recurrence of ACC and PCC EEG activity, but in gamma band, in comparison to a healthy population. On fMRI nucleus accumbens, ACC and PCC activation returned to the initial activation pattern. A pathophysiological approach is described to suppress alcohol craving temporarily by rTMS directed at the anterior cingulate. Linking functional imaging changes to craving intensity suggests this approach warrants further exploration.
    Neuroscience Letters 03/2011; 496(1):5-10. · 2.03 Impact Factor
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    ABSTRACT: Tinnitus is considered an auditory phantom percept analogous to phantom pain. Thalamocortical dysrhythmia has been proposed as a possible pathophysiological mechanism for both tinnitus and pain. Thalamocortical dysrhythmia refers to a persistent pathological resting state theta-gamma coupling that is spatially localized at an area where normally alpha oscillations predominate. Auditory cortex stimulation via implanted electrodes has been developed to treat tinnitus, targeting an area of activation on functional MR imaging elicited by tinnitus-matched sound presentation. The authors describe a case in which clinical improvement was correlated with changes in intracranial recordings. Maximal tinnitus suppression was obtained by current delivery exactly at the blood oxygen level-dependent activation hotspot, which colocalizes with increased gamma and theta activity, in contrast to the other electrode poles, which demonstrated a normal alpha peak. These spectral changes normalized when stimulation induced tinnitus suppression, both on electrode and source-localized electroencephalography recordings. These data suggest that thetagamma coupling as proposed by the thalamocortical dysrhythmia model might be causally related to a conscious auditory phantom percept.
    Journal of Neurosurgery 01/2011; 114(4):912-21. · 3.15 Impact Factor
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    ABSTRACT: Tinnitus is a prevalent symptom, with clinical, pathophysiological, and treatment features analogous to pain. Noninvasive transcranial magnetic stimulation (TMS) and intracranial auditory cortex stimulation (ACS) via implanted electrodes into the primary or overlying the secondary auditory cortex have been developed to treat severe cases of intractable tinnitus. A series of 43 patients who benefited transiently from 2 separate placebo-controlled TMS sessions underwent implantation of auditory cortex electrodes. Targeting was based on blood oxygen level-dependent activation evoked by tinnitus-matched sound, using functional MR imaging-guided neuronavigation. Thirty-seven percent of the patients responded to ACS with tonic stimulation. Of the 63% who were nonresponders, half benefited from burst stimulation. In total, 33% remained unaffected by the ACS. The average tinnitus reduction was 53% for the entire group. Burst stimulation was capable of suppressing tinnitus in more patients and was better than tonic stimulation, especially for noise-like tinnitus. For pure tone tinnitus, there were no differences between the 2 stimulation designs. The average pure tone tinnitus improvement was 71% versus 37% for noise-like tinnitus and 29% for a combination of both pure tone and noise-like tinnitus. Transcranial magnetic stimulation did not predict response to ACS, but in ACS responders, a correlation (r = 0.38) between the amount of TMS and ACS existed. A patient's sex, age, or tinnitus duration did not influence treatment outcome. Intracranial ACS might become a valuable treatment option for severe intractable tinnitus. Better understanding of the pathophysiological mechanisms of tinnitus, predictive functional imaging tests, new stimulation designs, and other stimulation targets are needed to improve ACS results.
    Journal of Neurosurgery 01/2011; 114(4):903-11. · 3.15 Impact Factor
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    ABSTRACT: To study the central effects of occipital nerve stimulation (ONS) using functional magnetic resonance imaging (fMRI). After phantom measurements, blocked design fMRI scanning was performed during intermittent ONS in a healthy volunteer with implanted electrodes connected to an external generator. To assess the effect of frequency and stimulation mode, seven different frequencies in either tonic or burst mode were generated by a neurostimulator. A qualitative analysis of the main effect of ONS demonstrated significantly decreased activity within the bilateral primary visual, auditory, and somatosensory cortices and in the amygdala. Significant increased activity was observed bilaterally in the thalamus, frontal, and parietal areas and the cerebellum. Subsequently, quantitative analysis revealed that, unlike tonic mode stimulation, burst mode stimulation appeared to be frequency-dependent. This study demonstrates the feasibility and safety of fMRI studies with simultaneous ONS in a subject with externalized electrodes. The activation and deactivation pattern induced by ONS depends on stimulation mode and frequency.
    Neuromodulation 01/2011; 14(1):46-55; discussion 56-7. · 1.19 Impact Factor
  • Surgical Neurology - SURG NEUROL. 01/2009; 71(1):153-153.
  • Surgical Neurology - SURG NEUROL. 01/2009; 71(1):147-147.
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    ABSTRACT: Plasticity is the collective term used for a number of mechanisms that lead to molecular and/or structural alterations of an organism. These changes occur throughout life during learning processes, novel experiences as well as in response to injury. This chapter consists of a review of functional magnetic resonance imaging findings on plasticity phenomena occurring in response to brain injury, epilepsy, and congenital lesions. First, in a brief introduction to the phenomenon ‘plasticity’, a number of factors influencing plasticity phenomena and recovery from brain injury are discussed. Next, we discuss the occurrence of plasticity phenomena in a number of diseases. In the section on plasticity phenomena in patients with brain Tumors, both preoperative and postoperative plastic changes are considered, with a focus on the motor system. The section on plasticity phenomena in patients with epilepsy is mainly focused on the lateralization (or dominance) of language in these patients.
    12/2007: pages 209-226;
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    ABSTRACT: 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. 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. 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. 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.
    Neuroradiology 08/2007; 49(8):669-79. · 2.70 Impact Factor
  • Neuroradiology 07/2007; 49(8):693-696. · 2.70 Impact Factor
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    ABSTRACT: Functional imaging techniques have demonstrated a relationship between the intensity of tinnitus and the degree of reorganization of the primary auditory cortex. Studies in experimental animals and humans have revealed that tinnitus is associated with a synchronized hyperactivity in the auditory cortex and proposed that the underlying pathophysiological mechanism is thalamocortical dysrhythmia; hence, decreased auditory stimulation results in decreased firing rate, and decreased lateral inhibition. Consequently, the surrounding brain area becomes hyperactive, firing at gamma band rates; this is considered a necessary precondition of auditory consciousness, and also tinnitus. Synchronization of the gamma band activity could possibly induce a topographical reorganization based on Hebbian mechanisms. Therefore, it seems logical to try to suppress tinnitus by modifying the tinnitus-related auditory cortex reorganization and hyperactivity. This can be achieved using neuronavigation-guided transcranial magnetic stimulation (TMS), which is capable of modulating cortical activity. If TMS is capable of suppressing tinnitus, the effect should be maintained by implanting electrodes over the area of electrophysiological signal abnormality on the auditory cortex. The results in the first patients treated by auditory cortex stimulation demonstrate a statistically significant tinnitus suppression in cases of unilateral pure tone tinnitus without suppression of white or narrow band noise. Hence, auditory cortex stimulation could become a physiologically guided treatment for a selected category of patients with severe tinnitus.
    Acta neurochirurgica. Supplement 02/2007; 97(Pt 2):451-62.
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    ABSTRACT: The efficacy of electrical stimulation of the auditory cortex using extradural implanted electrodes for treatment of tinnitus was studied in 12 patients suffering tinnitus. The effect of similar stimulation of the somatosensory cortex for treatment of neuropathic pain was studied in five patients. It was shown that patients with pure tone type of tinnitus experienced a significant 97% suppression on average while those who had noise type tinnitus only had non-significant 24% suppression. All patients with pain experienced a significant reduction of their pain (using a visual analog scale), and in four out of five it was clinically relevant, i.e., the patient is really helped by it. It is concluded that electrical stimulation of sensory cortices can be effective treatments of severe unilateral tinnitus and unilateral neuropathic pain in selected patients. The results suggest that similar pathophysiological mechanisms underlie some forms of these phantom sensations, and therefore, similar treatment such as electrical stimulation of the respective sensory cortices can suppress tinnitus and pain.
    Progress in brain research 02/2007; 166:377-88. · 4.19 Impact Factor
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    ABSTRACT: The preliminary results suggest that in chronic unilateral tinnitus the contralateral amygdalohippocampal complex does seem to be involved in tinnitus perception of pure tones. Functional neuroimaging studies have revealed that the hippocampus and amygdala are involved in tinnitus perception. The amygdala and hippocampus are supplied by the anterior choroidal artery. Selective amobarbital injections in the anterior choroidal artery result in a non-functional amygdalohippocampal area for 10 min. The aim of this study was to assess the influence of this procedure on tinnitus perception. Amobarbital (80 mg in total) was injected selectively in two sessions in the left and right anterior choroidal artery in six male patients with tinnitus: four with unilateral tinnitus, two with bilateral tinnitus. Of the patients with unilateral tinnitus, three had right-sided tinnitus and one had left-sided tinnitus. The average age was 57.3 years (range 43-69). Average tinnitus duration was 5.3 years (range 1-10). The differences in visual analogue scale (VAS) scores before and after the amytal tests were analysed. Amytal injection ipsilateral to the side where the tinnitus was perceived resulted in a maximum of 30% tinnitus suppression, whereas amytal injection contralateral to the tinnitus side yielded a 60-70% tinnitus suppression in three patients with unilateral chronic tinnitus (>4 years). Only pure tone tinnitus was suppressed, white noise was not. Two patients with bilateral tinnitus had no suppression, irrespective of the tinnitus type. A third patient without clinical tinnitus suppression had tinnitus of more recent origin (1.5 years).
    Acta oto-laryngologica. Supplementum 01/2007;
  • Surgical Neurology - SURG NEUROL. 01/2007; 68(2):192-193.
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    ABSTRACT: Visualization of functional magnetic resonance imaging (fMRI) activation of subcortical auditory structures remains challenging because of the cardiac-related pulsatile movement of both the brainstem and the cerebrospinal fluid and involved, until now, special scanning, pre- and postprocessing techniques, which are not convenient in clinical settings. The aim of this study is to examine the activation in both cortical and subcortical auditory structures by means of an fMRI paradigm, which is suitable for clinical use. Twenty subjects (13 volunteers and 7 patients) were examined on a 3 T imaging system with binaural musical stimulation. Both cortical and subcortical auditory structures are successfully visualized in volunteers and patients. Activation of both the cortical and subcortical auditory structures can be visualized by means of an appropriate fMRI setup at 3 T. This paradigm can easily be used in patients with tumors and/or hearing disorders.
    Investigative Radiology 03/2006; 41(2):87-96. · 5.46 Impact Factor
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    ABSTRACT: Recent research suggests tinnitus is a phantom phenomenon based on hyperactivity of the auditory system, which can be visualized by functional neuroimaging, and transiently modulated by transcranial magnetic stimulation (TMS). We present the results of the first implanted electrodes on the primary and secondary auditory cortex after a successful TMS suppression. Twelve patients underwent an auditory cortex implantation, 10 for unilateral and 2 for bilateral tinnitus, based on >50% suppression applying TMS. Results were analyzed for pure tone tinnitus and white noise tinnitus. TMS results in 77% pure tone tinnitus and 67% white noise reduction. Electrical stimulation via an implanted electrode results in a mean of 97% pure tone tinnitus and 24% white noise suppression. Mean Visual Analogue Scale score decreases from 9.5 to 1.5 for pure tone and from 8.8 to 6.8 for white noise postoperatively. Pure tone tinnitus might be the conscious percept of focal neuronal hyperactivity of the auditory cortex. Once visualized, this hyperactivity can be modulated by neurostimulation. The preliminary results of the first implantations suggest that patients with unilateral pure tone tinnitus are good surgical candidates for electrode implantation and permanent electrical stimulation of the auditory cortex, provided that the tinnitus is of recent origin and can be suppressed by TMS.
    ORL 01/2006; 68(1):48-54; discussion 54-5. · 1.10 Impact Factor

Publication Stats

342 Citations
27.43 Total Impact Points

Institutions

  • 2007–2011
    • Universitair Ziekenhuis Leuven
      • Department of Radiology
      Leuven, VLG, Belgium
    • Erasmus MC
      • Department of Radiology
      Rotterdam, South Holland, Netherlands
    • University of Antwerp
      • Faculty of Medicine
      Antwerpen, Flanders, Belgium
  • 2006–2011
    • Catholic University of Louvain
      Walloon Region, Belgium
    • KU Leuven
      • Division of Radiology
      Leuven, VLG, Belgium