Central Nervous Activity upon Systemic Salicylate Application in Animals with Kanamycin-Induced Hearing Loss - A Manganese-Enhanced MRI (MEMRI) Study

This study investigated the effect of systemic salicylate on central auditory and non-auditory structures in mice. Since cochlear hair cells are known to be one major target of salicylate, cochlear effects were reduced by using kanamycin to remove or impair hair cells. Neuronal brain activity was measured using the non-invasive manganese-enhanced magnetic resonance imaging technique. For all brain structures investigated, calcium-related neuronal activity was increased following systemic application of a sodium salicylate solution: probably due to neuronal hyperactivity. In addition, it was shown that the central effect of salicylate was not limited to the auditory system. A general alteration of calcium-related activity was indicated by an increase in manganese accumulation in the preoptic area of the anterior hypothalamus, as well as in the amygdala. The present data suggest that salicylate-induced activity changes in the auditory system differ from those shown in studies of noise trauma. Since salicylate action is reversible, central pharmacological effects of salicylate compared to those of (permanent) noise-induced hearing impairment and tinnitus might induce different pathophysiologies. These should therefore, be treated as different causes with the same symptoms

Efeitos do biofeedback vibrotátil na reabilitação do equilíbrio corporal - estudo preliminar

Introduction Some patients with severe impairment of body balance do not obtain adequate improvement from vestibular rehabilitation (VR). Objective To evaluate the effectiveness of Vertiguard™ biofeedback equipment as a sensory substitution (SS) of the vestibular system in patients who did not obtain sufficient improvement from VR. Methods This was a randomized prospective clinical study. Thirteen patients without satisfactory response to conventional VR were randomized into a study group (SG), which received the vibrotactile stimulus from Vertiguard™ for ten days, and a control group (CG), which used equipment without the stimulus. For pre- and post-treatment assessment, the Sensory Organization Test (SOT) protocol of the Computerized Dynamic Posturography (CDP) and two scales of balance self-perception, Activities-specific Balance Confidence (ABC) and Dizziness Handicap Inventory (DHI), were used. Results After treatment, only the SG showed statistically significant improvement in C5 (p = 0.007) and C6 (p = 0.01). On the ABC scale, there was a significant difference in the SG (p = 0.04). The DHI showed a significant difference in CG and SG with regard to the physical aspect, and only in the SG for the functional aspect (p = 0.04). Conclusion The present findings show that sensory substitution using the vibrotactile stimulus of the Vertiguard™ system helped with the integration of neural networks involved in maintaining posture, improving the strategies used in the recovery of body balance.Introdução Alguns pacientes com déficit severo do equilíbrio corporal submetidos à reabilitação vestibular (RV) podem não apresentar resultados satisfatórios. Objetivo Verificar a eficácia do equipamento de biofeedback Vertiguard™ como substituto sensorial do sistema vestibular em pacientes sem bons resultados à RV. Método Estudo prospectivo clínico randomizado. Treze pacientes sem resposta satisfatória à RV convencional foram randomizados entre grupo de estudo (GE), que utilizou o estímulo vibratório do Vertiguard™ por dez dias e grupo controle (GC) que usou o equipamento desligado. Para avaliação pré e pós-tratamento foi utilizado o protocolo Teste de Integração Sensorial (TIS) da Posturografia Dinâmica Computadorizada (PDC) e duas escalas de autopercepção do equilíbrio: ABC (Activities-specific Balance Confidence) e DHI (Dizziness Handicap Inventory). Resultados Apenas o GE apresentou melhora estatisticamente significante em C5 (p = 0,007) e C6 (p = 0,01) da PDC após treinamento. Na escala ABC houve diferença significante no GE (p = 0,04). No DHI ocorreu diferença significante no aspecto físico em ambos os grupos e no aspecto funcional (p = 0,04) apenas no GE. Conclusão O estímulo de substituição sensorial do Vertiguard™ auxiliou a integração das redes neurais e na manutenção da postura, melhorando as estratégias utilizadas na recuperação do equilíbrio corporal

Advances to Electrode Pullback in Cochlear Implant Surgery

Objective. To observe the intracochlear behavior of a cochlear implant electrode insertion technique (called "pullback") in temporal bones. Study Design. Experimental. Settings. Tertiary referral center. Method. The change of the intracochlear electrode position was investigated under various conditions of an electrode pullback (N = 54) in 9 radiologically, size-estimated temporal bones (TBs). Those TBs were prepared by removal of the cochlear scalar roof to apply digital video capture procedures to monitor the pullback procedures. The digitally captured pictures were analyzed with specific software. Results. An optimal pullback of the electrode varied between 1.37 mm and 2.67 mm. While a limited pullback is without risk, an extended pullback bears the risk of removing the electrode tip out of its initial position or out of the cochlea. A correlation between cochlear size and the amount of pullback was not found. Conclusion. An initial insertion to the first or the second marker on the electrode followed by a limited pullback of about 1.37 mm to 1.5 mm can be recommended to achieve an optimized perimodiolar position. A pullback of up to two marker positions bears the risk of removing the electrode tip out of its initial position

Physiological and pathophysiological studies on the otolith function in the human vestibular system

Die vorliegende Arbeit beschreibt anhand von 10 publizierten bzw. zur Publikation angenommenen Artikeln physiologische und pathophysiologische Aspekte der Otolithenfunktion. Ausgehend von der Reizaufnahme und Weiterleitung innerhalb vestibulärer Reflexbögen wird auch der Einfluss der Otolithenfunktion auf die posturale Kontrolle sowie die Möglichkeit einer zentralen Kompensation von Gleichgewichtsdefiziten mit Hilfe von nicht- vestibulären sensorischen Stimuli untersucht. Im Rahmen der Charakterisierung des VCR wurde der sensorische Ursprung von VEMPs beim Menschen mit Hilfe intraoperativer elektrischer Stimulation am Nervus vestibularis inferior bestimmt. Die Ergebnisse belegen eindeutig, dass VEMPs durch die Aktivität des Sacculus ausgelöst werden. Um sie für die Diagnostik der Sacculusfunktion im klinischen Alltag heranziehen zu können, wurden Parameter bestimmt, die auf die Ausprägung der Potentiale bei akustischer Stimulation Einfluss nehmen können. Es wurden Normwerte für die Latenzen und die Amplitude erstellt, die alle wesentlichen Parameter (Alter, Geschlecht, Stimulus, tonische Aktivität des Halsmuskels) berücksichtigen. Durch die in der Arbeit beschriebene Berechnung ist es zudem erstmals möglich, auch quantitative Aussagen über den Zustand der Macula sacculi eines Patienten zu machen. Im weiteren wurden exogene und endogene Faktoren ermittelt, die pathologische Veränderungen in der Funktion des VCR hervorrufen. Es konnte gezeigt werden, dass die Einführung eines Cochlea-Implantat-Elektrodenträgers sowie die Aktivierung des Cochlea-Implantat-Systems den VCR beeinflussen können. Die Insertion des Elektrodenträgers in die Cochlea schädigt wahrscheinlich das Sinnesepithel des Sacculus infolge der dabei auftretenden Druckveränderungen. Eine intracochleäre elektrische Stimulation mit hoher Stromstärke verursacht hingegen eine Co-Stimulation des Nervus vestibularis inferior. Außerdem wurde nachgewiesen, dass die Otolithenorgane auch durch ein Kopfanpralltrauma, otosklerotische Veränderungen oder eine Connexin 26-Mutation in ihrer Funktion stark beeinträchtigt werden können. Bei MVKS- und vor allem bei AKN-Patienten war der VCR auf der betroffenen Seite oft nicht mehr auslösbar, was bei Patienten mit MVKS durch eine mikrovaskuläre Dekompression meist wiederhergestellt werden konnte. Die posturale Kontrolle war bei Patienten mit einer Otolithenfunktionsstörung in spezifischen Stand- und Gangübungen erheblich beeinträchtigt. In besonderem Maße war das bei der Reduzierung von propriozeptiven und/oder visuellen Inputs zu beobachten. Die Patienten setzten dabei verstärkt Oberkörperbewegungen für die Aufrechterhaltung der posturalen Kontrolle ein. Eine kombinierte Funktionsstörung der Otolithenorgane (Sacculus und Utriculus) steigerte zudem die Empfindlichkeit der Patienten auf sensomotorische Reize deutlich. Abschließend konnte ein Therapieansatz beschrieben werden, der eine erfolgreiche zentrale Kompensation der Gleichgewichtsdefizite mit Hilfe eines Neurofeedback-Trainings bewirkt. Die Verwendung eines sensorischen Feedbacksystems im Rahmen des Gleichgewichtstrainings scheint in erheblichem Maße die zentrale Kompensation einer Otolithenfunktionsstörung zu unterstützen.This book describes physiological and pathophysiological aspects of otolith function. The introduced 10 published papers deals with the receptor function, the pathway within the reflex arch and the influence of otolith function on postural control. Further a vestibular neurofeedback training concept for the rehabilitation of postural control in otolith disorders is presented. The inferior vestibular nerve was electrically stimulated to characterize the sensory origin of vestibular evoked myogenic potentials (VEMPs) in humans. The results clearly suggest that VEMPs are generated by the activation of the saccular macula. For the application of VEMPs in clinical practice it was necessary to determine all parameters, which influence the latencies and amplitude of the potential. Thus normative values were calculated for VEMP- latencies and -amplitudes with respect to age, gender, stimulus design and tonic neck muscle activity. By using the equation developed in this work, a quantitative evaluation of saccular function was possible for the first time. Further, different exogenous and endogenous factors were described which induce pathological changes of the vestibulo - collic reflex arch (VCR). It could be demonstrated that the insertion of a cochlea implant electrode as well as the intra - cochlear electrical stimulation interferes with the VCR. The insertion of the cochlear implant electrode into the Scala tympani leads to a damage of the saccular macula. In contrast to this finding, the activation of the implant electrode can induce a co-stimulation of the inferior vestibular nerve. It could be shown that otolith disorders are often induced by a head trauma, otosclerosis or genetically predispositions (e. g. connexin 26-mutation). The VCR is also impaired in patients with an acoustic neuroma or a microvascular compression syndrome. However, the VCR was normalized after a decompression of the inferior vestibular nerve. The postural control in otolith disorders was highly reduced during stance and gait tasks. This was especially true if the proprioceptive and/or visual inputs were reduced. Patients with otolith disorders use the trunk sway to ensure postural control during different senso-motoric conditions. Since otolith disorders are difficult to treat in clinical practice a new therapeutic approach was introduced to enhance the central vestibular compensation. This rehabilitation training reduced the trunk sway of the patients very effectively by applying a non-vestibular neurofeedback signal

Advances to Electrode Pullback in Cochlear Implant Surgery

Objective. To observe the intracochlear behavior of a cochlear implant electrode insertion technique (called “pullback”) in temporal bones. Study Design. Experimental. Settings. Tertiary referral center. Method. The change of the intracochlear electrode position was investigated under various conditions of an electrode pullback (N=54) in 9 radiologically, size-estimated temporal bones (TBs). Those TBs were prepared by removal of the cochlear scalar roof to apply digital video capture procedures to monitor the pullback procedures. The digitally captured pictures were analyzed with specific software. Results. An optimal pullback of the electrode varied between 1.37 mm and 2.67 mm. While a limited pullback is without risk, an extended pullback bears the risk of removing the electrode tip out of its initial position or out of the cochlea. A correlation between cochlear size and the amount of pullback was not found. Conclusion. An initial insertion to the first or the second marker on the electrode followed by a limited pullback of about 1.37 mm to 1.5 mm can be recommended to achieve an optimized perimodiolar position. A pullback of up to two marker positions bears the risk of removing the electrode tip out of its initial position

Can hearing amplification improve presbyvestibulopathy and/or the risk-to-fall ?

Purpose!#!The decline of sensory systems during aging has been widely investigated and several papers have correlated the visual, hearing and vestibular systems and the consequences of their functional degeneration. Hearing loss and presbyvestibulopathy have been found to be positively correlated as is with the risk-to-fall.!##!Material and methods!#!The present study was therefore designed as systematic review (due to PRISMA criteria) which should correlate hearing amplification by hearing aids and/or cochlear implants with balance outcome. However, the literature review (Cochrane, PubMed) revealed ten paper (prospective, controlled trials and acute trials) with heterogenous patient popiulations and non-uniform outcome measures (i.e., gait analysis, questionnaires, postural stabilometry) so that no quantitative, statistical analysis could be performed.!##!Results!#!The qualitative analysis oft he identified studies showed that hearing amplification in the elderly improves spatio-temporal orientation (particularly with cochlear implants) and that the process of utilizing auditory information for balance control takes some time (i.e., the neuroplasticity-based, learning processes), usually some months in cochlear implantees.!##!Discussion!#!Hearing and balance function degenerate independently from each other and large interindividual differences require a separate neurotological examination of each patient. However, hearing amplification is most helpful to improve postural stability, particularly in the elderly. Future research should focus on controlled, prospective clinical trials where a standardized test battery covering the audiological and neurotological profile of each elderly patient pre/post prescription of hearing aids and/or cochlear implantation should be followed up (for at least 1 year) so that also the balance improvements and the risk-to-fall can be reliably assessed (e.g., by mobile posturography and standardized questionnaires, e.g., the DHI)

Acute and Long-Term Effects of Noise Exposure on the Neuronal Spontaneous Activity in Cochlear Nucleus and Inferior Colliculus Brain Slices

Noise exposure leads to an immediate hearing loss and is followed by a long-lasting permanent threshold shift, accompanied by changes of cellular properties within the central auditory pathway. Electrophysiological recordings have demonstrated an upregulation of spontaneous neuronal activity. It is still discussed if the observed effects are related to changes of peripheral input or evoked within the central auditory system. The present study should describe the intrinsic temporal patterns of single-unit activity upon noise-induced hearing loss of the dorsal and ventral cochlear nucleus (DCN and VCN) and the inferior colliculus (IC) in adult mouse brain slices. Recordings showed a slight, but significant, elevation in spontaneous firing rates in DCN and VCN immediately after noise trauma, whereas no differences were found in IC. One week postexposure, neuronal responses remained unchanged compared to controls. At 14 days after noise trauma, intrinsic long-term hyperactivity in brain slices of the DCN and the IC was detected for the first time. Therefore, increase in spontaneous activity seems to develop within the period of two weeks, but not before day 7. The results give insight into the complex temporal neurophysiological alterations after noise trauma, leading to a better understanding of central mechanisms in noise-induced hearing loss

Acute Noise Exposure Is Associated With Intrinsic Apoptosis in Murine Central Auditory Pathway

Noise that is capable of inducing the hearing loss (NIHL) has a strong impact on the inner ear structures and causes early and most obvious pathophysiological changes in the auditory periphery. Several studies indicated that intrinsic apoptotic cell death mechanisms are the key factors inducing cellular degeneration immediately after noise exposure and are maintained for days or even weeks. In addition, studies demonstrated several changes in the central auditory system following noise exposure, consistent with early apoptosis-related pathologies. To clarify the underlying mechanisms, the present study focused on the noise-induced gene and protein expression of the pro-apoptotic protease activating factor-1 (APAF1) and the anti-apoptotic B-cell lymphoma 2 related protein a1a (BCL2A1A) in the cochlear nucleus (CN), inferior colliculus (IC) and auditory cortex (AC) of the murine central auditory pathway. The expression of Bcl2a1a mRNA was upregulated immediately after trauma in all tissues investigated, whereas the protein levels were significantly reduced at least in the auditory brainstem. Conversely, acute noise has decreased the expression of Apaf1 gene along the auditory pathway. The changes in APAF1 protein level were not statistically significant. It is tempting to speculate that the acoustic overstimulation leads to mitochondrial dysfunction and induction of apoptosis by regulation of proapoptotic and antiapoptotic proteins. The inverse expression pattern on the mRNA level of both genes might reflect a protective response to decrease cellular damage. Our results indicate the immediate presence of intrinsic apoptosis following noise trauma. This, in turn, may significantly contribute to the development of central structural deficits. Auditory pathway-specific inhibition of intrinsic apoptosis could be a therapeutic approach for the treatment of acute (noise-induced) hearing loss to prevent irreversible neuronal injury in auditory brain structures and to avoid profound deficits in complex auditory processing

Effects of vibrotactile vestibular substitution on vestibular rehabilitation - preliminary study,

ABSTRACT INTRODUCTION: Some patients with severe impairment of body balance do not obtain adequate improvement from vestibular rehabilitation (VR). OBJECTIVE: To evaluate the effectiveness of Vertiguard(tm) biofeedback equipment as a sensory substitution (SS) of the vestibular system in patients who did not obtain sufficient improvement from VR. METHODS: This was a randomized prospective clinical study. Thirteen patients without satisfactory response to conventional VR were randomized into a study group (SG), which received the vibrotactile stimulus from Vertiguard(tm) for ten days, and a control group (CG), which used equipment without the stimulus. For pre- and post-treatment assessment, the Sensory Organization Test (SOT) protocol of the Computerized Dynamic Posturography (CDP) and two scales of balance self-perception, Activities-specific Balance Confidence (ABC) and Dizziness Handicap Inventory (DHI), were used. RESULTS: After treatment, only the SG showed statistically significant improvement in C5 (p = 0.007) and C6 (p = 0.01). On the ABC scale, there was a significant difference in the SG (p= 0.04). The DHI showed a significant difference in CG and SG with regard to the physical aspect, and only in the SG for the functional aspect (p = 0.04). CONCLUSION: The present findings show that sensory substitution using the vibrotactile stimulus of the Vertiguard(tm) system helped with the integration of neural networks involved in maintaining posture, improving the strategies used in the recovery of body balance