This article reports the development of a neuro-rehabilitation approach, “constraint-induced sound therapy (CIST)” for sudden sensorineural hearing loss. The aim of CIST is to prevent maladaptive cortical reorganization by using an enriched acoustic environment. CIST represents a safe, easy, inexpensive, and effective approach to treat sudden sensorineural hearing loss.
Perda auditiva neurossensorial súbita (SS) é caracterizada por perda auditiva aguda, idiopática. A taxa de incidência estimada é de 5-30 casos por 100.000 pessoas por ano. As causas da surdez súbita e os mecanismos subjacentes SSHL atualmente permanecem desconhecidos. Com base em diversas hipóteses, como uma perturbação circulatória para a cóclea, infecção virai, e doenças auto-imunes, as abordagens fármaco-terapêutico têm sido aplicados para o tratamento de pacientes de SS; No entanto, a eficácia do tratamento padrão, a terapia corticosteróide, está ainda sob debate. A exposição a sons intensos foi mostrado para causar danos permanentes ao sistema auditivo; no entanto, a exposição a um nível moderado enriquecido ambiente acústico após o trauma ruído pode reduzir deficiências auditivas. Vários estudos de neuroimagiologia sugeriu recentemente que o início da SSS reorganização cortical induzida maladaptativa no córtex auditivo humano, e que o grau de reorganização cortical na fase aguda negativa SSS correxultante com a taxa de recuperação de perda auditiva. Este artigo relata o desenvolvimento de uma abordagem neuro-reabilitação romance para SSHL, "terapia de som induzido por restrição (CIST)". O objectivo do protocolo CIST é para prevenir ou reduzir a reorganização cortical maladaptativa usando um ambiente acústico enriquecido. O canal do ouvido intacto de pacientes de SS está ligado a fim de motivá-los a usar ativamente o ouvido afetado e, assim, impedir o progresso da reorganização cortical maladaptive. O ouvido afetado também está exposta a música através de um fone de ouvido durante 6 horas por dia durante a hospitalização. O protocolo CIST parece ser um tratamento seguro, fácil, barato e eficaz para o SS.
Súbita perda auditiva neurossensorial (SSS), ou surdez súbita, é uma condição idiopática que se caracteriza por uma rápida perda de audição 1. Vários estudos epidemiológicos 2,3 relatado taxas de incidência de SS de 5-30 casos por 100.000 pessoas por ano nos países industrializados. Mesmo que as causas de surdez neurossensorial súbita e os mecanismos subjacentes SSHL foram examinados extensivamente, o nosso conhecimento sobre SSS permanece limitado. Entre as muitas causas potenciais de surdez neurossensorial súbita idiopática, hipóteses comuns incluem um distúrbio circulatório 4, infecção viral 5-7, e 8,9 doença auto-imune. Embora a terapia de corticosteróides 10 foi proposta com base em tais hipóteses, e é o tratamento mais comumente aplicado, a eficácia desta terapia padrão ainda está sendo debatido 3,11-14. Portanto, as estratégias de tratamento da surdez súbita inovadoras, motivadas por diferentes perspectivas, são fortemente desejado.
SSHLafecta a actividade neural, não só na cóclea, mas também no córtex auditivo. Vários estudos de neuroimagem 15-17 sugeriu que SSHL induzida plasticidade cortical no córtex auditivo humano dentro de poucos dias de seu início. Além disso, o grau de reorganização cortical representado pela perda de dominância hemisférica contralateral da evocados auditivos campos apareceu correlacionar negativamente com as taxas de recuperação da perda auditiva 18. A plasticidade cortical induzida pelo início da surdez súbita pode ser considerada como má adaptação para a capacidade auditiva do ouvido afetado. Portanto, a prevenção dessa reorganização cortical mal-adaptativo associado à surdez súbita pode representar uma nova estratégia de tratamento.
Este artigo propõe uma abordagem neuro-reabilitação que impede 'aprendi a não utilização "alterações corticais, a fim de prevenir ou reduzir a reorganização cortical maladaptive. Por exemplo, em casos de disfunções motoras, aprendeu a não-utilização deum limbis um fenômeno em que o movimento é inicialmente suprimidos, devido a reações adversas eo fracasso de qualquer atividade tentada com o membro afetado, o que, eventualmente, resulta na supressão do comportamento e da correspondente actividade neural 19,20. Não-uso aprendido não parece ser limitado a disfunção motora, mas poderão incidir também sobre deficiências sensoriais 21. Pacientes de SS utilizam principalmente e preste atenção à orelha intacta para ouvir. Este comportamento de audição parece aumentar a actividade neural correspondente à orelha intacta e, ao mesmo tempo, reduzir as conexões neurais entre a cóclea afectada e córtex auditivo 22. A fim de evitar esta mudança cortical maladaptive induzida por «não utilização», que parece ser benéfico para pacientes de SS para executar "terapia de som induzido por restrição (CIST) '23, o que motiva os participantes a ouvir música intensivamente através do ouvido afetado e prestar atenção auditivo para o ouvido afetado(Figura 1). Em comparação com a farmacoterapia convencional, o CIST supostamente é uma abordagem de tratamento seguro, fácil, barata e eficaz para SSHL.
This article describes a behavioral treatment approach for SSHL. The CIST protocol merely requires the use of easily available devices. A comparison of the treatment effects of CIST + SCT with those of SCT alone revealed significantly better hearing improvements with the CIST + SCT treatment. No apparent side effects were associated with the CIST protocol. The cost of CIST is markedly lower than other newly suggested treatments (including a stellate ganglion block and hyperbaric oxygen therapy). The CIST protocol represents an effective, inexpensive, easy, and safe treatment for SSHL; however, several important points must be considered. One point is the prevention of acoustic trauma. Although the maximal volume settings of recent commercial portable music players are limited to remain below the harmful levels, the sound level needs to be observed when a large adjustment is made to the equalizer settings or when a headphone amplifier is used. The second point is ‘cross hearing’. The purpose of the CIST procedure is to enable SSHL patients to actively use their affected ear for listening. When patients develop severe hearing loss, they may still hear sounds with the intact ear despite plugging. The third point is ‘accidents’. In the case of traditional pharmacotherapy, the intact ear is not plugged, and thus SSHL patients can pick up environmental sounds via this intact ear. On the other hand, plugging and music listening inherent to the CIST protocol seal patients from environmental sounds, and thus the accident hazard is likely increased. Therefore, the CIST protocol should be conducted in a safe environment.
Unlike pharmacotherapy, the CIST protocol has no limitations concerning medications, allergies, or other diseases such as diabetes, hypertension, and hyperlipidemia. However, the limitation of this protocol is that it is intended for patients who are able to listen to sounds with their affected ear. As such, the CIST protocol is not suited for SSHL patients with severe hearing loss. This protocol is applied to acute stage SSHL (days since SSHL onset ≤ 5) because previous studies reported that a shorter time delay between the onset of SSHL and the start of treatment led to better hearing recovery2. It remains elusive whether there is a time restriction for starting the CIST protocol. Moreover, the optimum duration of the CIST protocol and the total music listening time require further investigation.
This protocol utilizes the corticosteroid therapy in addition to CIST. At present, corticosteroids are the most commonly used treatment for SSHL, and therefore it is ethically not feasible to stop this treatment. However, recent triple-blinded SSHL treatment studies14 revealed that the recovery of non-treated patients was similar to that of patients who had received corticosteroids. Even though one cannot exclude the possibility that the combination of CIST + SCT led to the results obtained, it appears reasonable to assume that CIST alone will be beneficial, especially for patients with diseases that are worsened by corticosteroids such as infections, diabetes, and glaucoma.
In this protocol, patients are hospitalized in order to avoid accidents. However, SSHL patients often cannot be hospitalized because of work, family, and financial reasons. The utilization of a hearing aid may allow these outpatients to perform the CIST protocol. SSHL patients who wear a hearing aid in their affected ear are ‘functionally’ exposed to an enriched acoustic environment, are not in danger to be exposed to harmful sound levels, and are able to detect warning sound signals. However, the daily monitoring of hearing threshold levels and appropriate adjustments to the hearing aid settings would be necessary since hearing capability of SSHL patients can improve rapidly. Generally, the CIST protocol will not disturb other treatment approaches and may actually manifest a synergic effect when used in combination with other SSHL treatment strategies.
In the present study, a limited number of SSHL patients underwent the CIST protocol, and the participants were not randomized to the different treatment conditions. Thus, a randomized controlled study including a larger number of patients should be executed in the future. Moreover, the effectiveness of the CIST protocol should be investigated in patients with different types of hearing loss. Further, in the present study, all participants who performed the CIST protocol also received the corticosteroid therapy. Therefore, it remains unresolved whether the CIST protocol alone can improve the hearing ability of SSHL patients. It would be valuable to perform a randomized controlled study in which SSHL patients, for whom corticosteroids may cause severe side effects (such asinfectious diseases or diabetes mellitus), would either merely receive the CIST protocol or merely a standard corticosteroid therapy. Notably, in our previous report23, the effects of the CIST protocol within the human auditory cortex were examined by means of magnetoencephalography35. The results showed that the CIST protocol could have prevented maladaptive cortical reorganization in the human primary and non-primary auditory cortices. Of course, it is difficult to conduct neuroimaging studies in practices and hospitals; however, speech test, hearing in noise test36, and tinnitus related examinations37 may contribute to reveal the functional plasticity in the central auditory system induced by the CIST protocol. Eventually, even though the CIST protocol is in a very early stage in development, and although further investigations are needed, the CIST protocol as an effective, inexpensive, and safe treatment option can complement the corticosteroid therapy, which may induce severe and potentially lethal side effects.
The authors have nothing to disclose.
We thank Yoshimasa Sekiya for demonstrating the protocol technique on film. This work was supported by the ”Japan Society for the Promotion of Science for Young Scientists (26861426)” and by the “COI STREAM (Center of Innovation Science and Technology based Radical Innovation and Entrepreneurship Program)”.
Ear mold | RION Co.Ltd, Tokyo, Japan | EM-59 | |
portable music player | Sony Corporation, Tokyo, Japan | NW-S775 | |
headphone | SENNHEISER Electronic GmbH & Co. KG, Hannover, Germany | HD280pro | |
equalizer | Roland Corporation, Hamamatsu, Japan | GE-7 | |
headphone amplifier | FiiO Electronics Technology Co. Ltd, Guangzhou, China | E11 | |
sound editing application | Adobe Systems Inc., CA, USA | Audition 3.0 |