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.
Plutselig sensorinevralt hørselstap (SSHL) er preget av akutt, idiopatisk hørselstap. Den estimerte forekomsten er 5-30 tilfeller per 100.000 personer per år. Årsakene til SSHL og mekanismene bak SSHL tiden forbli ukjent. Basert på flere hypoteser for eksempel en forstyrrelse i sirkulasjons sneglehuset, viral infeksjon, og autoimmune sykdommer, har farmako-terapeutisk tilnærmingsmåter vært anvendt for å behandle pasienter SSHL; imidlertid effekten av standard behandling, kortikosteroider, er fortsatt under debatt. Eksponering for intense lyder har vist seg å forårsake permanent skade på hørselssystemet; imidlertid eksponering for et moderat nivå beriket akustiske miljøet etter støy traumer kan redusere hørselshemmede. Flere bildediagnostiske undersøkelser har nylig foreslått at utbruddet av SSHL indusert mistilpasset kortikale omstilling i den menneskelige hørsels cortex, og at graden av kortikale omstilling i den akutte fasen SSHL negativt korropprømt med utvinningsgraden av hørselstap. Artikkelen rapporterer utviklingen av en ny neuro-rehabilitering tilnærming for SSHL, "restriksjons indusert lyd terapi (cist)". Målet for cist protokollen er å hindre eller redusere mistilpasset kortikal omstilling ved hjelp av en anriket akustisk miljø. Kanalen i den intakte øret av SSHL pasienter er plugget for å motivere dem til å aktivt bruke de berørte øret og dermed hindre fremdriften av mistilpasset kortikal reorganisering. Den berørte øret er også eksponert for musikk via hodetelefoner for seks timer per dag under sykehusoppholdet. Den kisten protokollen ser ut til å være en trygg, enkel, billig og effektiv behandling for SSHL.
Plutselig sensorinevralt hørselstap (SSHL), eller plutselig døvhet, er en idiopatisk tilstand som er preget av en rask tap av hørsel 1. Flere epidemiologiske studier 2,3 rapportert SSHL forekomst av 5-30 tilfeller per 100.000 personer per år i industrialiserte land. Selv om årsakene til SSHL og mekanismene bak SSHL er kontrollert omfattende, vår kunnskap om SSHL fortsatt begrenset. Blant de mange mulige årsaker til idiopatisk SSHL, vanlige hypoteser inkluderer en sirkulasjonsforstyrrelse 4, virusinfeksjon 5-7, og autoimmune sykdommer 8,9. Selv kortikosteroidterapi 10 ble foreslått på grunnlag av disse hypotesene, og er den mest søkt behandling, er effekten av denne standardbehandling fortsatt blir debattert 3,11-14. Derfor innovative SSHL behandlingsstrategier, motivert av ulike perspektiver, er sterkt ønsket.
SSHLpåvirker nevrale aktiviteten ikke bare i sneglehuset, men også i det auditive cortex. Flere bildediagnostiske undersøkelser 15-17 antydet at SSHL indusert kortikale plastisitet i den menneskelige auditive cortex løpet av noen få dager etter sin debut. Videre graden av kortikal reorganisering representert ved tap av kontralateral hemisfærisk dominancy av auditive evoked felt ut til negativt korrelert med utvinningsgraden fra hørselstap 18. Kortikale plastisitet indusert ved utbruddet av SSHL kan anses som mistilpasset for høreevnen til berørte øret. Derfor kan forebygge denne mistilpasset kortikal omstilling forbundet med SSHL representerer en ny behandlingsstrategi.
Denne artikkelen foreslår en nevro-rehabilitering tilnærming som hindrer 'lært ikke-bruk "cortical endringer for å hindre eller redusere mistilpasset kortikal reorganisering. For eksempel, i tilfeller av motorisk dysfunksjon, den lærte ikke-bruk aven limbis et fenomen der bevegelsen er i utgangspunktet undertrykkes på grunn av bivirkninger og svikt i enhver aktivitet forsøkt med de berørte lem, som til slutt resulterer i undertrykkelse av atferd og tilsvarende nevrale aktiviteten 19,20. Lært ikke-bruk ser ikke ut til å være begrenset til motorisk dysfunksjon, men kan også gjelde sensoriske funksjonshemninger 21. SSHL pasienter hovedsakelig bruker og ta hensyn til den intakte øret for å lytte. Dette lyttevirkemåten ser ut til å øke nevral aktivitet som tilsvarer den intakte øret og, på samme tid, redusere nerveforbindelser mellom de berørte sneglehuset og auditiv cortex 22. For å forhindre dette mistilpasset cortical endringer indusert av "ikke-bruk", ser det ut til å være gunstig for SSHL pasienter til å utføre "begrensningen-induced lyd terapi (kisten) '23, som motiverer deltakerne til å lytte til musikk intensivt via de berørte øret og til å betale auditiv oppmerksomhet til de berørte øret(Figur 1). Sammenlignet med konvensjonelle farmakoterapi, den kisten angivelig er en trygg, enkel, billig og effektiv behandling tilnærming for 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 |