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.
突然の感音難聴(SSHL)は、急性、突発性難聴によって特徴付けられます。推定発症率は年間10万人あたり5〜30例です。 SSHLの原因と現在SSHLの根底にあるメカニズムは不明のままです。このような蝸牛への循環障害、ウイルス感染、および自己免疫疾患などのいくつかの仮定に基づいて、薬理学的治療法はSSHL患者を治療するために適用されています。しかし、標準的な治療、コルチコステロイド療法の有効性は、議論中です。激しい音への暴露は、聴覚系に永久的な損傷を引き起こすことが示されています。しかし、適度なレベルへの暴露は、聴覚障害を減らすことができるノイズ外傷後の音響環境を豊かに。いくつかの神経画像研究は、最近SSHLの発症は、人間の聴覚皮質で不適応皮質再編を誘導することを示唆し、急性SSHL段階負CORRにおける皮質再編の度合いこと難聴からの回復率と大喜び。この記事ではSSHL、「制約によって誘発される音響療法(CIST)」のための新たなニューロリハビリテーション手法の開発を報告します。 CISTプロトコルの目的は、予防または濃縮された音響環境を使用して、不適応皮質の再編成を低減することです。 SSHL患者の無傷の耳の外耳道を積極的に影響を受けた耳を使用することにより、不適応皮質再編の進行を防ぐためにそれらをやる気にさせるために接続されています。影響を受けた耳も入院中の1日6時間、ヘッドホンで音楽にさらされています。 CISTプロトコルはSSHLため、安全で簡単に、安価で、かつ効果的な治療であるように思われます。
突然の感音難聴(SSHL)、または突発性難聴は、1を聞いての急速な損失によって特徴付けられる特発性状態です。いくつかの疫学的研究2,3は、先進国では年間10万人あたり5〜30例SSHL発生率を報告しました。 SSHLの原因とSSHLの基礎となるメカニズムは広く検討されているにもかかわらず、SSHLに関する我々の知識は限られています。特発性SSHLの多くの潜在的な原因の中で、一般的な仮説は、循環障害4、ウイルス感染5-7、および自己免疫疾患8,9が含まれます 。コルチコステロイド治療10は、これらの仮説に基づいて提案し、最も一般的に適用される治療法であるたが、この標準的治療の有効性はまだ3,11-14に議論されています。そのため、異なる視点が動機革新的なSSHLの治療戦略は、強く望まれています。
SSHL蝸牛ではなく、聴覚皮質だけでなく神経活動に影響を与えます。いくつかの神経画像研究15-17 SSHLはその発症の数日以内に、人間の聴覚皮質における皮質の可塑性を誘導することが示唆されました。また、聴覚誘発フィールドの対側半球優勢の損失によって表される皮質再編の程度が負損失18を聞いてから、回収率と相関するように見えました。 SSHLの発現によって誘導される皮質の可塑性は、影響を受けた耳の聴覚機能のための不適応と考えることができます。したがって、SSHLに関連したこの不適応皮質再編の予防は、新たな治療戦略を表すことができます。
この記事では、不適応皮質再編成を防止または軽減するために皮質の変化 '非使用を学んだ」防止ニューロリハビリテーションのアプローチを提案しています。例えば、運動機能障害の場合には、学習された未使用の最初に起因する副作用を抑制し、すべての活動の障害が最終的行動の抑制とそれに対応する神経活動19,20になり患肢で試行する動き現象をlimbis。学習された不使用は、運動機能障害に限定されるものでは表示されませんが、また、感覚障害21に関するものであってもよいです。 SSHL患者が主に使用し、リスニングのためにそのまま耳に注意を払います。このリスニングの動作はそのまま耳に対応する神経活動を増加させると同時に、影響を受けた蝸牛と聴覚皮質22との間の神経接続を減らすために表示されます。 「不使用」によって誘導され、この不適応皮質の変化を防止するためには、SSHL患者は、影響を受けた耳を介して集中的に音楽を聴くために、参加者の動機「制約によって誘発される音響療法(CIST)'23を実行するために有益であると思われます影響を受けた耳に聴覚注意を払います( 図1)。従来の薬物療法と比較すると、CISTはたぶんSSHLため、安全で簡単に、安価で、かつ効果的な治療法です。
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 |