Laryngeal Electromyography and Botulinum Toxin Injection in Exercise‐Induced Laryngeal Obstruction

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Exercise‐induced laryngeal obstruction (EILO) is the inappropriate inspiratory closure of the larynx during exercise.1 EILO is a common condition in elite athletes, impacting their performance.2 The gold standard for diagnosis is continuous laryngeal endoscopy, which allows the monitoring of laryngeal movements during exercise.3 Surgical and nonsurgical treatments have been reported, depending on the site of laryngeal obstruction and the severity of respiratory symptoms. To our knowledge, this is the first report of the successful use of botulinum toxin (BT) for treating EILO.

Case Report

A 22‐year‐old healthy female professional cyclist developed inspiratory dyspnea with stridor during intense physical activity. Dyspnea occurred systematically when the heart rate reached 180 beats per minute and was correlated with an effort of 250 W, reversible 5 minutes after the end of the exercise, with decreasing heart rate.

Laryngoscopy was performed at rest using a flexible Karl Storz fiberscope (SN 2828116, Tuttlingen, Germany). The supraglottic region and vocal fold mobility were normal during breathing, coughing, and phonation at rest. A continuous laryngeal endoscopy (telepack X led TP 100; Karl Storz) was performed using the patient's bicycle and home trainer. The work load was adjusted to a maximum heart rate of 180 beats per minute and a power of 250 W. When dyspnea occurred, both vocal folds moved to the paramedial position during inspiration (approximatively 80% of vocal fold adduction; Video S1). These symptoms and laryngeal dynamic abnormalities suggested the diagnosis of EILO. Laryngeal electromyography (LEMG) was performed at rest using The Dantec Keypoint EMG with a 27 G needle (37 mm; Dantec Keypoint, Natus, Pleasanton, CA). LEMG of the thyroarytenoid (TA) muscles showed normal activity during phonation. During deep inspiration, there was paradoxal activity of the TA muscles with higher amplitudes than during phonation (Fig. 1). Posterior cricoarytenoid muscle activity was normal during phonation and sniffing. The LEMG results were highly suggestive of laryngeal dystonia.4 BT injection into the TA muscles was performed under LEMG guidance. We injected 1.3 units of Xeomin (Merz Pharmaceuticals GmbH, Frankfurt am Main, Germany) in both vocal folds.

Figure 1.

Electromyography activity of thyroarytenoid muscles during phonation and deep inspiration.

Transient mild dysphonia occurred and lasted less than 15 days. There was no aspiration. One week after injection, exercise‐induced dyspnea and stridor completely disappeared, and the patient resumed the practice of training and competitions. Recurrence of the symptoms occurred 2 months after the injection, and the injections were repeated with the same efficacy. A total of 7 BT injections were performed during the course of 14 months.

Discussion

It is now well recognized that EILO is an important and prevalent cause of dyspnea on physical exertion.5 Various descriptions of EILO have been previously proposed, such as exercise‐induced inspiratory symptoms, exercise‐induced vocal cord dysfunction, paradoxical vocal fold motion, and exercise‐induced laryngomalacia. The acronym EILO for exercise‐induced laryngeal obstruction was consensually adopted in 2015.1 The management of EILO includes surgical and nonsurgical treatments. Endoscopic supraglottoplasty for supraglottic EILO was reported with a significant improvement in breathing.6 Psychotherapy, speech therapy, laryngeal control therapy, and inhaled ipratropium have been proposed.7 BT has been suggested to be a potential treatment of EILO, but has never been reported in the literature to the best of our knowledge.8 Baxter and colleagues8 suggested that EILO may represent a form of task‐specific muscle spasm (dystonia) similar to that found in writer's cramp, blepharospasm, and other comparable conditions, although diagnostic investigations such as laryngeal electromyography (EMG) have never been performed. Walsted and colleagues9 performed diaphragmatic electromyography in a prospective study of EILO with no significant results.

In normal subjects, LEMG in TA muscles shows no activity at rest and during deep inspiration. In our case, the LEMG of the TA muscles showed normal activity during phonation. During deep inspiration, there was paradoxical activity with higher amplitudes than in phonation. Such LEMG abnormalities are compatible with the diagnosis of laryngeal dystonia.4 In our opinion, EILO should be considered as a type of laryngeal dystonia. BT injection into the intrinsic laryngeal muscles is the gold standard for the treatment of laryngeal dystonia. Baxter and colleagues8 injected 2.5 U of Botox (Allergan, Irvine, CA) in patients with asthma and abnormal vocal cord movement with successful laryngeal results after 1 month. We arbitrarily decided to inject low doses of BT to avoid side effects such as dysphonia and aspiration. Despite the low dose, transient dysphonia occurred in our patient, but not aspiration. In our opinion, EILO should be considered as an atypical type of laryngeal dystonia. LEMG is a tool to confirm the diagnosis of laryngeal dystonia. To our knowledge, our case is the first report in the literature of a professional athlete suffering from EILO syndrome treated successfully with BT injected into the TA muscles under LEMG guidance. Since this first patient, we have treated 4 more patients with the same favorable results. Further studies including more patients are necessary to confirm the efficacy of BT injection in EILO syndrome.

Author Roles

(1) Research project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript: A. Writing of the first draft, B. Review and Critique.

C.R.: 3A

D.B.: 3B

S.L.G.: 3B

D.A.: 3B

M.M.: 3B

Disclosures

Ethical Compliance Statement: This study was approved by Comité d'Ethique de la Fondation Rothschild (réf. CE_20190416_11_MMY). Informed patient consent was not necessary for this work. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines.

Funding Sources and Conflict of Interest: No specific funding was received for this work, and the authors declare that there are no conflicts of interest relevant to this work.

Financial Disclosures for the Previous 12 Months: The authors declare that there are no additional disclosures to report.

Supporting information

Video S1. Continuous laryngeal endoscopy: adduction of the vocal fold during inspiration.