Arytenoid Cartilage Dislocation Caused by a Laryngeal Mask Airway Treated with Chemical Splinting

Abstract

Sore throat and hoarseness after laryngoscopy and short-term endotracheal intubation is not uncommon. The incidence ranges from 16% to 100% [1,2]. The cause of postintubation hoarseness is multifactoral including pharyngeal and laryngeal trauma, hematoma and edema, vocal cord paralysis, and arytenoid cartilage dislocation [3-5]. As of 1994 there were only 57 cases of arytenoid dislocation or subluxation reported in the world literature [6]. The laryngeal mask airway (LMA) is an airway management device which was introduced in 1988 [7]. It is an alternative to endotracheal intubation for certain routine anesthetics and is an adjunct in emergency airway management [8]. The LMA does not necessitate direct laryngoscopy for insertion and, therefore, should limit the airway trauma sometimes caused by instrumentation with rigid laryngoscopes. We present the first report of arytenoid cartilage dislocation secondary to LMA insertion. Treatment was by mechanical reduction and chemical splinting. Case Report A 57-year-old, 70-kg, 155-cm woman, ASA physical status I, underwent right total knee replacement under general anesthesia at another institution. Her airway was managed uneventfully with a LMA. While insertion was noted to be without difficulty on one attempt, the size of the LMA used was not recorded. The duration of the procedure was 50 min. The patient noticed hoarseness immediately postoperatively and sought consultation 4 wk later. Examination at that time by fiberoptic laryngoscopy showed an anteromedial dislocation of the right arytenoid cartilage with a flaccid and bowed vocal cord. Six weeks postoperatively, the patient returned to the operating room for reduction and chemical splinting of the right arytenoid cartilage. This was performed under general anesthesia using intravenous propofol for induction and maintenance supplemented with fentanyl and succinylcholine for muscle relaxation. The airway was managed with infraglottic jet ventilation. After arytenoid reduction a total of 7.5 U of botulinum toxin was injected into the right thyroarytenoid and lateral cricoarytenoid muscles. The patient's hoarseness resolved within 4 wk postoperatively, and she was symptom free 9 mo later with normal arytenoid position and mobility. Discussion The LMA has been in use in the United States since mid-1991 [7], and there are few reports of airway complications associated with its use. Care must be taken during insertion so as not to traumatize the uvula which can result in swelling [9]. Ezri et al. [10] reported two cases of pulmonary edema. This was probably negative pressure pulmonary edema which resulted from unrecognized partial glottic obstruction by the LMA [11]. This is surprisingly infrequent given the 10% incidence of partial airway obstruction that has been reported with LMA use [12,13]. Differentiating between vocal cord paralysis and arytenoid cartilage dislocation is sometimes difficult [14]. Electromyography and computed tomography are helpful in the differential diagnosis [15,16]. Arytenoid dislocations are usually anteromedial (as in our case) and involve disruption of the stabilizing posterior cricoarytenoid ligament resulting in an unopposed pull by the vocal cord adductor muscles perpetuating the dislocation. Traditional therapy for arytenoid dislocation is closed reduction. This is often unsuccessful by itself due to scarring and joint fixation especially in the case where the diagnosis has been delayed. Various open procedures then become necessary to eliminate the unopposed anteromedial pull on the arytenoid. This involves tenotomy and stenting techniques sometimes necessitating tracheostomy [14]. These procedures are permanent and irreversible sometimes resulting in poor voice quality. (1) 1 Rontal E, Rontal M. Chemical splinting of the larynx. Presented at the American Laryngologic Association meeting, Orlando, FL, May 5, 1996. To be published in the transactions of the American Laryngologic Association. Botulinum toxin has been used in the treatment of several laryngeal disorders to temporarily paralyze selective laryngeal muscles [17].1 This novel approach of chemical splinting was used to successfully treat our patient's arytenoid dislocation. (2) 2 Rontal E, Rontal M. Chemical splinting for the treatment of arytenoid dislocation. Presented at the Voice Foundation Meeting, Philadelphia, PA, June 7, 1996. The initial phase of the procedure involves closed reduction and freeing of adhesions by endoscopic arytenoid mobilization. The subsequent injection of the thyroarytenoid and lateral cricoarytenoid muscles (vocal cord adductors) with botulinum toxin causes a progressive weakness of these muscles which peaks at about one week and lasts for approximately three months. Their weakness allows the posterior cricoarytenoid muscle (the cord abductor) to pull back and splint in place the arytenoid cartilage. It accomplishes this by allowing the posterior cricoarytenoid muscle to pull the arytenoid cartilage, unopposed, in a posterolateral direction, which is opposite from the anteromedial direction of the dislocation. This splinting allows the injured posterior cricoarytenoid ligament to heal and thus the arytenoid cartilage returns to a normal position. In summary, we have reported a case of arytenoid cartilage dislocation caused by an LMA. Treatment was by closed reduction and chemical splinting using botulinum toxin. Chemical splinting is minimally invasive, not permanent, and provided excellent results in this patient.