Eur Arch Otorhinolaryngol (2003) 260 : 304–307 DOI 10.1007/s00405-002-0572-9
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L A RY N G O L O G Y
U. Schroeder · M. Motzko · C. Wittekindt · H. E. Eckel
Hoarseness after laryngeal blunt trauma: a differential diagnosis between an injury to the external branch of the superior laryngeal nerve and an arytenoid subluxation. A case report and literature review Received: 9 September 2002 / Accepted: 18 November 2002 / Published online: 11 February 2003 © Springer-Verlag 2003
Abstract Arytenoid subluxation is a well-known cause of hoarseness due to incomplete glottic closure with intact inferior laryngeal nerves after severe laryngeal trauma. We report the case of a young man presenting after laryngeal blunt trauma with hoarseness, easy fatigue during phonation, marked difficulty with his high-pitch and singing voice and decreased phonation time, but intact function of both inferior laryngeal nerves, intact endolaryngeal mucosa sensibility and normal CT scans of the larynx and the neck. Due to the asymmetric anteromedial position of the right arytenoid with incomplete glottic closure, the primary diagnosis was arytenoid subluxation, and the patient was referred for instantaneous relocation therapy. The stroboscopic and electromyographic diagnosis of a unilateral paresis of the external branch of the right superior laryngeal nerve caused the therapy to be changed. Without repositioning, the patient had a total recovery of voice quality when the paresis receded 2 months later. In conclusion, the unilateral paresis of the external branch of the superior laryngeal nerve after laryngeal blunt trauma is reported here for the first time. Although the clinical findings are familiar sequelae of thyroid surgery, they may be misdiagnosed as arytenoid subluxation after laryngeal blunt trauma. Stroboscopy and electromyography permitted the correct diagnosis. Keywords Case report · Laryngeal trauma · Paresis · Cricothyroid muscle · Superior laryngeal nerve
Introduction: The laryngoscopic appearance of an immobile vocal cord in a posttraumatic patient with injury to the larynx in the first line suggests deciding between inferior laryngeal nerve U. Schroeder (✉) · M. Motzko · C. Wittekindt · H. E. Eckel ENT Department, University of Cologne, Joseph-Stelzmann Str. 9, 50924 Cologne, Germany Tel.: +49-221-4784797, Fax: +49-221-4786425, e-mail:
[email protected]
paresis or arytenoid subluxation for the differential diagnosis. Although in some patients these two diagnoses are difficult to distinguish clinically, in most cases the etiology of the trauma, the additional clinical signs and the electromyographic findings permit the diagnosis: (1) in patients with external dissecting trauma of the neck without endolaryngeal injury, the primary diagnosis of an injury of the inferior laryngeal nerve will easily be proven by EMG; (2) in patients with endolaryngeal trauma (especially after complicated anesthesiological intubation or other upper airway instrumentation), the diagnosis of an arytenoid subluxation will be chosen without problems, too. Sometimes the diagnosis may be facilitated by the typical pathological anteromedial shift of one arytenoid resulting in cord immobility with a residual, slight, but ineffective movement of the subluxated arytenoid cartilage. In rare cases, an arytenoid subluxation may occur after blunt external trauma to the neck, but this is reported only once in the literature [12]. Overall, the incidence of arytenoid subluxation is relatively uncommon. Eight years ago, the disruption of the cricoarytenoid joint was still reported as a relatively uncommon event, according to the number of 31 reported cases of arytenoid dislocation or subluxation in the world literature up to 1994 [10]. These first reports still focused on the fact that knowledge of the signs and symptoms of arytenoid dislocation aids in making the correct diagnosis and in the early treatment [10]. In the meantime, there are manifold reports about arytenoid subluxation, and even if it is still an infrequent event, the diagnosis is well known. A paresis of the recurrent nerve or rheumatic disease were suggested as the predisposing factors [9, 13]. At present, the treatment of choice indicated in the literature is the invasive approach with immediate repositioning [9, 10], although the results are not satisfying. We wanted to present this case of a patient with hoarseness after laryngeal blunt trauma, because he was suspected of having an arytenoid subluxation and therefore was referred to our emergency room for immediate relocation
305 Fig. 1 a Laryngoscopic pictures of a patient with rightsided arytenoid subluxation on respiration, b on phonation and c of our reported patient with paresis of the external branch of the right superior laryngeal nerve on respiration and d on phonation. Although the underlying anatomical-pathological conditions of an arytenoid subluxation and a paresis of the cricothyroid muscle are quite different, there is a notable similarity in the laryngoscopic aspect regarding the slack right vocal cord, the asymmetric position of the arytenoid cartilages and the incomplete glottic closure
therapy. The rare diagnosis of an isolated paresis of the external branch of the superior laryngeal nerve caused his therapy to be changed and so guarded the intact arytenoid joint with a complete restoration of voice function after conservative therapy.
Case report Forty-eight hours prior to presentation, the 36-year-old patient received a forced hand attack on his right larynx (a sports accident, objectively considered to be minor laryngeal trauma). He felt “breath- and voiceless” for the first moment. After a few seconds he could breathe without effort or pain. Since he expected a similar spontaneous improvement of his hoarse and weak voice, too, he didn’t ask for medical advice at once. But the next day, he developed serious problems as a professional voice user (teacher) because of his persisting hoarse and easily fatigued voice. He visited an ENT specialist, who referred him to our emergency room for repositioning of the suspected arytenoid subluxation of the right side. On the first presentation, we saw a healthy man without stridor or dyspnea, but with a marked hoarse and weary voice. The soft tissues of the neck and the cartilagenous structures of the external larynx were intact on palpation. There were no signs of hematoma, emphysema or fractures. A fracture had also been ruled out by CT scan. The laryngoscopic picture 48 h after the trauma revealed a regular endolaryngeal mucosa without hematoma, emphysema or swelling. The left vocal cord and arytenoid were regular with free motility. The right arytenoid cartilage appeared asymmetrical, with its superior tip being displaced in the anteromedial direction. On
direct viewing, the right processus vocalis was hidden underneath the top of the right arytenoid cartilage, and the whole glottic space appeared to be twisted (Fig. 1c). On phonation the right vocal cord appeared slack with wavy, irregular edges, and the posterior commissure shifted to the right side. The incomplete glottic closure in the middle part of the vocal cords, the lower position of the right vocal process and the shifted posterior commissure suggested an impaired motility of the right side (Fig. 1d). The most striking findings were the considerable hyperfunctional compensatory gestures with increased tension of both false vocal cords and the reduction of the anterior posterior diameter of the endolarynx in order to return the previous voice capacity (Fig. 1d). Especially the head voice was lost completely (Fig. 2). This “oblique” glottis together with the asymmetric aspect of the arytenoids had led to the primary diagnosis of an arytenoid subluxation (Fig. 1a and Fig. 1b). Since there was an asymmetric but free motility of the right arytenoid cartilage, we discarded the diagnosis of an arytenoid subluxation. Instead of examining the arytenoid joint under general anesthesia, we delayed operative therapy for 12 h in order to complete the diagnostic measures by stroboscopy and electromyography. The next day, the voice was similarly impaired. The stroboscopic picture showed the loose right vocal cord with wavy edges and irregular vibratory motions, but free motility of the right arytenoid. On phonation the picture of the oblique glottis with a shift of the posterior commissure, a loose right vocal cord with a slight incomplete glottic closure and a lower position of the right-sided vocal process was identical to the prior finding. Electromyography determined the intact function of both inferior laryngeal nerves (Fig. 3a and Fig. 3b), but revealed a unilateral flat line in the electromyographic recording of the cricothyroid muscle in front of the larynx, indicating a paralysis of the external branch of the superior laryngeal nerve on the right site (Fig. 3c).
306 Fig. 2 The vocal fields show the reduced dynamic range with the loss of the head voice
In view of this diagnosis, we reduced therapy to conservative speech therapy exclusively. Two months later, the paresis had receded and the glottis regained its normal shape with total recovery of voice quality.
Discussion
Fig. 3 Laryngeal electromyographical recordings of the reported patient showing the right (a) and left (b) vocal muscles, respectively, and the right (c) and left (d) cricothyroid muscles, respectively. Both vocal muscles and the left cricothyroid muscle show regular motor unit action potentials on phonation, whereas the electromyographical recording of the right cricothyroid muscle shows a flat line only
The patient didn’t suffer any kind of aspiration or cough, and the sensibility of the endolaryngeal mucosa was intact on both sites, indicating a normal function of the internal branch of both superior laryngeal nerves. According to the trauma to the right side of the larynx, the final diagnosis was a singular paresis of the external branch of the right superior laryngeal nerve.
Although the term “arytenoid subluxation” is well known as a diagnosis, the anatomical-pathophysiological basis of this posttraumatic condition of the cricoarytenoid joint still is unclear. Various evidence indicates that the symptom of a vocal cord with impaired motility after complicated upper airway instrumentation doesn’t match an ordinary joint (sub-)luxation, for example, comparable to the classical luxation of the shoulder with a similar small articulation surface. First of all, the treatment of choice indicated in the literature, the instantaneous relocation of the subluxated arytenoid, has a quite uncertain prognosis. There is only a minor chance of full recovery of vocal-cord mobility. Paulsen experimentally simulated an arytenoid subluxation cartilage in intubation trials on 37 unfixed cadaver larynges and proved it impossible to produce any subluxation of a cricoarytenoid joint [8]. Histopathological investigations only showed injuries of synovial folds, joint-surface injuries of the articular cartilage or subchondral bone fractures [8]. These findings indicate some possible reasons for the familiar finding that a relocation trial of the cricoarytenoid joint seldom leads to restoration in a mobile vocal cord, but most often in an arytenoid ankylosis. Consequently, the indication for such a repositioning should be considered very critically.
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Besides, there are reports of patients with the diagnosis of arytenoid subluxation and spontaneous recovery of cord motility [12], assuming that the diagnosis as well as the therapy of an arytenoid subluxation are more troublesome than an ordinary (sub-)luxation of another joint of the human body. Although the clinical symptoms of an isolated paresis of the external branch of the superior laryngeal nerve are well known from complicated thyroid surgery [14], in our patient they were nearly misdiagnosed as arytenoid subluxation, since they have never before been reported as sequelae from an external blunt trauma to the neck. Already in 1951 and 1963, Moran and Faaborg-Andersen described the clinical symptoms of a unilateral paresis of the superior laryngeal nerve with the typical picture of the shift of the posterior commissure toward the inactive side and consequent oblique glottis with the lower position of the vocal process on the paretic site [4, 7]. FaaborgAndersen stated that this paralysis is not so unusual as previously supposed [4]. Four of his patients had a complete paresis of the superior laryngeal nerve (internal and external branch) as a result of thyroid surgery or malignant disease. But, interestingly, one patient was reported with a temporary neuritis of the superior laryngeal nerve, so that the author was able to discern the disappearance of the characteristic oblique glottis with cessation of the paresis in the follow-up of the patient [4]. It is remarkable that case reports about disturbances of the cricothyroid muscle with successive voice impairment most often concern patients who rely on their voices professionally [2, 11]. This feature indicates a notable dark number of patients with such disorders. On the other side recent studies emphasized that voice alteration together with the phoniatric evaluation (stroboscopy, voice range measurement) are useful diagnostic tools in singers and non-singers with a paresis of the external branch of the superior laryngeal nerve [1, 3]. Bellatone used videostroboscopy and did not find any patients with a paresis of the external branch of the superior laryngeal nerve out of 282 investigated asymptomatic patients after thyroid surgery, whereas all patients with voice alteration had a lesion of the inferior or the superior laryngeal nerve [1]. Although there are contradictory opinions concerning the identification of the external branch of the superior laryngeal nerve in thyroid surgery routinely [1, 5, 6], the knowledge of the anatomical variations of the external branch of the superior laryngeal nerve in normal and pathological thyroid glands [5, 6] and skilled surgery (ligation of the vessels close to the capsule of the superior pole of the thyroid gland) [1] secure optimal postoperative laryngeal function. The importance of the function of the cricothyroid muscle enhancing the length and viscoelastic tension of
the vocal fold regarding voice quality is well known, especially in professional voice users with wide dynamic voice ranges (head voice). This understanding consequently brought about the therapeutic cricothyroid subluxation in patients with laryngoplastic phonosurgery for paralytic dysphonia with convincing results [15]. In our opinion, ENT specialists should be familiar with the voice alterations resulting from a singular paresis of the external branch of the superior laryngeal nerve, not only in order to be able to exclude an arytenoid subluxation and to cancel inappropriate surgery, but also to be able to figure out the function of the cricothyroid muscle in patients with paresis of both the inferior and the superior laryngeal nerve, e.g., after thyroid surgery, with planned framework surgery.
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