CT Signs of vocal cord paralysis

Clinical History

A 56 year old patient with an endovascular procedure of the aortic arch in history presented with a left-sided vocal cord paralaysis. Endoscopy showed a fixed cord without a tumoral lesion. No lumps or lymphadenpathies were palpated in the neck.

Imaging Findings

A 56 year old male was referred by the otorhinolaryngologist to our radiology department because of hoarseness. On endoscopy he had a fixed, paralytic vocal cord on the left side. The mucosa was intact without tumoral lesions. Clinical examination of the neck did'nt reveal any lumps or lymphadenopathies. In history there was an endovascular procedure for an aneurysm of the aortic arch a year ago.The otorhinolaryngologist referred the patient to our radiology departement for a CT-scan of the neck. We did a contrast enhanced CT-scan of the head and neck including the superior part of the mediastinum. The scan was done during quiet respiration. Axial and coronal reformatted images confirmed a paralysis of the left vocal cord which was undoubtedly longstanding because of the fatty atrophy of the vocal muscle (fig 2a). In the superior mediastinum multiple aneurysmal dilatations of the aortic arch (fig 1)were demonstrated as the probable cause of the vocal paralysis. Paralysis of the left vocal cord due to aneurysm of the aortic arch is known as Ortner's syndrome.

Discussion

We present a case of vocal cord paralysis in which almost all radiological signs of paralysis are nicely demonstrated. It is important to know the features of paralysis because clinically it is not always easy to make the distinstion between a mechanical cord fixation or a paralysis in a patient with an immobile cord. Cord fixation occurs in tumors, traumatic / inflammatory/ iatrogenic arytenoid luxation. First sign of paralysis is a paramedian position of the vocal cord. The paralysed cord stays in that paramedian position during dynamic scanning. There is no abduction during quiet breathing (fig 2a), no adduction while 'i'-phonating. A normal vocal cord abducts slightly in comparison with the paralysed cord during quiet breathing as demonstrated in fig 2a. We did not add a scan during 'i'-phonation because all was already clear by the first scan. Second sign is an asymmetric, ipsilateral dilatation of the laryngeal ventricle (fig 2b+3a) due to decreased muscle bulk of the thyroarytenoid muscle (see 6th sign). Third sign is an anteromedial deviation of the ipsilateral arytenoid cartilage (fig 2a) resulting in the fourth and fifth signs. Fourth sign is an asymmetric, also ipsilateral dilatation of the piriform sinus (fig 2c+3b). Fifth sign is a thickening and medial position of the aryepiglottic fold compared to the normal side (fig 2c). Sixth sign is a fatty atrophy of the true vocal cord (fig 2a) which can also be demonstrated in the posterior crico-arytenoid muscle (fig 2d). The atrophy of the true vocal cord is responsible for the second, seventh and eighth signs. Denervation atrophy and fatty inflitration occurs within a few weeks after injury. Seventh sign is a flattening of the subglottic arch (fig 3a). Eighth sign is thinning of the paralysed vocal cord best seen at the medial edge on coronal reformatted images (fig 3c). Nineth sign (not present in this case) is an ipsilateral dilatation of the vallecula. A correct alignment of the reformatted axial images to the true vocal cord is very important to see the above described signs of paralysis. In order to make reformatted images in the appropriate plane I added a sagital image with a reference line in plane with the vocal cord (fig 4). In this case the cause of the left vocal cord paralysis was due to an aneurysm of the aortic arch compressing the recurrent laryngeal nerve which loops back around the aortic arch. On the right side the nerve loops around the subclavian artery which branches off from the brachiocephalic trunk. Knowing the particular anatomy of the recurrent laryngeal nerve compression by an aneurysm of the aortic arch is only expectable on the left side. The combination of an aortic arch aneurysm and left-sided vocal cord paralysis is known as Ortner's syndrome.Nevertheless in most cases cross-sectional images do not show any lesion along the course of the vagal or recurrent laryngeal nerves (up to 85%). In these cases a peripheral neuritis (infectious - toxic - alcohol ) is supposed to be responsible for the paralysis.

Differential Diagnosis List

Final Diagnosis

vocal cord paralysis due to aneurysm of the aortic arch

URL:	https://eurorad.org/case/5572
DOI:	10.1594/EURORAD/CASE.5572
ISSN:	1563-4086