338 THE RESPIRATORY SYSTEM 



muscles of the larynx are supplied by the recurrent (laryngeal) 

 nerve (p. 99). 



Laryngeal Paralysis. Bilateral paralysis of the laryngeal 

 muscles is practically always accompanied by paralysis of 

 other muscles, e.g., the soft palate, etc., innervated by the 

 vagus. Unilateral paralysis may occur in neuritis of the vagus 

 or it may be due to pressure on one of the recurrent nerves. 

 In the latter case, the condition occurs more frequently on 

 the left than on the right side, owing to the longer course 

 which the left recurrent nerve adopts (p. 99). Both nerves 

 may be affected in the neck by pleuritic thickening in apical 

 phthisis, by enlargements of the thyreoid gland and by tuber- 

 culous adenitis of the antero-inferior group of the deep cervical 

 lymph glands. In addition, the right recurrent may be com- 

 pressed at the root of the neck by aneurismal dilatation of 

 the innominate artery (p. 321). On the other hand, as it passes 

 upwards within the thorax, the left recurrent nerve may be 

 subjected to pressure from aortic aneurisms, mediastinal 

 tumours and enlargement of the para-tracheal lymph glands. 



When the recurrent (laryngeal) nerve is compressed, the 

 fibres which innervate the abductor muscles are invariably the 

 first to be affected. Unilateral abductor paralysis causes 

 no alteration in the voice, and the condition can only be 

 diagnosed by laryngoscopic examination, when it will be 

 observed that the affected vocal fold does not become 

 abducted during inspiration. Continuance of the pressure 

 produces complete paralysis of the fold, which then assumes 

 the cadaveric position. In this condition, the voice is 

 rendered husky, since the breadth of the rima glottidis is 

 greater than normal during phonation. The occurrence of 

 pure adductor paralysis indicates that the disorder is functional 

 in origin, and, as both folds are involved, the width of the 

 rima glottidis is greatly increased. The condition, therefore, 

 is characterised by complete aphonia. 



In the early stages of bilateral nuclear lesions, bilateral 

 abductor paralysis may occur. In this case, the voice is not 



