168 THE HEAD AND NECK 



platysma, and, after the external jugular vein has been dealt 

 with, the flap is undercut and turned downwards and laterally. 

 The investing layer of the deep cervical fascia is divided vertically 

 between the anterior jugular veins, which are both secured, and 

 the depressor muscles of the hyoid are then identified. Some- 

 times the muscles are spread out in a thin sheet over the tumour, 

 and the recognition of their edges may offer some difficulty. 

 The sterno-hyoid and the omo-hyoid are divided high up to 

 preserve their nerve-supply, and in such a way that they can be 

 reunited at a later stage. The sterno-thyreoid, which is now 

 exposed, is carefully raised from the surface of the gland so as 

 to avoid injuring the superior and the middle thyreoid veins 

 (p. 119); and it is then cut across. The thyreoid veins are now 

 doubly ligatured and divided lest they should be torn during 

 the subsequent manipulations. The incision is deepened in 

 the median line between the two sterno-thyreoids, and passes 

 through the pretracheal fascia, which forms the loose fascial 

 sheath of the gland. The surgeon can now introduce a finger 

 into the space between the sheath and the true capsule of the 

 gland. This space is crossed by the thyreoid veins and arteries. 

 The surgeon next ligatures the superior thyreoid artery within 

 the sheath, and in this way the external laryngeal nerve, which 

 is associated with the artery outside the sheath, cannot be 

 injured. The upper pole of the gland can now be brought up 

 into the wound, and the isthmus is divided, after it has been 

 separated from the adhesions which bind it to the sheath. The 

 tumour is now more movable, and by turning the lateral lobe 

 forwards and medially, the inferior thyreoid artery may be 

 secured within the sheath and close to the gland. If the sheath 

 is left intact postero-medially, the recurrent (laryngeal) nerve, 

 which crosses the artery in this situation, will not be seen, since 

 it lies outside the fascial sheath (Fig. 36). 



The thyreoid gland normally follows the movements of the 

 trachea in swallowing, but when it is the site of malignant disease 

 it becomes adherent to the surrounding structures and fails to 

 do so. This fixation of the thyreoid gland may also be produced 

 by syphilitic adhesions following a broken-down gumma. 



Simple tumours of the thyreoid gland rarely give rise to any 

 irritation of the recurrent nerve, but malignant tumours frequently 

 do so. Both varieties may cause severe dyspnoea by direct 

 pressure on the trachea. Thyreoid tumours may displace the 

 carotid sheath and its contents laterally into the posterior 



