3 DISCUSSION
The formation of a tracheocutaneous fistula following a thyroidectomy may be secondary to several etiologies. It has been previously reported following radiation therapy2, iatrogenic tracheal injury, prolonged intubation following procedure, infection of surgical site, excessive cautery on tracheal wall4, or pressure induced ischemia3. Many surgeons attempt to minimize excessive cautery around the trachea to prevent necrosis, using cautery on a lower setting when necessary4. Some authors report tracheomalacia as a potential cause of tracheal necrosis as thyroid tissue may act as framework for the trachea, causing tracheal collapse when removed.1
In our case we postulate the formation of a seroma postoperatively potentially led to a pressure induced necrosis of the anterior tracheal wall. Only one case has been reported to our knowledge of tracheal necrosis in the setting of a post-operative seroma. The pathogenesis of a seroma induced pressure necrosis is likely similar to the hypothesized manner in which elevated cuff pressure leads to tracheal necrosis. The hypothesis is the cuff pressure exceeds perfusion pressure of tracheal mucosa, resulting in pressure necrosis.5 The other manner in which tracheal necrosis may have occurred is due to disrupting the blood supply to the tracheal wall. Blood supplying the trachea stems from the inferior thyroid artery. These branches can be very delicate and easily interrupted with cauterization during removal of thyroid tissue.5 The largest risk factor in this patient for tracheal necrosis would be the need for a second procedure for complete removal of thyroid tissue. Compared to a single procedure, a two-step procedure would increase the amount of time intubated and lead to repeat use of cautery around anterior tracheal wall. Other common risk factors for tracheal necrosis that were not a factor in our patient include post-operative infection, large thyroid goiter that might have compromised tracheal blood supply, marked bleeding during procedure leading to excessive cauterization for hemostasis, prior chemoradiation, among others.7