Discussion
The paraglottic space is a potential space containing adipose tissue and
blood vessels, bordered laterally immediately adjacent to the thyroid
cartilage, medially adjacent to the thyroarytenoid muscle and bordered
dorsally to the piriformis sinus [3]. The paraglottic space can be
easily exposed if the thyroid cartilage plate is cut obliquely during
the operation and the posterior part of the thyroid cartilage plate is
pulled outward (such as the description of the previous surgical
method). The advantages of the paraglottic space approach are as
follows. ①The paraglottic space is a natural anatomical space, and the
tissue is easily separated through the paraglottic space approach with
less intraoperative blood loss and a clear surgical field. ②The
hypopharynx is easier to separate from the larynx and the highly
wrinkled pharyngeal cavity is easily planarised to fully expose the
tumour and removing the tumour in a 3D way under the full dissociation
of the mucous membrane through the paraglottic space approach. The
tumour is not squeezes in the process of surgical resection, which is in
line with the principle of tumour resection. ③The surgical field of view
via the paraglottic space approach is well exposed. Combined with the
preoperative narrow band imaging examination, the tumour can be
accurately removed under direct vision, and the normal hypopharyngeal
mucosa can be preserved as much as possible, which is conducive to
pharyngeal cavity reconstruction and function preservation.
How to improve the retention rate of laryngeal function without
affecting the survival rate of patients has become the focus of clinical
attention. Relevant scholars also confirmed the feasibility of laryngeal
function-preserving surgery for pyriform sinus carcinoma and provided a
pathological basis [4-6].The National Comprehensive Cancer Network
guidelines point out that surgery is feasible for patients with T1+N
positive and T2−3Nx hypopharyngeal cancer to preserve the laryngeal
structure, and partial laryngectomy (open or laser) combined with
postoperative radiotherapy can be considered. These patients are
expected to preserve laryngeal function. Although a part of pyriform
fossa carcinoma belongs to T4, only the posterior edge of the thyroid
cartilage, a small part of the cricoid cartilage, or the entrance of the
cervical esophagus are involved. After tumor resection, most of the
larynx can be preserved, the pectoralis major myocutaneous flap can be
used to reconstruct the pharyngeal cavity, and the preservation of
laryngeal function can be realised.
The paraglottic space of stage T1–T2 pyriform sinus carcinoma is rarely
invaded. It is the best indication for this surgical approach. In
addition, the paraglottic space approach can be used if the T3–T4
lesion does not involve the paraglottic space, because most cases of the
vocal cord fixation is caused by tumour compression and not by tumour
invasion of the paraglottic space [7]. For the carcinoma of the
lateral wall of the piriform sinus, the tumour rarely invades the larynx
because of its anatomical position. The approach through the paraglottic
space can fully separate the hypopharynx and larynx, that is, the entire
tumour can be directly exposed from the ventral side. The surgical field
of view is wide, and the tumour can be accurately removed. For the
primary tumour in the medial wall of the pyriform sinus, the
transglottic approach can firstly complete the resection of the deep
cutting edge of the tumour when entering the pharyngeal cavity, then
separate the tumour from the larynx by pulling the thyroid cartilage
plate outward and remove the tumour under direct vision. Preoperative
cervical enhanced CT and electronic laryngoscopic examination can
effectively determine the presence or absence of paraglottic space and
laryngeal cartilage involvement. If the paraglottic space is involved,
in the actual surgical operation, we can first enter through the
paraglottic space approach, separate the hypopharynx and larynx and then
combine the lateral pharyngeal approach, and observe the scope of tumour
invasion in multiple planes. Supraglottic hemilaryngopharygectomy,
partial pharyngectomy or total laryngectomy is performed according to
the actual extent of tumour invasion.
In addition, the incidence of pharyngeal fistula in this study was
4.3%, which was considerably lower than those in other
studies[6,8]. As mentioned above, the paraglottic space approach can
retain more normal hypopharyngeal mucosa, dissociate the pharynx from
the larynx, effectively reduce the suture tension during pharyngeal
reconstruction and prevent mucosal avulsion during pharyngeal movement.
In addition, the lifting of the uninvaded lateral thyroid lobe to
strengthen the pharyngeal wall is another main reason to reduce the
occurrence of pharyngeal fistula. The lateral thyroid lobe has good
blood circulation and large tissue volume, which can be used as the
strengthening plane of the new pharyngeal cavity.