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Effects of Surgical Resection

Oral Cavity

Cancers in the oral cavity can cause a range of predictable but complex swallowing problems.[29,30] The location, size, and extent of the tumor as well as the surgical reconstruction procedure can significantly affect the functional outcome. Groher[31] proposed that the removal of less than 50% of a structure involved with swallowing will not interfere or seriously impact swallowing function. However, Sessions et al[32] showed that the size of the lesion excised was less a prognostic indicator than the area excised and that resultant dysphagia could be predicted in cases of base of tongue and arytenoid cartilage resections. Another complication that may affect swallowing function is the loss of sensation that accompanies the interruption of nerve function with surgery. The use of nonsensate flap closures may interfere with the normal sensation needed to guide the bolus through the oropharynx for efficient swallowing.[33] Additionally, tissue flaps have no motor function resulting in the loss of propulsive force. They also may obstruct bolus passage if they are large and bulky.

Studies show that resections of up to one third of the tongue result in only transitory swallowing problems.[34] Optimal function is achieved when lesions of the anterior tongue are treated with composite resection and when neural control and some tongue movement are preserved.[35] If tongue tethering to the floor of mouth or hypoglossal nerve involvement occurs, the swallowing deficits will be more severe.[36] They may consist of problems with chewing, controlling food in the mouth, and initiating a swallow. Patients undergoing total glossectomy can regain functional swallowing. However, if glossectomy is combined with anterior mandible resection, recovery is poorer because the patient cannot adequately elevate the larynx, which impacts cricopharyngeal opening.[37] Outcome studies show that patients with oral tongue resections that are uncomplicated by involvement of other structures can regain oral nutrition 1 month post-healing. However, a significant percentage of patients must undergo more extensive resections to achieve adequate cancer control.

If the tumor is located in the posterior oral cavity including the base of tongue, soft palate, retromolar trigone or tonsillar fossa, surgical excision usually will cause more severe dysphagia.[38] The tongue base plays a critical role in initiating the swallow, propelling the bolus through the pharynx, and efficient pharyngeal peristalsis. Any procedure that minimizes the tongue base to posterior pharyngeal wall contact can result in reduced pressure generation causing pharyngeal stasis post-swallow,delayed initiation of the swallow resulting in aspiration before the swallow, or reduced hyolaryngeal elevation causing pharyngeal stasis and post-swallow aspiration. Resections of the tongue and hard palate result in loss of pressure needed to propel the bolus into the pharynx. Combined resection of the soft palate and tonsillar pillars may impact bolus transport through the oral cavity and pharynx causing nasopharyngeal reflux and pharyngeal stasis. Patients undergoing glossectomy and submental resections have reduced tongue propulsion and lip sensation. Sacrifice of the hyomandibular constrictors reduces the protective tilting action of the larynx with potential for significant aspiration. Total glossectomy with bilateral neck dissections has a poor swallowing outcome unless the superior laryngeal nerve, hyoid bone, and epiglottis remain intact.

Pharynx

Resection of cancer in the pharynx, including the pharyngeal wall, valleculae, or pyriform sinus, can result in significant dysphagia. The peristaltic contraction begins superiorly and courses inferiorly. Any disruption of the muscular contraction may cause food to coat the pharynx. The larger the pharyngeal resection, the greater the pharyngeal residue. Additionally, surgery that affects the lateral pharynx may cause fixation of the larynx so that it cannot elevate during swallowing. If this occurs, epiglottic inversion is compromised and laryngeal penetration or tracheal aspiration can occur. Scar tissue in the pharynx can also reduce laryngeal elevation.

Larynx

The laryngeal complex serves two critical functions during swallowing. First, the larynx elevates and moves anteriorly under the tongue base to move it from the path of the bolus and to assist in cricopharyngeal sphincter opening. Second, it protects the airway from aspiration by closing at three levels -- the epiglottis, false vocal folds, and true vocal folds. Any surgery that compromises this closure, especially of the true vocal folds, will likely result in aspiration during the swallow. Supraglottic laryngectomy can interfere with laryngeal elevation and sometimes vocal fold adduction.[39] If a laryngeal suspension procedure is performed during reconstruction, laryngeal elevation is improved and swallowing is safety enhanced.[40] If a supraglottic laryngectomy procedure encompasses more that the traditional procedure and includes portions of the hyoid bone, base of tongue, aryepiglottic folds, or false vocal folds, prognosis for swallowing recovery is diminished. Patients undergoing vertical hemilaryngectomy generally display reduced laryngeal closure due to the loss of one half of the larynx. If the procedure is limited to a unilateral true and false focal fold, then swallowing recovery is possible with a combination of increased effort during laryngeal adduction and compensatory head posturing. If the hemilaryngectomy extends to the opposite vocal fold, then swallowing recovery is prolonged and may require an exercise program to improve adduction or an augmentation or medialization procedure.

Patients undergoing total laryngectomy have few swallowing problems following surgery due to the permanent separation of the trachea and esophagus. However, occasionally the laryngectomee may have problems propelling the bolus through the oral cavity and pharynx as a result of the loss of hyoid bone, which is the anchor for the tongue. Increased pressure in the pharyngoesophagus following laryngectomy requires the tongue to move with greater force. Stricture at the anastomosis may cause narrowing and reduced bolus flow through the pharynx. Pseudoepiglottis, a postsurgical fold of tissue from the pharynx at the level of the base of tongue, may serve as a mechanical barrier to efficient bolus flow and trap food in its pocket.[41]

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