Technique of Transoral Laser Microsurgery for Carcinoma of the Base of the Tongue
Guy J. Petruzzelli
INTRODUCTION
The base of the tongue (BOT) is bounded anteriorly by the circumvallate papillae extending inferiorly to the vallecula and includes the anatomic regions of the lingual tonsils, pharyngoepiglottic folds, glossoepiglottic folds and, laterally, the glossopalatine sulcus. Carcinoma of the tongue represents approximately 25% of all head and neck malignancies with malignancies of the BOT accounting for one-third of all tongue neoplasms. Malignancies of the BOT reflect the histologic and embryologic complexity of this region and include squamous cell carcinoma (SCC), minor salivary gland carcinoma, lymphoma, mesenchymal malignancies, and carcinoma arising in lingual thyroid (Table 7.1).
Optimal treatment of nonlymphoreticular malignancies of the tongue base remains controversial. Traditional open approaches to the BOT included composite jaw-tongue resection, lateral pharyngotomy, suprahyoid pharyngotomy, and either lateral or midline mandibulotomy. Common among these approaches is a breach of the oral-oropharyngeal mucosa with concomitant salivary contamination of the neck, increased surgical morbidity, poorer functional outcomes, and the potential need for microvascular reconstruction of complex oropharyngeal defects.
These technical challenges coupled with the success of concurrent chemoradiation therapy protocols in treating SCC of the larynx lead to the wide acceptance of “organ-sparing” approaches in the treatment of oropharyngeal carcinoma. The concurrent use of platinum-based chemotherapy regimens with external beam radiation as definitive therapy for malignancies of the BOT is not without significant morbidity, including long-term gastrostomy tube dependence and osteoradionecrosis of the mandible.
Advances in laser and optical technologies and the development of specialized instrumentation for transoral exposure and access to tumors of the BOT have contributed to a renewed interest in primary surgical treatment for selected malignancies of the BOT. Benefits of transoral surgical resection include earlier return of speech and deglutition, reduced operative morbidity, and pathologic data obtained from histologic analysis of surgical specimens to more precisely select patients for adjuvant treatment protocols. This approach permits deintensification of adjuvant chemotherapy and radiation to employ its use only when necessary, and is associated with a decrease in the development of late toxicity and improved return of function and overall quality of life.
HISTORY
Individuals being considered for transoral laser microsurgery of the BOT should submit to a thorough medical and surgical history including current medications, allergies, and a complete review of systems. Typical chief complaints associated with malignancies of the BOT are otalgia, dysphagia, dysarthria, foreign body sensation, oral or pharyngeal pain, changes in the voice, worsening of snoring or exacerbation of sleep apnea
syndrome, foul breath (from necrotic tumor), and the asymptomatic mass in the neck. The prolonged use of tobacco and alcohol is thought to be the etiology of SCC of the head and neck. Frequently, the exposure to and abrupt withdrawal of these substances predispose patients to postoperative complications related to exacerbation of underlying ischemic cardiac disease, arrhythmias, chronic obstructive pulmonary disease, and alcohol withdrawal syndromes. Recently, the oncologic role of the human papilloma virus (HPV), which has become a major cause of increased rates of BOT SCC, particularly in younger patients without significant exposure to tobacco and alcohol, has been extensively discussed. Patients’ sexual history may give some indication as to their relative risk for HPV exposure.
syndrome, foul breath (from necrotic tumor), and the asymptomatic mass in the neck. The prolonged use of tobacco and alcohol is thought to be the etiology of SCC of the head and neck. Frequently, the exposure to and abrupt withdrawal of these substances predispose patients to postoperative complications related to exacerbation of underlying ischemic cardiac disease, arrhythmias, chronic obstructive pulmonary disease, and alcohol withdrawal syndromes. Recently, the oncologic role of the human papilloma virus (HPV), which has become a major cause of increased rates of BOT SCC, particularly in younger patients without significant exposure to tobacco and alcohol, has been extensively discussed. Patients’ sexual history may give some indication as to their relative risk for HPV exposure.
TABLE 7.1 Malignant Neoplasms Arising in the Base of the Tongue | ||||||||||||||
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Other factors that should be included in patients being considered for transoral laser microsurgery (TLM) are a clinical history of obstructive sleep apnea, morbid obesity, restriction of neck extension, trismus, prior head and neck surgery, and/or radiation therapy to the head and neck. These factors can be associated with decreased visualization of the BOT (Table 7.2).
Patients with SCC of the BOT will frequently present with cancer metastatic to Zone II as their sole presenting complaint. This is due to the abundance of submucosal lymphatic channels in the BOT. Local symptoms such as dysphagia and foreign body sensation are more commonly observed with exophytic tumors that ulcerate and interfere with oropharyngeal air movement and the passage of the food bolus in the second phase of swallowing. Dysarthria is observed when tumors of the BOT demonstrate a more endophytic growth pattern replacing the intrinsic tongue musculature and causing fixation of the tongue. Gross fasciculation of the tongue is an ominous finding and is associated with extensive perineural involvement of the hypoglossal nerve. Finally, otalgia in a normal-appearing ear can be a manifestation of referred pain from the sensory divisions of the pharyngeal branches of the ninth and tenth cranial nerves.
A subset of cancer of the BOT is carcinoma metastatic from an unknown primary site, often in those who have already undergone bilateral tonsillectomy. These patients present with metastatic SCC in a cervical node without a readily identified primary tumor. These patients harbor small tumors that are undetected on standard physical examination and that can be missed even on directed biopsies of the BOT during a staging panendoscopy. TLM examination of the BOT with laser lingual tonsillectomy provides a systematic method for safely obtaining satisfactory amounts of tissue to identify a primary site of the cancer in the majority of cases (see Section on page 67 entitled “Panendoscopy and Directed Biopsy”).
TABLE 7.2 Factors Associated with Unfavorable Exposure of the Base of the Tongue (T Principle) | |
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PHYSICAL EXAMINATION
A careful and comprehensive preoperative physical examination, including a complete assessment of comorbidities with appropriate cardiac and pulmonary risk stratification, should be performed on all patients undergoing transoral laser microsurgery. Carefully listening to the patient’s voice may give an indication as to the degree of extension of the cancer into the BOT. As expected, patients with a normal voice and few local symptoms tend to have smaller, more superficial tumors. Deeply infiltrative cancers can cause fixation of the tongue and paralysis due to hypoglossal nerve involvement resulting in dysarthria, dysphagia, and fasciculation of the tongue. Occasionally the head and neck surgeon will be surprised as to the degree of local infiltration of the tumor and the relative lack of symptoms.
A complete examination of the head and neck, including fiberoptic nasopharyngoscopy and inspection and palpation of the BOT, is also imperative. Aerosolized and topical anesthesia is often necessary to eliminate a bothersome gag reflex in order to achieve a comfortable examination. SCC can present with the typical ulcerating, erythematous, indurated lesion commonly observed in the oral cavity. However, tumors of the BOT are often very difficult to identify visually and separate from the at times exuberant lymphoid tissue of the region. Neoplasms of the BOT, particular minor salivary gland malignancies, are frequently submucosal. Therefore, the examiner must rely upon an asymmetric appearance or irregularity of the contour of the rounded edge of the BOT. Examination of the BOT with a magnified angled Hopkins telescope can be useful in identifying small lesions.
In addition to examining the BOT to assess the dimensions of the primary tumor, a detailed examination of the epiglottis should be performed. Cancer of the BOT may involve the supraglottis either by superficial extension or by deep infiltration. The former can be identified by careful preoperative examination, and the latter requires imaging for confirmation (see below). Superficial SCCs arising in the BOT can extend into the vallecula and migrate superiorly onto the squamous mucosa of the lingual surface of the epiglottis. An epiglottic sparing mucosal resection can be a satisfactory oncologic alternative in this setting. Conversely, deeply infiltrative tumors can involve the preepiglottic space by direct extension through the median thyroepiglottic ligament. The patient may have the classical “hot potato” voice associated with supraglottic carcinoma, and on physical examination the epiglottis will be erythematous, thickened, and firm.
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