Transoral Laser Microsurgery of the Base of the Tongue

Introduction

The base of the tongue (BOT) is the most anterior-superior portion of the oropharynx bounded anteriorly by the circumvallate papillae, laterally by the paired glosso-palatine sulci, and inferiorly by the vallecula. The BOT is formed from the medial fusion of elements from the first and second and is composed of both the endoderm and ectoderm. The branchial arch hypobranchial prominence, a specialized region of second branchial pouch mesoderm, is located posteriorly on the rudimentary tongue. This structure will eventually differentiate into the thyroid primordium and descent via the foramen cecum into the neck. Embryology provides the basis for the development of the benign tumors (lingual thyroid, hemangioma, dermoid) that are observed in this region. The BOT is histologically complex, with nonkeratinizing stratified squamous epithelium covering lymphoid aggregates (lingual tonsils), minor salivary glands, and striated muscle accounting for the multiple epithelial (squamous cell carcinoma, lymphoepithelioma) and nonepithelial (lymphoma, sarcoma, minor salivary gland) malignancies in this location. Transoral resection of the BOT can be used for definitive excision of low-grade and benign neoplasms, definitive resection of high-grade malignancies prior to adjuvant treatment, assessing the BOT in the survey for the occult primary, and volume reduction of the BOT in cases of obstructive sleep apnea.

Specialized retractor systems provide improved transoral exposure and access to tumors of the BOT, and the development of laser fibers and enhanced optics have provided greater surgical visualization and operative ability in this region. These elements have contributed to a renewed interest in primary surgical treatment for selected malignancies of the BOT. Since transoral laser microsurgery resections heal by re-epithelization reconstruction, flaps are not used, thereby eliminating donor site morbidity. Transoral resection of tumors obviates the need for a pharyngotomy, thus significantly reducing the likelihood of salivary contamination of the neck and wound infection. In selected patients, tracheostomy can also be avoided, thus providing an earlier return of speech and deglutition. Finally, data obtained from histologic analysis of surgical specimens can more precisely identify patients for appropriate adjuvant treatment. Clinical trials are currently being carried out that, based on human papilloma virus status, are looking to “deintensify” adjuvant chemotherapy and radiation, thus decreasing late toxicity and improving return of function and overall quality of life.

It is important that the head and neck surgeon understand that TLM resection of the tongue base is one technique in the armamentarium of surgical exposures to the oropharynx. The surgeon must consider not just the anatomic location but the biology of the tumor, the risks to surrounding structures, vascular control, airway protection, reconstructive options, and most critically the goals and wishes of the patient in making treatment recommendations.

Key Operative Learning Points

1.
TLM procedures are tedious and require extreme patience.
2.
Formal staging endoscopy and examination under anesthesia may be necessary to determine if transoral resection is feasible.
3.
Multiple oral retractor systems and/or fixed bore and bivalve laryngoscopes may all be needed to provide safe and complete resection of the tumor.
4.
Retractors may need to be repositioned several times during the resection.
5.
Multiple frozen sections may be needed.
6.
Suction cautery to supplement the laser for hemostasis
7.
The line of sight laser micromanipulator is not adequate in all cases. Laser fibers are needed to work on an upward angle into the BOT.
8.
Standard tonsillectomy instruments are too short to reach deep into the vallecula. Modified 22-cm working distance specialized insulated instruments are necessary.

Preoperative Period

History

1.
Medical and surgical history including active medical problems and comorbidities, current medications, allergies, and complete review of systems
2.
Otalgia in the normal appearing ear
3.
Social history should include a history tobacco and alcohol use and risk factors for exposure to the human papilloma virus.
4.
Prior environmental, history occupation of therapeutic exposure to low-dose ionizing radiation, particularly as a child
5.
Chief complaint and review of systems positive for otalgia, dysphagia, dysarthria, foreign body sensation, oral of pharyngeal pain, voice changes, worsening snoring or exacerbation of sleep apnea syndrome, foul breath (from necrotic tumor)
6.
Other factors that should be considered include history of obstructive sleep apnea, morbid obesity, prior head and neck surgery, and/or radiation therapy to the head and neck.
7.
Treatment with oral antibiotics for cervical lymph adenopathy without a history of symptoms of infection (no fever, malaise, pain)
8.
Asymptomatic mass in the neck
9.
“Hot potato” voice

Physical Examination

1.
Assessment of comorbidities with appropriate cardiac and pulmonary risk stratification
2.
Evaluate tongue motion, protrusion, fixation, and fasiculations.
3.
Fiberoptic naso-pharyngoscopy, inspection, and palpation of the base of the tongue
4.
Examination of the base of the tongue with a magnified angled Hopkins telescope
5.
Careful attention to the epiglottis should be performed as well. Cancer of the BOT may involve the supraglottis either by superficial extension or deep infiltration.
6.
Detailed palpation and office ultrasound of the neck. In our own experience approximately 85% of patients treated for cancer of the BOT will present with a mass in the neck on initial physical examination.

Imaging

1.
Initial imaging with contrast enhanced computed tomographic (CT) scanning
- Imaging cervical metastases is best performed with contrast-enhanced CT scan.
- Diameter greater than 15 mm, central necrosis, round shape, and loss of a clear margin of the node borders and obscured adipose tissue planes indicating extracapsular extension all indicate metastatic adenopathy.
2.
Contrast-enhanced magnetic resonance imaging (MRI)
- MRI acquires data in a multiplanar fashion and better visualization of subtle soft tissue details.
- Visualization of local extension of the cancer into the intrinsic muscles of the tongue, perineural spread, submucosal extension of the tumor, inferior extension into the preepiglottic space, and lateral extension into the parapharyngeal and carotid spaces
3.
PET-CT scan
- Patients with stage IV disease or those at increased risk of harboring metastatic cancer
- Patients with unknown primary carcinomas
- Restaging patients prior to aggressive salvage treatment

Indications

1.
Lingual tonsillectomy for chronic lingual tonsillitis or hypertrophy or biopsy of suspected lymphoma arising in Waldeyer ring
2.
Volume reduction of the tongue base for obstructive sleep apnea
3.
Management of obstructing lingual thyroid or other benign neoplasm of the base of the tongue
4.
Staging the patient with an occult primary of the head and neck—excisional biopsy of the lingual tonsils and base of the tongue
5.
Definitive resection of oropharyngeal (base of the tongue, tonsil, soft palate uvula, posterior pharyngeal wall) squamous cell carcinoma
6.
Definitive resection of minor salivary gland neoplasms of the base of the tongue

Contraindications

1.
Trismus—Reduced mandible-maxilla excursion with inability to place appropriate retractors
2.
Teeth—Visualization obscured by dentition
3.
Tumor—Bulky, friable, and/or hemorrhagic tumor obscuring visualization or a tumor with a depth of infiltration into the tongue base that precluded obtaining a satisfactory deep oncologic margin
4
Tori—Large obstruction maxillary or mandibular tori
5.
Tongue—Relative macroglossia and redundant tongue tissue that cannot be satisfactorily retracted by the blades of the operating oropharyngoscope, thus collapsing into lumen
6.
Tummy—Morbid obesity is frequently associated with a narrow oropharyngeal passage and poor visualization of the cancer.
7.
Tonsils (lingual)—Lingual tonsillar hypertrophy obscuring the view of the tumor and making differentiation from tumor challenging
8.
Throat—Elongated thin neck with narrow mandibular arch
9.
Tilt—Limitations in neck extension from fibrosis from prior radiotherapy, degenerative disease of the cervical spine, or morbid obesity with unfavorable body habitus
10.
Therapy—Prior surgical or nonsurgical therapy can limit exposure and make differentiation of normal from abnormal tissue difficult.

Preoperative Preparation

1.
Complete history and physical examination as noted above
2.
Fiberoptic laryngoscopy with careful assessment of airway anatomy, neck extension, intubation risks
3.
Review of imaging studies
4.
Pretreatment biopsy prior to TLM is essential in patients with a lesion of the base of the tongue to rule out lymphoreticular or other tumors not treated with primary surgery.
5.
Discussion at multidisciplinary tumor planning conference as indicated
6.
Careful informed consent included discussion of emergency airway management, including tracheostomy, postoperative hemorrhage requiring operative or angiographic control, dental injury, tongue numbness or paralysis, taste disturbance, and need for delayed extubation.
7.
Panendoscopy and biopsy as needed prior to TLM resection definitive resection
- Fine-needle aspiration of suspicious cervical masses
- Transoral biopsies of the tongue base when feasible
- Obtain definitive histopathologic biopsy material prior to definitive resection.
- Assess for synchronous primary head and neck malignancies.
- Determine anatomic constraints for access to the tumor.
- Evaluate the transoral exposure of the tongue base, microscopic visualization of the tumor, and ultimate suitability for transoral laser microsurgery.

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