Tongue base is one of the most common sites of upper airway obstruction in patients with persistent obstructive sleep apnea after removal of adenoids and palatine tonsils.
Tongue base obstruction can be caused by hypertrophied lingual tonsils (LT) and/or glossoptosis (retrograde collapse of tongue parenchyma).
Obstruction of the tongue base should be confirmed with drug-induced sleep endoscopy (DISE) and or cine MRI of upper airways.
Lingual tonsillar hypertrophy can be differentiated from glossoptosis by performing tongue extension (for LT hypertrophy) or jaw thrust maneuvers (for glossoptosis) during DISE.
Introduction: nature of the problem
Tongue base obstruction (TBO) is a common cause of persistent obstructive sleep apnea (OSA) after removal of adenoids and tonsils in children, particularly in those with rapid eye movement (REM) or supine-dominant OSA. The tongue is part of the collapsible pharyngeal airway and most amenable to collapse because of either loss of genioglossus tone during REM sleep or gravity-dependent collapse into the oropharyngeal airway during sleeping in the supine position. The tongue base, defined as the posterior one-third of the tongue from the circumvallate papillae to the vallecula, comprises both tongue musculature and the lingual tonsil (LT). The degree of TBO depends on 2 factors: LT hypertrophy and glossoptosis; sometimes both coexist. Obstruction of the laryngeal airway can be caused by either or both glossoptosis (retrograde collapse of the tongue) and LT hypertrophy. The most common risk factors for LT hypertrophy include Down syndrome, obesity, and significant allergies. In addition, children with Down syndrome have macroglossia and glossoptosis resulting in significant TBO.
Removal of LT and/or reduction in tongue base bulk can increase the retrolingual space and minimize the obstructive tendencies over the laryngeal inlet. Persistence of nasal obstruction may increase the negative pressure in the pharyngeal airway leading to worsening of the tongue base collapse; hence, it is critical to simultaneously assess and treat significant nasal obstruction.
Polysomnography (sleep study)
TBO can present with snoring and obstructive sleep disordered breathing that is particularly worse in REM sleep and in the supine position. The sleep study helps to assess the severity of the upper airway obstruction. If the LTs are massive, obstructive events are evident in both REM and non–rapid eye movement (NREM) sleep. However, at times, markedly enlarged LTs can present with a milder degree of OSA if the genioglossus muscle is able to contract and maintain the tone during sleep without causing glossoptosis. It is critical to analyze the sleep study parameters in detail and assess the severity and the extent of OSA in REM and NREM sleep and in the supine position. Also, one should evaluate obstructive apnea index (OAI) and obstructive hypopnea index (OHI) separately. Successful treatment of TBO may result in a significant reduction in obstructive apneas (OAI). Sometimes, however, the persistent OSA after lingual tonsillectomy may show mostly hypopneic events rather than apneic obstructive events with a modest change in the overall combined obstructive apnea and hypopnea index (OAHI). These hypopneic events are particularly likely if the TBO is also associated with glossoptosis. Hence, a preoperative and a postoperative sleep study should be done in any patient being treated with tongue base surgery ( Fig. 1 ).
Imaging studies may include lateral neck films to assess air column in the retroglossal space and soft tissue shadow of LTs. However, plain films may not be accurate many times because it is typically done while awake and in the erect position. A cone beam computed tomography (CBCT) scan of the upper airway may be better in delineating the bony as well as soft tissue structures; in addition, one can measure the volume of the airways in the retroglossal area. Again, CBCT scans are done while awake and in the erect position and hence fail to assess glossoptosis seen during sleep. Cine MRI is a high-resolution imaging study that captures the dynamic movement of the upper airways during a medically induced sleeplike state. The major advantage of cine MRI over drug-induced sleep endoscopy (DISE) is that it can differentiate LT hypertrophy–related TBO from glossoptosis and help visualize the multilevel obstruction simultaneously. This technique is not widely available and not used routinely. Sometimes cine MRI can be used as a complementary test to DISE.
Airway upper airway endoscopy
Awake flexible laryngoscopy can be done in clinic and help visualize airways from nose to larynx. Although it helps to visualize LTs, it cannot accurately assess glossoptosis seen during sleep; however, one can predict this based on the degree of laryngeal visualization. However, it is still a very useful tool. As DISE is performed in a medically induced sleeplike state like cine MRI, it is more effective in evaluating the site and the degree of TBO, and it most closely resembles events happening during sleep. Various grading systems have been developed to assess the severity of glossoptosis (Yellon grading system for epiglottic and tongue-base prolapse) and lingual tonsillar hypertrophy (Friedman Lingual Tonsil Scale).
An awake flexible fiberoptic laryngoscopy should be performed to assess the tongue base. TBO should be suspected if the glottic inlet is only partially or minimally visible; this is caused by tongue base deflection of the epiglottis in a retrograde fashion over the larynx or frank obliteration of the larynx by the tongue base structures. Jaw-thrust maneuver will relieve glossoptosis but will have minimal effect on a hypertrophic LT. Anterior tongue extension (tongue pull) will roll the LT anterosuperiorly and relieve obstruction but will have minimal effect on reducing glossoptosis. Performing these 2 maneuvers will help differentiate the cause of obstruction between these 2. If both components are contributing to obstruction, then a combination of the 2 maneuvers will successfully relieve the obstruction. These maneuvers should be repeated during DISE to confirm the obstructive site or sites.
Preparation and patient positioning
Nasal intubation provides optimal exposure of tongue base.
Patient should be supine with a shoulder roll in place.
A single dose of Unasyn or clindamycin and an airway dose of dexamethasone (0.5 mg/kg up to 12 mg) are administered.
Dental bite block or Jennings retractor is placed to retract the oral cavity.
A soft suction catheter is passed through the bilateral nasal cavities to retract the soft palate.
A 2-0 silk retraction suture is placed in the midline tongue and helps elevate and expose the tongue base.