1.1

Incidence of Multilevel Obstructions in OSAHS Patients

The true incidence of multilevel obstruction is a subject of much debate. Fujita first described different anatomic levels of obstruction in OSAHS. He recognized that half of the patients who underwent uvulopalatopharyngoplasty (UPPP) were nonresponders. Most of the nonresponders were identified as having multilevel obstruction. Combined oropharyngeal and hypopharyngeal obstruction was noted in 54.5% (36/66) of patients in his study. Thus it is clear that Fujita himself never intended to suggest that UPPP will cure most patients with OSAHS. In 1993, Riley et al. reported their surgical experience, outlining a multilevel concept. Each patient was classified as having single-level obstruction involving oropharynx only (type 1) or the hypopharynx only (type 3). Multilevel obstruction was identified as type 2 and implied a combination of oropharyngeal and hypopharyngeal obstruction. Of the 239 patients, 93.3% (223 patients) were identified as having multilevel obstruction type 2. Only 16 patients (6.7%) had single level obstruction. Of these, 10 patients had type 1 obstruction and 6 patients had type 3 obstruction.

This early classification by Fujita and Riley was based on physical examination of the patients with vague guidelines. Specific criteria for identifying unilevel versus multilevel obstruction were not reported. Subsequent development of the Friedman tongue position (FTP) allowed for a simplified method of staging the levels of obstruction. The early data based on FTP indicated that approximately 25% of patients presenting with OSAHS had responded to oropharyngeal surgery alone, whereas 75% of patients did not. Even those patients who responded to single-level surgery likely had some multilevel obstruction to a minor degree.

To more precisely identify the anatomic sites of obstruction during sleep, drug-induced sleep endoscopy (DISE) was proposed as a preferred method (Pringle and Croft 1991). den Herder et al. reported an unusually high number of single-level obstructions. In their study of 127 patients, 63% had single-level obstruction, whereas only 37% had multilevel disease. The study, however, may have misidentified the level of obstruction; tongue base obstruction pushing the palate backward causing secondary palatal obstruction may have been classified as primary palatal obstruction. Another study by Abdullah and van Hasselt confirmed the high incidence of multilevel disease, and 87% of their 893 patient population had multilevel obstruction. Furthermore, a study done by Hybaskova et al. (2016) reported multilevel collapse in 49 of the 51 patients (96.1%) who underwent DISE examination. The most common type of multilevel collapse was palatal, oropharyngeal, and base of tongue (33.3%). Vroegop et al. (2014) reported DISE results on 1249 patients (the largest sample in the literature) and found the incidence of multilevel obstruction at 68.2%.

A recent systematic review done on the identification of obstruction sites by DISE shows multilevel obstruction ranging from 31% to 76% of patients (Viana 2015). Kezirian et al. (2010) found that the reliability of global assessment of obstruction was somewhat higher than the degree of obstruction, especially for the hypopharynx. Rodriguez-Bruno et al. (2009) found high interobserver and intraobserver agreement for obstruction at the level of the tonsils, followed by the epiglottis. Furthermore, Kezirian et al. (2010) found that among experienced surgeons, assessment of the palate, tongue, and epiglottis showed greater reliability than for other structures, whereas in the study done by Vroegop et al. (2013), higher agreement was found for palatal, oropharyngeal, and tongue base collapse.

1.2

Single-Level Surgery Cannot Be the Only Treatment for Most OSAHS Patients

UPPP was designed to enlarge the oropharyngeal airway and remains the most common surgical intervention for OSAHS. Review of the literature indicates the success rate (a 50% reduction in Apnea/Hypopnea Index [AHI] and a postoperative AHI of less than 20) for UPPP as an isolated procedure ranges from 25% to 80%. However, Sher et al. reported success rates for UPPP around 41% based on a meta-analysis of unselected cases. Although there are many reasons UPPP may fail, uncorrected retrolingual obstruction has been clearly identified as a major cause. This seems to support the concept that multiple levels of obstruction exist and explains why UPPP alone frequently results in failure.

1.3

Multilevel Surgery Is Not Limited to Severe Disease

Many otolaryngologists presume that although UPPP may not cure patients with severe OSAHS, it is likely to be effective for patients with mild disease. There are, however, many studies indicating that the severity of disease is not a predictor of success with single-level surgery. Senior et al. studied a group of patients with mild OSAHS (AHI <5). These patients underwent UPPP, and the success rate was only 40%. Friedman further studied a series of patients with mild disease and showed an overall success rate of approximately 40% as well. If indeed most patients have multilevel disease, the success for the surgical treatment of mild OSAHS is not better than those for treating severe disease. In fact, the basis of the Friedman staging system is that anatomic findings are the most significant factors, rather than severity of disease. Multilevel surgery should not be reserved exclusively for the treatment of severe disease. It is therefore reasonable that multilevel treatment should be considered for most patients with mild disease, as well as most patients with severe disease. Because the majority of patients suffering from OSAHS do have multilevel disease and directing the therapy to a single anatomic level has a high potential for failure, the need for multilevel therapy is evident.