Detailed literature search flowchart.
Forest plot of the subjective overall surgical success rate for all procedures. The size of the box indicates the relative weight of the study (based on standard error estimates), with attached error bars. The dotted line indicates the summary estimate from the random-effects model of the subjective success rate, which was 81.6%. The thick bar (at bottom) represents the 95% confidence interval for this same summary estimate of subjective success (77.5%-85.7%; P < .001).
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Reed J, Mans CK, Brietzke SE. Surgical Management of Drooling: A Meta-analysis. Arch Otolaryngol Head Neck Surg. 2009;135(9):924–931. doi:https://doi.org/10.1001/archoto.2009.110
To review and assess the current published literature regarding the efficacy of surgical management of sialorrhea in pediatric patients.
The MEDLINE database was systematically reviewed for articles reporting on the use of surgical procedures to treat sialorrhea published from January 1, 1963, to November 30, 2008.
Inclusion criteria included presence of data on the success of surgical treatment of sialorrhea, English language, sample size greater than 5, and presentation of extractable data regarding the subjective success of surgical management of sialorrhea.
Data regarding demographic characteristics of study participants, follow-up duration, subjective success rates, and number and type of complications were extracted by blinded reviewers.
A total of 325 studies were identified on initial search. Abstract review reduced the sample to 46. Cross-referencing yielded an additional 4 articles, resulting in the final sample of 50 articles. Forty-seven studies were case series (Centre for Evidence-Based Medicine level 4 evidence), 2 were cohort studies (level 2), and 1 was a prospective cohort study (level 1b). Median sample size was 18 (range, 5-181), and median follow-up duration was 8.1 months (range, 0.1-50 months). Subjective success was reported in more than 50% of patients in 49 of 50 studies. Random-effects modeling estimated the overall subjective success rate for all procedures to be 81.6% (95% confidence interval, 77.5%-85.7%; P < .001). Bilateral submandibular gland excision and parotid duct rerouting appeared to have the highest subjective success rates at 87.8% (k = 8 studies; 95% confidence interval, 80.5%-95.1%; P <.001), and 4-duct ligation was the lowest at 64.1% (4 studies; 27.6%-100%; P = .001).
Most evidence regarding surgical outcomes of sialorrhea management is low quality and heterogeneous. Despite this, most patients experience a subjective improvement following surgical treatment.
Sialorrhea is defined as drooling or excessive saliva secretion. It can contribute to social reclusion; cause self-esteem problems, especially among school-aged children; and be uncomfortable. In addition, it can present a serious challenge for caregivers. A broad array of physicians, including pediatricians, internists, otolaryngologists, and neurologists, may treat patients with drooling problems. Not surprisingly, the causes of drooling are extensive, ranging from neurological to mechanical, which makes it a difficult problem to treat effectively. The most common cause of drooling is cerebral palsy in the pediatric population and Parkinson disease in adults,1 and other issues, such as facial paralysis, lip hypoesthesia, dental problems, and nasal obstruction or a combination of the aforementioned, may also cause or contribute to drooling.2
With the long list of possible inciting causes for drooling comes an equally long list of possible treatments. Various treatment modalities referenced in the literature include physical therapy, pharmacotherapy, radiotherapy, biofeedback, botulinum toxin injections, and surgical procedures.3 Once more conservative measures have failed to treat sialorrhea, subspecialists are often consulted about surgical solutions. Possible surgical treatments include tympanic neurectomy, submandibular gland (SMG) excision, SMG duct rerouting, sublingual gland excision, SMG duct ligation, parotid duct rerouting, parotid duct ligation, and any combination of these procedures. To date, there is no one procedure that is regarded as the most effective. Compounding this issue is the problem of evaluating the surgical efficacy of these procedures and defining success. The objective of this study is to systematically review the biomedical literature to identify and evaluate published studies reporting on the, primarily subjective, efficacy of surgical procedures to treat sialorrhea.
As a meta-analysis of existing data, this study is exempt from formal institutional review at our institution. The MEDLINE database was systematically reviewed from January 1, 1963, to November 30, 2008, for articles reporting on the use of surgical procedures to treat sialorrhea. Medical Subject Headings (MeSH) terms used were sialorrhea or drooling or hypersalivation and surgery. A total of 325 articles were identified and evaluated for inclusion. Inclusion criteria included (1) presence of data on the success of surgical treatment of sialorrhea, (2) English language, (3) sample size greater than 5, and (4) presentation of extractable data regarding subjective success of surgical management of sialorrhea. Exclusion criteria included tympanic neurectomy, which is no longer performed and of historical interest only, as the sole procedure evaluated and lack of extractable data. Article titles, abstracts, and references were reviewed to determine eligibility and to identify other relevant studies. An evidence table was constructed for display and analysis of results. Study design and level of evidence were categorized according to the guidelines provided by the Centre for Evidence-Based Medicine (CEBM) (http://www.cebm.net). Data were extracted individually by 2 investigators (J.R. and C.K.M.), and a third party (S.E.B.) resolved disputes as appropriate.
Data including author, year written, sample size, type of surgical treatment(s), criteria for surgical treatment success, follow-up duration, study conclusion, study design, and level of evidence were collected from each article. Many studies analyzed more than 1 type of surgical procedure and therefore contributed data on multiple procedures. The criteria for surgical treatment “success” and the resulting success rate were recorded for each procedure in each study as appropriate. Although there was some variation among the studies, a similar metric of assessing surgical treatment success was used by most studies. The most commonly used method of evaluating surgical treatment success was a caregiver-reported, subjective, qualitative scale: “Drooling is much better,” “Drooling is better,” “Drooling is the same,” or “Drooling is worse.” For purposes of meta-analysis, treatment success was modeled as a binary variable reflecting subjective overall improvement in drooling (“Drooling is much better” or “Drooling is better”) posttreatment compared with pretreatment. If this type of scale was not used, the authors' stated surgical treatment success rates were included instead.
Statistical analysis was performed using Intercooled Stata statistical software, version 8.2 (Stata Corp, College Station, Texas). Random-effects modeling was applied to the collected data (standard error estimate = inverse of the sample size) and was used to estimate summary outcomes measures. The null hypothesis was rejected with a probability of P < .05.
A total of 325 articles were identified during the initial search (Figure 1). Application of inclusion and exclusion criteria during abstract and article review eliminated all but 46 articles (14.2%). An additional 4 articles were discovered by cross-referencing the bibliographies. Therefore, 50 articles were included in the study (Table 1).4-53 Of 50 articles reviewed, 59 study subsets were identified because some studies compared different procedures and therefore included data on more than 1 type of procedure. Of these 59 study subsets, 55 were case series (CEBM level 4), 3 were retrospective cohort studies (CEBM level 2), and 1 was a prospective cohort study (CEBM level 1b). The 3 retrospective cohort studies contributed a total of 138 patients, whereas the prospective cohort study contributed 31 patients. The overall median sample size was 18 (range, 5-181), and median minimum follow-up duration was 8.1 months (range, 0.1-50 months). A total of 42 studies (84%) provided a year or more of mean follow-up duration.
The results of 13 different surgical procedures to treat drooling were included in this analysis (Table 1). However, sufficient data for comparison were available for only 5 types of procedures (Table 2). Overall, subjective surgical success rates of more than 50% were reported in 58 of 59 study subsets, indicating a high level of overall treatment success. Random-effects modeling estimated the overall subjective success rate for all procedures to be 81.6% (95% confidence interval [CI], 77.5%-85.7%; P < .001) (Figure 2). The most common procedure was bilateral SMG duct rerouting, which accounted for 21 study subsets (36%). Bilateral SMG excision with bilateral parotid duct rerouting had the highest subjective success rate at 87.8% (k = 8 studies; 95% CI, 80.5%-95.1%; P < .001), whereas 4-duct ligation had the lowest success rate at 64.1% (4 studies; 27.6%-100%; P < .001). Comparing the 95% CIs for each procedure, bilateral SMG excision with bilateral parotid duct rerouting was statistically superior to bilateral SMG duct rerouting and sublingual gland excision (subjective success estimate, 71.5%; k = 8 groups; 95% CI, 63.6%-79.4%; P < .001). No other differences between procedures were statistically significant.
Subgroup analysis was performed to determine the effect of follow-up duration and time period on success rates. The overall success rates of studies including more than 1 year of follow-up (k = 42 study subsets; subjective success estimate, 83.9%; 95% CI, 78.6%-89.1%; P < .001) was compared with studies with less than 1 year of follow-up (17 study subsets; estimate, 76.6%; 68.9%-84.4%; P < .001), and no significant difference was observed. Similarly, the overall subjective success rate was not significantly different between studies performed before 1990 (k = 28 study subsets; subjective success summary estimate, 86.8%; 95% CI, 82.8%-90.8%; P < .001) or in 1990 or later (31 study subsets; estimate, 83.9%; 95% CI, 78.6%-89.1%; P < .001).
This meta-analysis suggests that surgical management using a variety of surgical procedures provides significant subjective relief in 81.6% of pediatric patients with sialorrhea. Although several studies attempted to use objective criteria to assess the success of the different procedures, most of the noted improvements were subjective. This is not necessarily a weakness of these studies because sialorrhea is essentially a subjective problem, and, thus, subjective improvement is the targeted outcome. Bilateral SMG excision and parotid duct rerouting had the highest reported success rate, 87.8%. However, simple bilateral submandibular duct rerouting and bilateral submandibular duct rerouting with bilateral parotid duct ligation had similar levels of subjective success within the power limits of the study. The lowest subjective success rate was reported with 4-duct ligation, the least invasive procedure, but results of this procedure were only reported in 4 study subsets. Limited data prevented rigorous comparison of success rates between procedures. Follow-up duration and time period for the individual studies did not appear to strongly affect the results.
The limitations of this study are those inherent to any meta-analyses and stem from the heterogeneity of data from different sources. The diverse nature of the study samples, which varied in age, sex, severity of sialorrhea, and geographic location, including the United States, United Kingdom, Canada, and Australia, adds to this heterogeneity. Different outcome measures were evaluated in each study, with different criteria for treatment success and failure. Although the same general subjective rating scheme was used among the studies (ie, “Drooling is much better,” “Drooling is better,” “Drooling is unchanged,” and “Drooling is worse”), there were some variations of this scheme that introduce additional heterogeneity into the analysis. Also, despite the fact that surgical procedures were grouped together for this analysis, there were certainly expected differences in how the procedures were performed by different surgeons with different levels of experience and training, which introduces further heterogeneity. Yet, random-effects modeling accounts for a large portion of this type of variation by producing summary estimates and 95% CIs of desired parameters using approximations of the standard error of each study, and the results can therefore be considered valid. Last, a unique form of possible bias is that some author groups contributed multiple studies to the sample: Crysdale et al (4 studies),15,20,26,40 Wilkie et al (2 studies),4,8 and O’Dwyer et al (2 studies).27,35 To assess the possibility of bias from this source, the random-effects model of overall success was repeated with these studies removed. A virtually identical estimate of overall subjective success of 80.7% (95% CI, 75.8%-85.6%; P < .001) vs the estimate with all of the studies included (estimate, 81.6%; 77.5%-85.7%; P < .001) was found, indicating that the possibility of bias from this source is very small. However, as with all meta-analyses, the reader is cautioned to interpret the results with these limitations in mind.
The high overall subjective success rate for sialorrhea procedures is encouraging to otolaryngologists considering surgical treatment, but the selection of one procedure over another remains somewhat daunting. Because data are limited for some procedures, explicit conclusions cannot be definitively drawn. However, our evidence can be interpreted to suggest that more-invasive procedures that aggressively target all 4 major salivary glands are perhaps more effective than less-invasive procedures. The trend within the data shown in Table 2 illustrates that the 2 procedures involving excision of the SMG combined with a procedure to address the parotid gland (either ligation or rerouting) have the highest summary estimates of subjective success. The data are far from conclusive, but this is an interesting and important practical consideration. Certainly, the treating surgeon would want to choose the least invasive but potentially most effective procedure. Four-duct ligation has appeal for its simplicity and limited invasiveness, but success rates vary widely from 100%36 to 31%43 among a very limited group of studies with short-term duration of follow-up. However, attempted ligation would not preclude other procedures if problematic sialorrhea recurs or persists. Thus, the selection of 4-duct ligation as one's initial first-line surgical procedure because of its limited invasiveness is defensible within the context of an informed consent discussion. Anecdotal experience with these procedures suggests that they can result in significant pain and swelling because the ligated glands continue to produce saliva for a period of time before atrophy occurs. Unfortunately, postoperative pain levels were not the focus of any studies included in this analysis, and, therefore, no definitive conclusion can be reached. More studies focused on this procedure with longer duration of follow-up would be a worthwhile contribution to the sialorrhea literature and are urgently needed to better evaluate the appropriate place of 4-duct ligation in sialorrhea management.
In contrast to 4-duct ligation, the procedure most extensively studied in the literature is bilateral submandibular duct rerouting. Although not extremely difficult to perform, it is more complex than a simple submandibular duct ligation. The reported success rates with this procedure are consistently good and similar to procedures involving SMG excision. One would have to wonder how many submandibular duct rerouting procedures end up as actual ligations owing to eventual obstruction of the duct from scar tissue. Limited data regarding this question are available but suggest that this fibrosis does occur, but uncommonly, with most patients maintaining function in at least 1 gland.53 A directed study to address the question of long-term duct patency and ligation vs rerouting would also be a worthwhile contribution to the literature.
The directed purpose of this study was to evaluate surgical treatment for sialorrhea. Therefore, the use of botulinum toxin was not investigated. Nevertheless, no discussion of the modern treatment of sialorrhea is complete without mention of this technique. The use of botulinum toxin has grown in popularity because of its limited invasiveness and demonstrated effectiveness in many patients. Clearly, however, it will not supplant surgical treatment because its effect is temporary. Perhaps its most efficacious use might be for empirical selection of patients who would, in the future, be good candidates for durable surgical treatment of the major salivary glands. Undoubtedly, patients for whom botulinum toxin treatment of their major salivary glands is ineffective should be very carefully considered as candidates for surgical treatment because failure rates could be much higher owing to the contribution from minor salivary glands.
The preponderance of evidence regarding surgical outcomes of sialorrhea management is low quality and heterogeneous. Regardless, most patients experience a subjective improvement in sialorrhea following surgical treatment. Several different procedures have been described. Bilateral submandibular duct rerouting, bilateral SMG excision with bilateral parotid duct rerouting, and bilateral SMG excision with bilateral parotid duct ligation appear to be similarly successful, with comparable safety profiles. Four-duct ligation may have a lower success rate, but only limited studies with short-term follow-up are available. More rigorous, directly comparative studies need to be performed to identify a procedure of choice.
Correspondence: Scott E. Brietzke, MD, MPH, Department of Otolaryngology, Walter Reed Army Medical Center, 6900 Georgia Ave, Washington, DC 20307 (firstname.lastname@example.org).
Submitted for Publication: January 15, 2009; final revision received April 12, 2009; accepted April 23, 2009.
Author Contributions: All authors had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Mans and Brietzke. Acquisition of data: Reed, Mans, and Brietzke. Analysis and interpretation of data: Reed, Mans, and Brietzke. Drafting of the manuscript: Reed, Mans, and Brietzke. Critical revision of the manuscript for important intellectual content: Brietzke. Statistical analysis: Reed and Brietzke. Administrative, technical, and material support: Mans and Brietzke.
Financial Disclosure: None reported.
Disclaimer: The views herein are the private views of the authors and are not to be considered official views of the US Army or the Department of Defense.
Previous Presentation: This study was presented as a poster at the American Society of Pediatric Otolaryngology Annual Meeting; May 2-4, 2008; Orlando, Florida.
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