58 CHAPTER 2 There are some limitations to this study. First, we changed inclusion criteria to reduce inclusion delay, potentially resulting in an increase in heterogeneity of the patient population. We did not find any evidence support such an increase in the data, however. Another potential limitation is the fact that patients, caregivers and researchers were not blinded to treatment allocation. It should be noted, however, that the masked DQ was closely related to the unmasked DQ, suggesting limited bias. The length of follow-up is another limitation of the study. First, because recurrence seemed ongoing up to 32 weeks after 2-DL. This means that the effectiveness of 2-DL in the long-term cannot be fully extrapolated from the current data. Second, because the follow-up period is too short to asses potential dental disadvantages from diminished salivary flow. Since BoNT-A is a short and effective procedure for the treatment of drooling with very few postoperative complaints, BoNT-A injection is considered first step treatment when conservative treatment measures have failed. However, over time, patients and caregivers frequently prefer a longer-lasting therapy. Thus far there are no studies proving botulinum toxin mediated glandular atrophy resulting in long-term effect of botulinum toxin.17, 25 Moreover, the effectiveness of repeated BoNT-A injections might be limited as a result of antibody formation, which has been reported in up to 15% of patients.26-29 This study suggests that 2-DL can be an effective ‘follow-up therapy’ to BoNT-A: it is more effective and longer lasting, and carries only a slightly greater risk for adverse events and complaints. 2-DL also has specific advantages over SMDR or SMGE: unlike SMDR, it is a viable option in posterior drooling, and unlike SMGE, there is no external scar. It is also a much more limited and shorter procedure than SMDR or SMGE. If drooling recurs after 2-DL, it is our opinion that either SMGE, or parotid duct ligation (either unilateral or bilateral) should be considered. It should be noted that
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