Participants
Overall, there were 551 subjects included in the selected series. Despite that there was some heterogeneity in the distribution of gender among the series, overall, 48% of the enrolled subjects were female. The median of the mean ages from all studies was 44 years (range: 32–64 years). Body mass index (BMI) was available only in four series (median 26; range: 25–27). All but three studies adopted a predefined score to assess the severity of dysphagia, being the Eckardt score in most of the cases.