Data extraction
Data were extracted in duplicate from all reports and independently recorded on a piloted form by two authors. The data extracted from each study were as follows: (a) patient characteristics (mean age, country, and inclusion and exclusion criteria); (b) intervention characteristics; (c) characteristics of treatment as control; and (d) outcome measures (complete caloric recovery of CP, improvement of CP in caloric test, and DHI score). Other extracted data included author, year of publication, research design, number of samples, outcome variables, and follow up periods.