Study Selection
A total of 390 potentially relevant records were identified, reducing to 290 after duplicates were removed. A PRISMA flowchart is demonstrated in figure 1. On review of full text articles 17 were removed as the series contained less than five patients that were treated with ND alone (12–28). A further 15 were removed as they comprised conference abstracts only (29–43) while six were non-English language (44–49). A total of 14 studies have met the eligibility criteria and are presented herein. (50–63).