DISCUSSION
The principal finding of this literature review was that PNN is a safe procedure with an acceptable complication rate. It appears to be an effective procedure for patients with allergic and non-allergic rhinitis but the level, quality, and heterogeneity of the published evidence hampers the strength of the conclusions that can be drawn. Every study but one reported symptom improvement in patients undergoing PNN. Outcome measures were largely valid and improvements were observed in all individual nasal symptoms (particularly sneezing and rhinorrhoea) as well as QoL measures, but most studies did not have a control arm.