Effectiveness
The RCT in patients with persistent, moderate-severe allergic rhinitis(15),found that PNN resulted in an improved VAS score for pain and improved RQLQ scores at 1, 3, 6, and 12 months following the surgery compared with patients treated medically. The quality and site of the pain was not reported. There was no objective change in tearing/watery eyes in either group following intervention. One major limitation of this study was the duration of medical treatment in the control group – these patients only received intranasal corticosteroid spray (INCS) and an oral antihistamine for 3 months and therefore the improved scores in the PNN group beyond 3 months were measured at a time when the control group was not receiving any treatment whatsoever. One could also argue that INCS and an oral antihistamine alone do not constitute “maximal medical therapy” for allergic rhinitis and all this, together with the small sample size reduced the quality of this study and the conclusions that can be drawn.
The second RCT(16) compared PNN to PNN with pharyngeal neurectomy and therefore the focus was on assessing whether the pharyngeal neurectomy contributed to symptom control. Therefore, this study design did not allow us to draw any robust conclusions as to the effectiveness of PNN itself. Both groups had significant improved outcomes up to 2 years following the intervention.
Two case control studies(17, 18) directly compared patients who underwent turbinate reduction with and without PNN. Sample size, methodology and operative approach were similar in both studies. Albu(18) found no significant difference in VAS scores, RQLQ scores and rhinomanometry in patients who underwent PNN in addition to turbinate reduction. The only significant difference was an increased likelihood of post-operative haemorrhage in the PNN group. This study recruited (retrospectively) patients with severe inferior turbinate hypertrophy with allergic rhinitis and the predominant pre-operative symptom was nasal obstruction although rhinorrhoea, post-nasal drip, snoring, and sneezing were also present and all improved in both arms with no significant differences between the two. There was a larger improvement in rhinorrhoea in the turbinoplasty + PNN group but this was not statistically significant. One must bear in mind that terminal branches of the posterior nasal nerve within the inferior turbinate are potentially divided during a turbinoplasty. Suzuki(17) found significant improvement in the PNN group in VAS scores for sneezing, nasal obstruction and nose blowing, and improvement in olfaction using olfactometry. The risk of bias was deemed to be high in both studies.
Six studies(13,16,18-19,25,28) followed up patients for longer than 12 months. Of the studies that followed up at three years or greater, it would appear that benefits may diminish over time(25,28). Ogi et al.(25) reported that improvements in sneezing, rhinorrhoea and obstruction were no longer present after 6 years. Sonoda et al.(28) found that significant improvements in rhinorrhoea and sneezing had diminished at 8 years, but the improvement in nasal obstruction, JRQLQ, TNSS scores, and reduction in medication use was sustained over eight years. It was not possible with the data available from the various studies to infer whether patients with allergic backgrounds had a different outcome to those with non-allergic backgrounds.
Apart from 4 studies(15-18), the evidence was level 4. There was a high risk of bias and confidently attributing the outcomes to PNN was not possible. Follow up was quite variable and frequently timing of follow up was not cited. Study design varied considerably and a mixture of different outcome measures made the data too heterogeneous to undertake a meta-analysis. More than half of the subjects were yielded from the Kanaya case series(12). This study did not specify their patient population in terms of rhinitis status, previous treatment, follow up period, and symptomatic outcomes. Almost all studies were carried out in East and South Asian patients and this must be borne in mind when assessing the applicability of the results to Western populations.