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.