Main findings
The incidence of early and late postoperative complications in primary ETT pituitary surgery is low. Pre- and postoperative olfactory function is comparable, as long as no nasoseptal flap is harvested. Assessment of smell function before and after surgery, as well as regular postoperative rhinologic follow-up examinations may be important factors in optimal postoperative patient care.
The endoscopic approach to the pituitary gland is considered minimally invasive compared to the microscopic technique, because neither a sublabial approach, transseptal incision or speculum insertion is required [
17]. This translates into a reduced overall complication rate, operating room time, hospital stay and patient discomfort [
17]. With particular focus on rhinologic complications, White et al. found a higher rate of postoperative epistaxis and septal deviation in the microscopic group [
18]. In addition, higher rates of postoperative acute rhinosinusitis and synechiae were reported in the literature [
19,
20]. Regarding postoperative smell function, some authors reported a more favourable outcome for the endoscopic approach [
20,
21], while others could not confirm these findings, on the assertion that protecting the nasal mucosa is key, regardless of the approach [
22].
Consistent with previous reports, the retrospective analysis of our institutional cohort revealed low rates of early and late postoperative complications. In the early postoperative phase, the predominant complication was bleeding from the septal branch of the sphenopalatine artery, which occurred in 3.0% of patients. In the literature, reported rates of postoperative epistaxis after ETT surgery varied between 0 and 4% [
15,
23‐
32]. However, details on the origin of the postoperative epistaxis and treatment concepts were not provided in those studies. The five epistaxis episodes in our cohort consisted of two mild haemorrhages, which were managed conservatively with absorbable haemostatic gelatine sponge packing (Spongostan TM). However, in three patients we opted for surgical haemostasis under general anaesthesia with ligation of the septal branch of the sphenopalatine artery in two patients and coagulation of the sphenopalatine artery at the level of the sphenopalatine foramen in one patient due to diffuse bleeding. Thompson et al. even reported two patients with intrasellar haemorrhage after ETT surgery, which lead to temporary visual field defects [
33]. The course of the sphenopalatine artery and its septal branches has been described in detail [
34,
35]. According to Griffiths et al., the septal branches, also forming the arterial pedicle for the nasoseptal flap, run approximately 9 mm inferior to the sphenoid sinus ostium, allowing a safety margin to prevent transection [
36]. At the minimum, one side of the posterior nasal septal artery should be preserved to maintain the possibility of harvesting a secondary nasoseptal flap; however, we opted for a low threshold, exploring the postoperative situs under general anaesthesia to achieve surgical haemostasis in cases of early postoperative bleeding [
33].
The rate of postoperative acute rhinosinusitis has been reported to be between 2.0 and 3.8% (institutional cohort: 1.2%). This is most likely caused by stenosis of the sphenoidotomy, in which mucus retention combined with absorbable haemostatic packings cause stasis and consequential secondary infection. Therefore, certain authors claim that the entire mucosa of the sphenoid should be removed, to gain not only maximal exposure, but also minimal risk of postoperative infection. However, data supporting this manoeuvre is still lacking. Furthermore, a thorough postoperative care, with regular moisturising and rinsing, as well as endoscopic cleaning may prevent scarring and shrinking of the sphenoidotomy [
7]. In our series, all postoperative sinus infections were managed with intensive local care and systemic antibiotics.
The late complications in our series were similar to the findings in the systematic review. Usually, we opt for a mononostril ETT approach, with the contralateral mucosa almost completely preserved. Given that we included only primary cases and tumours limited to the pituitary gland, the rate of septal perforations needs to be interpreted with caution, since a nasoseptal flap was only harvested in 4/168 (2.4%) patients. A postoperative septal perforation was seen in only one patient (0.6%) with a past medical history of septoplasty. In this case, most of the cartilaginous septum had been resected, leaving a very thin mucosa on both sides. In an Italian series on ETT surgery, Schreiber et al. reported that all septal perforations occurred in the area where the mucosa had been incised with monopolar electrocautery to harvest a nasoseptal flap or to create a corridor for transseptal sphenoidotomy [
7]. In line with this observation, Kim et al. claimed that electrocautery causes more damage to the mucosa than the cold steel technique [
37]. Long-distance synechiae were observed in 11.9% of patients, but remained asymptomatic in all patients, obviating the need for surgical intervention. In particular, avoiding speculum insertion may have been an important factor since the reported rates of microscopic synechiae were up to 38% [
20].
Only seven studies involving a total of 206 patients reported adequate outcome measures for smell function before and after ETT [
8,
16,
32,
38‐
41] (Table
3). Many studies were excluded, because the surgical procedures were performed endoscopically with an inserted speculum or because the reported outcome was heterogeneous and did not specify whether a microscopic or an endoscopic technique was applied [
42‐
45]. In addition, many studies have relied on self-reported olfactory impairment, which is clearly inadequate [
15,
30,
31]. Overall, only one group reported a significant difference in smell function [
16]. In their series of 17 patients, all of whom had nasoseptal flaps, Rotenberg et al. reported an impairment in olfactory function at 6 months postoperatively [
16]. In a randomised controlled trial on ETT surgery with and without nasoseptal flaps, the same group found an impairment in smell function (pre- vs. postoperatively) in both groups at 6 months, with a greater loss in the nasoseptal flap group [
40]. In contrast, all other series, including our own, revealed preserved postoperative olfactory function. Despite the report of Sowerby et al. who did not find impairments of smell function in their subgroup of patients with nasoseptal flaps [
41], a thorough analysis of olfactory dysfunction after ETT surgery imperatively requires information on the rate of harvested nasoseptal flaps. As demonstrated in our series, olfactory impairment on the donor side is encountered frequently and justifies monorhinal smell testing before surgery, to prevent possible bilateral smell impairment in patients with pre-existing single-sided olfactory loss [
9]. Among the seven included studies with adequate outcome measures on smell function, 76/206 (36.9%) patients underwent reconstruction with a nasoseptal flap. As previously reported, this rate is even smaller in our series (2.4%). In summary and according to Harvey et al., minimising mucosal trauma combined with respecting the olfactory-bearing areas of the nasal cavity is likely to ensure minimal impact on olfaction after pituitary surgery [
46]. To avoid damage to the olfactory-bearing septal and turbinate areas, the authors proposed a small, olfactory-preserving nasoseptal flap, the so-called olfactory strip, which led to lower morbidity while maintaining reconstruction options [
46].
Strengths and limitations
To the best of our knowledge, this is the largest single-centre series focusing on objective rhinologic outcomes after ETT surgery and provides a comprehensive update of the current evidence on this topic. Although we aimed to gather available evidence as comprehensively as possible, certain limitations need to be addressed. First, our synopsis reflects the quality of the included studies, which are mostly retrospective case series, involving multiple centres, with study periods covering several decades. Second, the systematic search revealed a large heterogeneity in terms of the reported rhinologic outcomes, including different follow-up algorithms and methods of assessing smell function. Third, because of the heterogeneity of the included studies, no I2 values could be reported. Fourth, the search via PubMed could have missed certain studies, since other databases (e.g. Embase, Web of Science) were not systematically reviewed.