Risks and Complications of Balloon Dilation of the Eustachian Tube.

Obstructive eustachian tube (ET) dysfunction is a common condition associated with various otologic symptoms. The current lack of a diagnostic gold standard makes diagnosis and evaluation at follow-up difficult. The aim of the study was to determine the value and discriminative power of the seven-item Eustachian Tube Dysfunction Questionnaire (ETDQ-7) in patients with obstructive ET dysfunction and patulous ET. Diagnostic test study. The ETDQ-7 was completed by 39 patients with obstructive ET dysfunction, eight patients with patulous ET, and 22 healthy controls. The internal consistency was evaluated using the Cronbach α coefficient. Receiver operating characteristic (ROC) was determined as an accuracy measure. The mean ETDQ-7 total score was 9.91 in the control group, 25.77 in the patients with obstructive ET dysfunction, and 27 in the patulous ET group. The Cronbach α coefficient was 0.795 in the obstructive ET group and 0.72 in the patulous ET group, demonstrating adequate reliability. The area under the curve in ROC analysis for the obstructive ET group was 95% and 96% for the patulous ET dysfunction group, which confirms its excellent discriminant validity toward the healthy control group. However, the ETDQ-7 cannot discriminate between obstructive ET dysfunction and patulous ET. The ETDQ-7 can be a useful disease-specific rating scale for ET dysfunction but is unable to discriminate between patients with obstructive ET dysfunction and patulous ET. 3b.

HintergrundEine klaffende Tube kann insbesondere durch Autophonie, Druckgefühl und gestörten Höreindruck zu einer Einschränkung der Lebensqualität führen. Bei fehlenden spezifischen Symptomen kann die Diagnose der klaffenden Tube schwierig sein. Insbesondere die Abgrenzung zur chronisch obstruktiven Tubenfunktionsstörung stellt eine Herausforderung dar. Da derzeit kaum standardisierte Diagnostik- und Therapieoptionen zur Verfügung stehen, ist eine strukturierte Untersuchung zur sicheren Diagnostik und wissenschaftlichen Aufarbeitung dieser Erkrankung erforderlich. Für die Diagnostik der chronisch obstruktiven Tubenfunktionsstörung wurde 2012 bereits der „Eustachian Tube Dysfunction Questionnaire“ (ETDQ-7-Fragebogen) nach McCoul entwickelt. Für die klaffende Tube existiert seit 2017 der PHI-10-Fragebogen („patulous Eustachian tube handicap inventory“) nach Kobayashi.Material und MethodenDer PHI-10-Fragebogen wurde ins Deutsche übersetzt und an 41 Gesunden, 13 Patienten mit Tinnitus auris, 11 Patienten mit klaffender Tube und 18 Patienten mit chronisch obstruktiver Tubenventilationsstörung getestet. Zusätzlich erfolgte im Vergleich die Auswertung des ETDQ‑7 nach McCoul.ErgebnisseEs erfolgt die Präsentation der deutschen Übersetzung des PHI-10 und der Ergebnisse von PHI-10 und ETDQ‑7 in allen Patientengruppen. Der ETDQ‑7 hat das Risiko falsch-positiver Ergebnisse bei Patienten mit klaffender Tube und der PHI-10 bei Patienten mit obstruktiver Tubenfunktionsstörung. Beide untersuchten Fragebögen sind falsch-positiv bei Tinnituspatienten.SchlussfolgerungDer PHI-10 (deutsch) und ETDQ‑7 (deutsch) sind eine nützliche Unterstützung der Anamnese bezüglich Tubenfunktionsstörungen. Sie unterscheiden jedoch nur unzureichend zwischen klaffenden und obstruktiven Tubenfunktionsstörungen und eignen sich nicht für Patienten mit Tinnitus. Die Stärke der Fragebögen ist in der Verlaufskontrolle und dem Monitoring von Therapieergebnissen zu sehen.

Tubomanometry: An effective and promising assessment of Eustachian tube dysfunction in chronic rhinosinusitis patients

Objectives: To explore the relationship between aural symptoms during baro-challenge and the underlying measured Eustachian tube (ET) function. Two key questions were addressed. (1) In patients who have features of obstructive ET dysfunction, is there a measurable underlying difference in ET function between those who experience severe symptoms on baro-challenge and those that do not? (2) What is the diagnostic value of ET function tests in the identification of patients with severe symptoms on baro-challenge? Methods: Patients with symptoms of obstructive ET dysfunction were recruited, with the presence of aural symptoms on baro-challenge established via the clinical history and analysis of the Cambridge ET Dysfunction Assessment, a patient-reported outcome measure (PROM). ET function tests were assessed in each patient: 9 objective and semi-objective measures of ET opening, and 2 symptom-based PROMs. The tests’ results were grouped by type of ET opening assessed, generating passive and active dysfunction scores. Individual test results were assessed for diagnostic accuracy in reference to features in the history or PROM-based evidence of symptoms on baro-challenge. Results: Both passive and active opening of the ET was significantly reduced in ears with a history of pain on baro-challenge. Some patients had apparent severe obstructive ET dysfunction without symptoms on baro-challenge, whilst others had symptoms but normal test results. No individual test of ET opening was of diagnostic value in predicting those ears likely to experience pain or exacerbated symptoms on baro-challenge. Conclusion: The relationship between aural pain during baro-challenge and ET function appears more complex than had been assumed, with pain possibly related to factors other than just ET function.

Cochlear implantation (CI) has been successfully used to restore hearing in patients with severe to profound hearing loss. In addition to hearing loss, irradiated patients with nasopharyngeal carcinoma (NPC) also often have chronic otitis media and Eustachian tube (ET) dysfunction. These features may result in difficulties in CI. We conducted this study to review the management options for irradiated patients with NPC undergoing CI. Furthermore, we investigated the results of CI in irradiated patients with NPC with chronic otitis media and obstructive ET dysfunction, accordingly to different treatment strategies. We retrospectively reviewed the data of patients with NPC who underwent CI in our hospital between 2006 and 2020. All subjects were found to be eligible according to the following inclusion criteria: had NPC, received irradiation, underwent cochlear implant surgery, and had chronic otitis media with obstructive ET dysfunction. A total of 9 patients with obstructive ET dysfunction and chronic otitis media underwent cochlear implant surgery. Seven patients with an inflamed ETs underwent a 2-stage operation. Two patients with obliterated ETs, we performed a single-stage CI surgery. Only 1 patient had otitis media effusion after the surgery. With the proper management of chronic otitis media and ET dysfunction, cochlear implant is an effective treatment for irradiated patients with NPC when conventional hearing aids failed.

Eustachian tube balloon dilation (ETBD) is increasingly used to treat Eustachian tube (ET) dysfunction, but its benefit in patients requiring tympanoplasty for chronic inflammatory middle ear disease is unclear. To evaluate the efficacy of additional ETBD on the Eustachian Tube Score (ETS), hearing outcomes, and subjective ET function in patients with obstructive ET dysfunction undergoing tympanoplasty. This parallel-group, single-blind, monocentric, randomized clinical trial included patients with chronic inflammatory middle ear disease and ET dysfunction seen at a tertiary referral center and scheduled for tympanoplasty between January 2015 and November 2019. Data were analyzed between June 2022 and December 2023. Patients were randomized to tympanoplasty only or an additional ETBD of the affected side. The main outcome was the change in ETS, and secondary outcome measures were change in the air-bone gap (ABG) and Eustachian Tube Dysfunction Questionnaire (ETDQ-7) scores. From 76 randomized participants, 68 were included in the intention-to-treat analysis. Of the 34 patients in the tympanoplasty group, 20 participants (59%) were female, and the mean (SD) age was 53.4 (12.5) years. Of the 34 patients in the tympanoplasty plus ETBD group, 13 participants (38%) were female, and the mean (SD) age was 51.4 (14.5) years. During the first 12 months after the procedure, the difference in mean ETS changes between the tympanoplasty (1.62 [95% CI, 0.66-2.59]) and the tympanoplasty plus ETBD group (1.41 [95% CI, 0.43-2.39]) was 0.21 (95% CI, -1.17 to 1.59). These results rule out the possibility of a clinically meaningful difference of 3 points or more in ETS. Twelve months after the procedure, ABG improved from 26.1 dB to 19.0 dB hearing loss in the tympanoplasty group and from 30.1 dB to 20.1 dB hearing loss in the tympanoplasty plus ETBD group. The difference in ABG changes between the groups was -2.8 dB (95% CI, -9.1 dB to 3.5 dB), and the difference in mean ETDQ-7 changes was -0.2 (95% CI, -3.4 to 3.1). In this randomized clinical trial, the addition of ETBD to tympanoplasty in patients with chronic inflammatory middle ear disease and ET dysfunction did not improve the outcome regarding ETS, ABG, or subjective long-term ET function. ETBD should, therefore, not be routinely performed as an add-on procedure to tympanoplasty for this indication. Larger multicentric randomized trials could provide more insights into the efficacy of ETBD in patients with chronic inflammatory middle ear disease undergoing tympanoplasty and would allow for specific subgroup analyses. German Clinical Trials Register Identifier: DRKS00031807.

Baro-challenge-induced Eustachian tube (ET) dysfunction is defined as the presence of aural discomfort, popping, or pain, which only arises in case of ambient pressure changes, without abnormalities on otoscopy or tympanometry. Our primary aim was to determine the discriminative power of the 7-item Eustachian Tube Dysfunction Questionnaire (ETDQ-7) in patients with baro-challenge-induced ET dysfunction in comparison with that in healthy controls. The secondary aim was to determine the responsiveness of ETDQ-7 in patients with baro-challenge-induced obstructive ET dysfunction who underwent balloon dilation tuboplasty (BDET). The accuracy of the diagnostic test was determined on the basis of the area under the curve in receiver-operating curve (ROC) analysis. Responsiveness to change of ETDQ-7 was assessed by exploring preoperative and postoperative ETDQ-7 scores using Cohen's kappa coefficient. Patients were asked whether their complaints improved, remained stable, or deteriorated after BDET. The findings of subjective evaluation were then compared with the difference in the ETDQ-7 score after BDET. In the baro-challenge-induced ET dysfunction group, the median preoperative total ETDQ-7 score was 26, decreasing to 16 after BDET. ROC analysis demonstrated excellent discriminative power for the baro-challenge-induced ET dysfunction group. Cohen's kappa coefficient was 0.633, indicating that there was substantial agreement between the ETDQ-7 values before and after BDET. ETDQ-7 can discriminate between patients with baro-challenge-induced ET dysfunction and healthy controls and can therefore be useful in its diagnosis. Furthermore the ETDQ-7 is responsive to change in patients with baro-challenge-induced ET dysfunction who have undergone BDET, although a larger sample size is required to confirm these preliminary findings.

The objective of this study was to demonstrate the reliability of tubomanometry (TMM) described by Estéve in the diagnosis of chronic obstructive Eustachian tube (ET) dysfunction. Combined prospective and retrospective clinical study. Tertiary referral centre, affiliated to university. Two hundred and fifteen healthy subjects were examined once, 25 healthy subjects underwent TMM weekly for 6 weeks, and six healthy subjects were tested three times a day on at least three different days. The results of tubomanometry in healthy subjects were compared to data obtained from 171 patients with chronic obstructive ET dysfunction. In healthy subjects, there was an immediate opening of the ET at 30-50 mbar with an R-value ≤ 1 in at least 94% of the cases. In patients with chronic ET dysfunction, an opening of the ET could be registered in only 42% of patients at 30 mbar and in 58% at 50 mbar. The average of the R-value in these subjects always indicated towards a delayed opening (R > 1). When measurements are repeated in the same subject with a weekly interval, the intraclass correlation (ICC) was 0.49 for the TMM with 30 mbar, 0.51 for the TMM with 40 mbar and 0.52 for the TMM with 50 mbar in healthy people. For the patients with symptoms of ET dysfunction, the ICC for up to four repeated measures was 0.50 for the TMM with 30 mbar, 0.53 for the TMM with 40 mbar and 0.54 for the TMM with 50 mbar. A complete agreement of the results in repeated measurements within seconds was present in 86% for 30 and 40 mbar and in 79% for 50 mbar. The ICC was 0.61 for the TMM with 50 mbar, 0.62 for the TMM with 40 mbar and 0.68 for the TMM with 30 mbar. Tubomanometry can support the diagnosis of ET dysfunction. An R-value ≤ 1 indicates a regular function of the ET, an R-value >1 indicates a delayed opening of the ET, and no definable R-value means no detectable opening of the ET. TMM is a reliable and valid instrument to support the diagnosis of chronic obstructive ET dysfunction.

Obstructive Eustachian tube dysfunction (ETD) commonly complicates chronic otitis media (COM), yet microbial factors at the Eustachian tube (ET) openings remain poorly understood. In this prospective cohort study, we characterized the microbiota at both the middle ear (ME) and nasopharyngeal (NP) ET openings in COM patients undergoing ear surgery and examined associations with obstructive ETD over one year of follow-up. Using 16S rRNA gene sequencing and functional inference, we profiled microbial communities from the ME-side ET opening and the torus tubarius on both surgical-side and contralateral nasopharynx. Among 37 patients (18 with ETD, 19 without), ME and NP microbiota differed significantly in composition. Ears with ETD showed increased ME microbial diversity and enrichment of Neobacillus, Agrobacterium, and Sphingomonas. Paired NP-ME analyses indicated an altered NP-ME microbial relationship in ETD, with Neobacillus showing a nasopharyngeal source signal. Functional prediction revealed increased porphyrin metabolism and decreased pyruvate metabolism in ME microbiota with ETD, suggesting a shift toward biofilm formation and altered redox states. Anaerococcus was increased in the nasopharynx of patients with bilateral COM. These findings identify distinct microbial and metabolic features of COM with obstructive ETD, supporting a role for nasopharyngeal-microbial influence on ME pathology.IMPORTANCEChronic otitis media (COM) is a common and often persistent ear disease, especially when complicated by Eustachian tube dysfunction (ETD). By profiling microbiota at both Eustachian tube openings, this study links upper-airway microbial ecology with middle-ear microbial states in COM and helps clarify where clinically relevant signals may arise along the Eustachian tube pathway. The paired nasopharyngeal-middle ear design revealed that nasopharyngeal microbes may be linked to middle-ear community shifts in COM with obstructive ETD, consistent with a potential upper airway contribution to the middle-ear microbiota, generating testable hypotheses about microbial exchange and persistence. These findings highlight the upper airway microbiome as a potential target for developing new preventive and therapeutic strategies in COM.

Although balloon dilation has shown promising results in the treatment of dilatory Eustachian tube (ET) dysfunction, the histological effects of ET balloon dilation (ETBD) is unknown because histological examination of the whole human cartilaginous ET is impossible. Animal studies are needed to elucidate the effect of ETBD so we evaluated the histological changes after ETBD in a rat model. The left ET of 20 Wistar rats was dilated with a balloon catheter and the right ET was used as a control. Five rats were sacrificed immediately after ETBD, at 1, 4 and 12 weeks after the procedure for histological examination. The epithelial cells, presence of epithelial hyperplasia, and the proportion of the goblet cells in the epithelium; the vascular structures and dimensions of the submucosa; and presence of cartilage fracture and the area of the ET lumen were evaluated and compared between the groups. Desquamation of nearly all epithelial cells and the fracture of tubal cartilages were observed immediately after ETBD. At 1-week post-ETBD, the ciliated epithelial cells started to recover with epithelial hyperplasia. The goblet cells recovered by 4 weeks post-ETBD and epithelial hyperplasia decreased but was still present at 12 weeks post-ETBD. The depth of the submucosa increased and neovascularization in this region was observed at 1-week post-ETBD and persisted up to 12 weeks post-ETBD. The lumen of the cartilaginous ET increased immediately after ETBD but decreased at 1-week post-ETBD. The cartilaginous ET lumen recovered to the normal value at 4 weeks post-ETBD. This study is the first to describe the serial histological changes to the cartilaginous ET after ETBD and helps our understanding of the histological changes that occur after an ETBD intervention for intractable ET dysfunction.

Although balloon dilation has shown promising results in the treatment of dilatory Eustachian tube (ET) dysfunction, the histological effects of ET balloon dilation (ETBD) is unknown because histological examination of the whole human cartilaginous ET is impossible. Animal studies are needed to elucidate the effect of ETBD so we evaluated the histological changes after ETBD in a rat model. The left ET of 20 Wistar rats was dilated with a balloon catheter and the right ET was used as a control. Five rats were sacrificed immediately after ETBD, at 1, 4 and 12 weeks after the procedure for histological examination. The epithelial cells, presence of epithelial hyperplasia, and the proportion of the goblet cells in the epithelium; the vascular structures and dimensions of the submucosa; and presence of cartilage fracture and the area of the ET lumen were evaluated and compared between the groups. Desquamation of nearly all epithelial cells and the fracture of tubal cartilages were observed immediately after ETBD. At 1-week post-ETBD, the ciliated epithelial cells started to recover with epithelial hyperplasia. The goblet cells recovered by 4 weeks post-ETBD and epithelial hyperplasia decreased but was still present at 12 weeks post-ETBD. The depth of the submucosa increased and neovascularization in this region was observed at 1-week post-ETBD and persisted up to 12 weeks post-ETBD. The lumen of the cartilaginous ET increased immediately after ETBD but decreased at 1-week post-ETBD. The cartilaginous ET lumen recovered to the normal value at 4 weeks post-ETBD. This study is the first to describe the serial histological changes to the cartilaginous ET after ETBD and helps our understanding of the histological changes that occur after an ETBD intervention for intractable ET dysfunction.

Obstructive Eustachian tube dysfunction (OETD) is a common condition resulting from inadequate opening of the Eustachian tube (ET). A new surgical treatment involves high-pressure inflation of a balloon within the ET, with the aim of dilating the soft tissue structure. However, the mechanical effects of this intervention have not been established, nor the impact of changing device size or other technical parameters. A novel experimental technique allowed quantification of plastic and elastic tissue deformation in model materials and then human cadaver ETs during balloon dilation, based on the measured balloon inflation pressure-volume relationship. Plastic tissue deformation was found to be greater using larger balloons and deeper device insertion, but increasing the inflation pressure had a more limited effect, with most deformation occurring well below the clinically used pressures. Histological assessment of ET tissue suggested that mucosal tearing and cartilage cracking were in part responsible for the mechanical changes. Balloon dilation of the ET has huge potential if found to be clinically effective, but currently there is a need to understand and develop the technique further. The novel methods employed in this study will be valuable in future laboratory and in vivo studies of ET balloon dilation. Pressures are reported in Bar as this unit is used for medical balloon dilation procedures in clinical practice. 1 Bar = 100,000 Pa.Graphical abstract captionDilation of the Eustachian tube for obstructive dysfunction is performed clinically with 3- and 6-mm-diameter balloons of approximately the same overall length. Our data suggest that dilation with a 6-mm balloon causes greater deformation of the soft tissue structure than dilation with a 3-mm balloon. This difference has yet to be demonstrated clinically. Plastic deformation was measured in terms of energy (J) dissipated during balloon inflation.

The Eustachian tube (ET) is essential for middle ear ventilation. Chronic obstructive ET dysfunction may lead to chronic otitis media and cholesteatoma, but its pathophysiology remains unclear. Commensal bacterial colonization of the ET has not previously been studied in healthy individuals or affected patients. Prospective cohort study was conducted at a tertiary academic referral center including 13 patients with chronic obstructive ET dysfunction and 37controls. Between 2017 and 2020, intraoperative tissue samples and swabs were collected using acontamination-minimized Yankauer suction technique. Samples underwent conventional culturediagnostics, microbiome analysis via 16S rDNA sequencing, and histopathological examination. Culture identified 552 bacterial strains, with greater diversity in controls (34 genera) than in patients (19genera). Microbiome analysis confirmed a larger core microbiome in controls. Rothia was more abundant in patients, whereas Veillonella predominated in controls. Genera such as Rothia and Gemella may be linked to microbial alterations in chronic ET dysfunction. This first combined culture-based and molecular analysis using a novel sampling-technique demonstrated reduced bacterial diversity in chronic ET dysfunction patients, resembling patterns seen in other chronic respiratory morbidities. Future studies should incorporate complementary sampling approachesand cutting-edge sequencing technologies, additionally assessing viral etiologies.

Surgical intervention of the Eustachian tube (ET) has become increasingly common in the past decade, and balloon dilation has shown promising results in recent studies. It is unclear how balloon dilation enhances ET function. Our aim was to evaluate histological changes in the ET's mucosal lumen comparing before balloon dilation, immediately after, and postoperatively. Case series. Thirteen patients with bilateral ET dysfunction were enrolled. Biopsies of the ET mucosa were obtained just before balloon dilation; immediately after; and in three cases, 5 to 12 weeks postoperatively. Specimens were retrospectively examined under light microscopy by two pathologists blinded to the clinical information and whether specimens were pre- or postballoon dilation. Preoperative biopsies were characterized by inflammatory changes within the epithelium and submucosal layer. Immediate response to balloon dilation was thinning of the mucosa, shearing of epithelium and crush injury to the submucosa, especially to lymphocytic infiltrates. Postoperative biopsies demonstrated healthy pseudocolumnar epithelium and replacement of lymphocytic infiltrate with a thinner layer of fibrous tissue. Reduction of inflammatory epithelial changes and submucosal inflammatory infiltrate appeared to be the principal result of balloon dilation. The balloon may shear or crush portions of inflamed epithelium but usually spared the basal layer, allowing for rapid healing. Additionally, it appeared to effectively crush lymphocytes and lymphocytic follicles that may become replaced with thinner fibrous scar. Histopathology of the ET undergoing balloon dilation demonstrated effects that could reduce the overall inflammatory burden and may contribute to clinical improvement in ET function. 4.

Eustachian tube dysfunction (ETD) causes symptoms and signs of pressure dysregulation in the middle ear, and is associated with tympanic membrane retraction, otitis media with effusion, and chronic otitis media. Interventions aiming to improve symptoms can be non-surgical or surgical, including balloon dilatation of the Eustachian tube, also known as balloon eustachian tuboplasty (BET) for obstructive ETD. However, existing published evidence for the effectiveness and safety of BET remains unclear. To evaluate the effects of balloon dilatation of the Eustachian tube in adults with obstructive Eustachian tube dysfunction. The Cochrane ENT Information Specialist searched the Cochrane ENT Register; Central Register of Controlled Trials (CENTRAL); Ovid M>DLINE; Ovid Embase; Web of Science; Clinicaltrials.gov; ICTRP and additional sources for published and unpublished trials. The final search was updated on 18th January 2024. There were no restrictions on language, publication date or study setting. Randomised controlled trials were included if they allocated adult participants with chronic obstructive ETD to treatment randomly and compared BET with non-surgical treatment, no treatment, or other surgical treatment. Studies with other designs were excluded. At least two review authors independently selected trials using predetermined inclusion criteria, assessed the risk of bias, extracted data, and rated the certainty of evidence (CoE) according to GRADEpro. Statistical analyses were performed using a random-effects model and interpreted according to the most recent version of the Cochrane Handbook. Predefined primary outcomes were obstructive ETD symptoms, Eustachian tube function (objective or semi-objective tests), or serious adverse events. Secondary outcomes were hearing, tympanic membrane abnormalities, quality of life, and other adverse events. Nine trials were identified with 684 randomised participants across three comparisons: BET versus non-surgical treatment (five trials, 422 participants), BET versus no treatment (sham surgery; one trial, 17 participants), and BET versus other surgery (four trials, 275 participants). None of the studies were rated with an overall low risk of bias. Comparing BET to non-surgical treatment up to three months, there is low-certainty evidence showing that BET may reduce patient-reported ETD symptoms (change in ETDQ-7: mean difference (MD) -1.66 (95% CI -2.16 to -1.16; I2 = 63%; 4 RCTs, 362 participants)). There is very low-certainty evidence that BET may improve ETD as assessed by objective or semi-objective measures (improvement in tympanometry: RR 2.51 (95% CI 1.82 to 3.48; I2 = 0%; 3 RCTs, 369 participants). Between three and 12 months, the evidence is very uncertain whether BET reduces ETDQ-7: MD -0.55 (-1.31 to 0.21; 1 RCT, 24 participants). The evidence is very uncertain whether BET improves ETD as assessed by objective or semi-objective measures (improvement in tympanometry: RR 2.54 (95% CI 0.91 to 7.12)). Evidence was downgraded for risk of bias, imprecision, indirectness, or a combination of these. Comparing BET to no treatment (sham surgery trial) up to three months, there is very low-certainty evidence that BET improves ETD as assessed by patient-reported ETD symptoms (change in ETDQ-7: MD -0.54 (95% CI -2.55 to 1.47; 1 RCT, 17 participants)). Between three and 12 months, the evidence is very uncertain whether BET improves ETD as assessed by ETDQ-7 (MD 0.16 (95% CI -0.75 to 1.07; 1 RCT, 17 participants)). Evidence was downgraded for indirectness and twice for imprecision. Although there were no serious adverse events reported, these studies were underpowered to detect adverse events and were performed by highly trained and experienced investigators under strict study protocols. This could underestimate the true risk of adverse events by less experienced clinicians in everyday clinical practice. Evidence was rated as very low certainty, downgraded for risk of bias, imprecision, and indirectness. BET may lead to a clinically meaningful improvement in ETD symptoms compared to non-surgical or no treatment (in the form of sham surgery) at up to three months. The effects of BET on ETD compared to non-surgical treatment are very uncertain beyond three months. However, the certainty of evidence ranged from low to very low, with the studies being underpowered to detect adverse events. The findings of this review should help to inform further BET research and guidelines. Future research should focus on longer-term outcomes and the incidence of adverse events or complications in real-world practice settings.