Cholesteatoma labyrinthine fistula: prevalence and impact

Abstract Introduction: Labyrinthine fistula is one of the most common complications associated with cholesteatoma. It represents an erosive loss of the endochondral bone overlying the labyrinth. Reasons for cholesteatoma-induced labyrinthine fistula are still poorly understood. Objective: Evaluate patients with cholesteatoma, in order to identify possible risk factors or clinical findings associated with labyrinthine fistula. Secondary objectives were to determine the prevalence of labyrinthine fistula in the study cohort, to analyze the role of computed tomography and to describe the hearing results after surgery. Methods: This retrospective cohort study included patients with an acquired middle ear cholesteatoma in at least one ear with no prior surgery, who underwent audiometry and tomographic examination of the ears or surgery at our institution. Hearing results after surgery were analyzed according to the labyrinthine fistula classification and the employed technique. Results: We analyzed a total of 333 patients, of which 9 (2.7%) had labyrinthine fistula in the lateral semicircular canal. In 8 patients, the fistula was first identified on image studies and confirmed at surgery. In patients with posterior epitympanic and two-route cholesteatomas, the prevalence was 5.0%; and in cases with remaining cholesteatoma growth patterns, the prevalence was 0.6% (p = 0.16). In addition, the prevalence ratio for labyrinthine fistula between patients with and without vertigo was 2.1. Of patients without sensorineural hearing loss before surgery, 80.0% remained with the same bone conduction thresholds, whereas 20.0% progressed to profound hearing loss. Of patients with sensorineural hearing loss before surgery, 33.33% remained with the same hearing impairment, whereas 33.33% showed improvement of the bone conduction thresholds' Pure Tone Average. Conclusion: Labyrinthine fistula must be ruled out prior to ear surgery, particularly in cases of posterior epitympanic or two-route cholesteatoma. Computed tomography is a good diagnostic modality for lateral semicircular canal fistula. Sensorineural hearing loss can occur post-surgically, even in previously unaffected patients despite the technique employed.摘要 引言：迷路瘘管（labyrinthine fistula）是与胆脂瘤（cholesteatoma）相关的最常见并发症之一，表现为覆盖迷路的软骨内骨发生侵蚀性丢失。目前，胆脂瘤诱导迷路瘘管的具体病因仍不甚明确。研究目的：对胆脂瘤患者进行评估，以明确与迷路瘘管相关的潜在危险因素或临床特征。次要研究目标包括确定本研究队列中迷路瘘管的患病率、分析计算机断层扫描（computed tomography, CT）的诊断价值，以及描述术后听力结局。研究方法：本回顾性队列研究纳入了至少单耳罹患获得性中耳胆脂瘤且未接受过耳部手术的患者，所有患者均在本机构接受过听力测听、耳部断层影像学检查或手术治疗。术后听力结局根据迷路瘘管分类及所采用的手术术式进行分析。研究结果：本研究共纳入333例患者，其中9例（2.7%）存在外侧半规管（lateral semicircular canal）迷路瘘管。8例患者的瘘管首次通过影像学检查发现，并经手术证实。在后鼓室上隐窝型及双径路型胆脂瘤患者中，迷路瘘管患病率为5.0%；而在其余胆脂瘤生长类型患者中，患病率为0.6%（p = 0.16）。此外，伴眩晕与不伴眩晕患者的迷路瘘管患病率比值为2.1。术前无有感音神经性听力损失（sensorineural hearing loss）的患者中，80.0%术后骨导阈值保持不变，20.0%进展为重度感音神经性听力损失。术前存在感音神经性听力损失的患者中，33.33%术后听力损害无变化，33.33%的骨导阈值纯音平均值（Pure Tone Average）得到改善。研究结论：耳部手术前必须排查迷路瘘管，尤其针对后鼓室上隐窝型或双径路型胆脂瘤患者。计算机断层扫描是诊断外侧半规管瘘管的可靠影像学手段。无论采用何种手术术式，术前听力正常的患者仍可能在术后出现感音神经性听力损失。