Recurrent Conductive Hearing Loss and Malleus Fixation After Stapes Surgery

Abstract

Background/Objectives: Conductive hearing loss (CHL) recurrence or persistence after stapes surgery is often due to prosthesis displacement or malfunction, with malleus fixation being a less common cause. While persistent CHL linked to malleus fixation can be managed with appropriate diagnosis and surgical intervention, recurrent CHL cases remain poorly documented. This report describes a rare case of recurrent CHL due to malleus neck fixation, likely secondary to surgical trauma. Case Presentation: A 49-year-old woman underwent bilateral stapedectomy. CHL worsened after two years. CT showed right incus erosion and a left bony bridge. Revision surgery corrected the right side. Left tympanotomy revealed malleus fixation from a prior atticotomy. Removing the bony bridge restored ossicular mobility and hearing, stable at 6 and 12 months. Discussion: Malleus fixation after stapedectomy is rare and often related to congenital anomalies, chronic otitis media, tympanosclerosis, or surgical trauma. Bone dust or fragments from surgery may promote new bone formation, causing delayed fixation. Ossicular fixation can develop postoperatively and may be missed during primary surgery. High-resolution CT aids in diagnosis, especially in revision cases, while intraoperative palpation is key to detecting subtle abnormalities. Treatment options include ossicular mobilization, prosthesis revision, or chain reconstruction, tailored to the fixation’s location and severity. Conclusions: Surgical trauma should be considered a potential cause of recurrent CHL post-stapedectomy. Thorough removal of bone debris through aspiration and irrigation during surgery is essential to minimize this risk and optimize long-term hearing outcomes.

1. Introduction

Different cases of conductive hearing loss (CHL) recurrence and persistence after stapes surgery have been reported and described in the literature. Among the causes, the most common reason for primary stapes surgery failure is reported to be displacement or malfunction of the prosthesis, but pathological changes at the oval window are also frequently cited. Malleus head/neck fixation is not considered one of the most frequent causes; however, it should be taken into account during the diagnostic process for stapedectomy failure.

Malleus fixation can present with different patterns and anatomical features, involving various parts of the epitympanum or malleal ligaments. While the causes of persistent conductive hearing loss after stapedectomy due to malleus fixation are easier to manage with careful preoperative diagnosis and intraoperative exploration, no clear data in the literature addresses recurrent conductive hearing loss after stapedectomy.

After reviewing the literature on stapedectomy failure and malleus fixation during stapedectomy revision, we present our case report of recurrent hearing loss due to malleus neck fixation to the lateral epitympanum, probably caused by primary surgical trauma. To our knowledge, this is one of the very few cases described in scientific literature.

2. Case Presentation

A 49-year-old female patient underwent asynchronous bilateral stapedectomy at a different center to ours (right ear 8 years prior, left ear 6 years prior). During the left stapedectomy, a manual atticotomy with a curette was performed as usual.

After an initial subjective and audiometric improvement, bilateral subjective hearing deterioration began 2 years later. The patient was referred to our center, where a mild-to-moderate bilateral mixed hearing loss was assessed, with a more pronounced deficit in the left side at 1000 Hz. CT imaging revealed erosion of the right long process of the incus and a bony bridge connecting the malleolar neck to the scutum on the left (Figure 1). Due to the patient’s perception of worsened hearing on the right side, she first underwent right stapedectomy revision, which revealed erosion of the long process of the incus at the site where the prosthesis loop was anchored.

Postoperative audiometry showed normalization of the air-bone gap (ABG) on the right side, but a further worsening occurred in the left conductive hearing loss in the lower and mid-frequencies of up to 2000 Hz, with a 35 dB ABG at 500 and 1000 Hz. Consequently, an exploratory tympanotomy was planned for the left ear.

During surgery, performed using a microscopic transcanal approach, the prosthesis was found in the correct position within the footplate hole and properly anchored to a normal incus. Visualization of the ossicular chain excluded the presence of incudostapedial joint erosion. However, malleus palpation revealed impaired mobility. A bony tissue anchoring the malleolar neck to the scutum, as previously shown on the CT scan, was confirmed intraoperatively through both direct observation and palpation.

Ossicular chain mobility was restored by removing the bony tissue using a Skeeter drill and hook (Skeeter, Kilgore, TX, USA), re-establishing normal malleolar head and prosthesis mobility.

At the one-month postoperative follow-up, normacusis was achieved with the resolution of the left conductive hearing loss and ABG normalization (Figure 2). No further deterioration was observed in subsequent audiograms after 6 months and 1 year.

3. Discussion

3.1. Stapedectomy Revision and Ossicular Fixation

Several studies have investigated the different causes leading to stapedectomy revision.

Lesinski found prosthesis displacement in 81% of the 260 patients who underwent revision stapedectomy and stapedotomy, while complete or near-complete incus erosion was present in 31%, partial incus erosion in nearly 60%, malleus fixation in 4%, incus fixation in 2%, and incus dislocation in 4% [1].

Another study on stapes revision surgery for otosclerosis in Sweden, involving 254 patients, also identified prosthesis displacement as the most common finding at revision surgery (48.2% at first revision). Incus/malleus fixation was observed in 3.9% of the 227 patients at first revision, 6.6% of the 61 cases at second revision, 25% of the 8 cases at third revision, and 33.3% of the 3 cases at fourth revision. Other reported causes included prosthesis dislocation, incus erosion with or without fracture, and obliterated otosclerosis [2].

A retrospective review by Wierzbicka et al. [3] analyzed the long-term outcomes (at least 10 years) of otosclerosis surgery (stapedectomy and stapedotomy) in 1118 patients. Among them, 93 (8.3%) underwent reoperation due to conductive hearing loss (persistent or recurrent). The results were consistent with previous studies, with prosthesis displacement being the most frequent intraoperative finding (44.1%). Other causes included incus erosion or necrosis (28%), adhesions around the prosthesis (10.8%), a stapes footplate hole that was too small (8.6%), a prosthesis that was too short (8.6%), otosclerosis progression (7.5%), a prosthesis that was too long (6.4%), granuloma formation around the prosthesis (5.4%), incus displacement (4.3%), and other unspecified causes (4.3%). However, this study did not provide specific data on malleus fixation [3].

In a retrospective review by Lippy et al. on 522 revision stapedectomies, malleus/incus fixation was found in 7.5% of cases, a higher percentage than that reported by Lesinski and Lundman et al. [1,2,4]. This percentage was also significantly higher than in the findings of Hammerschlag et al., who reported malleus fixation in only 0.8% of revision stapedectomies. In their study, prosthesis dislocation was the most common cause (24.4%), while a short prosthesis, long process resorption, and fibrous adhesions accounted for 14%, 14%, and 13.6% of cases, respectively [5].

Additional data was provided by Fish et al. [6], who found that pathological changes, most frequently incus erosion, were present in 80% of the 80 patients who underwent revision stapes surgery. Malleus abnormalities were identified in 48.6% of cases, with total malleus fixation in 8.7% and partial fixation with ossification of the anterior malleal ligament in 37.5% [6]. Malleus fixation (mainly involving the anterior malleal ligament) was reported as a cause of primary surgery failure in 0.8% to 4% of cases. Notably, in the same study, when an enlarged endaural approach with superior canaloplasty was utilized during revision surgery, malleus fixation was detected in 46.2% of cases and incus fixation in 13.7%, despite being undetected during primary surgery. Among these cases, 79% of patients with impaired malleus mobility had calcification of the anterior malleal ligament [6]. Other studies have confirmed that complete or partial malleus fixation can contribute to stapes surgery failure [7,8,9].

Although closure of the air-bone gap (ABG) within 10 dB is achieved in approximately 90% of primary stapedectomies, residual conductive hearing loss (CHL) occurs in about 10% of cases, and recurrent CHL in up to 35% [10]. In the same study by Nadol, histopathological analysis of 22 cases of post-stapedectomy CHL (residual, recurrent, or both) revealed malleus fixation in the anterior epitympanum without evidence of otosclerosis in one case, which presented with a residual ABG of 44 dB two months after surgery, compared to a preoperative average ABG of 28 dB [10].

Focusing specifically on ossicular fixation, Nakajima et al. analyzed different degrees of stapes velocity loss due to adhesions and stiffening of the malleus, stapes, or both, using laser vibrometry on fresh cadaveric human temporal bones [11]. They found that anterior malleal ligament stiffening led to a 0–8 dB reduction in stapes velocity, fibrous tissue around the malleus head caused a reduction of less than 10 dB (a possible sequela of acute or chronic otitis media), and a bony bar to the malleus head led to a 10–30 dB reduction. Extensive neo-osteogenesis around the malleus head resulted in reductions greater than 35 dB. Chronic otitis media can also lead to neo-osteogenesis, tympanosclerosis, and dense fibrous tissue deposition in the epitympanum.

Different types of stapes fixation appear to result in similar degrees of conductive hearing loss due to the relationship between stapes velocity and inner ear input. The study also examined different sites of malleus stiffening. When a cement bar mimicking total calcification of the anterior malleal ligament (AML) was placed near the axis of rotation linking the AML to the posterior incudal ligament, malleus and stapes motion were less affected. However, when the bar was positioned farther from this axis, between the malleus head and the surrounding epitympanum, the reduction in ossicular mobility was greater [12]. The same study highlighted the importance of evaluating the low-frequency region (below 1 kHz), where ossicular motion is primarily influenced by stiffness rather than frequency [12]. However, a study by Gladiné et al. which used minimally invasive intraoperative laser vibrometry suggested that velocity measurements should be performed over a wide frequency range for better differentiation between stapes, incus, and incus–malleus fixations [13].

3.2. Malleus and Malleus Head Fixation

Regarding malleus fixation specifically, complete and partial fixation lead to different degrees of conductive hearing loss (CHL). According to Huber et al., 26% of patients with otosclerosis had anterior mallear ligament fixation [8]. Complete bony fixation can result in a 15 to 30 dB conductive hearing loss [8,10], while the air-bone gap (ABG) associated with partial malleus fixation is approximately 10 dB and predominantly affects low frequencies. Anterior mallear ligament (AML) and anterior mallear process (AMP) fixation are linked to a persistent post-surgical ABG of around 10 dB at low and mid-frequencies [8].

A study investigating hearing outcomes after stapedectomy in cases with varying degrees of malleus fixation followed 23 patients for 2 to 6 years postoperatively. Among them, 5 patients, representing all degrees of malleus fixation, showed no hearing changes for the first 4 years but later developed an increased ABG [4]. According to the authors, this could indicate a gradual progression of malleus fixation over time.

Malleus fixation can be idiopathic or secondary to conditions such as tympanosclerosis (most common), chronic otitis media, trauma, otosclerosis, or developmental anomalies. Another possible cause is Paget’s disease (osteitis deformans). Tympanosclerosis and idiopathic fixation together account for more than 80% of cases. Additionally, surgical trauma may predispose a patient to malleus fixation by leaving small bone fragments or dust from drilling behind, which can serve as sites for new bone formation [14,15,16,17,18].

A study by Sleeckx et al. [18] reported on 10 patients who developed recurrent, gradually worsening CHL (ranging from 10 to 30 dB) over a period of four months to four years after primary surgery for otosclerosis, despite initially normal postoperative audiometric results. At revision surgery, these patients were found to have fixation of the incus, malleus, or both [18]. The same study also described 33 other patients who experienced initial postoperative improvement but had a significant residual ABG. Revision surgery in these cases revealed incus and malleus fixation, suggesting that some degree of fixation may have been present before the primary surgery but was overlooked at the time of the first procedure.

In most cases, malleus fixation occurs in the epitympanum, specifically at the lateral tympanic wall, the epitympanic roof, or the anterior or superior malleal ligaments [15].

Congenital malleus fixation can also result from incomplete differentiation of the sphenomandibular ligament, leading to a bony spicule extending from the anterior malleus head to the anterior tympanic fissure [16]. It is rare and is likely caused by bony fusion of the malleus head to the attic roof or by a persistent bony bar connecting the malleus head to the posterior attic wall [19,20].

In acquired cases, malleus head fixation can involve the anterior, lateral, superior, or medial walls of the epitympanum [14,16].

A study by Martin et al. performed a histological analysis of 10 patients with surgically confirmed anterior and anterosuperior malleus head fixation (MHF) in the attic. They identified three types of MHF, distinguishing between congenital and acquired causes. The acquired forms were associated with idiopathic synostosis between the epitympanic lateral wall and the malleus head at various epitympanic sites, as well as bone remodeling following chronic inflammation, chronic otitis, tympanosclerosis, cholesteatoma, and cholesterol granuloma [21].

3.3. Diagnosis of Malleus Fixation and Therapy

Malleus head fixation can be identified both preoperatively and postoperatively, particularly in cases of acquired fixation due to surgical injury or other progressive causes. In the study by Huber et al., partial malleus fixation can be assessed intraoperatively by palpation or preoperatively using laser Doppler interferometry (LDI) [8]. Although laser interferometry has been investigated as a tool for predicting malleolar vibration preoperatively, its clinical application remains limited.

The most widely used diagnostic tool before stapes revision surgery is high-resolution computed tomography (CT), which is useful for detecting calcifications and pathological bony structures in the middle ear and ossicular chain. Moreover, as highlighted by Whetstone J. et al., the preoperative CT scan is crucial in the differential diagnosis between malleolar fixation and the more common otosclerosis [22]. In the review by Sakano and Harris [23], CT is performed before revision stapes surgery in cases of persistent CHL with an ABG >20 dB, which is more frequently associated with superior canal dehiscence syndrome (SCDS) or, more rarely (less than 4% of cases), ankylosis of the malleus and/or incus. CT is also performed in cases of recurrent CHL with an ABG >20 dB, which is often due to incus erosion (6–32%), prosthesis malfunction (60%), adhesions, or osseous regrowth at the stapedectomy or oval window fenestra [23]. According to the authors, palpation of the ossicular chain should always be performed, as persistent CHL could be due to malleus and/or incus fixation caused by congenital anomalies, residual bone dust, or fragments from the primary surgery. Some authors have reported highly relevant findings, particularly in revision surgeries. For example, Fisch U. et al. described calcification of the anterior tympanomalleolar ligament in 37.5% of revision cases [6]. Similarly, Huber A. observed it in 26% of cases [8].

A rare cause of early recurrent hearing loss (7–15 days postoperatively) is reparative granuloma, which leads to worsening sensorineural hearing loss after an initial improvement. This condition is not always associated with worsening imbalance. Reparative granuloma typically covers the incus and surrounds the prosthesis down to the oval window, appearing as a darkened area in the posterior mesotympanum on imaging [23].

Post-stapedectomy CHL can be either persistent or recurrent, but final auditory outcomes after surgical treatment of otosclerosis should not be assessed earlier than 3 to 6 months post-operation, with some authors even recommending extending this period to 12 months [24]. Therefore, except in urgent cases, the decision to perform revision stapedectomy should generally be postponed until then.

In revision stapedectomy, malleus fixation can be more easily diagnosed through palpation and direct visualization. Fish et al. systematically explored the anterior malleal process and ligament as well as the incudomalleolar joint in cases of persistent hearing loss after stapedotomy, using an endaural approach with superior canaloplasty [6]. In the same study, the authors recommended complete removal of the anterior malleal process and malleus head in cases of total or partial malleus fixation due to a calcified anterior malleal ligament.

Fernandez et al. reported a case of persistent conductive hearing loss after stapedotomy that was treated endoscopically, revealing ossification of the anterior mallear ligament and ossification between the malleolar head and the anterior epitympanic wall [7]. In that case, the use of an endoscopic approach facilitated direct identification of anatomical anomalies.

Both ossicular chain mobilization and ossicular chain reconstruction techniques have been described in the literature for the surgical management of isolated malleus and/or incus fixation. A systematic review and meta-analysis of 14 retrospective studies published between 1967 and 2015 found no significant audiometric differences between the two techniques [25].

To further investigate the difference between ossicular preservation and reconstruction, Martin et al. conducted a retrospective study on 25 ears that underwent surgery for isolated malleus head fixation, with a 1-year follow-up period. The study found no statistically significant difference between two surgical techniques:

1.

Transmastoid approach without ossicular chain disruption;

2.

Transcanal approach with ossiculoplasty, involving removal of the malleus head and incus, followed by ossicular chain reconstruction using incus interposition or a partial ossicular replacement prosthesis (PORP) [21].

Another study demonstrated that surgically creating a 2 mm space around the malleus head effectively closed the ABG [17]. However, Martin et al. excluded this technique from their study due to its high recurrence rate of fixation [21].

4. Conclusions

Malleus fixation after stapes surgery can be persistent or recurrent and may present with different anatomical features involving the epitympanum and malleal ligaments. It can be associated with various conditions including surgical trauma, which may lead to malleus fixation due to small bone fragments or drilling dust acting as sites for new bone formation.

To our knowledge, very few cases in the literature have focused on surgical trauma-related conductive hearing loss recurrence after primary stapedectomy. We believe that the case we reported clearly demonstrates this phenomenon, as it resulted in recurrent, progressive conductive hearing loss and was evident on CT imaging, which showed a bony bar between the malleus neck and the lateral epitympanum precisely at the site of the previous atticotomy. Complete hearing restoration was achieved once the bony bridge was removed.

In our opinion, careful removal of bone fragments and drilling dust through aspiration and middle ear irrigation during primary stapedectomy should always be performed to minimize the risk of surgical failure. Finally, we believe that the role of CT is indispensable to revision surgeries since conditions such as EVA syndrome and superior semicircular canal dehiscence can only be ruled out by CT.