Temporal Bone Meningoencephalocele Associated with Cholesteatoma: Systematic Literature Review and a Case Series Open Access

Temporal bone meningoencephalocele (TB-MEC) is a rare medical condition, yet it carries a potentially devastating consequence, such as meningitis, intracranial abscess, venous infarction, and seizures [1]. TB-MEC can occur primarily or, more commonly, as a secondary event [2, 3]. In the context of chronic ear disease with cholesteatoma, TB-MEC may originate from tegmen erosion due to the cholesteatoma and the accompanying chronic inflammation, or as a result of iatrogenic injury during surgical intervention aimed at addressing the cholesteatoma [4‒7].

This combination of TB-MEC and cholesteatoma creates a unique clinical entity that poses diagnostic and management challenges. The diagnosis can often be delayed due to the lack of specific clinical signs and symptoms [8], and while imaging is critical for diagnosis, differentiating TB-MEC from other complications of chronic ear disease may be complex. The erosive nature of cholesteatoma creates a pathological synergy that can both precipitate and obscure TB-MEC, leading to intricate clinical scenarios that require both awareness and knowledge of its nature. Surgical management is also challenging as it requires addressing both pathologies without compromising the approach, nor safety of the procedure.

Currently, there is limited evidence-based literature on TB-MEC in the context of cholesteatoma, mostly based on case reports or case series [2, 3, 9‒18]. Although it always must be kept in the differential diagnosis, its rare presentation precludes the development of official guidelines for management. Therefore, here we performed a systematic literature review, along with our original case series, on cholesteatoma associated with TB-MEC, aiming to characterize its presentation and management, providing direction for clinicians to improve diagnosis, treatment, and patient counseling.

The systematic literature review followed the PRISMA guidelines [19]. We reviewed all publications from PubMed and EMBASE between the years 1992 and 2022. The search of both databases was conducted using the following search algorithm: “(cholesteatoma) AND (brain herniation OR meningocele OR meningoencephalocele OR encephalocele OR cephalocele OR cerebral hernia).” Inclusion criteria included any study designs that (1) were published in the English language, (2) were available as full text, and (3) included clear evidence for cholesteatoma presence (via imaging or pathology). Exclusion criteria included duplicated publications and publications with insufficient relevant data for the diagnosis. Initially, all titles and/or abstracts were screened, and for the relevant recorders, the full-text articles were assessed for eligibility.

Following institutional review board approval, patients’ data were extracted from the institute’s electronic medical records. We included all patients from our center, a single tertiary medical center, who had cases of cholesteatoma associated with temporal meningoencephalocele between the years 1992 and 2022. All original cases were reported according to the CARE case report guidelines [20].

Data collected from both the literature review and the institutional cases included the following:

• 1.

  Clinical data: sex and age; presenting symptoms of the TB-MEC, any preoperative complications.

• 2.

  Imaging data: preoperative and postoperative radiological features, as dehiscence of the facial nerve bony canal, inner ear involvement, defects in the tegmen tympani and tegmen mastoideum, quantification of tegmen bony defect (i.e., minor when <1 cm, and major when >1 cm), and the presence of both dural and brain content or dural herniation only.

• 3.

  Surgical data: number of surgeries for cholesteatoma prior to TB-MEC diagnosis, including approach and complications; surgical approach for TB-MEC: trans-mastoid (TM), middle fossa approach (MFA), and combined approach; type of mastoidectomy: canal wall up (CWU) or canal wall down (CWD); type of graft employed to reconstruct the tegmen defect (alloplastic, autologous, or both); time from the last cholesteatoma surgery to definitive surgery to treat the MEC.

• 4.

  Postsurgical evaluation: postoperative complications, follow-up time from definitive surgery, need for revision surgery.

A flowchart of the systematic review inclusion and exclusion process is presented in online supplementary Figure S1 (for all online suppl. material, see https://doi.org/10.1159/000546748). Overall, we included 12 studies [2, 3, 9‒18], describing 72 cases of cholesteatoma associated with TB-MEC, published between 1992 and 2022.

Our data analysis included both the systematic review (n = 72) and our institutional cases (n = 3), resulting in a total cohort of 75 patients. The basic clinical characteristics of the combined cohort are summarized in Table 1.

The mean age at diagnosis was 44.34 ± 17.04 years. Males were affected in 46/75 (61.3%) of the cases. Symptoms upon presentation were reported for 72 cases, with 69/72 (95.8%) being symptomatic, whereas 3/72 (4.2%) were asymptomatic and had their TB-MEC detected during routine radiological follow-up for cholesteatoma.

Details on the specific presenting symptoms were available for 62 cases. Hearing loss was the most common symptom, reported in 49/62 cases (79%). This was followed by otorrhea in 29/62 cases (46.8%), and dizziness in 11/62 cases (17.8%). A mass in the external auditory canal was detected in 10/62 cases (16.1%).

Complications upon presentation, resulting either from previous surgery, cholesteatoma, or the TB-MEC, were detailed for 65 cases. These included labyrinthine fistula in 8/65 cases (12.3%), meningitis in 2/65 cases (3.1%), facial nerve palsy in 1/65 cases (1.5%), and sinus vein thrombosis in 1/65 cases (1.5%)

All patients underwent imaging, either a computed tomography (CT) scan, magnetic resonance imaging (MRI), or both. The exact location of the tegmental defect was reported for 50 cases, predominantly located in the tegmen mastoideum (34/50; 68.0%), followed by the tegmen tympani (22/50; 44.0%); 10 cases had defects in both locations.

Data regarding the timing of TB-MEC diagnosis were available for 38 cases. Intraoperative incidental discovery occurred in 15/38 (39.5%) cases, whereas preoperatively radiological diagnosis was available for 23/38 cases (60.5%). Case stratification according to the diagnostic timing is presented in Table 2. Cases diagnosed intraoperatively compared to cases diagnosed preoperatively were significantly older (37.43 ± 7.04 vs. 54.73 ± 17.04 years respectively; p < 0.01) and had a significantly higher rate of previous CWD procedures (80% vs. 39.1%, respectively; p = 0.01), and a significantly higher rate of major defects (65.2% vs. 26.7%, respectively, p = 0.05).

Case stratification according to defect size is provided in Table 3. Data on the herniation content and defect size were reported for 40 and 57 cases, respectively. In 31/40 (77.5%) cases, herniation of both dura and brain tissue was observed, while in 9/40 (22.5%) cases only the dura was involved.

In 40/57 (70.1%) cases, the defect was ≥1 cm (i.e., major defect), while 17/57 (29.9%) cases had a minor defect (<1 cm). Cases with major defects had a significantly higher rate of preceding cholesteatoma surgery compared to cases with minor defects who presented with primary cholesteatoma and accidental finding of concurrent TB-MEC (75.8% vs. 50%, respectively; p < 0.001).

TM approach was employed to address TB-MEC in 54/75 (72%) cases, with MFA or combined approach reserved only for major defects. For all cases with minor defects, one procedure was sufficient to address the TB-MEC, whereas 3/35 (8.6%) cases with major defects required more than one surgery.

For 40/75 (53%) cases, concurrent active cholesteatoma was reported during the surgical approach to address the TB-MEC, including 16 cases who had no previous surgical history, and 24 with a surgical history of ≥1 previous mastoidectomy for cholesteatoma. The TM approach was performed in 34/40 (85.0%), MFA in 3/40 (7.5%), and 3/40 (7.5%) underwent a combined approach.

Methods for reconstruction were detailed for 65 cases. Autologous grafts were employed in 64/65 (98.5%), including all 41 cases of the TM and 5 cases of combined approach, as well as in the vast majority of MFA cases (6/7; 85.7%). Additional alloplastic materials were used in 31/65 (47.7%) cases, while one case (1.5%) had only alloplastic graft. Fascia grafts (either temporalis or non-temporalis) were used in 64/65 (98.5%) cases, followed by cartilage (39/65; 60%), bone graft (33/65; 50.8%), temporalis muscle flap (23/65; 35.4%), and periosteum (18/65; 27.7%).

The mean follow-up time, available for 53 cases, was 39.4 ± 31.5 (4–124) months. Overall, 6/75 (8%) cases had postoperative complications, including CSF leak 4/75 (5.3%), followed by infection (1/75; 1.3%) and facial nerve paralysis (1/75; 1.3%).

A 65-year-old female underwent right ear CWU mastoidectomy due to cholesteatoma in 2010 and was lost to follow-up. A decade later, she presented with complaints of discharge from her right ear. Physical examination revealed deep anterior tympanic membrane retraction pocket with discharge. An audiological examination demonstrated severe mixed hearing loss on the right ear (SRT 65 dB; WRS 88%). MRI (including non-echoplanar diffusion-weighted imaging) demonstrated a large attic cholesteatoma extending to the tegmen, and CT scan demonstrated middle ear and attic fullness, with ossicular chain erosion (Fig. 1).

The patient was scheduled for a revision CWU mastoidectomy. Intraoperatively, a large, unexpected TB-MEC was identified, protruding through the tegmen tympani and extending to the antrum, with an additional 1-cm tegmen mastoideum defect. The intraoperative decision was to reconstruct the mastoid defect with temporalis fascia and biological glue and to remove the cholesteatoma as a first stage, while the MEC protruding from the tegmen tympani was left for a second-stage procedure planned via MFA.

A month later, the patient underwent MFA to address the TB-MEC. The TB-MEC was excised above the tegmen remaining in the tympanic cavity. This decision was not to combine MFA and TM procedure in order to avoid possible contamination via the middle ear and mastoid cavities (cholesteatoma and likely accompanying infectious pathogens). Therefore, a staged approach was chosen to safely and effectively address both pathologies under optimal conditions. The dura was closed with 3-0 silk sutures, and the skull base defect was treated in a layer fashion, using temporalis fascia, temporal bone chips, DURAFORM^®, TachoSil^®, and BioGlue^®. Postoperatively, CSF otorrhea was detected, necessitating the placement of a lumbar drain for 5 days. The subsequent healing process was uneventful.

Seven months later, the patient underwent a revision mastoidectomy to rule out residual cholesteatoma or TB-MEC. Intraoperatively, no cholesteatoma was found. Remnant of the excised TB-MEC was found adhered to the tegmen, neotympanum, and medial wall of the attic, and was removed uneventfully. A follow-up MRI 9 months postoperatively demonstrated no remnants of cholesteatoma nor TB-MEC.

A 16-year-old, otherwise healthy, male was diagnosed with cholesteatoma of the right ear in 2013. Consequently, he underwent CWU mastoidectomy. Four years later, during a follow-up MRI, a recurrent cholesteatoma was detected in the right ear. Audiogram demonstrated mild high-tone conductive hearing loss on the right side. In 2018, he underwent revision CWU mastoidectomy of the right ear, where a 2 × 3 cm TB-MEC was identified protruding from the tegmen mastoid defect toward the attic and external auditory canal (through a defect in the canal). The TB-MEC could not be reduced in this session due to size and location, while cholesteatoma was partially obscured by the TB-MEC. Consequently, the patient was planned for an additional procedure via MFA to control the TB-MEC prior to addressing the contaminated cholesteatoma.

Preoperative CT scan demonstrated right middle ear and attic fullness, ossicular erosion, and mastoid fullness extending into the retro-auricular subcutaneous tissue (Fig. 2). MRI verified TB-MEC of the middle ear and mastoid of the right ear.

The patient underwent MFA in 2018. Intraoperative findings revealed a 10–15-mm tegmen mastoideum defect with TB-MEC, which was consequently resected. The defect was reconstructed with temporalis fascia as well as BioGlue^®. Recovery was uneventful.

In 2019, he underwent a revision CWU mastoidectomy for removal of remnant middle ear and mastoid cholesteatoma. MRI follow-ups were free from cholesteatoma and MEC thereafter.

A 59-year-old female with a history of bilateral suppurative chronic otitis media underwent left atticotomy and tympanoplasty two decades ago. In 2022, she presented with complaints of discomfort, pain, and deteriorating hearing in the left ear. Otoscopy of the left ear revealed a retracted tympanic membrane. Audiogram identified right-sided mixed hearing loss (SRT 45 dB; WRS 96%). MRI was done and demonstrated a left mastoid lesion with tegmen erosion (Fig. 3) with a differential diagnosis of cholesteatoma versus cholesterol granuloma versus TB-MEC, and the patients were consequently scheduled for surgery.

In 2023, the patient underwent revision CWU mastoidectomy, which revealed ossicular erosion and cholesterol granuloma in the antrum, as well as TB-MEC protruding from a minor defect (<1 cm) of the tegmen superior to the aditus ad antrum with CSF leak. The MEC was excised, and the defect was reconnected with temporalis fascia. Her postoperative recovery and follow-up were uneventful.

In this work, we performed a systematic literature review aiming to provide evidence-based data to improve the clinical approach to the rare yet challenging cases of TB-MEC associated with cholesteatoma. Previous mastoid surgery and cholesteatoma are among the leading causes for TB-MEC [2, 21‒23]. Yet, due to its complexity and rarity, comparative studies to guide management are not available nor likely to be feasible. Therefore, with this literature-based large cohort, we have characterized the clinical presentation, diagnosis tools, and managemental strategies aiming to guide the treating physician.

One of the most notable and concerning findings was the high rate of incidental discovery of TB-MEC during surgery (39.5%). The inability to anticipate such a significant finding as TB-MEC compromises the ability of the surgeon to obtain appropriate patient consent and optimal surgical planning, particularly when different approaches may be needed (TM vs. MFA). The lack of preoperative diagnosis may be attributed to the fact that although most patients are symptomatic at presentation, the common symptoms, including hearing loss and otorrhea, are highly nonspecific among cholesteatoma patients, rendering them insufficient for diagnosis. Moreover, imaging, even when performed, may be challenging to identify TB-MEC in the presence of cholesteatoma and postoperative changes, specifically in revision cases with reconstructed and obliterated attic and/or mastoid cavity [24, 25].

To address this challenge, we synthesized our findings to suggest several characteristics that comprise the “suspected profile” and should raise a high level of suspicion for TB-MEC, supporting the need for further evaluation with a targeted assessment of preoperative imaging for diagnosis. First, in terms of demographics, TB-MEC presents at a relatively older age (44.34 ± 17.04 years) compared to the average age of noncomplicated cholesteatoma surgery patients, which was described as 35.6 ± 21.5 years [26]. Not surprisingly, and consistent with Wootten et al. [14] review, we found that TB-MEC is present in patients with a longstanding chronic ear disease. The majority (78.6%) of the patients with TB-MEC in our cohort had undergone ≥1 procedure before the diagnosis. It is important to note that prior surgery was 6 years on average before TB-MEC diagnosis, signifying that TB-MEC should be suspected, particularly in revision cases, even years past previous intervention.

The association with previous mastoid surgery might be attributed to drilling or dissection in proximity to the tegmen, which may have caused inadvertent and unnoticed damage. Such damage can potentially lead to brain herniation even years later. This is further supported by the high rate of tegmen mastoideum involvement (68%), which is a relatively accessible location during mastoid surgery [22, 23]. Additionally, the predominance of CWD mastoidectomy (92.3%) as the primary surgical approach may result in over-skeletonizing of the tegmen during the process of mastoid saucerization [22, 24].

We found that patients with TB-MEC also exhibited a relatively high rate of complications upon presentation, prior to TB-MEC diagnosis (15.3%). This may suggest not only a history of longstanding disease but also the occurrence of challenging surgery, possibly due to an aggressive cholesteatoma. This raises the likelihood of a “second hit” scenario involving also tegmen defect and TB-MEC.

Transmastoid was the most common approach used in our cohort (74.6%). Although it has been suggested before that large TB-MECs are best managed with an MFA [9, 14], we found that 50% of the major defects were managed successfully via TM [2, 11‒13, 17]. The feasibility of the TM approach for major defects, as observed in the present study, was reported before [9, 12, 13, 18]. In our cohort, one study demonstrated the practical use of TM approach in up to 2.5 cm tegmen defects [13], and another study described 2 patients who underwent a successful TM approach for a tegmental defect of 3 cm [18].

While some advocate that MFA allows better temporal lobe visualization and facilitates primary suturing of dural defects [9] it carries additional potential risks related to temporal lobe retraction [18]. Moreover, in the context of cholesteatoma there is an additional drawback; MFA does not allow sufficient evaluation of the middle ear and mastoid for residual or recurrent disease [22, 27]. A very low complication rate was found in our cohort for all approaches employed to address TB-MEC. Only a single case of postoperative CSF leak, following MFA, was reported.

An important implication of our findings relates to patients’ consent and expectation management. It may be beneficial, prior to the revision of longstanding chronic ear, for patients to be informed about the possibility of intraoperative identification of TB-MEC. This could mandate surgical modification of the approach, possibly combining MFA, and at times additional procedures [22, 27]. On the other hand, when TB-MEC is diagnosed preoperatively, if TM approach is chosen, patients must be informed that a future MFA may be required in case of postoperative CSF leak, recurrence of the TB-MEC, or in very large tegmen defects that may not be sufficiently addressed via the TM approach [12]. One study stated that to mitigate patient expectations when choosing TM approach for major defects, they “explicitly counseled that revision surgery via an intracranial approach may be required in case of failure [12].”

In 2 of our cases, when the TB-MEC was encountered intraoperatively, we addressed the cholesteatoma and the TB-MEC in consecutive procedures. Both had major (≥1 cm) tegmen defect and with TB-MEC obstructing direct and indirect (endoscopic) approaches to address the cholesteatoma. One of our main concerns was seeding contaminated cholesteatoma intracranially via dural tear or epidurally. We also appreciated that either MFA or a combined approach was warranted in both cases, given the defect size. Due to a lack of appropriate preoperative consent, the primary procedure was terminated, demanding an additional procedure to address the TB-MEC and the cholesteatoma. Following our literature review, we believe that these concerns can be mitigated. While non-echo planar diffusion-weighted MRI is routinely used in our practice for cholesteatoma surveillance when there is suspicion of TB-MEC – based on imaging, intraoperative findings, or surgical history – surgery is warranted for definitive diagnosis and treatment [25].

Our findings underscore the importance of considering TB-MEC in patients with prior CWD mastoidectomy, a history of complications, or extensive bony erosion. In these high-risk cases, we recommend a combination of high-resolution temporal bone CT to assess tegmen integrity and non-EPI DWI for detection of residual cholesteatoma and possible TB-MEC [25]. Based on our data, surgical approach selection should consider defect size and location: TM repair is typically sufficient for minor defects (<1 cm), including many cases involving the tegmen mastoideum and tympani. In contrast, major defects (≥1 cm), especially those with herniation in several locations along the tegmen, CSF leak, or poor access to the attic, may require a middle fossa or combined approach to ensure safe and complete repair.

Our study has several limitations. The retrospective design of our study, while valuable for accumulating a substantial cohort, inherently limits the ability to control for confounding variables and introduces potential biases in patient selection and data collection. The variability in reporting, which arises from differences in study design, as well as in institutional protocols, surgeon preferences, and follow-up procedures, may affect the generalizability of our findings.

In conclusion, TB-MEC still poses challenges despite imaging advancements and is often detected during surgery. We recommend proactive evaluations for high-risk patients, particularly those with complex otologic surgical history, such as CWD and/or previous complication. Major defects can be effectively managed using TM approach. Overall outcomes provide reassurance for both patients and clinicians.

This study protocol of the original series was reviewed and approved by the Sheba Medical Center review board, Approval No. 0126-23-SMC. Written informed consent was obtained from the patient for publication of the details of their medical case and any accompanying images. In systematic review, statement of ethics is not applicable because this study is based exclusively on published literature.

The authors have no conflicts of interest to declare.

The authors have no funding to declare.

Amit Wolfovitz and Idit Tessler: conceptualization, formal analysis, and writing – original draft. Omer Shaked: data collection, and writing – original draft.

Amit Wolfovitz and Omer Shaked contributed equally to this work.

The data that support the findings of this study are not publicly available as it contains information that could compromise the privacy of research participants, but are available from the corresponding author (I.T.).