Facial Canal Dehiscence: Are You at Risk? What You Need to Know
"Understanding the causes, risks, and prevention of facial nerve damage during chronic otitis media surgery."
Imagine undergoing ear surgery only to face an unexpected complication: facial paralysis. This is a real concern for otolaryngologists (ENT surgeons) and patients dealing with chronic otitis media (COM), an ongoing ear infection. Facial nerve paralysis doesn't just affect physical appearance; it can lead to social isolation and a hit to one's self-esteem.
The culprit behind this complication can be a condition called Facial Canal Dehiscence (FCD). FCD refers to an absence of bone covering the facial nerve canal, leaving the nerve vulnerable during surgery. While a solid understanding of anatomy is crucial, surgeons also need to be aware of the possibility of FCD during ear operations to prevent nerve damage.
A recent study investigated the rate and location of FCD in patients undergoing surgery for chronic otitis media, both with and without cholesteatoma (a skin cyst in the middle ear). By understanding the prevalence and common locations of FCD, surgeons can take extra precautions to protect the facial nerve.
Surgical Findings in Chronic Otitis Media
A retrospective study examined facial canal dehiscence (FCD) observed during surgery for chronic otitis media (COM), with or without cholesteatoma. It included operative details from 1,296 patients who underwent COM surgery by the same surgeon between January 2000 and January 2017. The study focused on the rate and location of FCD, but the available source summaries do not provide its results. A separate study aimed to assess how external and middle-ear findings relate to FCD during mastoidectomy for COM.
What is Facial Canal Dehiscence (FCD) and Why Does It Matter?
Facial Canal Dehiscence (FCD) is a condition where the bony covering of the facial nerve canal is missing. This leaves the facial nerve exposed and vulnerable to injury during ear surgeries. FCD can be present from birth or develop over time due to bone erosion caused by chronic ear infections, particularly those involving cholesteatoma.
- Prevalence: FCD was found in 11.29% of the patients.
- Association with Cholesteatoma: FCD was more common in patients with cholesteatoma (88.1%) compared to those without (11.9%).
- Location: The most frequent location of FCD was in the tympanic segment (76.19%) of the facial canal, which is near the oval window.
- Ossicular Erosion: In cases where FCD was present, erosion of all three ossicles (small bones in the middle ear) was statistically more frequent.
Recent Prevalence and Imaging Research
A study titled “The prevalence of facial canal dehiscence: first cross-sectional study in Iraq” cites a study by Kalcioglu et al. involving 372 patients admitted for surgery for chronic suppurative otitis media (CSOM), with and without cholesteatoma: 42 patients (11.29%) had a dehiscent facial nerve canal. It also cites a study by Bayazit et al. of 202 patients, 8.9% of whom had FCD. Separately, Kozerska et al. reported that one-third of FCD involved the inferior wall and was located above and behind the oval window; FCD may also be on or near the first genu. A 2025 article describes prevalence and risk factors, including microdehiscence and macrodehiscence, as still poorly defined.
Limits of HRCT Detection
A study comparing cone-beam computed tomography and micro-computed tomography reports that, in the same study it discusses, HRCT detected facial canal dehiscence in 34% of cases. The authors attributed the low observation rate to the thinness of the facial nerve in the tympanic region, which makes it difficult to visualize. The source also identifies the analyzed material as HRCT images from 76 ears in 72 patients with chronic otitis media and cholesteatoma.
Protecting the Facial Nerve: What Surgeons Can Do
The study emphasizes the need for surgeons to be extra vigilant when operating on patients with chronic otitis media, especially those with cholesteatoma. Given that FCD is most commonly found near the oval window, careful examination of this area is crucial.
External and Middle-Ear Findings
A 2022 study titled “Clues for facial canal dehiscence in chronic otitis media” set out to determine how external- and middle-ear findings affect the incidence of facial canal dehiscence during mastoidectomy for chronic otitis media. The available source summary describes the study’s objective but does not report its findings. It therefore supports noting the clinical question, but not drawing conclusions about which findings predict FCD.
Middle-Ear Disease and Facial Nerve Risk
An introduction to “Clues for facial canal dehiscence in chronic otitis media” identifies otitis media, mastoiditis, and the pressure effect of tumorous lesions such as cholesteatoma as possible causes of facial canal dehiscence and facial nerve paralysis. The source frames these conditions as potential causes rather than providing estimates of their frequency or comparative risk. Its summary does not describe broader systemic challenges or quantify their impact.
The study suggests that if the stapes (one of the ossicles) or all three ossicles are eroded, the risk of FCD is higher. Surgeons should exercise extreme caution in these situations to minimize the risk of facial nerve injury.
While preoperative imaging, such as micro-CT scans, can help identify FCD, the ultimate determination often relies on careful intraoperative examination. By staying informed about the prevalence, location, and associated factors of FCD, surgeons can enhance their ability to protect the facial nerve and improve patient outcomes.