A novel imaging scoring method for identifying facial canal dehiscence: an ultra-high-resolution CT study

Abstract

Objectives Facial canal dehiscence (FCD), typically found in the tympanic segment, is a risk factor for facial nerve injury. An imaging scoring method was proposed to identify FCD based on ultra-high-resolution CT. Methods Forty patients (21 females and 19 males, mean age 44.3 ± 17.4 years), whose tympanic facial canal (FC) was examined during otological surgery, were divided into the FCD group (n = 29) and the control group (n = 11) based on surgical findings. Imaging appearance of tympanic FC was scored 0–3: 0 = no evident bony covering, 1 = discontinuous bony covering with linear deficiency, 2 = discontinuous bony covering with dotted deficiency, and 3 = continuous bony covering. Both lateral and inferior walls were assigned a score as LFCD and IFCD, respectively. An FCD score was calculated as LFCD + IFCD. The diagnostic value of the FCD score was tested using the ROC curve. Results The inter-observer agreement was moderate for the lateral wall (Cohen’s κ coefficient 0.416, 95% CI 0.193–0.639), and good for the inferior wall (Cohen’s κ coefficient 0.702, 95% CI 0.516–0.888). In the FCD group, the most common appearance for both walls was discontinuous bony covering with linear deficiency (LFCD = 1, 22/29, 75.9%; IFCD = 1, 15/29, 51.7%). An FCD score of less than 4 was associated with high sensitivity (0.82) and specificity (0.93) for identifying FCD, with an AUC of 0.928. Conclusions Using the proposed scoring method, FCD score < 4 could identify FCD of the tympanic segment with high concordance with surgical findings. Key Points • Imaging appearance of the tympanic facial canal (FC) is divided into four types based on ultra-high-resolution CT images. • The most common appearance of FC with facial canal dehiscence (FCD) is discontinuous bony covering with linear deficiency. • An FCD score, consisting of scores of the lateral and inferior walls, less than 4 is highly indicative of FCD.

Endoscopic Findings on Facial Nerve Anatomy During Exclusive Endoscopic Stapedotomy: Clinical Considerations and Impact on Surgical Results

“… 26 Recently, Wang et al, with the aim of ultra-high-resolution CT (U-HRCT), classified the imaging appearance of the lateral and inferior walls of the tympanic facial canal into 4 types, from no evident to continuous bone covering, and proposed a novel dehiscence’s scoring method as the sum of lateral and inferior scores. 27 Similarly, Zhang et al demonstrated how U-HRCT images could reveal a downward protrusion of the tympanic segment of FN and measured some quantitative indices from simple radiological landmarks that might predict an overhanging FN; among these, the distance between FN and both anterior and posterior stapes crura significantly appeared as 2 independent predictors. 28 To date, a considerable issue of such promising radiological assessments is that they are mostly still experimental and not daily available for clinical practice.…”

Association Between Vestibular Aqueduct Morphology and Meniere's Disease

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“…Although HRCT can show most structures of the inner and middle ear, 12 it cannot meet the need for a clear display of tiny structures and occult lesions in the inner ear. U‐HRCT uses a small‐focus, high‐stability x‐ray generator combined with a flat panel detector, with a resolution scale of up to 0.05 mm 9,13 . VA is divided into proximal, isthmus, and distal segments, with the isthmus as the transition zone around which the proximal and distal segments shift.…”

A case of cochlear-facial dehiscence revealed after bilateral cochlear implants

“…Studies have demonstrated the capability of U-HRCT in delineating fine structures of the temporal bone, both in cadavers and in patients with otologic diseases. Based on observation from U-HRCT images, recent studies introduced 2 new different entities: discontinuous bony covering with linear deficiency versus discontinuous bony covering with dotted deficiency (instead of the binary classification of imaging: lack of bony coating versus continuous bony covering) [11] . In the future, the U-HRCT would improve the preoperative CT evaluation that plays a key role in preventing iatrogenic injury or complication in CI.…”