Computed Tomography Evaluation of the Correspondence Between the Arcuate Eminence and the Superior Semicircular Canal.

ABSTRACT

BACKGROUND: The arcuate eminence (AE) has been traditionally used in middle cranial fossa (MCF) surgery as a guide to accurate location of the superior semicircular canal (SSC) deep within the temporal bone. However, the anatomic relationship between the AE and SSC is controversial. We evaluated the anatomic coincidence between the AE and the SSC in the MCF surface. Distances between the most relevant anatomic structures in the MCF and prevalence of SSC dehiscence were measured. METHODS: We analyzed 75 (150 sides) 0.75-mm slice thickness temporal bone computed tomography scans and classified the AE and SSC relationship as coincident and noncoincident. Radiologic findings were reported independently in a blind fashion by 2 authors. Data were presented as mean ± SD or frequency and percentage. Student t test or an unequal variance t test was used. Interobserver agreement among readings was assessed using κ statistic for categorical variables and intraclass Kendall tau-a correlations for continuous measures. P < 0.05 was considered to indicate statistical significance. RESULTS: The AE matched the SSC in only 31.3% of cases. The AE could be localized as lateral as 11.6 mm from the SSC. It was impossible to identify the AE in 33 scans (22.0%). SSC dehiscence was found in 5 cases (3.3%). A few millimeters separated most analyzed landmarks, and a wide variability in secondary measurements was observed. CONCLUSIONS: The AE does not systematically overlie the SSC and should not be routinely used as a reference to reach this structure in MCF surgery.