Eustachian Dehiscence: Is This a New Cranial Foramen?

Purpose The Eustachian tube (ET) is a narrow canal connecting the middle ear to the nasopharynx, traditionally considered to have no direct communication with the intracranial cavity. Contrary to current anatomical literature, we identified a previously undescribed bony defect between the ET and the middle cranial fossa on high-resolution temporal bone CT scans. We propose naming this structure the “Eustachian dehiscence” or “Baris foramen” and aim to characterize its radiological features and prevalence. Methods We retrospectively reviewed high-resolution temporal bone CT scans of 426 patients (186 males, 240 females) obtained between January 2021 and December 2023. Inclusion criteria covered patients over 18 undergoing imaging for hearing-related concerns; exclusions included prior trauma, surgery, tumors, or poor image quality. Imaging was performed using a 128-slice Phillips Brilliance iCT scanner with 0.5–0.6 mm slices and multiplanar reconstructions were performed. In addition, anatomical assessments were conducted on 51 cadaveric specimens. Results The foramen was identified in 172 cases (40.4%): 87 unilateral (51%) and 85 bilateral (49%). Right-sided foramina were observed in 124 patients (29.1%) and left-sided in 133 (31.2%). Foramina were classified as small (< 2 mm) or large (≥ 2 mm), with no significant sex-based differences. Cadaveric dissection confirmed the presence of the foramen in 23 specimens (45%), predominantly unilateral. Conclusion We report a novel, unrecognized ET feature, the Eustachian dehiscence, consistently visualized on imaging and confirmed by cadaveric dissection. Further studies are warranted to investigate its clinical significance and potential implications for skull base anatomy.