Exploring the critical distance and position relationships between the Eustachian tube and the internal carotid artery.

OBJECTIVE: Endoscopic surgery to the nasopharyngeal portion of the Eustachian tube (ET) has been advocated for ET dysfunction. It is therefore essential to understand the relationship between the ET and the internal carotid artery (ICA) from an endoscopic perspective.

STUDY DESIGN: Retrospective database review.

SETTING: Tertiary and University Hospital.

PATIENTS: General population undergoing cervical CT scanning.

INTERVENTION(S): 397 sides were reviewed in 200 CT scans.

MAIN OUTCOME MEASURE(S): Measurements were taken from the anterosuperior ET torus to the ICA and from the fossa of Rosenmüller (FR) to the ICA. The data were analyzed for any minimum "safe distance." The ICA variability was further investigated by its distance from the midline, and the angle the midline makes with a line drawn from the ET to the ICA. The artery was assessed for an aberrant path.

RESULTS: The minimum distance from ET to ICA was 10.4 mm (average 23.5 mm). The predicted "safe distance" decreases with age from 8.0 mm to 5.4 mm in females and 10.2 to 7.8 mm in males. FR to ICA distance was very small in some patients (minimum 0.2 mm). The ICA was an average 23.7 mm from the midline (minimum 11.5 mm). The ET/ICA/midline angle varied from 17.0- to 53.6- (average 37.7-). 36% have at least 1 aberrant ICA. These patients have significantly shorter ET/ICA distances (95% CI 0.4 Y 2.2 mm, p = 0.004).

CONCLUSION: The distance from ICA to ET varies between males and females. There is no safe distance from FR to ICA. Patients with an aberrant ICA have shorter distances, so contrast CT scanning is advised prior to surgery so that each patient's own carotid anatomy may be known.