CT of the normal suspensory ligaments of the ossicles in the middle ear

To establish the range of normal variation in the CT appearance of the middle ear ligaments and the stapedius tendon as an aid in detecting abnormal changes in these structures.

CT scans of the temporal bone in 75 normal middle ears, obtained with 1-mm-thick sections, were reviewed by two observers, who rated the visibility of the structures of interest on a scale of 1 to 5.

The anterior, superior, and lateral malleal ligaments and the medial and lateral parts of the posterior incudal ligament were seen in 68%, 46%, 95%, 26%, and 34% of the ears, respectively. The stapedius tendon was seen in 27% of the cases. When visible, the ligaments were judged to be complete in 90% to 100% of the ears and the stapedius tendon was complete in 65% of cases. Their width varied considerably. Interobserver variability was high for most observations.

CT scans are more likely to show the malleal than the incudal ligaments. Although the interobserver agreement was statistically significant for most study parameters, the percentage of agreement above that expected by chance was low. When seen, the ligaments usually appeared complete. Understanding the normal range of appearance may help identify abnormalities of the ligaments and tendons of the middle ear.