Fig. 7. Transverse plane ultrasound image of the basihyoid bone (arrowheads) and the ceratohyoid bones (arrows) of a normal larynx, obtained with the transducer positioned ventrally. Left is to the right of the image and right is to the left of the image.
sion of the thyroid cartilage dorsal to the muscular process of the arytenoid cartilage can best be imaged in the transverse plane (Fig. 11), whereas the lack of a cricothyroid articulation is best imaged in the dor-
Fig. 6. Transverse plane ultrasound image (A) of the ventral aspect of the thyroid cartilage (arrows) of a normal larynx at the level of the vocal folds (arrowheads). B, Transducer posi- tion. The movement of the vocal folds can be observed during respiration. Left is to the right of the image and right is to the left of the image.
The contour of the arytenoid cartilages should
be assessed critically. The arytenoid cartilages should have a trumpet bell shape with smooth mar- gins. Horses with chondritis have irregularity of the axial and abaxial margins with thickening of the cartilage and abnormal echogenicity within the ar- ytenoid cartilage compared with normal arytenoid cartilages (Fig. 10).27 Horses may have only a granuloma or chondroma on the axial surface of the arytenoid cartilage without diffuse arytenoid chon- dritis. Ultrasonographically, this manifests as fo- cal irregularity of the axial margin and a smooth abaxial margin and normal arytenoid cartilage width. The anatomic abnormalities characteristic of la- ryngeal dysplasia can also be observed. The exten-
412 2015 Vol. 61 AAEP PROCEEDINGS
Fig. 8. Transverse plane ultrasound image of the lateral aspect of a normal larynx. Note the mineralization of the muscular process of the arytenoid cartilage (arrow). Dorsal is to the left of the image and ventral is to the right of the image.
