MRI features of presumed normal palatine tonsils in dogs

Abstract

Objective To describe the MRI characteristics of normal palatine tonsils in dogs. Materials and Methods Retrospective study of 95 dogs with presumed normal tonsils. Tonsillar margination, shape and signal intensity in pre‐ and postcontrast studies were assessed and the cross‐sectional area was measured at the point of maximal size on transverse images. Results In all cases the tonsils were located with their largest transverse cross‐section at the level of the temporomandibular joints. Their margins were well‐defined in all dogs; in 57 (60%) the borders were smooth and in 38 (40%) slightly irregular. The majority (96%) of the tonsils were rounded to oval in cross‐section and the remainder were elongated. All tonsils were hyperintense to the medial pterygoid muscles in T1‐weighted, T2‐weighted, FLAIR and T2* gradient echo images and they showed either homogeneous (53%) or heterogeneous (47%) signal intensity. Contrast enhancement was marked (65%) or moderate (33%) in the majority of animals. Median tonsillar cross‐sectional area was approximately 29 mm2 (90% confidence interval: 10.0 to 64.4 mm2). There was significant positive correlation between bodyweight and tonsillar cross‐sectional area and a weak negative correlation between age and tonsillar cross‐sectional area. Clinical Significance MRI is of value in assessing normal palatine tonsils in dogs. This study could be used as a baseline for the investigation of the value of MRI in assessment of tonsillar disease in dogs.

3T MRI characteristics of the palatine tonsil in brachycephalic dogs

“…who reported median cross‐sectional values 0.29 cm 2 for the left and 0.30 cm 2 for the right tonsils. Ruiz‐Drebing et al 17 . found no significant difference in cross‐sectional size between brachy‐ and normocephalic animals either, whereby, in contrast to the present study with n = 85, the number of brachycephalic animals with n = 16 was comparatively small.…”

“…The cross‐sectional values determined in the normocephalic animals in the present study were on average identical to the results of similar measurements in normocephalic animals in the study by Ruiz‐Drebing et al 17 . who reported median cross‐sectional values 0.29 cm 2 for the left and 0.30 cm 2 for the right tonsils.…”

“…The margination of tonsils was assessed as 'good' in the majority of the brachycephalic animals examined (87%); however, this result is worse compared to that in the literature with a margination of 100% assessed as 'good' in normocephalic dogs 17 . The margination was sufficient in all animals, and size could be determined.…”

“…Since the discrepancy in anatomy compared to the values given in the literature is very large, we assume that this phenomenon is only partly explained by different methodology used in this study (comparison of measurements on cadavers compared to in vivo measurements). More likely, in the MRI‐based tonsil measurement in both Ruiz‐Drebing et al 17 . and in the present study, portions of tonsillar fossa were included in the measurement since a clear delineation of the tonsil fold was not possible.…”

“…The decisive advantage of MRI compared to CT is a better soft tissue contrast, which allows a clearer demarcation of the tonsils from the surrounding soft tissue, especially from the soft palate and the lateral pharyngeal wall 14–16 . The MRI characteristics of the palatine tonsils of healthy normocephalic dogs have been recently described by Ruiz‐Drebing et al 17 . The aim of our study was to determine the cross‐sectional area and volumes of tonsils in brachycephalic dogs and to compare them with those in normocephalic dogs.…”