76 - Otitis Media and the Shape of the of the Pharyngotympanic Tube: A 3D MRI Study

Poster Board Number: 76
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Abstract Body : Introduction:
Otitis media (OM) is among the most common of childhood illnesses. It has long been hypothesized that the angle of the pharyngotympanic tube may predispose children, particularly young children under 2 years of age, to middle ear pathologies. The study of the pharyngotympanic tube is particularly challenging for several reasons: 1) its position is deep within the cranial base, 2) that it is largely a soft tissue structure, 3) the lumen is generally closed making it challenging to find on standard imaging. Previous studies have approximated its position on dry skulls, CT scans, MRI, and radiographs, all of which lack the ability to analyze soft tissue shape in three dimensions. The present study attempts to test whether the shape of the pharyngotympanic tube, cranial base, and palate is significantly different between children with and without OM.
Materials and Methods:
MRI scans were performed on 22 children between 2011 and 2015. Sixteen landmarks representing the shape of the pharyngotympanic tube, cranial base, and palate were placed using Stratovan Checkpoint. The effects of rotation, translation, and scale were minimized using a Procrustes partial superimposition. Procrustes Anova was performed to test for significant difference in shape between children with and without a history of OM. A generalized principal components analysis and a Kruskal-Wallis test was performed to test which principal components (PC) were significantly associated with OM. A canonical variates analysis was also performed.

Results and Discussion:
There were 9 control children (no history of OM) and 13 children with a history of OM with an average age of 6 years 10 months (range: 6 years 0 months to 7 years 11 months). There were 12 males and 10 females. The race was reported as 3 black, 17 white and 2 American Indian. The results of the Procrustes Anova indicate that shape of the pharyngotympanic tube significantly varies between the OM and control groups (P< 0.001). Based on the Kruskal-Wallis test, the differences are best summarized by PC3. PC3 describes a medial and low attachment site of the tensor veli palatini muscle, posterior and high torus tubarius, and an anteriorly projected palate among the OM group. Results of the canonical variates analysis support these results. These findings support previous research indicating that the relative horizontality of the pharyngotympanic tube may be associated with predisposition for OM.
Conclusion:
There are differences in the pharyngotympanic tube anatomy between 6- and 7-year-old children with and without a history of OM which may help elucidate age-related relationships between pharyngotympanic tube anatomy, physiology, and pathophysiology.