Association of Lymphatic Fluid Volume in the Inner Ear of Beagle Dogs with the Susceptibility to Motion Sickness.

Background: This study aimed to quantify total lymphatic fluid spaces of the inner ears volumetrically in the dog in order to find a correlation between the lymphatic volume of the inner ears and motion sickness susceptibility.

Methods: A total of 16 healthy adult Beagle dogs were used to delineate the lymphatic fluid spaces of inner ears by magnetic resonance imag- ing with a 3-dimensional-constructive interference steady-state sequence. Manual segmentation was applied for 3-dimensional reconstruction and volumetric quantification of total lymphatic space. The susceptibility of Beagle dogs to motion sickness was judged by latency of vomiting during rotatory stimulus.

Results: The volume range of total fluid space in the vestibule and cochlea of Beagle dogs is 55.07 ± 6.2 mm3. There is no significant difference in the total lymphatic volume of bilateral inner ears between 2 different motion sickness susceptibility groups (i.e., sensitive group and insensi- tive group), but the difference of lymphatic volume in the cochlea and vestibule between bilateral inner ears in insensitive group is greater than that of sensitive group. Moreover, a significant positive correlation was found between bilateral inner ear difference in lymphatic volume and vomiting latency.

Conclusion: Magnetic resonance imaging could be used as a method to evaluate the inner ear lymphatic fluid volume of Beagle dogs with different susceptibilities to motion sickness, through which we found that motion sickness susceptibility is related to the difference in lymphatic volume in the vestibule and cochlea between bilateral inner ears, and the larger the volume difference, the lower the susceptibility.