(0948) Mild Blast Wave Trauma Produces Vestibular Receptor Damage

Introduction: Blast wave survivors often report vestibular issues like vertigo and imbalance. Our prior study in mice revealed damage and reduced reflex responses to severe blast waves (Lien and Dickman 2016). However, the impact of mild to moderate blast exposure on vestibular receptors remains unexplored

Methods: Mice were implanted with a head stability post, allowed to recover, and then exposed to a single induced air blast wave of either 0 (control), 10, or 30 kpa while anesthetized and suspended inside a rigid tube. Following blast exposure, animals were allowed to survive for periods of 1, 7, 14, or 28 days, then perfused with aldehyde fixatives. Vestibular receptors were histologically prepared and the following measures quantified: stereocilia hair bundle counts, density of hair cells (both type I and type II), hair cells morphometrics, and axon density and diameter beneath the stroma (Neurolucida MicroBrightfield inc.).

Results: To date, type I hair cells, distinguished through calretinin staining, exhibit a flask-shaped morphology and are predominantly situated in the central region of the semicircular canal cristae. These cells intricately associate with mostly single large calyx nerve endings, although a few instances of double calyces, innervated by a single afferent fiber, have been observed. Ongoing quantitative measurements are being conducted on individual cells. Additionally, simultaneous staining using MYO7A and calmodulin was employed for both types of hair cells. CTBP2 and PSD95 served as synaptic markers, while Phalloidin labeled stereocilia, and NF200 labeled nerve afferents. The maximum cross-sectional area of a calyx averages at 64.67 µm² (n = 35) in the horizontal cristae and 77.68 µm² (n = 45) in the anterior canal, encompassing the double calyces. Mice exposed to high blast levels exhibit stereocilia and hair cell loss, primarily in the central regions of the receptor cristae.

Conclusions: These findings suggest that even low-level blast-wave exposure can cause peripheral vestibular damage, offering insights into potential causes of vestibular dysfunction in blast-trauma victims.