Short-term Peripheral Auditory Effects of Cranial Irradiation

Abstract

Objectives Assess post-cranial irradiation short-term threshold shift short-term peripheral auditory histopathology the mouse as an experimental model Methods Adult mice were exposed to single-dose radiation of 10 – 60 Gy. Pre- and post-irradiation (baseline, 2 – 8 days) audiometric brainstem response data were recorded with analysis of cochlear ultrastructure. Results Significant threshold shift occurred at all test frequencies in mice exposed to ≥ 20 Gy at 4 – 6 days post-irradiation. Ultrastructurally in Rosenthal’s canal and the spiral lamina, neuronal density and extracellular matrix decreased dramatically. There was overall preservation of hair cells, stria vascularis, and vasculature. No difference within Gy group was noted in the frequency or severity of pathology along the length of the cochlea. Conclusions The initial impact of radiation in the first week post-exposure focuses on spiral ganglion cell bodies and peripheral projections, resulting in significant threshold shift for irradiation dosages ≥ 20 Gy. This study demonstrates that the mouse is a viable model for study of short-term peripheral auditory effects using single-dose cranial irradiation. Additionally, with access to a precise animal irradiator, the mouse may be used as an experimental model for a fractionated irradiation dosage of 10 Gy, simulating stereotactic therapeutic cranial irradiation.

High Doses of Radiation Cause Cochlear Immunological Stress and Sensorineural Hearing Loss

“…No differences were noted within the Gy group in the frequency or severity of pathology along the length of the cochlea. At the same time, hair cells, stria vascularis, and vasculature showed negligible changes [45]. Liu, Z., et al [11] gave cobalt-60 rays at doses of 10 Gy or 20 Gy to mice heads, and they also verified no significant changes in the number of hair cells or the array for the treatments.…”

Mechanism and Protection of Radiotherapy Induced Sensorineural Hearing Loss for Head and Neck Cancer

“…Krysta et al found that the density of spiral ganglion cell bodies and surrounding protrusions exposed to 60 Gy IR was significantly decreased in mice, and the related extracellular matrix was also lost. In the 20 Gy IR group, only a slight threshold shift, with pathological examination revealing signs of vacuolation and separation of spiral ganglion cells, and early demyelination [ 68 ]. While demyelination is also found responsible for the hearing loss caused by excessive sound stimulation [ 69 ] and aging [ 70 ].…”