Experimental otoacoustic emission and auditory brainstem response changes by stellate ganglion blockage in rat

Introduction: To investigate the effect of stellate ganglion (SG) block on hearing in rats. Materials and methods: Sixteen male adult rats were randomly divided into 2 equal groups. Both groups underwent preblock auditory brainstem responses (ABRs) in response to tone bursts at 4, 6, and 8 kHz and otoacoustic emissions in response to distortion products as a function of f2 frequency at 1, 2, 4, and 6 kHz. Local anesthetic (0.2 mL of 2% prilokain) was administered to the left SG of the study group by posterior cervical percutaneous approach for cervical sympathetic blockage. In the control group, 0.2 mL of physiological saline was injected to the left SG. Postblock hearing evaluations were made after 15 minutes of injections. Results: Both Dp-gram and I/O function records suggested that whereas hearing thresholds were not affected in lower frequencies after SG blockage, it tended to increase at higher frequencies. In ABR records, waves I and II showed marked latency shift across all frequencies. The interpeak latency of waves I and II was shortened after blockage. Saline injection did not show any significant ABR or distortion-product otoacoustic emission threshold shift across frequencies at 60, 70, 80, and 90 dB sound pressure level. Conclusion: Our data demonstrate that SG block improved the hearing parameters in rats with normal cochlear blood flow. To recommend SG blockage as a treatment option in the vascular pathologies of cochlea, further investigation should assess the efficiency of ganglion blockage in hearing parameters of rats with impaired cochlear blood flow. (C) 2008 Elsevier Inc. All rights reserved.