What Are The Risks And Success Rates Of Intratympanic Injection For Sudden Hearing Loss?

I recently had sudden hearing loss in my left ear. After a couple weeks of prednisone with little improvements, my ENT thinks I should try intratympanic injection. Is there a risk of further hearing loss from possible complications of this injection? She told me there was a 40% chance that it would restore some of my hearing. Have you had success with intratympanic injection for patients? I can still hear; after 1000Hz my hearing starts dropping off progressivley to a max of around 20DB loss. I m 30 years old.