Dear Dr. Roach: About a month ago, I woke up without hearing in my left ear. I initially suspected a wax blockage or a blocked eustachian tube but eventually realized that it was more serious. I saw an ENT doctor who gave me a steroid shot and put me on prednisone. An MRI doesn’t show a stroke or tumor.

About 5% to 10% of my hearing seems to have returned after two weeks of treatment. I had never heard of this problem before but have since learned of others who’ve had it. Usually they’ve had permanent hearing loss. What causes this? Is there anything else I can do? — T.D.S.

Answer: This is called sudden sensorineural hearing loss. It is uncommon, with less than 1 person per 1,000 being affected each year. Although sometimes a cause can be identified, often no cause can be found. Viruses and blood clots have been suspected as underlying causes in some people.

Sudden hearing loss on one side or both should prompt immediate evaluation. Oral prednisone is recommended as an initial treatment, ideally within a few days of the symptom onset. People who cannot take oral steroids receive an injection directly into the ear, and those with profound hearing loss like yours often get both.

Unfortunately, the greater the initial hearing loss, the worse the prognosis. However, the fact that you have recovered some within a month is good news, and you may continue to improve in the next few months. But after six months, additional recovery is unlikely.

Hyperbaric oxygen is a promising treatment for this condition, although availability and cost can be a problem. A future column will address this further.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu.