There are two basic types of hearing loss: conductive and sensorineural.
Conductive hearing loss happens when something keeps sound waves from traveling through the ear. The obstacle can be anything from a chunk of earwax to inflamed tissue to a benign growth.
Sensorineural hearing loss is a problem stemming from one of two things. One, with the intricate apparatus that translates sound waves into nerve impulses (the sensory part of sensorineural). Or it can be a problem with the auditory nerve that sends those impulses to the brain (the neural part).
I cant stress enough the importance of getting a hearing test as soon as possible if youve lost hearing suddenly. Early diagnosis and treatment can prevent permanent damage and loss of hearing.
Judging by the steroid treatment your son received, my guess is that he had a sensorineural problem caused by inflammation.
Steroids in this instance is short for corticosteroids. They are powerful anti-inflammatories. They should not be confused with the anabolic steroids used by athletes to get stronger.
Early treatment with corticosteroids has the potential to reverse the inflammation before there is permanent damage. But it doesnt always work.
Your son should ask his doctor about a bone-anchored hearing aid. It can be very useful for people with one-sided sensorineural hearing loss. The procedure doesnt restore nerve function. But it can make it easier for him to hear with the good ear without always turning his head.