Initially, he treated it as a short-term indisposition of the body, but over time, he realized that deafness was irreversible. The cause was probably otosclerosis, possibly accompanied by degeneration of the auditory nerve. The composer broke down and in 1802, during his stay in Heiligenstadt near Vienna, he wrote a letter to his brothers (which he did not send), the so-called Heiligenstadt testament, in which the composer says that the only thing that stopped him from committing suicide is his art.
