The exact date of the onset of the deafness is unknown, but it must have happened in the period 1796/1798. It was a very slow process and not until 1817 Beethoven began to use the so-called Konversationshefte (conversation books), because he couldn't communicate anymore with his visitors. They had to write down their questions and remarks. However, as late as 1825 he was still able to hear very loud sounds. The first who tried to write a complete anamnesis of all Beethoven's illnesses, including, of course, his deafness was Schweisheimer and he did so in 1922. He thought that Beethoven's other chronic illness, his bowel problems, had had the same background, most probably an underlying chronic disease, maybe an infection. To this day there is no consensus about the cause of those problems, nor about the deafness. We only know for sure that from about 1820/1 Beethoven began to suffer from chronic liver problems and that this ended in cirrhosis. Liver failure caused his death. Lead poisoning, due to bad medicines or contamination of food and wine, as the cause of his cirrhosis and/or his deafness is not very likely, though it may have added something. However, it is an uneasy fact that Beethoven drank too much and we can safely assume that this was the most important cause of his lethal liver illness. As for his deafness: otosclerosis is the most likely candidate, but without the lost hearing bones certainty is far away and probably this will never change.
Schweisheimer, Waldemar. Beethovens Leiden. Ihr Einfluss auf sein Leben und Schaffen. (Munchen, 1922).
Forster, Walther. Beethovens Krankheiten und ihre Beurteilung. (Wiesbaden, 1955).
Larkin, Edward. Beethovens Medical History. In: M.Cooper. Beethoven. The last decade. (London, 1970).
Franken, Franz. Die Krankheiten grossen Komponisten. (Wilhelmshaven, 1986).
Bankl, Hans und H. Jesserer. Die Krankheiten Ludwig van Beethovens. Pathographie seines Lebens und Pathologie seiner Leiden. (Vienna, 1987).
Neumayr, Anton. Musik und Medizin. (Vienna, 1987).
O'Shea, John. Music and medicine. (London, 1990).
Palferman, Thomas. Beethoven's Medical History: Themes and Variations. In: The Beethoven Journal (San Jose, 1992).
Scherf, Horst. Die Legende vom Trinker Beethoven. (Munchen, 1992).
Kubba, Adam and M. Young. Ludwig van Beethoven: A Medical History. In: The Lancet (1996).
Walsh, William J. Press release of October 17 of The Health Institute and Pfeiffer Treatment Center on the chemical study of Beethoven's hair. (Naperville, USA, 2000).
Davies, Peter J. Beethoven in person. His Deafness, Illnesses, and Death. (Westport/London, 2001).
Weiss, Rick. Study Concludes Beethoven Died of Lead Poisoning. In: The Washington Post. (December, 6, 2005).
Klinger, Wolfram. Das Ratsel von Beethovens Gehorleiden. In: Bonner Beethoven-Studien. (2006).
Reiter, Christian. Beethovens Todesursachen und seine Locken. In: Mitteilungsblatt der Wiener Beethoven-Gesellschaft. (2007).
Lorenz, Michael. Commentary on Wawruch's report: Biographies of Andreas Wawruch and Johann Seibert, Schindler's Responses to Wawruch's Report and Beethoven's Medical Condition and Alcohol Consumption. In: The Beethoven Journal. (San Jose, 2007).
Neumayr, Anton. Beruhmte Komponisten im Spiegel der Medizin. (Wien, 2007)
Mai, Francois Martin. Diagnosing Genius: The Life and Death of Beethoven. (Montreal, 2007)
Eisinger, Joseph. Was Beethoven Lead-Poisoned? In: The Beethoven Journal. (San Jose, 2008).