From a book review of a recent biography of Beethoven by Doctor Mai: Diagnosing Genius: The Life and Death of Beethoven.
“The cause of Beethoven’s death was liver failure due to alcohol abuse. The autopsy was performed by Dr. Johann Wagner, who was assisted by Dr. Karl von Rokitansky. Rokitansky was a resident in pathology, and Beethoven’s autopsy was the first one he performed. He subsequently performed 59,786 autopsies in his outstanding career as a pathologist and became famous for his observations on the gross features of pathologic abnormalities of organs.
At Beethoven’s autopsy, Wagner and Rokitansky found — besides cirrhosis of the liver due to alcohol abuse — ascites, splenomegaly, pancreatitis, and thickened bones of the skull. The eighth cranial nerves were wrinkled and shriveled because they had been compressed by the thick skull bones, a finding consistent with Paget’s disease of bone, which can cause deafness. Other conditions that have been put forth as the cause of Beethoven’s deafness — including head trauma inflicted by his alcoholic father, syphilis, and otosclerosis — lack credibility. There is also some question of whether lead poisoning caused Beethoven’s illnesses. In 1996, a lock of his hair was found to contain high levels of lead. Lead poisoning was common in Europe during Beethoven’s time because wine contained lead that had leached from its containers.”