Complex sentence: In 1889, at age 44, he suffered a collapse and a complete loss of his mental faculties that was later ascribed to atypical general paresis due to tertiary syphilis, though this diagnosis has come into question.
Split into simpler sentences: In 1889, at age 44, he suffered a collapse and a complete loss of his mental faculties. The breakdown was later ascribed to atypical general paresis due to tertiary syphilis, but this diagnosis has come into question.