Arguably, the most famous painting in the world today is The Mona Lisa, partly because of the mystery surrounding this sixteenth century painting. One is that it was never finished. Art historians have tried to answer why Leonardo DaVinci didn't finish it and now a new theory is being explored. Perhaps Da Vinci injured his arm when he fainted.

The ongoing belief had been that the man had suffered a stroke partly because a drawing of an elderly da Vinci seems to have his right arm in a sling. His ring and little fingers are contracted into what's termed as a claw hand. But his face looks normal and a hand paralyzed by stroke normally contracts all the fingers. Written records also don't support the stroke theory.

A diary entry by an assistant to Cardinal Luigi D'aragona in fifteen seventeen says quote 'One cannot indeed expect any more good work from him, as a certain paralysis has crippled his right hand.' The new theory that Da Vinci most likely fell explains that the clawed hand was caused by ulnar palsy or ulnar neuropathy.

The ulnar nerve runs from the shoulder to the hand and into the little and ring fingers. But at the elbow, it's close to the surface and we know it's there when we knock what we call our funny bone. It's not uncommon for the elderly to fall and injure their ulnar nerve. They end up with abnormal sensations in the little finger and have weakness and loss of coordination in the last two fingers.

This could explain why da Vinci stopped painting in his later years. He was still capable of drawing because while he painted with his right hand, he sketched with his left. Da Vinci did die from a stroke at age seventy five. And we'll never know if he intended to finish the Mona Lisa.