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(CNN) —  

A 16th-century drawing of Leonardo da Vinci suggests that the artist sustained traumatic nerve damage to his right hand that impaired his painting skills late in life, according to a new study.

A portrait of Leonardo da Vinci from the 16th century by Giovanni Ambrogio Figino, drawn in red chalk.
PHOTO: Journal of the Royal Society of Medicine
A portrait of Leonardo da Vinci from the 16th century by Giovanni Ambrogio Figino, drawn in red chalk.

Dr. David Lazzeri, a plastic reconstructive surgery specialist at Villa Salaria Clinic in Rome, and Dr. Carlo Rossi, a neurology specialist at Hospital of Pontedera, analyzed a red chalk drawing of Leonardo by Giovanni Ambrogio Figino and compared it with an engraving of Leonardo, as well as a biography. Their study was published Friday in the Journal of the Royal Society of Medicine, coinciding with the 500th anniversary of Leonardo’s death.

The drawing is an undated rare depiction of Leonardo late in his life that shows his right arm wrapped in clothing, as if it was being used as a kind of bandage. His right hand is stiff and contracted.

Leonardo, the defining figure of a Renaissance man, was known for being ambidextrous. Analysis of his drawings, writings and paintings over the years has revealed that he wrote and drew with his left hand but never painted with it.

But something happened during the last years of his life. He struggled to hold palettes and paint brushes with his right hand, but he continued to draw and teach with his left hand. He died in 1519 due to an acute cardiovascular event.

Many researchers have assumed that this palsy of his right hand was a weakness on one side of the body, known as right hemiparesis, probably caused by a stroke. The stroke was associated with his known vegetarian diet, because high cholesterol is a risk factor of vegetarians who consume a lot of dairy products, according to the study.

Other researchers also suggested Dupuytren’s disease, in which tissue under the hand’s skin thickens and tightens.

But in the red chalk drawing, Leonardo’s right hand isn’t in the clenched position associated with muscular spasticity after a stroke, the researchers said in the new study. Instead, his wrist and thumb are flexed.

This was compared with an engraving dated to 1505 by Marcantonio Raimondi that depicts Leonardo playing a lira da braccio, a bowed musical instrument associated with the Renaissance era. This indicates that he was in optimal condition to play the very instrument he constructed. The researchers believe that this, combined with Vasari’s writings about Leonardo’s strength from 1550, helps rule out Dupuytren’s disease.

After analyzing the chalk drawing, the researchers think that a fainting episode caused acute trauma and nerve damage to his right arm, which caused ulnar palsy. The ulnar nerve, which runs from the shoulder to the pinky, allows for most hand muscle and fine motor movements. It would also explain why he has a “claw hand” appearance, which is associated with ulnar palsy.

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Leonardo’s hand impairment wasn’t associated with any other degenerative issues, cognitive or muscular, which also suggests that a stroke was unlikely.

“This may explain why he left numerous paintings incomplete, including the Mona Lisa, during the last five years of his career as a painter while he continued teaching and drawing,” Lazzeri said in a statement.