Leonardo da Vinci’s “claw hand” may have been caused by nerve damage and not a stroke, a new study suggests.
A pair of doctors, writing in a British medical journal, have concluded that da Vinci's right hand was affected by ulnar palsy, known as claw hand, rather than a stroke as was previously thought.
Their analysis is based on a 16th-century portrait of an elderly da Vinci which shows his right arm in folds of clothing as if it was a sling, with his right hand suspended in a stiff, contracted position.
“Rather than depicting the typical clenched hand seen in post-stroke muscular spasticity, the picture suggests an alternative diagnosis such as ulnar palsy, commonly known as claw hand,” said Dr. Davide Lazzeri, a specialist in plastic reconstructive and aesthetic surgery at the Villa Salaria Clinic in Rome.
The authors believe a fainting episode, during which da Vinci might have sustained traumatic nerve damage of his right upper limb, resulted in ulnar palsy.
The ulnar nerve runs from the shoulder to the pinky finger and manages almost all the intrinsic hand muscles that allow fine motor movements.
Dr. Lazzeri and Dr Carlo Rossi, a specialist in neurology at the Hospital of Pontedera, writing in the Journal of the Royal Society of Medicine, analysed the 16th-century drawing, together with a biography and an engraving of the Renaissance polymath artist and inventor.
Art historians have long debated which hand the Italian genius used to draw and paint with.
“Analyses of the shading and hatching in drawings attributed to da Vinci show that the shading and hatching slopes from upper left to lower right, leaving few doubts about his left-handedness,” the authors wrote.
“Although the numerous documents in mirror-writing with his left hand confirmed that he was likely more skilled in using his left hand than the common right-handed artists, it is claimed that he never painted using his left hand.”
While the impairment affected his ability to hold palettes and brushes with his right hand, he was able to continue teaching and drawing with his left hand, the authors wrote.
"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," Dr. Lazzeri said.
While an acute cardiovascular event may have been the cause of da Vinci's death, his hand impairment was not associated with cognitive decline or further motor impairment, meaning a stroke was unlikely, the doctors said.
Further evidence was obtained from a diary entry by a cardinal's assistant about a visit to the artist's house in 1517.
"One cannot indeed expect any more good work from him as a certain paralysis has crippled his right hand... And although Messer Leonardo can no longer paint with the sweetness which was peculiar to him, he can still design and instruct others," the assistant, Antonio de Beatis wrote.
The new insights were published to coincide with the 500th anniversary of the Italian master’s death on May 2.
Da Vinci was born out of wedlock to a Florentine legal notary and a peasant in Vinci in 1452.
He died in the French town of Amboise in 1519.
