By modifying a muscle transplant operation, Johns Hopkins surgeons report they are able to restore authentic facial expressions of joy -- wide and even smiles -- to selected patients with one-sided facial muscle paralysis due to birth defects, stroke, tumors or Bell’s palsy.

“The smile has been judged as the most important sign to express positive emotions, and people are judged to be angry when they can’t smile,” says Kofi Boahene, M.D., associate professor of otolaryngology–head and neck surgery and dermatology at the Johns Hopkins University School of Medicine. “Previously, the best we could hope for most of the time with surgery was a smirk where just the corners of the mouth upturn in a smile like the one Mona Lisa has in DaVinci’s famous painting. But that isn’t a joyful, expressive smile where the lips move up, teeth show and eyes narrow. Now we’re able to really restore a true smile.”

Standard surgical fixes for people with one-sided facial paralysis transplanted muscle tissue from a person’s thigh that pulled up on the paralyzed side of the mouth. The modified procedure uses gracilis muscles from the thigh placed in two directions and sometimes three placed at the corner of the mouth or the upper lip to the cheek and eyelid to recreate an authentic smile that shows teeth and gum on both sides of the face.

The surgeons published their findings on 12 adult patients, along with measurements of improvement, online March 22 in JAMA Facial Plastic Surgery.

Boahene notes that one-sided facial paralysis creates social awkwardness and depression, making those who have it self-conscious about their appearance when speaking or eating in front of others. It also creates a tendency to drool and difficulty with normal blinking, which can cause dry and uncomfortable eyes.

For the current study, the surgeons recruited 10 women and two men between the ages of 20 and 64, all of whom received the updated procedure between June 2015 and December 2016.

Prior to surgery, the physicians videoed and measured the type, angle and degree of smile on the nonparalyzed side of the patients’ faces. During surgery, they positioned the new muscles so that they pulled the lips up to match the nonparalyzed half-smile when contracted. Then they rerouted blood vessels and one or more types of nerves to the transplanted tissue from the nonparalyzed side of the face.