Sister Bernadette Moriau from northern France visited the holy spring in the foothills of the Pyrenees mountains in July 2008, then aged 69, seeking a cure to her ailment like millions of other pilgrims each year.
Shortly after returning home, her chronic sciatica or pinched spinal nerve disappeared for the first time since her condition was diagnosed at the age of 27.
Sister Bernadette had undergone four unsuccessful operations.
“She experienced an unusual feeling of relaxation and heat in the whole of her body (and) heard a voice telling her to take off her equipment, the corset and the leg brace,” said a statement from her Catholic parish in Beauvais in the north of France.
After further examinations by doctors and three meetings of church figures in Lourdes, the medical committee in the town confirmed that Moriau's recovery could not be explained scientifically, the statement said.
“Sister Bernadette Moriau now has a perfectly normal life,” the committee's president Alessandro de Franciscis told AFP. “She is in very good health and herself visits the sick on a regular basis.”
Lourdes is one of the most revered sites for the world's 1.2 billion Catholics because the town is said to be where the Virgin Mary appeared to a peasant girl in a grotto.
A press conference will be held Tuesday in Beauvais featuring Sister Bernadette, De Franciscis and the bishop of the local diocese, Jacques Benoit-Gonnin.