Walter Bast, 49, regained both his power of speech and the use of his right arm after the revolutionary operation. Mr Bast, who lives in Germany, agreed to be the first to test the treatment after suffering two strokes in quick succession.
The treatment, called CellBeads, uses stem cells taken from bone marrow, which are genetically engineered to make a drug known as CM1. This drug protects brain cells from dying and allows the cells to rejuvenate and repair the damage caused by the stroke.
The stem cells are enclosed in beads to hide them from the immune system and ensure that they are not rejected by the body.
Enclosing everything in the 2cm square 'teabag' ensures the surgeon can easily remove it at the end of the treatment period, which lasts about two weeks.
The CellBeads treatment was pioneered by scientists at the British medical technology firm Biocompatibles International, based in Farnham, Surrey.
Dr Peter Stratford, of Biocompatibles, said a one-size-fits-all treatment could be stored in hospital freezers ready for use when required.
If further trials of the treatment are successful, it could be available to the public in as little as five years. However, stem cell scientists cautioned that many safety and ethical hurdles would have to be crossed before the treatment was accepted for widespread use.
If effective, the treatment could have a huge impact on patients' quality of life and save the NHS billions.