On the other hand, Sayad et al. in a study of 27 Algerian PD STN-DBS patients reported that PD patients with the G2019S LRRK2 mutation had a better surgical response compared to non-carriers, with greater improvement in UPDRS III in mutation carriers when switched from the off-medication, off-stimulation condition to off-medication, on-stimulation condition, and greater improvement in functional status in mutation carriers when stimulated without medications. Here, LRRK2 is linked to Parkinson disease.