The bilateral dose that will be administered to the 18 patients (initially 3 groups of 6 patients, randomised 4:2 NTCELL:sham surgery) enrolled in this trial will be up to a total of twice the human equivalent dose administered unilaterally in LCT's non-human primate study. Thus up to 240 NTCELL microcapsules (± 5%) administered on each side of the brain.