Cognition following bilateral implants of embryonic dopamine neurons in PD: a double blind study

To determine if bilateral transplantation of embryonic mesencephalic dopamine cells into the putamen of patients with PD significantly affected their cognitive functioning when compared with patients receiving sham surgery and to examine the effect of age on cognitive performance after implantation.

Forty patients (19 women, 21 men; age 34 to 75 years) with idiopathic PD of at least 7 years' duration (mean 14 years) who had disabling motor signs despite optimal drug management were randomly assigned to tissue implants or sham craniotomies in a double-blind design. Neuropsychological tests assessing orientation, attention, language, verbal and visual memory, abstract reasoning, executive function, and visuospatial and construction abilities were administered before and 1 year after surgery. Treatment groups did not differ at baseline in demographic, neuropsychological, motor, depression, or levodopa equivalent measures.

Postsurgical change in cognitive performance was not significantly different for real or sham surgery groups. Performance in both groups remained unchanged at follow-up for most measures.

Embryonic dopamine producing neurons can be implanted safely into the putamen bilaterally without impairing cognition in patients with PD, but within the first year, improved cognition should not be expected.