Patients with Parkinson's disease tend to have a reduced response to levodopa after 5 to 20 years of therapy, with "on—off" fluctuations consisting of dyskinesia alternating with immobility. In an effort to modify the motor disability of advanced Parkinson's disease, we implanted embryonic mesencephalic tissue containing dopamine cells into the caudate and putamen of seven patients. Two patients received unilateral grafts in the caudate and the putamen on the side opposite the side with worse symptoms. Five patients received bilateral grafts implanted in the putamen only. In six of the seven patients, the fetal tissue was obtained from a single embryo with a gestational age of seven to eight weeks. The tissue was injected by means of 10 to 14 needle passes. There were no surgical complications. Four of the seven patients underwent immunosuppression with cyclosporine and prednisone.

All patients reported improvement according to the Activities of Daily Living Scale when in the on state 3 to 12 months after surgery (P<0.01). Neurologic examination according to the Unified Disease Rating Scale showed that five of the seven patients improved when in the on state six months after surgery. The mean group Hoehn—Yahr score improved from 3.71 to 2.50 (P<0.01). Computer and videotape testing in the home supported these findings. Fluctuations in the patients' clinical state were moderated, and periods of dyskinesia and off episodes were shorter and less severe than before implantation. Drug doses were reduced by an average of 39 percent (P<0.01; maximum, 58 percent). The results of clinical evaluation and fluorodopa positron-emission tomography in one patient were compatible with transplant survival for as long as 46 months. Both immunosuppressed and nonimmunosuppressed patients improved.

Fetal-tissue implants appear to offer long-term clinical benefit to some patients with advanced Parkinson's disease. (N Engl J Med 1992;327:1549–55.)