Parkinson's patients in the US, who are suing a drugs company for withdrawing a pioneering treatment, say a man treated in Bristol has given them fresh hope.
Mr Webb had advance Parkinson's Disease when he began the trials
Amgen halted medical trials of glial cell line-derived neurotrophic factor (GDNF) because of side effects.
But an autopsy on the brain of Henry Webb, who volunteered to undergo tests at Frenchay Hospital, showed signs that his nerve fibres were regrowing.
The company said it had no plans to restart the trials.
Mr Webb, from Blackwood in South Wales, died from a heart attack last December.
He was one of four patients with advanced Parkinson's Disease involved in GDNF trials at Frenchay.
He told BBC News in 2003 the drug had given him back his life.
Kristen Suthers, daughter of one of the US patients fighting to get the medical trials restarted, said: "We believe high doses of GDNF causes lesions. But we've seen the study from Mr Webb that it is not the case if you give patients a lower dosage of GDNF.
"Mr Webb's case is important because it shows that GDNF is a safe and effective treatment."
A spokeswoman for Amgen told the BBC: "It is a case of interest, but you have to remember, it was phase one of the study.
"In the phase two study, those on placebos did well, sometimes better, than those on the drug."