Louis is a 66 year old architect. Some 6 years ago he first noticed he had occasional difficulty with “tightness’’ in his arm muscles. Two years later he developed a tremor in his left hand when it was at rest. At this time he was told he had Parkinson's disease. The tremor has gradually become more pronounced and affects his right hand as well. He can still do most things he could do before, although he finds walking increasingly difficult. “It seems,” he says, “as if the muscles just seize up if I go too far.” The change has been gradual and it is only looking back on things he could do a year ago, but cannot do now, that makes him realise the disease is progressing.