- Age at onset before 45 Presence of at least two of the three cardinal signs: bradykinesia, rigidity with dental wheel, postural tremor Frank response to L-Dopa (> 30 %) Absence of personal history of meningitis-encephalopathy, neuroleptic treatment, absence of pyramidal, cerebellar or oculomotor signs, absence of dysautonomia or dementia that occurred less than 2 years before the onset of the disease Exclusion of Wilson's disease by usual biological tests Normal cerebral MRI