SWEDDs non Parkinson's disease

4-15 % of patients entered into trials for PD had normal presynaptic nigrostriatal dopaminergic imaging and were termed "subjects with scans without evidence of dopaminergic deficits." (SWEDD's). Withdrawal of dopamine was nondeleterious and rescanning 4 years later continued to show no deficit. Case was presented of a subject with jerky assymmetric rest and action tremor, arm dystonia, hypomimia, increased limb tone, and slow repetitive finger movements. 3/10 had abnormal thumb extension (Froment's sign in this case), none had micrographia, and none had loss of sense of smell. True bradykinesia, as defined by progressive decrement of speed and amplitude of repetitive movement (decremental bradykinesia) was not present and should be contrasted to just slowing or hesitation of voluntary movement. The action tremor occurred as the arms were held up (postural tremor).

Blogger note: differential diagnosis could include corticobasal ganglionic degeneration, difference being more rapid progression in that condition, particularly if functional imaging is not done or not available.