Do parkinsonian symptoms and levodopa‐induced dyskinesias start in the foot?

Parkinsonian symptoms and levodopa-induced dyskinesias (LIDs) are often considered to occur first, and to predominate, in the upper limbs. We studied the topography, type, sequence, and severity of LIDs in 20 consecutive patients with Parkinson's disease (PD) experiencing LIDs for less than 6 months (Hoehn and Yahr stage II-III; average age at onset of PD, 57 years; average duration of PD, 7.2 years; percent of improvement with levodopa > 50) and compared them with the initial site, form, and evolution of the patient's motor disability. Parkinsonism started in the foot in six of 20 patients. Motor disability in the "off" state was similar in upper and lower extremities, except for akinesia, which was worse in the lower limbs. A careful interview indicated that LIDs had started in the foot in all patients. After administration of a single dose of levodopa ("levodopa test"), LIDs appeared in all patients as dystonia of the foot homolateral to the side most affected by PD (onset-of-dose dyskinesia). LIDs were preceded by "off" dystonia (dystonic foot) in six patients and were followed by mid-dose dyskinesia in eight. This is consistent with an early loss of dopaminergic innervation corresponding somatotopically to the foot area. The similarities among initial LIDs, early morning dystonia, and onset-of-dose dyskinesia suggest a similar pathophysiology.