Upper airway muscles dysfunction and levodopa responsiveness in Parkinson's disease.

Pulmonary function tests were performed before and at different times after 250 mg L-Dopa in 12 patients with Parkinson's disease (PD). Six were de-novo patients, the other six patients had been taking L-Dopa over different periods. All patients had an abnormal basal flow-volume loop, which significantly improved only in de-novo patients. This improvement occurred early and was independent on improvement of neurological symptoms. The effect of L-Dopa on pulmonary function could be a useful test in differentiating PD from related extrapyramidal syndromes.