Clinical characteristics of Restless legs syndrome in patients with Parkinson's disease.

To assess the characteristics, clinical significance and pathology of Restless legs syndrome (RLS) in patients with Parkinson's disease (PD), we studied clinical backgrounds, RLS symptoms, polysomnographic (PSG) variables and therapeutic outcomes in 13 PD patients with RLS (pRLS), and compared them with those of 22 idiopathic RLS patients (iRLS). In all but one pRLS patient, RLS symptoms arose within 5 years of PD onset. pRLS patients had a lower prevalence of family history of RLS, and the age at onset was higher than in iRLS subjects. Scores for the severity scale established by the International Restless Legs Syndrome Study Group (IRLS), the Pittsburgh Sleep Quality Index, and the suggested immobilization test did not differ between groups. However, the periodic limb movements index measured by polysomnogram was smaller in pRLS subjects. After RLS treatment, symptoms improved significantly in both groups; however, pRLS subjects showed higher IRLS scores despite receiving similar doses of RLS medications. The severity of RLS before treatment was quite similar between the two groups, but the response to treatment could be poorer in pRLS than in iRLS. Thus, degeneration of the diencephalospinal dopaminergic pathway due to PD itself and physiological aging could overlap in the pathology of pRLS.