Is there a polysomnographic signature of augmentation in restless legs syndrome?

Augmentation of restless legs syndrome (RLS) is a potentially severe side-effect of dopaminergic treatment. Data on objective motor characteristics in augmentation are scarce. The aim of this study was to investigate in detail different variables of leg movements (LM) in untreated, treated, and augmented RLS patients.

Forty-five patients with idiopathic RLS [15 untreated, 15 treated (non-augmented), 15 augmented] underwent RLS severity assessment, one night of video-polysomnography with extended electromyographic montage, and a suggested immobilization test (SIT).

Standard LM parameters as well as periodicity index (PI) and muscle recruitment pattern did not differ between the three groups. The ultradian distribution of periodic leg movements (PLM) in sleep during the night revealed significant differences only during the second hour of sleep (P <0.05). However, augmented patients scored highest on RLS severity scales (P <0.05) and were the only group with a substantial number of PLM during the SIT.

This study demonstrates that polysomnography is of limited usefulness for the diagnosis and evaluation of RLS augmentation. In contrast, the SIT showed borderline differences in PLM, and differences on subjective scales were marked. According to these results, augmentation of RLS is a phenomenon that predominantly manifests in wakefulness.