Restless legs syndrome in the dominant Parkinson's side related to subthalamic deep-brain stimulation

Restless legs syndrome (RLS) has an increased estimated prevalence in patients with Parkinson's disease (PS). RLS frequently mimics symptoms intrinsic to PD, such as motor restlessness, contributing to making its diagnosis challenging in this population. We report the case of a patient with new-onset RLS following subthalamic deep-brain stimulation (DBS-STN). We assessed symptoms using suggested immobilization test (SIT) with both DBS-STN activated and switched off.

A 59-year-old man with idiopathic PD developed disabling RLS following DBS-STN at age 58, with PD onset at 50 manifesting as left arm tremor. Despite improved motor symptoms during the month following surgery, the patient experienced left leg discomfort at rest, transiently alleviated by movements due to an irrepressible urge to move, and worsened at night. Symptoms had no temporal relationship with oral dopa-therapy and disappeared when DBS-STN was deactivated. A 1 h SIT assessed motor behavior with irrepressible urge to move, as well as sensory symptoms by visual analog scale. After 30 m DBS-STN was switched off followed by the appearance of tremor in the left arm while both motor and sensory symptoms of RLS disappeared in the left leg.

The mechanisms of DBS-STN's impact on RLS remain controversial. We hypothesize the DBS-STN to induce in our patient a hyperdopaminergic tone. DBS-induced and DBS-ameliorated RLS represent interesting conditions to further understand the pathophysiology of RLS. Moreover, the present observation suggests that SIT can be a valuable tool to assess RLS in PD patients before and after DBS-STN in future prospective studies.