Comparisons of Akathisia and Restless Legs Syndrome: An Electrophysiologic Study

Objective: There are clinical similarities between akathisia and restless legs syndrome (RLS). Thus, we aimed to investigate the functional changes of the brainstem and its rostral connections in akathisia in comparison with RLS.
Materials and Methods: Seven patients with akathisia were included in the study. We also included a group of patients with RLS (n=14), and a control group was formed including healthy volunteers (n=39). Blink reflex (BR), auditory startle reflex (ASR), and somatosensory startle (SSS) reflexes were studied in all participants. Onset latency, probability of response, amplitude, pattern and duration of responses were compared between the 3 groups.
Results: Mean onset latencies of bilateral R2 and R2c were longer in the akathisia group compared with patients with RLS and healthy individuals. The mean latencies of responses after auditory stimulation were similar among the groups. The total ASR probability was higher in the akathisia and RLS groups compared with healthy subjects and this difference showed borderline significance (p=0.047). Duration of responses after auditory stimulation was longer in the akathisia group. Presence and latency of SSS were similar among the three groups.
Conclusion: Longer-onset latencies and the higher probability of ASR in the akathisia group suggest that there is a hypodopaminergic state in this group. On the other hand, the longer latencies of R2-BR in patients akathisia suggest a delayed transmission in its pathway, indirectly showing involvement of serotoninergic pathways in the absence of a structural lesion. Thus, in akathisia, there are findings suggestive of serotoninergic involvement, differing from RLS, whereas findings attributed to dopaminergic deficits were quite similar to patients with RLS.