Objective: We aimed to investigate brainstem reflexes in patients with akathisia.

Background: Akathisia is characterized by urge, inner restlessness and constant movement of predominantly lower limbs. Based on its association with anti-dopaminergic drugs, striatal dopamine blockage has been proposed as the underlying mechanism. In RLS, which has similar clinical features to akathisia, electrophysiological studies have been used to understand underlying mechanisms. They may also provide a way to elucidate the underlying functional changes in akathisia. 

Methods: Seven patients with neuroleptic-induced akathisia, 14 RLS patients and 39 healthy subjects were enrolled in the study. Age and gender were similar. Blink reflex (BR), auditory startle response (ASR), and startle response to somatosensory stimuli (SSS) were recorded in all participants. Startle responses were recorded from orbicularis oculi (O.oc), sternocleidomastoid (SCM), biceps brachii and tibialis anterior (TA) muscles. Latency of BR, latency, probability, amplitude and duration of ASR, latency and presence of SSS were compared between three groups.

Results:

BR was present in all participants and mean latency was similar among groups. Recruitment pattern and mean latency of each muscle response and total ASR probability were also similar. However, amplitude and duration of O.oc and SCM muscle responses were higher in akathisia and RLS groups compared to controls and in akathisia group compared to patients with RLS. Although there was a trend of more frequent response on TA in patients with akathisia and RLS, the difference did not reach statistical significance. Regarding mean latency and presence rate of each muscle response in SSS test, all three groups were similar.

Conclusions: In neuroleptic-induced akathisia, excitability of ASR circuit was increased compared to both patients with RLS and healthy subjects whereas pattern of ASR as well as pattern of SSS and integrity of BR circuits were unchanged. Excitability of ASR pathway is under modulatory control of basal ganglia dopaminergic system, amygdala and cortex. We may propose that hyperactive ASR in akathisia with features similar to that seen in RLS may indicate hypodopaminergic state in patients with neuroleptic-induced akathisia with contribution of rostral pathways since patients with akathisia have more enhanced responses.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/brainstem-reflexes-in-patients-with-neuroleptic-induced-akathisia/