A potential mechanism underlying the voluntary suppression of tardive dyskinesia

Many clinicians have observed that patients with tardive dyskinesia (TD) can voluntarily suppress the movements to some extent. The mechanism by which voluntary control is exerted most likely involves peripheral feedback. Quantitative analyses of isometric and isotonic jaw stability were conducted in patients with and without TD to test the general hypothesis that involuntary movements of TD may be brought under voluntary control via one of two receptor mechanisms; muscle length and/or muscle force. Results indicated that in the absence of length feedback patients with TD exhibited significantly greater instability while patients without TD performed within normal limits. This suggests that patients with TD utilized muscle length feedback to suppress motor instability but were unable to utilize muscle force feedback to suppress instability. Implications for the use of laboratory procedures in the measurement and clinical management of TD are discussed.