A DISTURBANCE IN THE CONTROL OF MUSCLE FORCE IN NEUROLEPTIC-NAIVE SCHIZOPHRENIC-PATIENTS

The voluntary motor disturbances found among many schizophrenic patien ts consist of motor incoordination, disturbed pursuit tracking, diffic ulty following movement sequences, desynchronized tapping, and a myria d of neurologic soft signs. The problem with many of these observation s is that it is extremely difficult to distinguish,movement disorders related to neuroleptic treatment from those that may have occurred spo ntaneously. The aim of the present study was to examine potential dist urbances in the voluntary control of steady-state force in neuroleptic -naive schizophrenic patients and normal comparison subjects. Twenty-o ne patients and 21 age- and gender-matched comparison subjects were st udied. Spectral analyses of hand force instability revealed a signific ant difference between patients and comparison subjects. In 52 of the patients, the disturbance in the control of force exceeded the 95th pe rcentile of the comparison mean. Degree of force instability was corre lated with positive but nor negative symptoms of schizophrenia. These findings suggest that schizophrenic patients may exhibit a disturbance in the control of muscle force that cannot be attributed to the neuro leptic effects of antipsychotic medication. The pattern of disruption, characterized by abnormal spectral energy within the 1.5 to 3.0 Hz ra nge, suggests a motor disturbance that resembles tardive dyskinesia. I mplicit within these findings of neuroleptic naive patients is the pos sibility that disturbances in the control of isometric force may repre sent spontaneous dyskinesia.