Neurological soft signs in schizophrenia: Are they related to negative or positive symptoms, neuropsychological performance, and violence?

This investigation was carried out on 31 unemployed schizophrenic outpatient men. The general purpose was to explore new aspects of neurological soft signs in schizophrenia. A 108-item version of the Nathan Kline Institute scale of soft signs, the Schedule for Affective Disorders and Schizophrenia psychiatric interview, the negative and positive symptom scale (PANSS), a comprehensive scale of life-time history of violence, and a large set of neuropsychological tests were administered. It was found that “motor” soft signs were significantly more prevalent than “sensory-perceptual” signs, but that each body side manifested equal numbers of neurological signs. Before and after statistical correction for age, education, alcoholism, drug abuse disorder, and daily and cumulative neuroleptic dosage, orbitofrontal-type neuropsychological tasks measuring “impulsivity” related very robustly to the soft signs. Furthermore, before and after the same statistical corrections, right body-side signs correlated significantly with the same neuropsychological tests, whereas left body-side signs did not. The PANSS scores and levels of lifetime violence generally did not correlate significantly with neurological soft signs. The latter negative findings, we think relate to the fact that these were relatively high-functioning (i.e., outpatient) schizophrenics. Overall, the results support notions of frontal lobe and left hemisphere involvement in schizophrenia, these two dysfunctional systems being apparently linked at the level of the orbitofrontal area of the brain.